kingchenc
91e05e3c26
## What
Introduces `wickra-c` — a `cdylib` + `staticlib` that exposes the Rust core over a **C ABI**. This is the hub every C-capable language (C, C++, Go, C#, Java, R) links against, instead of re-wiring each indicator natively. The native Python/Node/WASM bindings are untouched; this is purely additive, for ecosystems without first-class Rust tooling.
## Scope (foundation slice)
This PR deliberately validates the **whole pipeline end to end with one indicator (SMA)** before scaling to all 514, so the CI / cross-OS / header-drift mechanics are proven green first.
- Opaque `*mut T` handles; `wickra_<ind>_{new,update,batch,reset,free}`.
- NaN sentinel for warmup / NULL handles; caller-owned batch buffers; every function NULL-safe.
- cbindgen generates and commits `bindings/c/include/wickra.h` with opaque handle typedefs.
- A C smoke example (`examples/c/`) links the header + compiled library and runs (CMake + ctest).
- A `c-abi` CI job builds the library and runs the smoke test on **Linux, macOS and Windows**, plus a header drift check on Linux.
## Notes
- The per-indicator FFI blocks are plain `#[no_mangle]` functions, **not** a macro: cbindgen cannot see macro-generated functions on stable Rust (macro expansion needs nightly), so the blocks are written literally and will be generated mechanically by the ScriptHelpers `capi` wrapper in a follow-up (same model as the committed-but-generated Node `index.js`).
- `bindings/c` cannot inherit the workspace `forbid(unsafe_code)` lint (the C boundary needs raw pointers), so it mirrors every workspace lint and only relaxes `unsafe_code`. The Rust core stays `unsafe`-forbidden.
## Follow-ups (separate PRs)
- ScriptHelpers `capi` generator + wire the scalar family (~235).
- Hand-written blocks for multi-output / custom-input / bars (~279).
- Docs consistency wave (README / docs / webpage: Python·Node·WASM·Rust → +C).
- Release wiring (native-lib matrix + header/lib GH-release assets) — gated.
Wickra — C / C++ examples
The Wickra C ABI is a single shared/static library plus a generated header
(bindings/c/include/wickra.h). Any
C-capable language links against the same artifact; these examples show the
plain-C path.
Build the library
From the workspace root:
cargo build -p wickra-c --release
This produces, in target/release/:
| Platform | Shared library | Link target |
|---|---|---|
| Linux | libwickra.so |
-lwickra |
| macOS | libwickra.dylib |
-lwickra |
| Windows (MSVC) | wickra.dll |
wickra.dll.lib (import lib) |
A static library (libwickra.a / wickra.lib) is emitted alongside.
Build and run the smoke example
With CMake (portable, used by CI)
cmake -S examples/c -B examples/c/build -DWICKRA_LIB_DIR="$PWD/target/release"
cmake --build examples/c/build
ctest --test-dir examples/c/build --output-on-failure
Directly with a compiler
# Linux / macOS
cc examples/c/smoke.c -I bindings/c/include -L target/release -lwickra -lm -o smoke
LD_LIBRARY_PATH=target/release ./smoke # macOS: DYLD_LIBRARY_PATH
# Windows (MinGW gcc, linking the DLL directly)
gcc examples/c/smoke.c -I bindings/c/include target/release/wickra.dll -lm -o smoke.exe
Expected output:
OK: wickra C ABI smoke passed (SMA streaming + batch + reset + NULL-safety + free)
Usage shape
Every indicator follows the same five-function pattern over an opaque handle:
#include "wickra.h"
struct Sma *sma = wickra_sma_new(14); /* NULL on invalid params */
double v = wickra_sma_update(sma, 42.0); /* NaN during warmup */
wickra_sma_reset(sma); /* back to fresh state */
wickra_sma_free(sma); /* exactly once per _new */
There is no RAII across the C boundary: every wickra_<ind>_new must be paired
with exactly one wickra_<ind>_free. All functions are NULL-safe (a NULL handle
yields NaN / a no-op, never a crash).