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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/gcd.c \
-I crates/c-api/include \
target/release/libwasmtime.a \
-lpthread -ldl -lm \
-o gcd
./gcd
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-gcd
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <wasm.h>
#include <wasmtime.h>
static void exit_with_error(const char *message, wasmtime_error_t *error,
wasm_trap_t *trap);
int main() {
int ret = 0;
// Set up our context
wasm_engine_t *engine = wasm_engine_new();
assert(engine != NULL);
wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
assert(store != NULL);
wasmtime_context_t *context = wasmtime_store_context(store);
// Load our input file to parse it next
FILE *file = fopen("examples/gcd.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 wasm;
wasmtime_error_t *error = wasmtime_wat2wasm(wat.data, wat.size, &wasm);
if (error != NULL)
exit_with_error("failed to parse wat", error, NULL);
wasm_byte_vec_delete(&wat);
// Compile and instantiate our module
wasmtime_module_t *module = NULL;
error = wasmtime_module_new(engine, (uint8_t *)wasm.data, wasm.size, &module);
if (module == NULL)
exit_with_error("failed to compile module", error, NULL);
wasm_byte_vec_delete(&wasm);
wasm_trap_t *trap = NULL;
wasmtime_instance_t instance;
error = wasmtime_instance_new(context, module, NULL, 0, &instance, &trap);
if (error != NULL || trap != NULL)
exit_with_error("failed to instantiate", error, trap);
// Lookup our `gcd` export function
wasmtime_extern_t gcd;
bool ok = wasmtime_instance_export_get(context, &instance, "gcd", 3, &gcd);
assert(ok);
assert(gcd.kind == WASMTIME_EXTERN_FUNC);
// And call it!
int a = 6;
int b = 27;
wasmtime_val_t params[2];
params[0].kind = WASMTIME_I32;
params[0].of.i32 = a;
params[1].kind = WASMTIME_I32;
params[1].of.i32 = b;
wasmtime_val_t results[1];
error =
wasmtime_func_call(context, &gcd.of.func, params, 2, results, 1, &trap);
if (error != NULL || trap != NULL)
exit_with_error("failed to call gcd", error, trap);
assert(results[0].kind == WASMTIME_I32);
printf("gcd(%d, %d) = %d\n", a, b, results[0].of.i32);
// Clean up after ourselves at this point
ret = 0;
wasmtime_module_delete(module);
wasmtime_store_delete(store);
wasm_engine_delete(engine);
return ret;
}
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);
} else {
wasm_trap_message(trap, &error_message);
}
fprintf(stderr, "%.*s\n", (int)error_message.size, error_message.data);
wasm_byte_vec_delete(&error_message);
exit(1);
}
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