to-wit: A C/C++ WIT Parser

Attention: The code in this repository is intended for experimental use only and is not fully tested, documented, or supported by SingleStore. Visit the SingleStore Forums to ask questions about this repository.

This library provides an C-based FFI wrapper around the wit-bindgen parsing API (written natively in Rust). It enables C/C++ programs to parse WIT specs and extract information about the their ASTs.

Building

Just run:

make all

If you need to, you can update the paths at the top of the Makefile. The following will be generated:

• target/debug/* - Debug libs
• target/release/* - Release libs
• target/to-wit.h - Generated header file
• target/to-wit - Example program

Usage

Just copy the target/to-wit.h file to wherever you want and #include it.
You'll also need to make sure you link against target/release/libto_wit.a or target/release/libto_wit.so.

See the target/to-wit target in the Makefile for a simple example.

Example

An example driver program is included, called to-wit. Its C source can be found in the example directory. To build it, run make example.

While it is intended primarily as an example, it is also useful in its own right. It will output parsed info about a WIT spec. It has two modes -- summary and detail.

To get a summary of the exports available in a WIT spec, run it like this:

target/to-wit example/example.wit

You'll get this back:

Functions:
  sentiment
  square
  split
  hilbert_encode

To get detailed ABI information about one of the exports, run it like this:

target/to-wit example/example.wit sentiment

And you'll get this back:

Func Name: sentiment
Signature:
  Params: [I32, I32]
  Result: [I32]
  RetPtr: [F64, F64, F64, F64]
Params:
  [name=input, type=List, size=8, align=4]
    [name=, type=Char, size=4, align=4]
Results:
  [name=, type=Record, size=32, align=8]
    [name=compound, type=F64, size=8, align=8]
    [name=positive, type=F64, size=8, align=8]
    [name=negative, type=F64, size=8, align=8]
    [name=neutral, type=F64, size=8, align=8]

Issues

The WIT spec is parsed as a set of guest Exports. There is currently no switch to make it parse the spec as Imports, although an easy workaround is to flip the constant abi::AbiVariant::GuestExport to abi::AbiVariant::GuestImport in the source file.

Resources

• wit-bindgen