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+@dir /ext
+@brief Externally maintained code
+
+The "ext" directory holds code that was written elsewhere, and is not
+reliably packaged as a library where we want to build, so we ship
+it along with Tor.
+
+In general, you should not edit this code: we are not the maintainers.
+Instead, you should submit patches upstream.
+
+OpenBSD_malloc_Linux.c:
+
+> The OpenBSD malloc implementation, ported to Linux.  Used only when
+> --enable-openbsd-malloc is passed to the configure script.
+
+strlcat.c
+strlcpy.c
+
+> Implementations of strlcat and strlcpy, the more sane replacements
+> for strcat and strcpy.  These are nonstandard, and some libc
+> implementations refuse to add them for religious reasons.
+
+ht.h
+
+> An implementation of a hash table in the style of Niels Provos's
+> tree.h.  Shared with Libevent.
+
+tinytest.c tinytest.h
+tinytest_demos.c
+tinytest_macros.h
+
+> A unit testing framework. https://github.com/nmathewson/tinytest
+
+tor_queue.h
+
+> A copy of sys/queue.h from OpenBSD.  We keep our own copy rather
+> than using sys/queue.h, since some platforms don't have a
+> sys/queue.h, and the ones that do have diverged in incompatible
+> ways.  (CIRCLEQ or no CIRCLEQ? SIMPLQ or STAILQ?)  We also rename
+> the identifiers with a TOR_ prefix to avoid conflicts with
+> the system headers.
+
+curve25519_donna/*.c
+
+> A copy of Adam Langley's curve25519-donna mostly-portable
+> implementations of curve25519.
+
+csiphash.c
+siphash.h
+
+> Marek Majkowski's implementation of siphash 2-4, a secure keyed
+> hash algorithm to avoid collision-based DoS attacks against hash
+> tables.
+
+trunnel/*.[ch]
+
+> Headers and runtime code for Trunnel, a system for generating
+> code to encode and decode binary formats.
+
+ed25519/ref10/*
+
+> Daniel Bernsten's portable ref10 implementation of ed25519.
+> Public domain.
+
+ed25519/donna/*
+
+> Andrew Moon's semi-portable ed25519-donna implementation of
+> ed25519. Public domain.
+
+keccak-tiny/
+
+> David Leon Gil's portable Keccak implementation. CC0.
+
+readpassphrase.[ch]
+
+> Portable readpassphrase implementation from OpenSSH portable, version
+> 6.8p1.
+
+timeouts/
+
+> William Ahern's hierarchical timer-wheel implementation. MIT license.
+
+mulodi/
+
+> Contains an overflow-checking 64-bit signed integer multiply
+> from LLVM's compiler_rt.  For some reason, this is missing from
+> 32-bit libclang in many places. Dual licensed MIT-license and
+> BSD-like license; see mulodi/LICENSE.TXT.