1 files changed, 61 insertions, 0 deletions
diff --git a/src/lib/log/win32err.c b/src/lib/log/win32err.c
new file mode 100644
index 0000000000..dc45cb4c3d
--- /dev/null
+++ b/src/lib/log/win32err.c
@@ -0,0 +1,61 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file win32err.c
+ * \brief Convert windows error codes to useful C strings.
+ **/
+
+#ifdef _WIN32
+#include "orconfig.h"
+#include "lib/log/win32err.h"
+#include "lib/malloc/malloc.h"
+
+#include <tchar.h>
+#include <windows.h>
+
+/** Return a newly allocated string describing the windows system error code
+ * <b>err</b>.  Note that error codes are different from errno.  Error codes
+ * come from GetLastError() when a winapi call fails.  errno is set only when
+ * ANSI functions fail.  Whee. */
+char *
+format_win32_error(DWORD err)
+{
+  TCHAR *str = NULL;
+  char *result;
+  DWORD n;
+
+  /* Somebody once decided that this interface was better than strerror(). */
+  n = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                 FORMAT_MESSAGE_FROM_SYSTEM |
+                 FORMAT_MESSAGE_IGNORE_INSERTS,
+                 NULL, err,
+                 MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT),
+                 (LPVOID)&str,
+                 0, NULL);
+
+  if (str && n) {
+#ifdef UNICODE
+    size_t len;
+    if (n > 128*1024)
+      len = (128 * 1024) * 2 + 1; /* This shouldn't be possible, but let's
+                                   * make sure. */
+    else
+      len = n * 2 + 1;
+    result = tor_malloc(len);
+    wcstombs(result,str,len);
+    result[len-1] = '\0';
+#else /* !(defined(UNICODE)) */
+    result = tor_strdup(str);
+#endif /* defined(UNICODE) */
+  } else {
+    result = tor_strdup("<unformattable error>");
+  }
+  if (str) {
+    LocalFree(str); /* LocalFree != free() */
+  }
+  return result;
+}
+#endif /* defined(_WIN32) */