wasm-c-api introduction

wasm-c-api is an engine-agnostic API to embed a WASM engine. In wasm-micro-runtime, it's provided by the header file wasm_c_api.h. Its functionalities are overlapping with wasm_export.h, which is a native API of wasm-micro-runtime. An embedder is supposed to pick one of these APIs, rather than mixing both of them.

All samples come from the commit 340fd9528cc3b26d22fe30ee1628c8c3f2b8c53b of wasm-c-api.

Developer can learn these APIs from wasm.h.

And here are examples which are helpful.

FYI

• The thread model of wasm_c_api is

  • An wasm_engine_t instance may only be created once per process
  • Every wasm_store_t and its objects may only be accessed in a single thread

• wasm_engine_new, wasm_engine_new_with_config, wasm_engine_new_with_args, wasm_engine_deleteshould be called in a thread-safe environment. Such behaviors are not recommended, and please make sure an appropriate calling sequence if it has to be.

  • call wasm_engine_new and wasm_engine_delete in different threads
  • call wasm_engine_new or wasm_engine_delete multiple times in different threads

unsupported list

Currently WAMR supports most of the APIs, the unsupported APIs are listed as below:

• References

WASM_API_EXTERN own wasm_shared_##name##_t* wasm_##name##_share(const wasm_##name##_t*);
WASM_API_EXTERN own wasm_##name##_t* wasm_##name##_obtain(wasm_store_t*, const wasm_shared_##name##_t*);

• Several Module APIs

WASM_API_EXTERN void wasm_module_serialize(const wasm_module_t*, own wasm_byte_vec_t* out);
WASM_API_EXTERN own wasm_module_t* wasm_module_deserialize(wasm_store_t*, const wasm_byte_vec_t*);

Currently growing a table or memory by wasm opcode is supported and it is not supported to grow them by host-side function callings.

• Table Grow APIs

WASM_API_EXTERN bool wasm_table_grow(wasm_table_t*, wasm_table_size_t delta, wasm_ref_t* init);

• Memory Grow APIs

WASM_API_EXTERN bool wasm_memory_grow(wasm_memory_t*, wasm_memory_pages_t delta);