Refactor container into a library.

3 files changed, 2316 insertions, 0 deletions

diff --git a/src/lib/container/container.c b/src/lib/container/container.c
new file mode 100644
index 0000000000..a7810ba90b
--- /dev/null
+++ b/src/lib/container/container.c
@@ -0,0 +1,1549 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file container.c
+ * \brief Implements a smartlist (a resizable array) along
+ * with helper functions to use smartlists.  Also includes
+ * hash table implementations of a string-to-void* map, and of
+ * a digest-to-void* map.
+ **/
+
+#include "common/util.h"
+#include "common/container.h"
+#include "lib/crypt_ops/crypto_digest.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "ht.h"
+
+/** All newly allocated smartlists have this capacity. */
+#define SMARTLIST_DEFAULT_CAPACITY 16
+
+/** Allocate and return an empty smartlist.
+ */
+MOCK_IMPL(smartlist_t *,
+smartlist_new,(void))
+{
+  smartlist_t *sl = tor_malloc(sizeof(smartlist_t));
+  sl->num_used = 0;
+  sl->capacity = SMARTLIST_DEFAULT_CAPACITY;
+  sl->list = tor_calloc(sizeof(void *), sl->capacity);
+  return sl;
+}
+
+/** Deallocate a smartlist.  Does not release storage associated with the
+ * list's elements.
+ */
+MOCK_IMPL(void,
+smartlist_free_,(smartlist_t *sl))
+{
+  if (!sl)
+    return;
+  tor_free(sl->list);
+  tor_free(sl);
+}
+
+/** Remove all elements from the list.
+ */
+void
+smartlist_clear(smartlist_t *sl)
+{
+  memset(sl->list, 0, sizeof(void *) * sl->num_used);
+  sl->num_used = 0;
+}
+
+#if SIZE_MAX < INT_MAX
+#error "We don't support systems where size_t is smaller than int."
+#endif
+
+/** Make sure that <b>sl</b> can hold at least <b>size</b> entries. */
+static inline void
+smartlist_ensure_capacity(smartlist_t *sl, size_t size)
+{
+  /* Set MAX_CAPACITY to MIN(INT_MAX, SIZE_MAX / sizeof(void*)) */
+#if (SIZE_MAX/SIZEOF_VOID_P) > INT_MAX
+#define MAX_CAPACITY (INT_MAX)
+#else
+#define MAX_CAPACITY (int)((SIZE_MAX / (sizeof(void*))))
+#endif
+
+  raw_assert(size <= MAX_CAPACITY);
+
+  if (size > (size_t) sl->capacity) {
+    size_t higher = (size_t) sl->capacity;
+    if (PREDICT_UNLIKELY(size > MAX_CAPACITY/2)) {
+      higher = MAX_CAPACITY;
+    } else {
+      while (size > higher)
+        higher *= 2;
+    }
+    sl->list = tor_reallocarray(sl->list, sizeof(void *),
+                                ((size_t)higher));
+    memset(sl->list + sl->capacity, 0,
+           sizeof(void *) * (higher - sl->capacity));
+    sl->capacity = (int) higher;
+  }
+#undef ASSERT_CAPACITY
+#undef MAX_CAPACITY
+}
+
+/** Append element to the end of the list. */
+void
+smartlist_add(smartlist_t *sl, void *element)
+{
+  smartlist_ensure_capacity(sl, ((size_t) sl->num_used)+1);
+  sl->list[sl->num_used++] = element;
+}
+
+/** Append each element from S2 to the end of S1. */
+void
+smartlist_add_all(smartlist_t *s1, const smartlist_t *s2)
+{
+  size_t new_size = (size_t)s1->num_used + (size_t)s2->num_used;
+  tor_assert(new_size >= (size_t) s1->num_used); /* check for overflow. */
+  smartlist_ensure_capacity(s1, new_size);
+  memcpy(s1->list + s1->num_used, s2->list, s2->num_used*sizeof(void*));
+  tor_assert(new_size <= INT_MAX); /* redundant. */
+  s1->num_used = (int) new_size;
+}
+
+/** Append a copy of string to sl */
+void
+smartlist_add_strdup(struct smartlist_t *sl, const char *string)
+{
+  char *copy;
+
+  copy = tor_strdup(string);
+
+  smartlist_add(sl, copy);
+}
+
+/** Remove all elements E from sl such that E==element.  Preserve
+ * the order of any elements before E, but elements after E can be
+ * rearranged.
+ */
+void
+smartlist_remove(smartlist_t *sl, const void *element)
+{
+  int i;
+  if (element == NULL)
+    return;
+  for (i=0; i < sl->num_used; i++)
+    if (sl->list[i] == element) {
+      sl->list[i] = sl->list[--sl->num_used]; /* swap with the end */
+      i--; /* so we process the new i'th element */
+      sl->list[sl->num_used] = NULL;
+    }
+}
+
+/** As <b>smartlist_remove</b>, but do not change the order of
+ * any elements not removed */
+void
+smartlist_remove_keeporder(smartlist_t *sl, const void *element)
+{
+  int i, j, num_used_orig = sl->num_used;
+  if (element == NULL)
+    return;
+
+  for (i=j=0; j < num_used_orig; ++j) {
+    if (sl->list[j] == element) {
+      --sl->num_used;
+    } else {
+      sl->list[i++] = sl->list[j];
+    }
+  }
+}
+
+/** If <b>sl</b> is nonempty, remove and return the final element.  Otherwise,
+ * return NULL. */
+void *
+smartlist_pop_last(smartlist_t *sl)
+{
+  tor_assert(sl);
+  if (sl->num_used) {
+    void *tmp = sl->list[--sl->num_used];
+    sl->list[sl->num_used] = NULL;
+    return tmp;
+  } else
+    return NULL;
+}
+
+/** Reverse the order of the items in <b>sl</b>. */
+void
+smartlist_reverse(smartlist_t *sl)
+{
+  int i, j;
+  void *tmp;
+  tor_assert(sl);
+  for (i = 0, j = sl->num_used-1; i < j; ++i, --j) {
+    tmp = sl->list[i];
+    sl->list[i] = sl->list[j];
+    sl->list[j] = tmp;
+  }
+}
+
+/** If there are any strings in sl equal to element, remove and free them.
+ * Does not preserve order. */
+void
+smartlist_string_remove(smartlist_t *sl, const char *element)
+{
+  int i;
+  tor_assert(sl);
+  tor_assert(element);
+  for (i = 0; i < sl->num_used; ++i) {
+    if (!strcmp(element, sl->list[i])) {
+      tor_free(sl->list[i]);
+      sl->list[i] = sl->list[--sl->num_used]; /* swap with the end */
+      i--; /* so we process the new i'th element */
+      sl->list[sl->num_used] = NULL;
+    }
+  }
+}
+
+/** Return true iff some element E of sl has E==element.
+ */
+int
+smartlist_contains(const smartlist_t *sl, const void *element)
+{
+  int i;
+  for (i=0; i < sl->num_used; i++)
+    if (sl->list[i] == element)
+      return 1;
+  return 0;
+}
+
+/** Return true iff <b>sl</b> has some element E such that
+ * !strcmp(E,<b>element</b>)
+ */
+int
+smartlist_contains_string(const smartlist_t *sl, const char *element)
+{
+  int i;
+  if (!sl) return 0;
+  for (i=0; i < sl->num_used; i++)
+    if (strcmp((const char*)sl->list[i],element)==0)
+      return 1;
+  return 0;
+}
+
+/** If <b>element</b> is equal to an element of <b>sl</b>, return that
+ * element's index.  Otherwise, return -1. */
+int
+smartlist_string_pos(const smartlist_t *sl, const char *element)
+{
+  int i;
+  if (!sl) return -1;
+  for (i=0; i < sl->num_used; i++)
+    if (strcmp((const char*)sl->list[i],element)==0)
+      return i;
+  return -1;
+}
+
+/** If <b>element</b> is the same pointer as an element of <b>sl</b>, return
+ * that element's index.  Otherwise, return -1. */
+int
+smartlist_pos(const smartlist_t *sl, const void *element)
+{
+  int i;
+  if (!sl) return -1;
+  for (i=0; i < sl->num_used; i++)
+    if (element == sl->list[i])
+      return i;
+  return -1;
+}
+
+/** Return true iff <b>sl</b> has some element E such that
+ * !strcasecmp(E,<b>element</b>)
+ */
+int
+smartlist_contains_string_case(const smartlist_t *sl, const char *element)
+{
+  int i;
+  if (!sl) return 0;
+  for (i=0; i < sl->num_used; i++)
+    if (strcasecmp((const char*)sl->list[i],element)==0)
+      return 1;
+  return 0;
+}
+
+/** Return true iff <b>sl</b> has some element E such that E is equal
+ * to the decimal encoding of <b>num</b>.
+ */
+int
+smartlist_contains_int_as_string(const smartlist_t *sl, int num)
+{
+  char buf[32]; /* long enough for 64-bit int, and then some. */
+  tor_snprintf(buf,sizeof(buf),"%d", num);
+  return smartlist_contains_string(sl, buf);
+}
+
+/** Return true iff the two lists contain the same strings in the same
+ * order, or if they are both NULL. */
+int
+smartlist_strings_eq(const smartlist_t *sl1, const smartlist_t *sl2)
+{
+  if (sl1 == NULL)
+    return sl2 == NULL;
+  if (sl2 == NULL)
+    return 0;
+  if (smartlist_len(sl1) != smartlist_len(sl2))
+    return 0;
+  SMARTLIST_FOREACH(sl1, const char *, cp1, {
+      const char *cp2 = smartlist_get(sl2, cp1_sl_idx);
+      if (strcmp(cp1, cp2))
+        return 0;
+    });
+  return 1;
+}
+
+/** Return true iff the two lists contain the same int pointer values in
+ * the same order, or if they are both NULL. */
+int
+smartlist_ints_eq(const smartlist_t *sl1, const smartlist_t *sl2)
+{
+  if (sl1 == NULL)
+    return sl2 == NULL;
+  if (sl2 == NULL)
+    return 0;
+  if (smartlist_len(sl1) != smartlist_len(sl2))
+    return 0;
+  SMARTLIST_FOREACH(sl1, int *, cp1, {
+      int *cp2 = smartlist_get(sl2, cp1_sl_idx);
+      if (*cp1 != *cp2)
+        return 0;
+    });
+  return 1;
+}
+
+/** Return true iff <b>sl</b> has some element E such that
+ * tor_memeq(E,<b>element</b>,DIGEST_LEN)
+ */
+int
+smartlist_contains_digest(const smartlist_t *sl, const char *element)
+{
+  int i;
+  if (!sl) return 0;
+  for (i=0; i < sl->num_used; i++)
+    if (tor_memeq((const char*)sl->list[i],element,DIGEST_LEN))
+      return 1;
+  return 0;
+}
+
+/** Return true iff some element E of sl2 has smartlist_contains(sl1,E).
+ */
+int
+smartlist_overlap(const smartlist_t *sl1, const smartlist_t *sl2)
+{
+  int i;
+  for (i=0; i < sl2->num_used; i++)
+    if (smartlist_contains(sl1, sl2->list[i]))
+      return 1;
+  return 0;
+}
+
+/** Remove every element E of sl1 such that !smartlist_contains(sl2,E).
+ * Does not preserve the order of sl1.
+ */
+void
+smartlist_intersect(smartlist_t *sl1, const smartlist_t *sl2)
+{
+  int i;
+  for (i=0; i < sl1->num_used; i++)
+    if (!smartlist_contains(sl2, sl1->list[i])) {
+      sl1->list[i] = sl1->list[--sl1->num_used]; /* swap with the end */
+      i--; /* so we process the new i'th element */
+      sl1->list[sl1->num_used] = NULL;
+    }
+}
+
+/** Remove every element E of sl1 such that smartlist_contains(sl2,E).
+ * Does not preserve the order of sl1.
+ */
+void
+smartlist_subtract(smartlist_t *sl1, const smartlist_t *sl2)
+{
+  int i;
+  for (i=0; i < sl2->num_used; i++)
+    smartlist_remove(sl1, sl2->list[i]);
+}
+
+/** Remove the <b>idx</b>th element of sl; if idx is not the last
+ * element, swap the last element of sl into the <b>idx</b>th space.
+ */
+void
+smartlist_del(smartlist_t *sl, int idx)
+{
+  tor_assert(sl);
+  tor_assert(idx>=0);
+  tor_assert(idx < sl->num_used);
+  sl->list[idx] = sl->list[--sl->num_used];
+  sl->list[sl->num_used] = NULL;
+}
+
+/** Remove the <b>idx</b>th element of sl; if idx is not the last element,
+ * moving all subsequent elements back one space. Return the old value
+ * of the <b>idx</b>th element.
+ */
+void
+smartlist_del_keeporder(smartlist_t *sl, int idx)
+{
+  tor_assert(sl);
+  tor_assert(idx>=0);
+  tor_assert(idx < sl->num_used);
+  --sl->num_used;
+  if (idx < sl->num_used)
+    memmove(sl->list+idx, sl->list+idx+1, sizeof(void*)*(sl->num_used-idx));
+  sl->list[sl->num_used] = NULL;
+}
+
+/** Insert the value <b>val</b> as the new <b>idx</b>th element of
+ * <b>sl</b>, moving all items previously at <b>idx</b> or later
+ * forward one space.
+ */
+void
+smartlist_insert(smartlist_t *sl, int idx, void *val)
+{
+  tor_assert(sl);
+  tor_assert(idx>=0);
+  tor_assert(idx <= sl->num_used);
+  if (idx == sl->num_used) {
+    smartlist_add(sl, val);
+  } else {
+    smartlist_ensure_capacity(sl, ((size_t) sl->num_used)+1);
+    /* Move other elements away */
+    if (idx < sl->num_used)
+      memmove(sl->list + idx + 1, sl->list + idx,
+              sizeof(void*)*(sl->num_used-idx));
+    sl->num_used++;
+    sl->list[idx] = val;
+  }
+}
+
+/**
+ * Split a string <b>str</b> along all occurrences of <b>sep</b>,
+ * appending the (newly allocated) split strings, in order, to
+ * <b>sl</b>.  Return the number of strings added to <b>sl</b>.
+ *
+ * If <b>flags</b>&amp;SPLIT_SKIP_SPACE is true, remove initial and
+ * trailing space from each entry.
+ * If <b>flags</b>&amp;SPLIT_IGNORE_BLANK is true, remove any entries
+ * of length 0.
+ * If <b>flags</b>&amp;SPLIT_STRIP_SPACE is true, strip spaces from each
+ * split string.
+ *
+ * If <b>max</b>\>0, divide the string into no more than <b>max</b> pieces. If
+ * <b>sep</b> is NULL, split on any sequence of horizontal space.
+ */
+int
+smartlist_split_string(smartlist_t *sl, const char *str, const char *sep,
+                       int flags, int max)
+{
+  const char *cp, *end, *next;
+  int n = 0;
+
+  tor_assert(sl);
+  tor_assert(str);
+
+  cp = str;
+  while (1) {
+    if (flags&SPLIT_SKIP_SPACE) {
+      while (TOR_ISSPACE(*cp)) ++cp;
+    }
+
+    if (max>0 && n == max-1) {
+      end = strchr(cp,'\0');
+    } else if (sep) {
+      end = strstr(cp,sep);
+      if (!end)
+        end = strchr(cp,'\0');
+    } else {
+      for (end = cp; *end && *end != '\t' && *end != ' '; ++end)
+        ;
+    }
+
+    tor_assert(end);
+
+    if (!*end) {
+      next = NULL;
+    } else if (sep) {
+      next = end+strlen(sep);
+    } else {
+      next = end+1;
+      while (*next == '\t' || *next == ' ')
+        ++next;
+    }
+
+    if (flags&SPLIT_SKIP_SPACE) {
+      while (end > cp && TOR_ISSPACE(*(end-1)))
+        --end;
+    }
+    if (end != cp || !(flags&SPLIT_IGNORE_BLANK)) {
+      char *string = tor_strndup(cp, end-cp);
+      if (flags&SPLIT_STRIP_SPACE)
+        tor_strstrip(string, " ");
+      smartlist_add(sl, string);
+      ++n;
+    }
+    if (!next)
+      break;
+    cp = next;
+  }
+
+  return n;
+}
+
+/** Allocate and return a new string containing the concatenation of
+ * the elements of <b>sl</b>, in order, separated by <b>join</b>.  If
+ * <b>terminate</b> is true, also terminate the string with <b>join</b>.
+ * If <b>len_out</b> is not NULL, set <b>len_out</b> to the length of
+ * the returned string. Requires that every element of <b>sl</b> is
+ * NUL-terminated string.
+ */
+char *
+smartlist_join_strings(smartlist_t *sl, const char *join,
+                       int terminate, size_t *len_out)
+{
+  return smartlist_join_strings2(sl,join,strlen(join),terminate,len_out);
+}
+
+/** As smartlist_join_strings, but instead of separating/terminated with a
+ * NUL-terminated string <b>join</b>, uses the <b>join_len</b>-byte sequence
+ * at <b>join</b>.  (Useful for generating a sequence of NUL-terminated
+ * strings.)
+ */
+char *
+smartlist_join_strings2(smartlist_t *sl, const char *join,
+                        size_t join_len, int terminate, size_t *len_out)
+{
+  int i;
+  size_t n = 0;
+  char *r = NULL, *dst, *src;
+
+  tor_assert(sl);
+  tor_assert(join);
+
+  if (terminate)
+    n = join_len;
+
+  for (i = 0; i < sl->num_used; ++i) {
+    n += strlen(sl->list[i]);
+    if (i+1 < sl->num_used) /* avoid double-counting the last one */
+      n += join_len;
+  }
+  dst = r = tor_malloc(n+1);
+  for (i = 0; i < sl->num_used; ) {
+    for (src = sl->list[i]; *src; )
+      *dst++ = *src++;
+    if (++i < sl->num_used) {
+      memcpy(dst, join, join_len);
+      dst += join_len;
+    }
+  }
+  if (terminate) {
+    memcpy(dst, join, join_len);
+    dst += join_len;
+  }
+  *dst = '\0';
+
+  if (len_out)
+    *len_out = dst-r;
+  return r;
+}
+
+/** Sort the members of <b>sl</b> into an order defined by
+ * the ordering function <b>compare</b>, which returns less then 0 if a
+ * precedes b, greater than 0 if b precedes a, and 0 if a 'equals' b.
+ */
+void
+smartlist_sort(smartlist_t *sl, int (*compare)(const void **a, const void **b))
+{
+  if (!sl->num_used)
+    return;
+  qsort(sl->list, sl->num_used, sizeof(void*),
+        (int (*)(const void *,const void*))compare);
+}
+
+/** Given a smartlist <b>sl</b> sorted with the function <b>compare</b>,
+ * return the most frequent member in the list.  Break ties in favor of
+ * later elements.  If the list is empty, return NULL.  If count_out is
+ * non-null, set it to the count of the most frequent member.
+ */
+void *
+smartlist_get_most_frequent_(const smartlist_t *sl,
+                             int (*compare)(const void **a, const void **b),
+                             int *count_out)
+{
+  const void *most_frequent = NULL;
+  int most_frequent_count = 0;
+
+  const void *cur = NULL;
+  int i, count=0;
+
+  if (!sl->num_used) {
+    if (count_out)
+      *count_out = 0;
+    return NULL;
+  }
+  for (i = 0; i < sl->num_used; ++i) {
+    const void *item = sl->list[i];
+    if (cur && 0 == compare(&cur, &item)) {
+      ++count;
+    } else {
+      if (cur && count >= most_frequent_count) {
+        most_frequent = cur;
+        most_frequent_count = count;
+      }
+      cur = item;
+      count = 1;
+    }
+  }
+  if (cur && count >= most_frequent_count) {
+    most_frequent = cur;
+    most_frequent_count = count;
+  }
+  if (count_out)
+    *count_out = most_frequent_count;
+  return (void*)most_frequent;
+}
+
+/** Given a sorted smartlist <b>sl</b> and the comparison function used to
+ * sort it, remove all duplicate members.  If free_fn is provided, calls
+ * free_fn on each duplicate.  Otherwise, just removes them.  Preserves order.
+ */
+void
+smartlist_uniq(smartlist_t *sl,
+               int (*compare)(const void **a, const void **b),
+               void (*free_fn)(void *a))
+{
+  int i;
+  for (i=1; i < sl->num_used; ++i) {
+    if (compare((const void **)&(sl->list[i-1]),
+                (const void **)&(sl->list[i])) == 0) {
+      if (free_fn)
+        free_fn(sl->list[i]);
+      smartlist_del_keeporder(sl, i--);
+    }
+  }
+}
+
+/** Assuming the members of <b>sl</b> are in order, return a pointer to the
+ * member that matches <b>key</b>.  Ordering and matching are defined by a
+ * <b>compare</b> function that returns 0 on a match; less than 0 if key is
+ * less than member, and greater than 0 if key is greater then member.
+ */
+void *
+smartlist_bsearch(smartlist_t *sl, const void *key,
+                  int (*compare)(const void *key, const void **member))
+{
+  int found, idx;
+  idx = smartlist_bsearch_idx(sl, key, compare, &found);
+  return found ? smartlist_get(sl, idx) : NULL;
+}
+
+/** Assuming the members of <b>sl</b> are in order, return the index of the
+ * member that matches <b>key</b>.  If no member matches, return the index of
+ * the first member greater than <b>key</b>, or smartlist_len(sl) if no member
+ * is greater than <b>key</b>.  Set <b>found_out</b> to true on a match, to
+ * false otherwise.  Ordering and matching are defined by a <b>compare</b>
+ * function that returns 0 on a match; less than 0 if key is less than member,
+ * and greater than 0 if key is greater then member.
+ */
+int
+smartlist_bsearch_idx(const smartlist_t *sl, const void *key,
+                      int (*compare)(const void *key, const void **member),
+                      int *found_out)
+{
+  int hi, lo, cmp, mid, len, diff;
+
+  tor_assert(sl);
+  tor_assert(compare);
+  tor_assert(found_out);
+
+  len = smartlist_len(sl);
+
+  /* Check for the trivial case of a zero-length list */
+  if (len == 0) {
+    *found_out = 0;
+    /* We already know smartlist_len(sl) is 0 in this case */
+    return 0;
+  }
+
+  /* Okay, we have a real search to do */
+  tor_assert(len > 0);
+  lo = 0;
+  hi = len - 1;
+
+  /*
+   * These invariants are always true:
+   *
+   * For all i such that 0 <= i < lo, sl[i] < key
+   * For all i such that hi < i <= len, sl[i] > key
+   */
+
+  while (lo <= hi) {
+    diff = hi - lo;
+    /*
+     * We want mid = (lo + hi) / 2, but that could lead to overflow, so
+     * instead diff = hi - lo (non-negative because of loop condition), and
+     * then hi = lo + diff, mid = (lo + lo + diff) / 2 = lo + (diff / 2).
+     */
+    mid = lo + (diff / 2);
+    cmp = compare(key, (const void**) &(sl->list[mid]));
+    if (cmp == 0) {
+      /* sl[mid] == key; we found it */
+      *found_out = 1;
+      return mid;
+    } else if (cmp > 0) {
+      /*
+       * key > sl[mid] and an index i such that sl[i] == key must
+       * have i > mid if it exists.
+       */
+
+      /*
+       * Since lo <= mid <= hi, hi can only decrease on each iteration (by
+       * being set to mid - 1) and hi is initially len - 1, mid < len should
+       * always hold, and this is not symmetric with the left end of list
+       * mid > 0 test below.  A key greater than the right end of the list
+       * should eventually lead to lo == hi == mid == len - 1, and then
+       * we set lo to len below and fall out to the same exit we hit for
+       * a key in the middle of the list but not matching.  Thus, we just
+       * assert for consistency here rather than handle a mid == len case.
+       */
+      tor_assert(mid < len);
+      /* Move lo to the element immediately after sl[mid] */
+      lo = mid + 1;
+    } else {
+      /* This should always be true in this case */
+      tor_assert(cmp < 0);
+
+      /*
+       * key < sl[mid] and an index i such that sl[i] == key must
+       * have i < mid if it exists.
+       */
+
+      if (mid > 0) {
+        /* Normal case, move hi to the element immediately before sl[mid] */
+        hi = mid - 1;
+      } else {
+        /* These should always be true in this case */
+        tor_assert(mid == lo);
+        tor_assert(mid == 0);
+        /*
+         * We were at the beginning of the list and concluded that every
+         * element e compares e > key.
+         */
+        *found_out = 0;
+        return 0;
+      }
+    }
+  }
+
+  /*
+   * lo > hi; we have no element matching key but we have elements falling
+   * on both sides of it.  The lo index points to the first element > key.
+   */
+  tor_assert(lo == hi + 1); /* All other cases should have been handled */
+  tor_assert(lo >= 0);
+  tor_assert(lo <= len);
+  tor_assert(hi >= 0);
+  tor_assert(hi <= len);
+
+  if (lo < len) {
+    cmp = compare(key, (const void **) &(sl->list[lo]));
+    tor_assert(cmp < 0);
+  } else {
+    cmp = compare(key, (const void **) &(sl->list[len-1]));
+    tor_assert(cmp > 0);
+  }
+
+  *found_out = 0;
+  return lo;
+}
+
+/** Helper: compare two const char **s. */
+static int
+compare_string_ptrs_(const void **_a, const void **_b)
+{
+  return strcmp((const char*)*_a, (const char*)*_b);
+}
+
+/** Sort a smartlist <b>sl</b> containing strings into lexically ascending
+ * order. */
+void
+smartlist_sort_strings(smartlist_t *sl)
+{
+  smartlist_sort(sl, compare_string_ptrs_);
+}
+
+/** Return the most frequent string in the sorted list <b>sl</b> */
+const char *
+smartlist_get_most_frequent_string(smartlist_t *sl)
+{
+  return smartlist_get_most_frequent(sl, compare_string_ptrs_);
+}
+
+/** Return the most frequent string in the sorted list <b>sl</b>.
+ * If <b>count_out</b> is provided, set <b>count_out</b> to the
+ * number of times that string appears.
+ */
+const char *
+smartlist_get_most_frequent_string_(smartlist_t *sl, int *count_out)
+{
+  return smartlist_get_most_frequent_(sl, compare_string_ptrs_, count_out);
+}
+
+/** Remove duplicate strings from a sorted list, and free them with tor_free().
+ */
+void
+smartlist_uniq_strings(smartlist_t *sl)
+{
+  smartlist_uniq(sl, compare_string_ptrs_, tor_free_);
+}
+
+/** Helper: compare two pointers. */
+static int
+compare_ptrs_(const void **_a, const void **_b)
+{
+  const void *a = *_a, *b = *_b;
+  if (a<b)
+    return -1;
+  else if (a==b)
+    return 0;
+  else
+    return 1;
+}
+
+/** Sort <b>sl</b> in ascending order of the pointers it contains. */
+void
+smartlist_sort_pointers(smartlist_t *sl)
+{
+  smartlist_sort(sl, compare_ptrs_);
+}
+
+/* Heap-based priority queue implementation for O(lg N) insert and remove.
+ * Recall that the heap property is that, for every index I, h[I] <
+ * H[LEFT_CHILD[I]] and h[I] < H[RIGHT_CHILD[I]].
+ *
+ * For us to remove items other than the topmost item, each item must store
+ * its own index within the heap.  When calling the pqueue functions, tell
+ * them about the offset of the field that stores the index within the item.
+ *
+ * Example:
+ *
+ *   typedef struct timer_t {
+ *     struct timeval tv;
+ *     int heap_index;
+ *   } timer_t;
+ *
+ *   static int compare(const void *p1, const void *p2) {
+ *     const timer_t *t1 = p1, *t2 = p2;
+ *     if (t1->tv.tv_sec < t2->tv.tv_sec) {
+ *        return -1;
+ *     } else if (t1->tv.tv_sec > t2->tv.tv_sec) {
+ *        return 1;
+ *     } else {
+ *        return t1->tv.tv_usec - t2->tv_usec;
+ *     }
+ *   }
+ *
+ *   void timer_heap_insert(smartlist_t *heap, timer_t *timer) {
+ *      smartlist_pqueue_add(heap, compare, offsetof(timer_t, heap_index),
+ *         timer);
+ *   }
+ *
+ *   void timer_heap_pop(smartlist_t *heap) {
+ *      return smartlist_pqueue_pop(heap, compare,
+ *         offsetof(timer_t, heap_index));
+ *   }
+ */
+
+/** @{ */
+/** Functions to manipulate heap indices to find a node's parent and children.
+ *
+ * For a 1-indexed array, we would use LEFT_CHILD[x] = 2*x and RIGHT_CHILD[x]
+ *   = 2*x + 1.  But this is C, so we have to adjust a little. */
+
+/* MAX_PARENT_IDX is the largest IDX in the smartlist which might have
+ * children whose indices fit inside an int.
+ * LEFT_CHILD(MAX_PARENT_IDX) == INT_MAX-2;
+ * RIGHT_CHILD(MAX_PARENT_IDX) == INT_MAX-1;
+ * LEFT_CHILD(MAX_PARENT_IDX + 1) == INT_MAX // impossible, see max list size.
+ */
+#define MAX_PARENT_IDX ((INT_MAX - 2) / 2)
+/* If this is true, then i is small enough to potentially have children
+ * in the smartlist, and it is save to use LEFT_CHILD/RIGHT_CHILD on it. */
+#define IDX_MAY_HAVE_CHILDREN(i) ((i) <= MAX_PARENT_IDX)
+#define LEFT_CHILD(i)  ( 2*(i) + 1 )
+#define RIGHT_CHILD(i) ( 2*(i) + 2 )
+#define PARENT(i)      ( ((i)-1) / 2 )
+/** }@ */
+
+/** @{ */
+/** Helper macros for heaps: Given a local variable <b>idx_field_offset</b>
+ * set to the offset of an integer index within the heap element structure,
+ * IDX_OF_ITEM(p) gives you the index of p, and IDXP(p) gives you a pointer to
+ * where p's index is stored.  Given additionally a local smartlist <b>sl</b>,
+ * UPDATE_IDX(i) sets the index of the element at <b>i</b> to the correct
+ * value (that is, to <b>i</b>).
+ */
+#define IDXP(p) ((int*)STRUCT_VAR_P(p, idx_field_offset))
+
+#define UPDATE_IDX(i)  do {                            \
+    void *updated = sl->list[i];                       \
+    *IDXP(updated) = i;                                \
+  } while (0)
+
+#define IDX_OF_ITEM(p) (*IDXP(p))
+/** @} */
+
+/** Helper. <b>sl</b> may have at most one violation of the heap property:
+ * the item at <b>idx</b> may be greater than one or both of its children.
+ * Restore the heap property. */
+static inline void
+smartlist_heapify(smartlist_t *sl,
+                  int (*compare)(const void *a, const void *b),
+                  int idx_field_offset,
+                  int idx)
+{
+  while (1) {
+    if (! IDX_MAY_HAVE_CHILDREN(idx)) {
+      /* idx is so large that it cannot have any children, since doing so
+       * would mean the smartlist was over-capacity. Therefore it cannot
+       * violate the heap property by being greater than a child (since it
+       * doesn't have any). */
+      return;
+    }
+
+    int left_idx = LEFT_CHILD(idx);
+    int best_idx;
+
+    if (left_idx >= sl->num_used)
+      return;
+    if (compare(sl->list[idx],sl->list[left_idx]) < 0)
+      best_idx = idx;
+    else
+      best_idx = left_idx;
+    if (left_idx+1 < sl->num_used &&
+        compare(sl->list[left_idx+1],sl->list[best_idx]) < 0)
+      best_idx = left_idx + 1;
+
+    if (best_idx == idx) {
+      return;
+    } else {
+      void *tmp = sl->list[idx];
+      sl->list[idx] = sl->list[best_idx];
+      sl->list[best_idx] = tmp;
+      UPDATE_IDX(idx);
+      UPDATE_IDX(best_idx);
+
+      idx = best_idx;
+    }
+  }
+}
+
+/** Insert <b>item</b> into the heap stored in <b>sl</b>, where order is
+ * determined by <b>compare</b> and the offset of the item in the heap is
+ * stored in an int-typed field at position <b>idx_field_offset</b> within
+ * item.
+ */
+void
+smartlist_pqueue_add(smartlist_t *sl,
+                     int (*compare)(const void *a, const void *b),
+                     int idx_field_offset,
+                     void *item)
+{
+  int idx;
+  smartlist_add(sl,item);
+  UPDATE_IDX(sl->num_used-1);
+
+  for (idx = sl->num_used - 1; idx; ) {
+    int parent = PARENT(idx);
+    if (compare(sl->list[idx], sl->list[parent]) < 0) {
+      void *tmp = sl->list[parent];
+      sl->list[parent] = sl->list[idx];
+      sl->list[idx] = tmp;
+      UPDATE_IDX(parent);
+      UPDATE_IDX(idx);
+      idx = parent;
+    } else {
+      return;
+    }
+  }
+}
+
+/** Remove and return the top-priority item from the heap stored in <b>sl</b>,
+ * where order is determined by <b>compare</b> and the item's position is
+ * stored at position <b>idx_field_offset</b> within the item.  <b>sl</b> must
+ * not be empty. */
+void *
+smartlist_pqueue_pop(smartlist_t *sl,
+                     int (*compare)(const void *a, const void *b),
+                     int idx_field_offset)
+{
+  void *top;
+  tor_assert(sl->num_used);
+
+  top = sl->list[0];
+  *IDXP(top)=-1;
+  if (--sl->num_used) {
+    sl->list[0] = sl->list[sl->num_used];
+    sl->list[sl->num_used] = NULL;
+    UPDATE_IDX(0);
+    smartlist_heapify(sl, compare, idx_field_offset, 0);
+  }
+  sl->list[sl->num_used] = NULL;
+  return top;
+}
+
+/** Remove the item <b>item</b> from the heap stored in <b>sl</b>,
+ * where order is determined by <b>compare</b> and the item's position is
+ * stored at position <b>idx_field_offset</b> within the item.  <b>sl</b> must
+ * not be empty. */
+void
+smartlist_pqueue_remove(smartlist_t *sl,
+                        int (*compare)(const void *a, const void *b),
+                        int idx_field_offset,
+                        void *item)
+{
+  int idx = IDX_OF_ITEM(item);
+  tor_assert(idx >= 0);
+  tor_assert(sl->list[idx] == item);
+  --sl->num_used;
+  *IDXP(item) = -1;
+  if (idx == sl->num_used) {
+    sl->list[sl->num_used] = NULL;
+    return;
+  } else {
+    sl->list[idx] = sl->list[sl->num_used];
+    sl->list[sl->num_used] = NULL;
+    UPDATE_IDX(idx);
+    smartlist_heapify(sl, compare, idx_field_offset, idx);
+  }
+}
+
+/** Assert that the heap property is correctly maintained by the heap stored
+ * in <b>sl</b>, where order is determined by <b>compare</b>. */
+void
+smartlist_pqueue_assert_ok(smartlist_t *sl,
+                           int (*compare)(const void *a, const void *b),
+                           int idx_field_offset)
+{
+  int i;
+  for (i = sl->num_used - 1; i >= 0; --i) {
+    if (i>0)
+      tor_assert(compare(sl->list[PARENT(i)], sl->list[i]) <= 0);
+    tor_assert(IDX_OF_ITEM(sl->list[i]) == i);
+  }
+}
+
+/** Helper: compare two DIGEST_LEN digests. */
+static int
+compare_digests_(const void **_a, const void **_b)
+{
+  return tor_memcmp((const char*)*_a, (const char*)*_b, DIGEST_LEN);
+}
+
+/** Sort the list of DIGEST_LEN-byte digests into ascending order. */
+void
+smartlist_sort_digests(smartlist_t *sl)
+{
+  smartlist_sort(sl, compare_digests_);
+}
+
+/** Remove duplicate digests from a sorted list, and free them with tor_free().
+ */
+void
+smartlist_uniq_digests(smartlist_t *sl)
+{
+  smartlist_uniq(sl, compare_digests_, tor_free_);
+}
+
+/** Helper: compare two DIGEST256_LEN digests. */
+static int
+compare_digests256_(const void **_a, const void **_b)
+{
+  return tor_memcmp((const char*)*_a, (const char*)*_b, DIGEST256_LEN);
+}
+
+/** Sort the list of DIGEST256_LEN-byte digests into ascending order. */
+void
+smartlist_sort_digests256(smartlist_t *sl)
+{
+  smartlist_sort(sl, compare_digests256_);
+}
+
+/** Return the most frequent member of the sorted list of DIGEST256_LEN
+ * digests in <b>sl</b> */
+const uint8_t *
+smartlist_get_most_frequent_digest256(smartlist_t *sl)
+{
+  return smartlist_get_most_frequent(sl, compare_digests256_);
+}
+
+/** Remove duplicate 256-bit digests from a sorted list, and free them with
+ * tor_free().
+ */
+void
+smartlist_uniq_digests256(smartlist_t *sl)
+{
+  smartlist_uniq(sl, compare_digests256_, tor_free_);
+}
+
+/** Helper: Declare an entry type and a map type to implement a mapping using
+ * ht.h.  The map type will be called <b>maptype</b>.  The key part of each
+ * entry is declared using the C declaration <b>keydecl</b>.  All functions
+ * and types associated with the map get prefixed with <b>prefix</b> */
+#define DEFINE_MAP_STRUCTS(maptype, keydecl, prefix)      \
+  typedef struct prefix ## entry_t {                      \
+    HT_ENTRY(prefix ## entry_t) node;                     \
+    void *val;                                            \
+    keydecl;                                              \
+  } prefix ## entry_t;                                    \
+  struct maptype {                                        \
+    HT_HEAD(prefix ## impl, prefix ## entry_t) head;      \
+  }
+
+DEFINE_MAP_STRUCTS(strmap_t, char *key, strmap_);
+DEFINE_MAP_STRUCTS(digestmap_t, char key[DIGEST_LEN], digestmap_);
+DEFINE_MAP_STRUCTS(digest256map_t, uint8_t key[DIGEST256_LEN], digest256map_);
+
+/** Helper: compare strmap_entry_t objects by key value. */
+static inline int
+strmap_entries_eq(const strmap_entry_t *a, const strmap_entry_t *b)
+{
+  return !strcmp(a->key, b->key);
+}
+
+/** Helper: return a hash value for a strmap_entry_t. */
+static inline unsigned int
+strmap_entry_hash(const strmap_entry_t *a)
+{
+  return (unsigned) siphash24g(a->key, strlen(a->key));
+}
+
+/** Helper: compare digestmap_entry_t objects by key value. */
+static inline int
+digestmap_entries_eq(const digestmap_entry_t *a, const digestmap_entry_t *b)
+{
+  return tor_memeq(a->key, b->key, DIGEST_LEN);
+}
+
+/** Helper: return a hash value for a digest_map_t. */
+static inline unsigned int
+digestmap_entry_hash(const digestmap_entry_t *a)
+{
+  return (unsigned) siphash24g(a->key, DIGEST_LEN);
+}
+
+/** Helper: compare digestmap_entry_t objects by key value. */
+static inline int
+digest256map_entries_eq(const digest256map_entry_t *a,
+                        const digest256map_entry_t *b)
+{
+  return tor_memeq(a->key, b->key, DIGEST256_LEN);
+}
+
+/** Helper: return a hash value for a digest_map_t. */
+static inline unsigned int
+digest256map_entry_hash(const digest256map_entry_t *a)
+{
+  return (unsigned) siphash24g(a->key, DIGEST256_LEN);
+}
+
+HT_PROTOTYPE(strmap_impl, strmap_entry_t, node, strmap_entry_hash,
+             strmap_entries_eq)
+HT_GENERATE2(strmap_impl, strmap_entry_t, node, strmap_entry_hash,
+             strmap_entries_eq, 0.6, tor_reallocarray_, tor_free_)
+
+HT_PROTOTYPE(digestmap_impl, digestmap_entry_t, node, digestmap_entry_hash,
+             digestmap_entries_eq)
+HT_GENERATE2(digestmap_impl, digestmap_entry_t, node, digestmap_entry_hash,
+             digestmap_entries_eq, 0.6, tor_reallocarray_, tor_free_)
+
+HT_PROTOTYPE(digest256map_impl, digest256map_entry_t, node,
+             digest256map_entry_hash,
+             digest256map_entries_eq)
+HT_GENERATE2(digest256map_impl, digest256map_entry_t, node,
+             digest256map_entry_hash,
+             digest256map_entries_eq, 0.6, tor_reallocarray_, tor_free_)
+
+#define strmap_entry_free(ent) \
+  FREE_AND_NULL(strmap_entry_t, strmap_entry_free_, (ent))
+#define digestmap_entry_free(ent) \
+  FREE_AND_NULL(digestmap_entry_t, digestmap_entry_free_, (ent))
+#define digest256map_entry_free(ent) \
+  FREE_AND_NULL(digest256map_entry_t, digest256map_entry_free_, (ent))
+
+static inline void
+strmap_entry_free_(strmap_entry_t *ent)
+{
+  tor_free(ent->key);
+  tor_free(ent);
+}
+static inline void
+digestmap_entry_free_(digestmap_entry_t *ent)
+{
+  tor_free(ent);
+}
+static inline void
+digest256map_entry_free_(digest256map_entry_t *ent)
+{
+  tor_free(ent);
+}
+
+static inline void
+strmap_assign_tmp_key(strmap_entry_t *ent, const char *key)
+{
+  ent->key = (char*)key;
+}
+static inline void
+digestmap_assign_tmp_key(digestmap_entry_t *ent, const char *key)
+{
+  memcpy(ent->key, key, DIGEST_LEN);
+}
+static inline void
+digest256map_assign_tmp_key(digest256map_entry_t *ent, const uint8_t *key)
+{
+  memcpy(ent->key, key, DIGEST256_LEN);
+}
+static inline void
+strmap_assign_key(strmap_entry_t *ent, const char *key)
+{
+  ent->key = tor_strdup(key);
+}
+static inline void
+digestmap_assign_key(digestmap_entry_t *ent, const char *key)
+{
+  memcpy(ent->key, key, DIGEST_LEN);
+}
+static inline void
+digest256map_assign_key(digest256map_entry_t *ent, const uint8_t *key)
+{
+  memcpy(ent->key, key, DIGEST256_LEN);
+}
+
+/**
+ * Macro: implement all the functions for a map that are declared in
+ * container.h by the DECLARE_MAP_FNS() macro.  You must additionally define a
+ * prefix_entry_free_() function to free entries (and their keys), a
+ * prefix_assign_tmp_key() function to temporarily set a stack-allocated
+ * entry to hold a key, and a prefix_assign_key() function to set a
+ * heap-allocated entry to hold a key.
+ */
+#define IMPLEMENT_MAP_FNS(maptype, keytype, prefix)                     \
+  /** Create and return a new empty map. */                             \
+  MOCK_IMPL(maptype *,                                                  \
+  prefix##_new,(void))                                                  \
+  {                                                                     \
+    maptype *result;                                                    \
+    result = tor_malloc(sizeof(maptype));                               \
+    HT_INIT(prefix##_impl, &result->head);                              \
+    return result;                                                      \
+  }                                                                     \
+                                                                        \
+  /** Return the item from <b>map</b> whose key matches <b>key</b>, or  \
+   * NULL if no such value exists. */                                   \
+  void *                                                                \
+  prefix##_get(const maptype *map, const keytype key)                   \
+  {                                                                     \
+    prefix ##_entry_t *resolve;                                         \
+    prefix ##_entry_t search;                                           \
+    tor_assert(map);                                                    \
+    tor_assert(key);                                                    \
+    prefix ##_assign_tmp_key(&search, key);                             \
+    resolve = HT_FIND(prefix ##_impl, &map->head, &search);             \
+    if (resolve) {                                                      \
+      return resolve->val;                                              \
+    } else {                                                            \
+      return NULL;                                                      \
+    }                                                                   \
+  }                                                                     \
+                                                                        \
+  /** Add an entry to <b>map</b> mapping <b>key</b> to <b>val</b>;      \
+   * return the previous value, or NULL if no such value existed. */     \
+  void *                                                                \
+  prefix##_set(maptype *map, const keytype key, void *val)              \
+  {                                                                     \
+    prefix##_entry_t search;                                            \
+    void *oldval;                                                       \
+    tor_assert(map);                                                    \
+    tor_assert(key);                                                    \
+    tor_assert(val);                                                    \
+    prefix##_assign_tmp_key(&search, key);                              \
+    /* We a lot of our time in this function, so the code below is */   \
+    /* meant to optimize the check/alloc/set cycle by avoiding the two */\
+    /* trips to the hash table that we would do in the unoptimized */   \
+    /* version of this code. (Each of HT_INSERT and HT_FIND calls */     \
+    /* HT_SET_HASH and HT_FIND_P.) */                                   \
+    HT_FIND_OR_INSERT_(prefix##_impl, node, prefix##_entry_hash,        \
+                       &(map->head),                                    \
+                       prefix##_entry_t, &search, ptr,                  \
+                       {                                                \
+                         /* we found an entry. */                       \
+                         oldval = (*ptr)->val;                          \
+                         (*ptr)->val = val;                             \
+                         return oldval;                                 \
+                       },                                               \
+                       {                                                \
+                         /* We didn't find the entry. */                \
+                         prefix##_entry_t *newent =                     \
+                           tor_malloc_zero(sizeof(prefix##_entry_t));   \
+                         prefix##_assign_key(newent, key);              \
+                         newent->val = val;                             \
+                         HT_FOI_INSERT_(node, &(map->head),             \
+                            &search, newent, ptr);                      \
+                         return NULL;                                   \
+    });                                                                 \
+  }                                                                     \
+                                                                        \
+  /** Remove the value currently associated with <b>key</b> from the map. \
+   * Return the value if one was set, or NULL if there was no entry for \
+   * <b>key</b>.                                                        \
+   *                                                                    \
+   * Note: you must free any storage associated with the returned value. \
+   */                                                                   \
+  void *                                                                \
+  prefix##_remove(maptype *map, const keytype key)                      \
+  {                                                                     \
+    prefix##_entry_t *resolve;                                          \
+    prefix##_entry_t search;                                            \
+    void *oldval;                                                       \
+    tor_assert(map);                                                    \
+    tor_assert(key);                                                    \
+    prefix##_assign_tmp_key(&search, key);                              \
+    resolve = HT_REMOVE(prefix##_impl, &map->head, &search);            \
+    if (resolve) {                                                      \
+      oldval = resolve->val;                                            \
+      prefix##_entry_free(resolve);                                     \
+      return oldval;                                                    \
+    } else {                                                            \
+      return NULL;                                                      \
+    }                                                                   \
+  }                                                                     \
+                                                                        \
+  /** Return the number of elements in <b>map</b>. */                   \
+  int                                                                   \
+  prefix##_size(const maptype *map)                                     \
+  {                                                                     \
+    return HT_SIZE(&map->head);                                         \
+  }                                                                     \
+                                                                        \
+  /** Return true iff <b>map</b> has no entries. */                     \
+  int                                                                   \
+  prefix##_isempty(const maptype *map)                                  \
+  {                                                                     \
+    return HT_EMPTY(&map->head);                                        \
+  }                                                                     \
+                                                                        \
+  /** Assert that <b>map</b> is not corrupt. */                         \
+  void                                                                  \
+  prefix##_assert_ok(const maptype *map)                                \
+  {                                                                     \
+    tor_assert(!prefix##_impl_HT_REP_IS_BAD_(&map->head));              \
+  }                                                                     \
+                                                                        \
+  /** Remove all entries from <b>map</b>, and deallocate storage for    \
+   * those entries.  If free_val is provided, invoked it every value in \
+   * <b>map</b>. */                                                     \
+  MOCK_IMPL(void,                                                       \
+  prefix##_free_, (maptype *map, void (*free_val)(void*)))              \
+  {                                                                     \
+    prefix##_entry_t **ent, **next, *this;                              \
+    if (!map)                                                           \
+      return;                                                           \
+    for (ent = HT_START(prefix##_impl, &map->head); ent != NULL;        \
+         ent = next) {                                                  \
+      this = *ent;                                                      \
+      next = HT_NEXT_RMV(prefix##_impl, &map->head, ent);               \
+      if (free_val)                                                     \
+        free_val(this->val);                                            \
+      prefix##_entry_free(this);                                        \
+    }                                                                   \
+    tor_assert(HT_EMPTY(&map->head));                                   \
+    HT_CLEAR(prefix##_impl, &map->head);                                \
+    tor_free(map);                                                      \
+  }                                                                     \
+                                                                        \
+  /** return an <b>iterator</b> pointer to the front of a map.          \
+   *                                                                    \
+   * Iterator example:                                                  \
+   *                                                                    \
+   * \code                                                              \
+   * // uppercase values in "map", removing empty values.               \
+   *                                                                    \
+   * strmap_iter_t *iter;                                               \
+   * const char *key;                                                   \
+   * void *val;                                                         \
+   * char *cp;                                                          \
+   *                                                                    \
+   * for (iter = strmap_iter_init(map); !strmap_iter_done(iter); ) {    \
+   *    strmap_iter_get(iter, &key, &val);                              \
+   *    cp = (char*)val;                                                \
+   *    if (!*cp) {                                                     \
+   *       iter = strmap_iter_next_rmv(map,iter);                       \
+   *       free(val);                                                   \
+   *    } else {                                                        \
+   *       for (;*cp;cp++) *cp = TOR_TOUPPER(*cp);                      \
+   */                                                                   \
+  prefix##_iter_t *                                                     \
+  prefix##_iter_init(maptype *map)                                      \
+  {                                                                     \
+    tor_assert(map);                                                    \
+    return HT_START(prefix##_impl, &map->head);                         \
+  }                                                                     \
+                                                                        \
+  /** Advance <b>iter</b> a single step to the next entry, and return   \
+   * its new value. */                                                  \
+  prefix##_iter_t *                                                     \
+  prefix##_iter_next(maptype *map, prefix##_iter_t *iter)               \
+  {                                                                     \
+    tor_assert(map);                                                    \
+    tor_assert(iter);                                                   \
+    return HT_NEXT(prefix##_impl, &map->head, iter);                    \
+  }                                                                     \
+  /** Advance <b>iter</b> a single step to the next entry, removing the \
+   * current entry, and return its new value. */                        \
+  prefix##_iter_t *                                                     \
+  prefix##_iter_next_rmv(maptype *map, prefix##_iter_t *iter)           \
+  {                                                                     \
+    prefix##_entry_t *rmv;                                              \
+    tor_assert(map);                                                    \
+    tor_assert(iter);                                                   \
+    tor_assert(*iter);                                                  \
+    rmv = *iter;                                                        \
+    iter = HT_NEXT_RMV(prefix##_impl, &map->head, iter);                \
+    prefix##_entry_free(rmv);                                           \
+    return iter;                                                        \
+  }                                                                     \
+  /** Set *<b>keyp</b> and *<b>valp</b> to the current entry pointed    \
+   * to by iter. */                                                     \
+  void                                                                  \
+  prefix##_iter_get(prefix##_iter_t *iter, const keytype *keyp,         \
+                    void **valp)                                        \
+  {                                                                     \
+    tor_assert(iter);                                                   \
+    tor_assert(*iter);                                                  \
+    tor_assert(keyp);                                                   \
+    tor_assert(valp);                                                   \
+    *keyp = (*iter)->key;                                               \
+    *valp = (*iter)->val;                                               \
+  }                                                                     \
+  /** Return true iff <b>iter</b> has advanced past the last entry of   \
+   * <b>map</b>. */                                                     \
+  int                                                                   \
+  prefix##_iter_done(prefix##_iter_t *iter)                             \
+  {                                                                     \
+    return iter == NULL;                                                \
+  }
+
+IMPLEMENT_MAP_FNS(strmap_t, char *, strmap)
+IMPLEMENT_MAP_FNS(digestmap_t, char *, digestmap)
+IMPLEMENT_MAP_FNS(digest256map_t, uint8_t *, digest256map)
+
+/** Same as strmap_set, but first converts <b>key</b> to lowercase. */
+void *
+strmap_set_lc(strmap_t *map, const char *key, void *val)
+{
+  /* We could be a little faster by using strcasecmp instead, and a separate
+   * type, but I don't think it matters. */
+  void *v;
+  char *lc_key = tor_strdup(key);
+  tor_strlower(lc_key);
+  v = strmap_set(map,lc_key,val);
+  tor_free(lc_key);
+  return v;
+}
+
+/** Same as strmap_get, but first converts <b>key</b> to lowercase. */
+void *
+strmap_get_lc(const strmap_t *map, const char *key)
+{
+  void *v;
+  char *lc_key = tor_strdup(key);
+  tor_strlower(lc_key);
+  v = strmap_get(map,lc_key);
+  tor_free(lc_key);
+  return v;
+}
+
+/** Same as strmap_remove, but first converts <b>key</b> to lowercase */
+void *
+strmap_remove_lc(strmap_t *map, const char *key)
+{
+  void *v;
+  char *lc_key = tor_strdup(key);
+  tor_strlower(lc_key);
+  v = strmap_remove(map,lc_key);
+  tor_free(lc_key);
+  return v;
+}
+
+/** Declare a function called <b>funcname</b> that acts as a find_nth_FOO
+ * function for an array of type <b>elt_t</b>*.
+ *
+ * NOTE: The implementation kind of sucks: It's O(n log n), whereas finding
+ * the kth element of an n-element list can be done in O(n).  Then again, this
+ * implementation is not in critical path, and it is obviously correct. */
+#define IMPLEMENT_ORDER_FUNC(funcname, elt_t)                   \
+  static int                                                    \
+  _cmp_ ## elt_t(const void *_a, const void *_b)                \
+  {                                                             \
+    const elt_t *a = _a, *b = _b;                               \
+    if (*a<*b)                                                  \
+      return -1;                                                \
+    else if (*a>*b)                                             \
+      return 1;                                                 \
+    else                                                        \
+      return 0;                                                 \
+  }                                                             \
+  elt_t                                                         \
+  funcname(elt_t *array, int n_elements, int nth)               \
+  {                                                             \
+    tor_assert(nth >= 0);                                       \
+    tor_assert(nth < n_elements);                               \
+    qsort(array, n_elements, sizeof(elt_t), _cmp_ ##elt_t);     \
+    return array[nth];                                          \
+  }
+
+IMPLEMENT_ORDER_FUNC(find_nth_int, int)
+IMPLEMENT_ORDER_FUNC(find_nth_time, time_t)
+IMPLEMENT_ORDER_FUNC(find_nth_double, double)
+IMPLEMENT_ORDER_FUNC(find_nth_uint32, uint32_t)
+IMPLEMENT_ORDER_FUNC(find_nth_int32, int32_t)
+IMPLEMENT_ORDER_FUNC(find_nth_long, long)
+
+/** Return a newly allocated digestset_t, optimized to hold a total of
+ * <b>max_elements</b> digests with a reasonably low false positive weight. */
+digestset_t *
+digestset_new(int max_elements)
+{
+  /* The probability of false positives is about P=(1 - exp(-kn/m))^k, where k
+   * is the number of hash functions per entry, m is the bits in the array,
+   * and n is the number of elements inserted.  For us, k==4, n<=max_elements,
+   * and m==n_bits= approximately max_elements*32.  This gives
+   *   P<(1-exp(-4*n/(32*n)))^4 == (1-exp(1/-8))^4 == .00019
+   *
+   * It would be more optimal in space vs false positives to get this false
+   * positive rate by going for k==13, and m==18.5n, but we also want to
+   * conserve CPU, and k==13 is pretty big.
+   */
+  int n_bits = 1u << (tor_log2(max_elements)+5);
+  digestset_t *r = tor_malloc(sizeof(digestset_t));
+  r->mask = n_bits - 1;
+  r->ba = bitarray_init_zero(n_bits);
+  return r;
+}
+
+/** Free all storage held in <b>set</b>. */
+void
+digestset_free_(digestset_t *set)
+{
+  if (!set)
+    return;
+  bitarray_free(set->ba);
+  tor_free(set);
+}
diff --git a/src/lib/container/container.h b/src/lib/container/container.h
new file mode 100644
index 0000000000..c45bfc359b
--- /dev/null
+++ b/src/lib/container/container.h
@@ -0,0 +1,750 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_CONTAINER_H
+#define TOR_CONTAINER_H
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lib/cc/compat_compiler.h"
+#include "lib/cc/torint.h"
+#include "lib/testsupport/testsupport.h"
+#include "lib/malloc/util_malloc.h"
+#include "common/util_bug.h"
+#include "siphash.h"
+
+/** A resizeable list of pointers, with associated helpful functionality.
+ *
+ * The members of this struct are exposed only so that macros and inlines can
+ * use them; all access to smartlist internals should go through the functions
+ * and macros defined here.
+ **/
+typedef struct smartlist_t {
+  /** @{ */
+  /** <b>list</b> has enough capacity to store exactly <b>capacity</b> elements
+   * before it needs to be resized.  Only the first <b>num_used</b> (\<=
+   * capacity) elements point to valid data.
+   */
+  void **list;
+  int num_used;
+  int capacity;
+  /** @} */
+} smartlist_t;
+
+MOCK_DECL(smartlist_t *, smartlist_new, (void));
+MOCK_DECL(void, smartlist_free_, (smartlist_t *sl));
+#define smartlist_free(sl) FREE_AND_NULL(smartlist_t, smartlist_free_, (sl))
+
+void smartlist_clear(smartlist_t *sl);
+void smartlist_add(smartlist_t *sl, void *element);
+void smartlist_add_all(smartlist_t *sl, const smartlist_t *s2);
+void smartlist_add_strdup(struct smartlist_t *sl, const char *string);
+void smartlist_remove(smartlist_t *sl, const void *element);
+void smartlist_remove_keeporder(smartlist_t *sl, const void *element);
+void *smartlist_pop_last(smartlist_t *sl);
+void smartlist_reverse(smartlist_t *sl);
+void smartlist_string_remove(smartlist_t *sl, const char *element);
+int smartlist_contains(const smartlist_t *sl, const void *element);
+int smartlist_contains_string(const smartlist_t *sl, const char *element);
+int smartlist_pos(const smartlist_t *sl, const void *element);
+int smartlist_string_pos(const smartlist_t *, const char *elt);
+int smartlist_contains_string_case(const smartlist_t *sl, const char *element);
+int smartlist_contains_int_as_string(const smartlist_t *sl, int num);
+int smartlist_strings_eq(const smartlist_t *sl1, const smartlist_t *sl2);
+int smartlist_contains_digest(const smartlist_t *sl, const char *element);
+int smartlist_ints_eq(const smartlist_t *sl1, const smartlist_t *sl2);
+int smartlist_overlap(const smartlist_t *sl1, const smartlist_t *sl2);
+void smartlist_intersect(smartlist_t *sl1, const smartlist_t *sl2);
+void smartlist_subtract(smartlist_t *sl1, const smartlist_t *sl2);
+
+/* smartlist_choose() is defined in crypto.[ch] */
+#ifdef DEBUG_SMARTLIST
+/** Return the number of items in sl.
+ */
+static inline int smartlist_len(const smartlist_t *sl);
+static inline int smartlist_len(const smartlist_t *sl) {
+  tor_assert(sl);
+  return (sl)->num_used;
+}
+/** Return the <b>idx</b>th element of sl.
+ */
+static inline void *smartlist_get(const smartlist_t *sl, int idx);
+static inline void *smartlist_get(const smartlist_t *sl, int idx) {
+  tor_assert(sl);
+  tor_assert(idx>=0);
+  tor_assert(sl->num_used > idx);
+  return sl->list[idx];
+}
+static inline void smartlist_set(smartlist_t *sl, int idx, void *val) {
+  tor_assert(sl);
+  tor_assert(idx>=0);
+  tor_assert(sl->num_used > idx);
+  sl->list[idx] = val;
+}
+#else /* !(defined(DEBUG_SMARTLIST)) */
+#define smartlist_len(sl) ((sl)->num_used)
+#define smartlist_get(sl, idx) ((sl)->list[idx])
+#define smartlist_set(sl, idx, val) ((sl)->list[idx] = (val))
+#endif /* defined(DEBUG_SMARTLIST) */
+
+/** Exchange the elements at indices <b>idx1</b> and <b>idx2</b> of the
+ * smartlist <b>sl</b>. */
+static inline void smartlist_swap(smartlist_t *sl, int idx1, int idx2)
+{
+  if (idx1 != idx2) {
+    void *elt = smartlist_get(sl, idx1);
+    smartlist_set(sl, idx1, smartlist_get(sl, idx2));
+    smartlist_set(sl, idx2, elt);
+  }
+}
+
+void smartlist_del(smartlist_t *sl, int idx);
+void smartlist_del_keeporder(smartlist_t *sl, int idx);
+void smartlist_insert(smartlist_t *sl, int idx, void *val);
+void smartlist_sort(smartlist_t *sl,
+                    int (*compare)(const void **a, const void **b));
+void *smartlist_get_most_frequent_(const smartlist_t *sl,
+                    int (*compare)(const void **a, const void **b),
+                    int *count_out);
+#define smartlist_get_most_frequent(sl, compare) \
+  smartlist_get_most_frequent_((sl), (compare), NULL)
+void smartlist_uniq(smartlist_t *sl,
+                    int (*compare)(const void **a, const void **b),
+                    void (*free_fn)(void *elt));
+
+void smartlist_sort_strings(smartlist_t *sl);
+void smartlist_sort_digests(smartlist_t *sl);
+void smartlist_sort_digests256(smartlist_t *sl);
+void smartlist_sort_pointers(smartlist_t *sl);
+
+const char *smartlist_get_most_frequent_string(smartlist_t *sl);
+const char *smartlist_get_most_frequent_string_(smartlist_t *sl,
+                                                int *count_out);
+const uint8_t *smartlist_get_most_frequent_digest256(smartlist_t *sl);
+
+void smartlist_uniq_strings(smartlist_t *sl);
+void smartlist_uniq_digests(smartlist_t *sl);
+void smartlist_uniq_digests256(smartlist_t *sl);
+void *smartlist_bsearch(smartlist_t *sl, const void *key,
+                        int (*compare)(const void *key, const void **member));
+int smartlist_bsearch_idx(const smartlist_t *sl, const void *key,
+                          int (*compare)(const void *key, const void **member),
+                          int *found_out);
+
+void smartlist_pqueue_add(smartlist_t *sl,
+                          int (*compare)(const void *a, const void *b),
+                          int idx_field_offset,
+                          void *item);
+void *smartlist_pqueue_pop(smartlist_t *sl,
+                           int (*compare)(const void *a, const void *b),
+                           int idx_field_offset);
+void smartlist_pqueue_remove(smartlist_t *sl,
+                             int (*compare)(const void *a, const void *b),
+                             int idx_field_offset,
+                             void *item);
+void smartlist_pqueue_assert_ok(smartlist_t *sl,
+                                int (*compare)(const void *a, const void *b),
+                                int idx_field_offset);
+
+#define SPLIT_SKIP_SPACE   0x01
+#define SPLIT_IGNORE_BLANK 0x02
+#define SPLIT_STRIP_SPACE  0x04
+int smartlist_split_string(smartlist_t *sl, const char *str, const char *sep,
+                           int flags, int max);
+char *smartlist_join_strings(smartlist_t *sl, const char *join, int terminate,
+                             size_t *len_out) ATTR_MALLOC;
+char *smartlist_join_strings2(smartlist_t *sl, const char *join,
+                              size_t join_len, int terminate, size_t *len_out)
+  ATTR_MALLOC;
+
+/** Iterate over the items in a smartlist <b>sl</b>, in order.  For each item,
+ * assign it to a new local variable of type <b>type</b> named <b>var</b>, and
+ * execute the statements inside the loop body.  Inside the loop, the loop
+ * index can be accessed as <b>var</b>_sl_idx and the length of the list can
+ * be accessed as <b>var</b>_sl_len.
+ *
+ * NOTE: Do not change the length of the list while the loop is in progress,
+ * unless you adjust the _sl_len variable correspondingly.  See second example
+ * below.
+ *
+ * Example use:
+ * <pre>
+ *   smartlist_t *list = smartlist_split("A:B:C", ":", 0, 0);
+ *   SMARTLIST_FOREACH_BEGIN(list, char *, cp) {
+ *     printf("%d: %s\n", cp_sl_idx, cp);
+ *     tor_free(cp);
+ *   } SMARTLIST_FOREACH_END(cp);
+ *   smartlist_free(list);
+ * </pre>
+ *
+ * Example use (advanced):
+ * <pre>
+ *   SMARTLIST_FOREACH_BEGIN(list, char *, cp) {
+ *     if (!strcmp(cp, "junk")) {
+ *       tor_free(cp);
+ *       SMARTLIST_DEL_CURRENT(list, cp);
+ *     }
+ *   } SMARTLIST_FOREACH_END(cp);
+ * </pre>
+ */
+/* Note: these macros use token pasting, and reach into smartlist internals.
+ * This can make them a little daunting. Here's the approximate unpacking of
+ * the above examples, for entertainment value:
+ *
+ * <pre>
+ * smartlist_t *list = smartlist_split("A:B:C", ":", 0, 0);
+ * {
+ *   int cp_sl_idx, cp_sl_len = smartlist_len(list);
+ *   char *cp;
+ *   for (cp_sl_idx = 0; cp_sl_idx < cp_sl_len; ++cp_sl_idx) {
+ *     cp = smartlist_get(list, cp_sl_idx);
+ *     printf("%d: %s\n", cp_sl_idx, cp);
+ *     tor_free(cp);
+ *   }
+ * }
+ * smartlist_free(list);
+ * </pre>
+ *
+ * <pre>
+ * {
+ *   int cp_sl_idx, cp_sl_len = smartlist_len(list);
+ *   char *cp;
+ *   for (cp_sl_idx = 0; cp_sl_idx < cp_sl_len; ++cp_sl_idx) {
+ *     cp = smartlist_get(list, cp_sl_idx);
+ *     if (!strcmp(cp, "junk")) {
+ *       tor_free(cp);
+ *       smartlist_del(list, cp_sl_idx);
+ *       --cp_sl_idx;
+ *       --cp_sl_len;
+ *     }
+ *   }
+ * }
+ * </pre>
+ */
+#define SMARTLIST_FOREACH_BEGIN(sl, type, var)  \
+  STMT_BEGIN                                                    \
+    int var ## _sl_idx, var ## _sl_len=(sl)->num_used;          \
+    type var;                                                   \
+    for (var ## _sl_idx = 0; var ## _sl_idx < var ## _sl_len;   \
+         ++var ## _sl_idx) {                                    \
+      var = (sl)->list[var ## _sl_idx];
+
+#define SMARTLIST_FOREACH_END(var)              \
+    var = NULL;                                 \
+    (void) var ## _sl_idx;                      \
+  } STMT_END
+
+/**
+ * An alias for SMARTLIST_FOREACH_BEGIN and SMARTLIST_FOREACH_END, using
+ * <b>cmd</b> as the loop body.  This wrapper is here for convenience with
+ * very short loops.
+ *
+ * By convention, we do not use this for loops which nest, or for loops over
+ * 10 lines or so.  Use SMARTLIST_FOREACH_{BEGIN,END} for those.
+ */
+#define SMARTLIST_FOREACH(sl, type, var, cmd)                   \
+  SMARTLIST_FOREACH_BEGIN(sl,type,var) {                        \
+    cmd;                                                        \
+  } SMARTLIST_FOREACH_END(var)
+
+/** Helper: While in a SMARTLIST_FOREACH loop over the list <b>sl</b> indexed
+ * with the variable <b>var</b>, remove the current element in a way that
+ * won't confuse the loop. */
+#define SMARTLIST_DEL_CURRENT(sl, var)          \
+  STMT_BEGIN                                    \
+    smartlist_del(sl, var ## _sl_idx);          \
+    --var ## _sl_idx;                           \
+    --var ## _sl_len;                           \
+  STMT_END
+
+/** Helper: While in a SMARTLIST_FOREACH loop over the list <b>sl</b> indexed
+ * with the variable <b>var</b>, remove the current element in a way that
+ * won't confuse the loop. */
+#define SMARTLIST_DEL_CURRENT_KEEPORDER(sl, var)          \
+  STMT_BEGIN                                              \
+     smartlist_del_keeporder(sl, var ## _sl_idx);         \
+     --var ## _sl_idx;                                    \
+     --var ## _sl_len;                                    \
+  STMT_END
+
+/** Helper: While in a SMARTLIST_FOREACH loop over the list <b>sl</b> indexed
+ * with the variable <b>var</b>, replace the current element with <b>val</b>.
+ * Does not deallocate the current value of <b>var</b>.
+ */
+#define SMARTLIST_REPLACE_CURRENT(sl, var, val) \
+  STMT_BEGIN                                    \
+    smartlist_set(sl, var ## _sl_idx, val);     \
+  STMT_END
+
+/* Helper: Given two lists of items, possibly of different types, such that
+ * both lists are sorted on some common field (as determined by a comparison
+ * expression <b>cmpexpr</b>), and such that one list (<b>sl1</b>) has no
+ * duplicates on the common field, loop through the lists in lockstep, and
+ * execute <b>unmatched_var2</b> on items in var2 that do not appear in
+ * var1.
+ *
+ * WARNING: It isn't safe to add remove elements from either list while the
+ * loop is in progress.
+ *
+ * Example use:
+ *  SMARTLIST_FOREACH_JOIN(routerstatus_list, routerstatus_t *, rs,
+ *                     routerinfo_list, routerinfo_t *, ri,
+ *                    tor_memcmp(rs->identity_digest, ri->identity_digest, 20),
+ *                     log_info(LD_GENERAL,"No match for %s", ri->nickname)) {
+ *    log_info(LD_GENERAL, "%s matches routerstatus %p", ri->nickname, rs);
+ * } SMARTLIST_FOREACH_JOIN_END(rs, ri);
+ **/
+/* The example above unpacks (approximately) to:
+ *  int rs_sl_idx = 0, rs_sl_len = smartlist_len(routerstatus_list);
+ *  int ri_sl_idx, ri_sl_len = smartlist_len(routerinfo_list);
+ *  int rs_ri_cmp;
+ *  routerstatus_t *rs;
+ *  routerinfo_t *ri;
+ *  for (; ri_sl_idx < ri_sl_len; ++ri_sl_idx) {
+ *    ri = smartlist_get(routerinfo_list, ri_sl_idx);
+ *    while (rs_sl_idx < rs_sl_len) {
+ *      rs = smartlist_get(routerstatus_list, rs_sl_idx);
+ *      rs_ri_cmp = tor_memcmp(rs->identity_digest, ri->identity_digest, 20);
+ *      if (rs_ri_cmp > 0) {
+ *        break;
+ *      } else if (rs_ri_cmp == 0) {
+ *        goto matched_ri;
+ *      } else {
+ *        ++rs_sl_idx;
+ *      }
+ *    }
+ *    log_info(LD_GENERAL,"No match for %s", ri->nickname);
+ *    continue;
+ *   matched_ri: {
+ *    log_info(LD_GENERAL,"%s matches with routerstatus %p",ri->nickname,rs);
+ *    }
+ *  }
+ */
+#define SMARTLIST_FOREACH_JOIN(sl1, type1, var1, sl2, type2, var2,      \
+                                cmpexpr, unmatched_var2)                \
+  STMT_BEGIN                                                            \
+  int var1 ## _sl_idx = 0, var1 ## _sl_len=(sl1)->num_used;             \
+  int var2 ## _sl_idx = 0, var2 ## _sl_len=(sl2)->num_used;             \
+  int var1 ## _ ## var2 ## _cmp;                                        \
+  type1 var1;                                                           \
+  type2 var2;                                                           \
+  for (; var2##_sl_idx < var2##_sl_len; ++var2##_sl_idx) {              \
+    var2 = (sl2)->list[var2##_sl_idx];                                  \
+    while (var1##_sl_idx < var1##_sl_len) {                             \
+      var1 = (sl1)->list[var1##_sl_idx];                                \
+      var1##_##var2##_cmp = (cmpexpr);                                  \
+      if (var1##_##var2##_cmp > 0) {                                    \
+        break;                                                          \
+      } else if (var1##_##var2##_cmp == 0) {                            \
+        goto matched_##var2;                                            \
+      } else {                                                          \
+        ++var1##_sl_idx;                                                \
+      }                                                                 \
+    }                                                                   \
+    /* Ran out of v1, or no match for var2. */                          \
+    unmatched_var2;                                                     \
+    continue;                                                           \
+    matched_##var2: ;                                                   \
+
+#define SMARTLIST_FOREACH_JOIN_END(var1, var2)  \
+  }                                             \
+  STMT_END
+
+#define DECLARE_MAP_FNS(maptype, keytype, prefix)                       \
+  typedef struct maptype maptype;                                       \
+  typedef struct prefix##entry_t *prefix##iter_t;                       \
+  MOCK_DECL(maptype*, prefix##new, (void));                             \
+  void* prefix##set(maptype *map, keytype key, void *val);              \
+  void* prefix##get(const maptype *map, keytype key);                   \
+  void* prefix##remove(maptype *map, keytype key);                      \
+  MOCK_DECL(void, prefix##free_, (maptype *map, void (*free_val)(void*))); \
+  int prefix##isempty(const maptype *map);                              \
+  int prefix##size(const maptype *map);                                 \
+  prefix##iter_t *prefix##iter_init(maptype *map);                      \
+  prefix##iter_t *prefix##iter_next(maptype *map, prefix##iter_t *iter); \
+  prefix##iter_t *prefix##iter_next_rmv(maptype *map, prefix##iter_t *iter); \
+  void prefix##iter_get(prefix##iter_t *iter, keytype *keyp, void **valp); \
+  int prefix##iter_done(prefix##iter_t *iter);                          \
+  void prefix##assert_ok(const maptype *map)
+
+/* Map from const char * to void *. Implemented with a hash table. */
+DECLARE_MAP_FNS(strmap_t, const char *, strmap_);
+/* Map from const char[DIGEST_LEN] to void *. Implemented with a hash table. */
+DECLARE_MAP_FNS(digestmap_t, const char *, digestmap_);
+/* Map from const uint8_t[DIGEST256_LEN] to void *. Implemented with a hash
+ * table. */
+DECLARE_MAP_FNS(digest256map_t, const uint8_t *, digest256map_);
+
+#define MAP_FREE_AND_NULL(maptype, map, fn)     \
+  do {                                          \
+    maptype ## _free_((map), (fn));             \
+    (map) = NULL;                               \
+  } while (0)
+
+#define strmap_free(map, fn) MAP_FREE_AND_NULL(strmap, (map), (fn))
+#define digestmap_free(map, fn) MAP_FREE_AND_NULL(digestmap, (map), (fn))
+#define digest256map_free(map, fn) MAP_FREE_AND_NULL(digest256map, (map), (fn))
+
+#undef DECLARE_MAP_FNS
+
+/** Iterates over the key-value pairs in a map <b>map</b> in order.
+ * <b>prefix</b> is as for DECLARE_MAP_FNS (i.e., strmap_ or digestmap_).
+ * The map's keys and values are of type keytype and valtype respectively;
+ * each iteration assigns them to keyvar and valvar.
+ *
+ * Example use:
+ *   MAP_FOREACH(digestmap_, m, const char *, k, routerinfo_t *, r) {
+ *     // use k and r
+ *   } MAP_FOREACH_END.
+ */
+/* Unpacks to, approximately:
+ * {
+ *   digestmap_iter_t *k_iter;
+ *   for (k_iter = digestmap_iter_init(m); !digestmap_iter_done(k_iter);
+ *        k_iter = digestmap_iter_next(m, k_iter)) {
+ *     const char *k;
+ *     void *r_voidp;
+ *     routerinfo_t *r;
+ *     digestmap_iter_get(k_iter, &k, &r_voidp);
+ *     r = r_voidp;
+ *     // use k and r
+ *   }
+ * }
+ */
+#define MAP_FOREACH(prefix, map, keytype, keyvar, valtype, valvar)      \
+  STMT_BEGIN                                                            \
+    prefix##iter_t *keyvar##_iter;                                      \
+    for (keyvar##_iter = prefix##iter_init(map);                        \
+         !prefix##iter_done(keyvar##_iter);                             \
+         keyvar##_iter = prefix##iter_next(map, keyvar##_iter)) {       \
+      keytype keyvar;                                                   \
+      void *valvar##_voidp;                                             \
+      valtype valvar;                                                   \
+      prefix##iter_get(keyvar##_iter, &keyvar, &valvar##_voidp);        \
+      valvar = valvar##_voidp;
+
+/** As MAP_FOREACH, except allows members to be removed from the map
+ * during the iteration via MAP_DEL_CURRENT.  Example use:
+ *
+ * Example use:
+ *   MAP_FOREACH(digestmap_, m, const char *, k, routerinfo_t *, r) {
+ *      if (is_very_old(r))
+ *       MAP_DEL_CURRENT(k);
+ *   } MAP_FOREACH_END.
+ **/
+/* Unpacks to, approximately:
+ * {
+ *   digestmap_iter_t *k_iter;
+ *   int k_del=0;
+ *   for (k_iter = digestmap_iter_init(m); !digestmap_iter_done(k_iter);
+ *        k_iter = k_del ? digestmap_iter_next(m, k_iter)
+ *                       : digestmap_iter_next_rmv(m, k_iter)) {
+ *     const char *k;
+ *     void *r_voidp;
+ *     routerinfo_t *r;
+ *     k_del=0;
+ *     digestmap_iter_get(k_iter, &k, &r_voidp);
+ *     r = r_voidp;
+ *     if (is_very_old(r)) {
+ *       k_del = 1;
+ *     }
+ *   }
+ * }
+ */
+#define MAP_FOREACH_MODIFY(prefix, map, keytype, keyvar, valtype, valvar) \
+  STMT_BEGIN                                                            \
+    prefix##iter_t *keyvar##_iter;                                      \
+    int keyvar##_del=0;                                                 \
+    for (keyvar##_iter = prefix##iter_init(map);                        \
+         !prefix##iter_done(keyvar##_iter);                             \
+         keyvar##_iter = keyvar##_del ?                                 \
+           prefix##iter_next_rmv(map, keyvar##_iter) :                  \
+           prefix##iter_next(map, keyvar##_iter)) {                     \
+      keytype keyvar;                                                   \
+      void *valvar##_voidp;                                             \
+      valtype valvar;                                                   \
+      keyvar##_del=0;                                                   \
+      prefix##iter_get(keyvar##_iter, &keyvar, &valvar##_voidp);        \
+      valvar = valvar##_voidp;
+
+/** Used with MAP_FOREACH_MODIFY to remove the currently-iterated-upon
+ * member of the map.  */
+#define MAP_DEL_CURRENT(keyvar)                   \
+  STMT_BEGIN                                      \
+    keyvar##_del = 1;                             \
+  STMT_END
+
+/** Used to end a MAP_FOREACH() block. */
+#define MAP_FOREACH_END } STMT_END ;
+
+/** As MAP_FOREACH, but does not require declaration of prefix or keytype.
+ * Example use:
+ *   DIGESTMAP_FOREACH(m, k, routerinfo_t *, r) {
+ *     // use k and r
+ *   } DIGESTMAP_FOREACH_END.
+ */
+#define DIGESTMAP_FOREACH(map, keyvar, valtype, valvar)                 \
+  MAP_FOREACH(digestmap_, map, const char *, keyvar, valtype, valvar)
+
+/** As MAP_FOREACH_MODIFY, but does not require declaration of prefix or
+ * keytype.
+ * Example use:
+ *   DIGESTMAP_FOREACH_MODIFY(m, k, routerinfo_t *, r) {
+ *      if (is_very_old(r))
+ *       MAP_DEL_CURRENT(k);
+ *   } DIGESTMAP_FOREACH_END.
+ */
+#define DIGESTMAP_FOREACH_MODIFY(map, keyvar, valtype, valvar)          \
+  MAP_FOREACH_MODIFY(digestmap_, map, const char *, keyvar, valtype, valvar)
+/** Used to end a DIGESTMAP_FOREACH() block. */
+#define DIGESTMAP_FOREACH_END MAP_FOREACH_END
+
+#define DIGEST256MAP_FOREACH(map, keyvar, valtype, valvar)               \
+  MAP_FOREACH(digest256map_, map, const uint8_t *, keyvar, valtype, valvar)
+#define DIGEST256MAP_FOREACH_MODIFY(map, keyvar, valtype, valvar)       \
+  MAP_FOREACH_MODIFY(digest256map_, map, const uint8_t *,               \
+                     keyvar, valtype, valvar)
+#define DIGEST256MAP_FOREACH_END MAP_FOREACH_END
+
+#define STRMAP_FOREACH(map, keyvar, valtype, valvar)                 \
+  MAP_FOREACH(strmap_, map, const char *, keyvar, valtype, valvar)
+#define STRMAP_FOREACH_MODIFY(map, keyvar, valtype, valvar)          \
+  MAP_FOREACH_MODIFY(strmap_, map, const char *, keyvar, valtype, valvar)
+#define STRMAP_FOREACH_END MAP_FOREACH_END
+
+void* strmap_set_lc(strmap_t *map, const char *key, void *val);
+void* strmap_get_lc(const strmap_t *map, const char *key);
+void* strmap_remove_lc(strmap_t *map, const char *key);
+
+#define DECLARE_TYPED_DIGESTMAP_FNS(prefix, maptype, valtype)           \
+  typedef struct maptype maptype;                                       \
+  typedef struct prefix##iter_t *prefix##iter_t;                        \
+  ATTR_UNUSED static inline maptype*                                    \
+  prefix##new(void)                                                     \
+  {                                                                     \
+    return (maptype*)digestmap_new();                                   \
+  }                                                                     \
+  ATTR_UNUSED static inline digestmap_t*                                \
+  prefix##to_digestmap(maptype *map)                                    \
+  {                                                                     \
+    return (digestmap_t*)map;                                           \
+  }                                                                     \
+  ATTR_UNUSED static inline valtype*                                    \
+  prefix##get(maptype *map, const char *key)     \
+  {                                                                     \
+    return (valtype*)digestmap_get((digestmap_t*)map, key);             \
+  }                                                                     \
+  ATTR_UNUSED static inline valtype*                                    \
+  prefix##set(maptype *map, const char *key, valtype *val)              \
+  {                                                                     \
+    return (valtype*)digestmap_set((digestmap_t*)map, key, val);        \
+  }                                                                     \
+  ATTR_UNUSED static inline valtype*                                    \
+  prefix##remove(maptype *map, const char *key)                         \
+  {                                                                     \
+    return (valtype*)digestmap_remove((digestmap_t*)map, key);          \
+  }                                                                     \
+  ATTR_UNUSED static inline void                                        \
+  prefix##f##ree_(maptype *map, void (*free_val)(void*))                \
+  {                                                                     \
+    digestmap_free_((digestmap_t*)map, free_val);                       \
+  }                                                                     \
+  ATTR_UNUSED static inline int                                         \
+  prefix##isempty(maptype *map)                                         \
+  {                                                                     \
+    return digestmap_isempty((digestmap_t*)map);                        \
+  }                                                                     \
+  ATTR_UNUSED static inline int                                         \
+  prefix##size(maptype *map)                                            \
+  {                                                                     \
+    return digestmap_size((digestmap_t*)map);                           \
+  }                                                                     \
+  ATTR_UNUSED static inline                                             \
+  prefix##iter_t *prefix##iter_init(maptype *map)                       \
+  {                                                                     \
+    return (prefix##iter_t*) digestmap_iter_init((digestmap_t*)map);    \
+  }                                                                     \
+  ATTR_UNUSED static inline                                             \
+  prefix##iter_t *prefix##iter_next(maptype *map, prefix##iter_t *iter) \
+  {                                                                     \
+    return (prefix##iter_t*) digestmap_iter_next(                       \
+                       (digestmap_t*)map, (digestmap_iter_t*)iter);     \
+  }                                                                     \
+  ATTR_UNUSED static inline prefix##iter_t*                             \
+  prefix##iter_next_rmv(maptype *map, prefix##iter_t *iter)             \
+  {                                                                     \
+    return (prefix##iter_t*) digestmap_iter_next_rmv(                   \
+                       (digestmap_t*)map, (digestmap_iter_t*)iter);     \
+  }                                                                     \
+  ATTR_UNUSED static inline void                                        \
+  prefix##iter_get(prefix##iter_t *iter,                                \
+                   const char **keyp,                                   \
+                   valtype **valp)                                      \
+  {                                                                     \
+    void *v;                                                            \
+    digestmap_iter_get((digestmap_iter_t*) iter, keyp, &v);             \
+    *valp = v;                                                          \
+  }                                                                     \
+  ATTR_UNUSED static inline int                                         \
+  prefix##iter_done(prefix##iter_t *iter)                               \
+  {                                                                     \
+    return digestmap_iter_done((digestmap_iter_t*)iter);                \
+  }
+
+#if SIZEOF_INT == 4
+#define BITARRAY_SHIFT 5
+#elif SIZEOF_INT == 8
+#define BITARRAY_SHIFT 6
+#else
+#error "int is neither 4 nor 8 bytes. I can't deal with that."
+#endif /* SIZEOF_INT == 4 || ... */
+#define BITARRAY_MASK ((1u<<BITARRAY_SHIFT)-1)
+
+/** A random-access array of one-bit-wide elements. */
+typedef unsigned int bitarray_t;
+/** Create a new bit array that can hold <b>n_bits</b> bits. */
+static inline bitarray_t *
+bitarray_init_zero(unsigned int n_bits)
+{
+  /* round up to the next int. */
+  size_t sz = (n_bits+BITARRAY_MASK) >> BITARRAY_SHIFT;
+  return tor_calloc(sz, sizeof(unsigned int));
+}
+/** Expand <b>ba</b> from holding <b>n_bits_old</b> to <b>n_bits_new</b>,
+ * clearing all new bits.  Returns a possibly changed pointer to the
+ * bitarray. */
+static inline bitarray_t *
+bitarray_expand(bitarray_t *ba,
+                unsigned int n_bits_old, unsigned int n_bits_new)
+{
+  size_t sz_old = (n_bits_old+BITARRAY_MASK) >> BITARRAY_SHIFT;
+  size_t sz_new = (n_bits_new+BITARRAY_MASK) >> BITARRAY_SHIFT;
+  char *ptr;
+  if (sz_new <= sz_old)
+    return ba;
+  ptr = tor_reallocarray(ba, sz_new, sizeof(unsigned int));
+  /* This memset does nothing to the older excess bytes.  But they were
+   * already set to 0 by bitarry_init_zero. */
+  memset(ptr+sz_old*sizeof(unsigned int), 0,
+         (sz_new-sz_old)*sizeof(unsigned int));
+  return (bitarray_t*) ptr;
+}
+/** Free the bit array <b>ba</b>. */
+static inline void
+bitarray_free_(bitarray_t *ba)
+{
+  tor_free(ba);
+}
+#define bitarray_free(ba) FREE_AND_NULL(bitarray_t, bitarray_free_, (ba))
+
+/** Set the <b>bit</b>th bit in <b>b</b> to 1. */
+static inline void
+bitarray_set(bitarray_t *b, int bit)
+{
+  b[bit >> BITARRAY_SHIFT] |= (1u << (bit & BITARRAY_MASK));
+}
+/** Set the <b>bit</b>th bit in <b>b</b> to 0. */
+static inline void
+bitarray_clear(bitarray_t *b, int bit)
+{
+  b[bit >> BITARRAY_SHIFT] &= ~ (1u << (bit & BITARRAY_MASK));
+}
+/** Return true iff <b>bit</b>th bit in <b>b</b> is nonzero.  NOTE: does
+ * not necessarily return 1 on true. */
+static inline unsigned int
+bitarray_is_set(bitarray_t *b, int bit)
+{
+  return b[bit >> BITARRAY_SHIFT] & (1u << (bit & BITARRAY_MASK));
+}
+
+/** A set of digests, implemented as a Bloom filter. */
+typedef struct {
+  int mask; /**< One less than the number of bits in <b>ba</b>; always one less
+             * than a power of two. */
+  bitarray_t *ba; /**< A bit array to implement the Bloom filter. */
+} digestset_t;
+
+#define BIT(n) ((n) & set->mask)
+/** Add the digest <b>digest</b> to <b>set</b>. */
+static inline void
+digestset_add(digestset_t *set, const char *digest)
+{
+  const uint64_t x = siphash24g(digest, 20);
+  const uint32_t d1 = (uint32_t) x;
+  const uint32_t d2 = (uint32_t)( (x>>16) + x);
+  const uint32_t d3 = (uint32_t)( (x>>32) + x);
+  const uint32_t d4 = (uint32_t)( (x>>48) + x);
+  bitarray_set(set->ba, BIT(d1));
+  bitarray_set(set->ba, BIT(d2));
+  bitarray_set(set->ba, BIT(d3));
+  bitarray_set(set->ba, BIT(d4));
+}
+
+/** If <b>digest</b> is in <b>set</b>, return nonzero.  Otherwise,
+ * <em>probably</em> return zero. */
+static inline int
+digestset_contains(const digestset_t *set, const char *digest)
+{
+  const uint64_t x = siphash24g(digest, 20);
+  const uint32_t d1 = (uint32_t) x;
+  const uint32_t d2 = (uint32_t)( (x>>16) + x);
+  const uint32_t d3 = (uint32_t)( (x>>32) + x);
+  const uint32_t d4 = (uint32_t)( (x>>48) + x);
+  return bitarray_is_set(set->ba, BIT(d1)) &&
+         bitarray_is_set(set->ba, BIT(d2)) &&
+         bitarray_is_set(set->ba, BIT(d3)) &&
+         bitarray_is_set(set->ba, BIT(d4));
+}
+#undef BIT
+
+digestset_t *digestset_new(int max_elements);
+void digestset_free_(digestset_t* set);
+#define digestset_free(set) FREE_AND_NULL(digestset_t, digestset_free_, (set))
+
+/* These functions, given an <b>array</b> of <b>n_elements</b>, return the
+ * <b>nth</b> lowest element. <b>nth</b>=0 gives the lowest element;
+ * <b>n_elements</b>-1 gives the highest; and (<b>n_elements</b>-1) / 2 gives
+ * the median.  As a side effect, the elements of <b>array</b> are sorted. */
+int find_nth_int(int *array, int n_elements, int nth);
+time_t find_nth_time(time_t *array, int n_elements, int nth);
+double find_nth_double(double *array, int n_elements, int nth);
+int32_t find_nth_int32(int32_t *array, int n_elements, int nth);
+uint32_t find_nth_uint32(uint32_t *array, int n_elements, int nth);
+long find_nth_long(long *array, int n_elements, int nth);
+static inline int
+median_int(int *array, int n_elements)
+{
+  return find_nth_int(array, n_elements, (n_elements-1)/2);
+}
+static inline time_t
+median_time(time_t *array, int n_elements)
+{
+  return find_nth_time(array, n_elements, (n_elements-1)/2);
+}
+static inline double
+median_double(double *array, int n_elements)
+{
+  return find_nth_double(array, n_elements, (n_elements-1)/2);
+}
+static inline uint32_t
+median_uint32(uint32_t *array, int n_elements)
+{
+  return find_nth_uint32(array, n_elements, (n_elements-1)/2);
+}
+static inline int32_t
+median_int32(int32_t *array, int n_elements)
+{
+  return find_nth_int32(array, n_elements, (n_elements-1)/2);
+}
+
+static inline uint32_t
+third_quartile_uint32(uint32_t *array, int n_elements)
+{
+  return find_nth_uint32(array, n_elements, (n_elements*3)/4);
+}
+
+#endif /* !defined(TOR_CONTAINER_H) */
diff --git a/src/lib/container/include.am b/src/lib/container/include.am
new file mode 100644
index 0000000000..d7648c80c0
--- /dev/null
+++ b/src/lib/container/include.am
@@ -0,0 +1,17 @@
+
+noinst_LIBRARIES += src/lib/libtor-container.a
+
+if UNITTESTS_ENABLED
+noinst_LIBRARIES += src/lib/libtor-container-testing.a
+endif
+
+src_lib_libtor_container_a_SOURCES =			\
+	src/lib/container/container.c
+
+src_lib_libtor_container_testing_a_SOURCES = \
+	$(src_lib_libtor_container_a_SOURCES)
+src_lib_libtor_container_testing_a_CPPFLAGS = $(AM_CPPFLAGS) $(TEST_CPPFLAGS)
+src_lib_libtor_container_testing_a_CFLAGS = $(AM_CFLAGS) $(TEST_CFLAGS)
+
+noinst_HEADERS +=					\
+	src/lib/container/container.h