Function wasmedge_sys::ffi::WasmEdge_FunctionInstanceCreateBinding

pub unsafe extern "C" fn WasmEdge_FunctionInstanceCreateBinding(
    Type: *const WasmEdge_FunctionTypeContext,
    WrapFunc: WasmEdge_WrapFunc_t,
    Binding: *mut c_void,
    Data: *mut c_void,
    Cost: u64
) -> *mut WasmEdge_FunctionInstanceContext

Creation of the WasmEdge_FunctionInstanceContext for host functions.

This function is for the languages which cannot pass the function pointer of the host function into this shared library directly. The caller owns the object and should call WasmEdge_FunctionInstanceDelete to destroy it if the returned object is not added into a WasmEdge_ModuleInstanceContext. The following is an example to create a host function context for other languages.

// `RealFunc` is the pointer to the function in other languages.

WasmEdge_Result FuncAddWrap(
    void *This, void *Data,
    const WasmEdge_CallingFrameContext *CallFrameCxt,
    const WasmEdge_Value *In, const uint32_t InLen, WasmEdge_Value *Out,
    const uint32_t OutLen) {
  // Wrapper function of host function to return A + B.

  // `This` is the same as `RealFunc`.
  int32_t A = WasmEdge_ValueGetI32(In[0]);
  int32_t B = WasmEdge_ValueGetI32(In[1]);

  // Call the function of `This` in the host language ...
  int32_t Result = ...;

  Out[0] = Result;
  // Return the execution status.
  return WasmEdge_Result_Success;
}

enum WasmEdge_ValType Params[2] = {WasmEdge_ValType_I32,
                                   WasmEdge_ValType_I32};
enum WasmEdge_ValType Returns[1] = {WasmEdge_ValType_I32};
WasmEdge_FunctionTypeContext *FuncType =
    WasmEdge_FunctionTypeCreate(Params, 2, Returns, 1);
WasmEdge_FunctionInstanceContext *HostFunc =
    WasmEdge_FunctionInstanceCreateBinding(
        FuncType, FuncAddWrap, RealFunc, NULL, 0);
WasmEdge_FunctionTypeDelete(FuncType);
...

\param Type the function type context to describe the host function signature. \param WrapFunc the wrapper function pointer. The wrapper function signature must be as following:

typedef WasmEdge_Result (*WasmEdge_WrapFunc_t)(
    void *This,
    void *Data,
    WasmEdge_CallingFrameContext *FrameCxt,
    const WasmEdge_Value *Params,
    const uint32_t ParamLen,
    WasmEdge_Value *Returns,
    const uint32_t ReturnLen);

The This is the pointer the same as the Binding parameter of this function. The Params is the input parameters array with length guaranteed to be the same as the parameter types in the Type, and the ParamLen is the length of the array. The Returns is the output results array with length guaranteed to be the same as the result types in the Type, and the ReturnLen is the length of the array. The return value is WasmEdge_Result for the execution status. \param Binding the this pointer of the host function target or the function indexing maintained by the caller which can specify the host function. When invoking the host function, this pointer will be the first argument of the wrapper function. \param Data the additional object, such as the pointer to a data structure, to set to this host function context. The caller should guarantee the life cycle of the object. NULL if the additional data object is not needed. \param Cost the function cost in statistics. Pass 0 if the calculation is not needed.

\returns pointer to context, NULL if failed.