# wickra-c

C ABI for [Wickra](https://github.com/wickra-lib/wickra) — streaming-first
technical indicators with a Rust core. This crate is the **hub**: it compiles the
core to a C-compatible shared/static library plus a generated header, so any
C-capable language (C, C++, Go, C#, Java, R) links against one artifact instead
of re-wiring every indicator natively.

The native Python, Node, and WebAssembly bindings are unaffected — this is
additive, for the ecosystems without first-class Rust tooling.

## Artifacts

```sh
cargo build -p wickra-c --release
```

- `target/release/libwickra.{so,dylib}` / `wickra.dll` (+ `wickra.dll.lib` import lib on Windows)
- `target/release/libwickra.a` / `wickra.lib` (static)
- [`include/wickra.h`](include/wickra.h) — generated by cbindgen, committed.

## API shape

Each indicator is exposed as five `extern "C"` functions over an opaque handle:

```c
struct Sma *wickra_sma_new(uintptr_t period);                 /* NULL on bad params */
double      wickra_sma_update(struct Sma *h, double value);   /* NaN during warmup */
void        wickra_sma_batch(struct Sma *h, const double *in, double *out, uintptr_t n);
void        wickra_sma_reset(struct Sma *h);
void        wickra_sma_free(struct Sma *h);                   /* exactly once per _new */
```

Conventions:

- **Opaque handles.** `wickra_<ind>_new` returns a `T *` you must release with
  exactly one `wickra_<ind>_free`. There is no RAII across the boundary.
- **NaN sentinel.** Scalar outputs return `NaN` while warming up or on a `NULL`
  handle, mirroring the other bindings — no error codes for the common path.
- **Caller-owned batch buffers.** `wickra_<ind>_batch` writes one output per
  input into a buffer you provide; nothing is allocated across the boundary.
- **NULL-safe.** Every function tolerates a `NULL` handle without crashing.

## Header regeneration

The header is generated and committed; CI checks it is in sync:

```sh
cbindgen --config bindings/c/cbindgen.toml --crate wickra-c --output bindings/c/include/wickra.h
```

## Examples

Runnable C examples (build via CMake or a direct compiler invocation) live in
[`examples/c`](../../examples/c).

## License

`MIT OR Apache-2.0`, the same as the rest of Wickra.