WasmEdge C SDK

The WasmEdge C API denotes an interface to embed the WasmEdge runtime into a C program. The followings are the quick start guides to working with the C APIs of WasmEdge. For the details of the WasmEdge C API, please refer to the full documentation.

The WasmEdge C API also the fundamental API for other languages’ SDK.

Quick Start Guide for the WasmEdge runner

The following is an example for running a WASM file. Assume that the WASM file fibonacci.wasm is copied into the current directory, and the C file test_wasmedge.c is as following:

  1. #include <wasmedge/wasmedge.h>
  2. #include <stdio.h>
  3. int main(int Argc, const char* Argv[]) {
  4.   /* Create the configure context and add the WASI support. */
  5.   /* This step is not necessary unless you need WASI support. */
  6.   WasmEdge_ConfigureContext *ConfCxt = WasmEdge_ConfigureCreate();
  7.   WasmEdge_ConfigureAddHostRegistration(ConfCxt, WasmEdge_HostRegistration_Wasi);
  8.   /* The configure and store context to the VM creation can be NULL. */
  9.   WasmEdge_VMContext *VMCxt = WasmEdge_VMCreate(ConfCxt, NULL);
  11.   /* The parameters and returns arrays. */
  12.   WasmEdge_Value Params[1] = { WasmEdge_ValueGenI32(32) };
  13.   WasmEdge_Value Returns[1];
  14.   /* Function name. */
  15.   WasmEdge_String FuncName = WasmEdge_StringCreateByCString("fib");
  16.   /* Run the WASM function from file. */
  17.   WasmEdge_Result Res = WasmEdge_VMRunWasmFromFile(VMCxt, Argv[1], FuncName, Params, 1, Returns, 1);
  19.   if (WasmEdge_ResultOK(Res)) {
  20.     printf("Get result: %d\n", WasmEdge_ValueGetI32(Returns[0]));
  21.   } else {
  22.     printf("Error message: %s\n", WasmEdge_ResultGetMessage(Res));
  23.   }
  25.   /* Resources deallocations. */
  26.   WasmEdge_VMDelete(VMCxt);
  27.   WasmEdge_ConfigureDelete(ConfCxt);
  28.   WasmEdge_StringDelete(FuncName);
  29.   return 0;
  30. }

Then you can compile and run: (the 32th fibonacci number is 3524578 in 0-based index)

  1. $ gcc test_wasmedge.c -lwasmedge_c -o test_wasmedge
  2. $ ./test_wasmedge fibonacci.wasm
  3. Get result: 3524578

Quick Start Guide for the WasmEdge AOT compiler

Assume that the WASM file fibonacci.wasm is copied into the current directory, and the C file test_wasmedge_compiler.c is as following:

  1. #include <wasmedge/wasmedge.h>
  2. #include <stdio.h>
  3. int main(int Argc, const char* Argv[]) {
  4.   /* Create the configure context. */
  5.   WasmEdge_ConfigureContext *ConfCxt = WasmEdge_ConfigureCreate();
  6.   /* ... Adjust settings in the configure context. */
  7.   /* Result. */
  8.   WasmEdge_Result Res;
  10.   /* Create the compiler context. The configure context can be NULL. */
  11.   WasmEdge_CompilerContext *CompilerCxt = WasmEdge_CompilerCreate(ConfCxt);
  12.   /* Compile the WASM file with input and output paths. */
  13.   Res = WasmEdge_CompilerCompile(CompilerCxt, Argv[1], Argv[2]);
  14.   if (!WasmEdge_ResultOK(Res)) {
  15.     printf("Compilation failed: %s\n", WasmEdge_ResultGetMessage(Res));
  16.     return 1;
  17.   }
  19.   WasmEdge_CompilerDelete(CompilerCxt);
  20.   WasmEdge_ConfigureDelete(ConfCxt);
  21.   return 0;
  22. }

Then you can compile and run (the output file is fibonacci.wasm.so):

  1. $ gcc test_wasmedge_compiler.c -lwasmedge_c -o test_wasmedge_compiler
  2. $ ./test_wasmedge_compiler fibonacci.wasm fibonacci.wasm.so
  3. [2021-07-02 11:08:08.651] [info] compile start
  4. [2021-07-02 11:08:08.653] [info] verify start
  5. [2021-07-02 11:08:08.653] [info] optimize start
  6. [2021-07-02 11:08:08.670] [info] codegen start
  7. [2021-07-02 11:08:08.706] [info] compile done

The compiled-WASM file can be used as a WASM input for the WasmEdge runner. The following is the comparison of the interpreter mode and the AOT mode:

  1. $ time ./test_wasmedge fibonacci.wasm
  2. Get result: 5702887
  4. real 0m2.715s
  5. user 0m2.700s
  6. sys 0m0.008s
  8. $ time ./test_wasmedge fibonacci.wasm.so
  9. Get result: 5702887
  11. real 0m0.036s
  12. user 0m0.022s
  13. sys 0m0.011s