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/*
Example of instantiating of the WebAssembly module and invoking its exported
function.
You can compile and run this example on Linux with:
cargo build --release -p wasmtime-c-api
cc examples/multi.c \
-I crates/c-api/include \
target/release/libwasmtime.a \
-lpthread -ldl -lm \
-o multi
./multi
Note that on Windows and macOS the command will be similar, but you'll need
to tweak the `-lpthread` and such annotations.
You can also build using cmake:
mkdir build && cd build && cmake .. && cmake --build . --target wasmtime-multi
Also note that this example was taken from
https://github.com/WebAssembly/wasm-c-api/blob/master/example/multi.c
originally
*/
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wasm.h>
#include <wasmtime.h>
static void exit_with_error(const char *message, wasmtime_error_t *error,
wasm_trap_t *trap);
// A function to be called from Wasm code.
wasm_trap_t *callback(void *env, wasmtime_caller_t *caller,
const wasmtime_val_t *args, size_t nargs,
wasmtime_val_t *results, size_t nresults) {
printf("Calling back...\n");
printf("> %" PRIu32 " %" PRIu64 "\n", args[0].of.i32, args[1].of.i64);
printf("\n");
results[0] = args[1];
results[1] = args[0];
return NULL;
}
// A function closure.
wasm_trap_t *closure_callback(void *env, wasmtime_caller_t *caller,
const wasmtime_val_t *args, size_t nargs,
wasmtime_val_t *results, size_t nresults) {
int i = *(int *)env;
printf("Calling back closure...\n");
printf("> %d\n", i);
results[0].kind = WASMTIME_I32;
results[0].of.i32 = (int32_t)i;
return NULL;
}
int main(int argc, const char *argv[]) {
// Initialize.
printf("Initializing...\n");
wasm_engine_t *engine = wasm_engine_new();
wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
wasmtime_context_t *context = wasmtime_store_context(store);
// Load our input file to parse it next
FILE *file = fopen("examples/multi.wat", "r");
if (!file) {
printf("> Error loading file!\n");
return 1;
}
fseek(file, 0L, SEEK_END);
size_t file_size = ftell(file);
fseek(file, 0L, SEEK_SET);
wasm_byte_vec_t wat;
wasm_byte_vec_new_uninitialized(&wat, file_size);
if (fread(wat.data, file_size, 1, file) != 1) {
printf("> Error loading module!\n");
return 1;
}
fclose(file);
// Parse the wat into the binary wasm format
wasm_byte_vec_t binary;
wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &binary);
if (error != NULL)
exit_with_error("failed to parse wat", error, NULL);
wasm_byte_vec_delete(&wat);
// Compile.
printf("Compiling module...\n");
wasmtime_module_t *module = NULL;
error =
wasmtime_module_new(engine, (uint8_t *)binary.data, binary.size, &module);
if (error)
exit_with_error("failed to compile module", error, NULL);
wasm_byte_vec_delete(&binary);
// Create external print functions.
printf("Creating callback...\n");
wasm_functype_t *callback_type =
wasm_functype_new_2_2(wasm_valtype_new_i32(), wasm_valtype_new_i64(),
wasm_valtype_new_i64(), wasm_valtype_new_i32());
wasmtime_func_t callback_func;
wasmtime_func_new(context, callback_type, callback, NULL, NULL,
&callback_func);
wasm_functype_delete(callback_type);
// Instantiate.
printf("Instantiating module...\n");
wasmtime_extern_t imports[1];
imports[0].kind = WASMTIME_EXTERN_FUNC;
imports[0].of.func = callback_func;
wasmtime_instance_t instance;
wasm_trap_t *trap = NULL;
error = wasmtime_instance_new(context, module, imports, 1, &instance, &trap);
if (error != NULL || trap != NULL)
exit_with_error("failed to instantiate", error, trap);
wasmtime_module_delete(module);
// Extract export.
printf("Extracting export...\n");
wasmtime_extern_t run;
bool ok = wasmtime_instance_export_get(context, &instance, "g", 1, &run);
assert(ok);
assert(run.kind == WASMTIME_EXTERN_FUNC);
// Call.
printf("Calling export...\n");
wasmtime_val_t args[2];
args[0].kind = WASMTIME_I32;
args[0].of.i32 = 1;
args[1].kind = WASMTIME_I64;
args[1].of.i64 = 2;
wasmtime_val_t results[2];
error = wasmtime_func_call(context, &run.of.func, args, 2, results, 2, &trap);
if (error != NULL || trap != NULL)
exit_with_error("failed to call run", error, trap);
// Print result.
printf("Printing result...\n");
printf("> %" PRIu64 " %" PRIu32 "\n", results[0].of.i64, results[1].of.i32);
assert(results[0].kind == WASMTIME_I64);
assert(results[0].of.i64 == 2);
assert(results[1].kind == WASMTIME_I32);
assert(results[1].of.i32 == 1);
// Shut down.
printf("Shutting down...\n");
wasmtime_store_delete(store);
wasm_engine_delete(engine);
// All done.
printf("Done.\n");
return 0;
}
static void exit_with_error(const char *message, wasmtime_error_t *error,
wasm_trap_t *trap) {
fprintf(stderr, "error: %s\n", message);
wasm_byte_vec_t error_message;
if (error != NULL) {
wasmtime_error_message(error, &error_message);
wasmtime_error_delete(error);
} else {
wasm_trap_message(trap, &error_message);
wasm_trap_delete(trap);
}
fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
wasm_byte_vec_delete(&error_message);
exit(1);
}
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