cwisstable is a single-header C11 port of the Abseil project's
SwissTables.
This project is intended to bring the proven performance and flexibility
of SwissTables to C projects which cannot require a C++ compiler or for projects
which otherwise struggle with dependency management.
The public API is currently in flux, as is test coverage, but the C programs in
the examples directory illustrate portions of the API.
Code in this project follows the Google C++ Style Guide where applicable; variations due to C are described in STYLE.md.
TL;DR: run
./unified.py cwisstable/*.h, grabcwisstable.h, and get cwissing.
There are two options for using this library: Bazel, or single-header.
Bazel support exists by virtue of that being how the tests and benchmarks are
build and run. All development on cwisstable itself requires Bazel. Downstream
projects may use git_repository to depend on this workspace; two build
targets are available:
//:splitis the "native" split form of the headers (i.e., as they are checked in).//:unifiedis the generated unified header, which is functionality identical.
Most C projects use other build systems: Make, CMake, Autoconf, Meson, and artisanal shell scripts; expecting projects to fuss with Bazel is an accessibility barrier. This is the raison d-être: you generate the unified header, vendor it into your project, and never think about it again. Even generating the file doesn't require installing Bazel; all you need is Python:
git clone https://github.com/google/cwisstable.git && cd cwisstable
./unify.pyThis will output a cwisstable.h file that you can vendor in; the checkout
and generation step is only necessary for upgrading the header.
That said, if you're writing C++, this library is very much not for you. Please use https://github.com/abseil/abseil-cpp instead!
To use cwisstable, include cwisstable.h and use the code-generating macros
to create a new map type:
#include "cwisstable.h"
CWISS_DECLARE_FLAT_HASHSET(MyIntSet, int);
int main(void) {
MyIntSet set = MyIntSet_new(8);
for (int i = 0; i < 8; ++i) {
int val = i * i + 1;
MyIntSet_insert(&set, &val);
}
int k = 4;
assert(!MyIntSet_contains(&set, &k));
}cwisstable/declare.h has a detailed description of
these macros and their generated API.
cwisstable/policy.h describes how to use hash table
policies to define more complex sets and maps.
examples/stringmap.c shows this in action!
We don't version cwisstable.h; instead, users are expected to vendor the
unified file into their projects and manually update it; cwisstable's
distribution method (or, lack of one) is intended to eliminate all friction to
its use in traditional C projects.
That said, we do not provide any kind of ABI or API stability from one revision
to another that would allow cwisstable.h to appear in another library's public
headers. You must not, under any circumstances, expose this header in your
public headers. Doing so may clash with another project making the same
mistake, and potentially destroy compile times due to the enormous number of
inline functions generated in every translation unit.
Including cwisstable.h into a public header will also cause it to become part
of your API, due to Hyrum's Law, even if our
types do not appear in your interfaces. Such a mistake may be difficult to
unwind, and we will not provide support for it.
The intended use of cwisstable.h is that it will either be included directly
into your .c files, or a private .h file that declares common table types
which is then includes in your .c files.
This is not an officially supported Google product.
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