Initial import of libdpf.

Co-authored-by: Cursor <cursoragent@cursor.com>

thirdparty/portable-snippets/README.md

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+# Portable Snippets
+
+This is a collection of public domain (CC0) code snippets written in C
+for performing various common tasks which are typically OS,
+architecture, and/or compiler-dependent.  Basically, our goal is to
+move those annoying preprocessor conditionals from your code to ours.
+
+Modules have no fixed target (such as C89) since that would preclude
+some functionality; instead, we simply try to provide the widest
+support we can for each module.  If you have a platform which isn't
+supported for a particular feature but could be, please let us know;
+we'd be happy to try to work out a way to support it.
+
+Everything is tested continuously with various versions of GCC, Clang,
+and PGI ([on Travis
+CI](https://travis-ci.org/nemequ/portable-snippets)), MSVC ([on
+AppVeyor](https://ci.appveyor.com/project/quixdb/portable-snippets)),
+and Emscripten (on
+[Codefresh](https://g.codefresh.io/repositories/nemequ/portable-snippets/builds?filter=trigger:build;branch:master;service:591f783d728f4b0001051d3e~portable-snippets)):
+
+[![Travis CI status](https://travis-ci.org/nemequ/portable-snippets.svg?branch=master)](https://travis-ci.org/nemequ/portable-snippets) [![AppVeyor status](https://ci.appveyor.com/api/projects/status/quoq2hwes530p29w/branch/master?svg=true)](https://ci.appveyor.com/project/quixdb/portable-snippets/branch/master) [![Codefresh status](https://g.codefresh.io/api/badges/build?repoOwner=nemequ&repoName=portable-snippets&branch=master&pipelineName=portable-snippets&accountName=nemequ&type=cf-1)](https://g.codefresh.io/repositories/nemequ/portable-snippets/builds?filter=trigger:build;branch:master;service:591f783d728f4b0001051d3e~portable-snippets)
+
+Currently ready-to-use modules include:
+
+ * [builtin](https://github.com/nemequ/portable-snippets/tree/master/builtin) —
+   use compiler built-ins/intrinsics, or fall back on standard C
+ * [endian](https://github.com/nemequ/portable-snippets/tree/master/endian) —
+   endianness detection and swapping
+ * [atomic](https://github.com/nemequ/portable-snippets/tree/master/atomic) —
+   common atomic synchronization operations
+ * [safe-math](https://github.com/nemequ/portable-snippets/tree/master/safe-math) —
+   overflow-safe integer functions
+ * [exact-int](https://github.com/nemequ/portable-snippets/tree/master/exact-int) —
+   exact-width integer types (think `<stdint.h>`)
+ * [clock](https://github.com/nemequ/portable-snippets/tree/master/clock) —
+   cross-platform wall clock, CPU time, and monotonic time
+
+There are also modules which may not yet be ready for widespread use, but
+would benefit greatly from testing:
+
+ * [unaligned](https://github.com/nemequ/portable-snippets/tree/master/unaligned) —
+   fast unaligned loads & stores
+ * [once](https://github.com/nemequ/portable-snippets/tree/master/once) —
+   one-time initialization
+ * [random](https://github.com/nemequ/portable-snippets/tree/master/random) —
+   random number generation (3 flavors: cryptographic, reproducible, and fast)
+ * [debug-trap](https://github.com/nemequ/portable-snippets/tree/master/debug-trap) —
+   debugging traps and assertions
+ * [check](https://github.com/nemequ/portable-snippets/tree/master/check) —
+   assertion checking
+
+Modules can be used in isolation, though some do work better together,
+so if you can keep the whole repository together instead of just
+copying a single file we recommend you do so.
+
+Please don't be shy about filing issues about any of these; if you
+have problems it's likely others will, as well, so we would like to
+fix them.
+
+If you have something you would like to contribute, please file an
+issue or pull request.  If you'd like to help out by writing something
+new, take a look at the ["enhancement"
+issues](https://github.com/nemequ/portable-snippets/issues?q=is%3Aissue+is%3Aopen+label%3Aenhancement)
+in our issue tracker for ideas.
+
+Some things don't really fit this repository, so here are a few
+small-ish projects for doing things portably which you may be
+interested in:
+
+ * [Hedley](https://nemequ.github.io/hedley/) — macros to enable
+   compiler-specific features which make your code easier to use,
+   harder to misuse, safer, faster, and more portable.
+ * [parg](https://github.com/jibsen/parg) —
+   Argument parsing similar to getopt/getopt_long.  Public domain.
+ * [TinyCThread](https://tinycthread.github.io/) — Implements the C11
+   threads API on top of pthreads and the Windows API.  zlib license.
+ * [win-iconv](https://github.com/win-iconv/win-iconv) — Windows
+   implementation of the iconv API (character set conversion).
+ * [mman-win32](https://github.com/witwall/mman-win32) — `mman.h`
+   (`mmap()`, *etc.*) implementation for Windows.
+
+If there is a project you'd like to see added to the list, please file
+an issue or pull request.