wasm.c

#include <stdio.h>
#include <stdlib.h>
#include <wasmtime/error.h>

#include "sqlite3.h"
#include "wasm.h"
#include "wasmtime.h"

const char fib_source[] =
"(module"
" (export \"fib\" (func $fib))"
" (func $fib (param $n i32) (result i32)"
"  (if"
"   (i32.lt_s"
"    (get_local $n)"
"    (i32.const 2)"
"   )"
"   (return"
"    (i32.const 1)"
"   )"
"  )"
"  (return"
"   (i32.add"
"    (call $fib"
"     (i32.sub"
"      (get_local $n)"
"      (i32.const 2)"
"     )"
"    )"
"    (call $fib"
"     (i32.sub"
"      (get_local $n)"
"      (i32.const 1)"
"     )"
"    )"
"   )"
"  )"
" )"
")";

static void fib_but_wasm(sqlite3_context *context, int argc, sqlite3_value **argv) {
 wasm_engine_t *engine = wasm_engine_new();
 wasmtime_store_t *store = wasmtime_store_new(engine, NULL, NULL);
 wasmtime_context_t *wasm_ctx = wasmtime_store_context(store);

 wasm_byte_vec_t wasm;
 wasmtime_error_t *error = wasmtime_wat2wasm(fib_source, sizeof(fib_source) - 1, &wasm);
 if (error) {
  wasm_name_t message;
  wasmtime_error_message(error, &message);
  fprintf(stderr, "msg\n");
  fprintf(stderr, "%s\n", message.data);
  wasm_byte_vec_delete(&message);
  abort();
 }

 // Compile & instantiate the module (should be done once)
 wasmtime_module_t *module = NULL;
 wasmtime_module_new(engine, (uint8_t*) wasm.data, wasm.size, &module);
 wasm_byte_vec_delete(&wasm);

 wasm_trap_t *trap = NULL;
 wasmtime_instance_t instance;
 error = wasmtime_instance_new(wasm_ctx, module, NULL, 0, &instance, &trap);

 // Lookup our `fib` export function
 wasmtime_extern_t fib;
 bool ok = wasmtime_instance_export_get(wasm_ctx, &instance, "fib", 3, &fib);
 assert(ok);
 assert(fib.kind == WASMTIME_EXTERN_FUNC);

 // Call it
 wasmtime_val_t params[1];
 params[0].kind = WASMTIME_I32;
 params[0].of.i32 = sqlite3_value_int(argv[0]);;
 wasmtime_val_t results[1];
 error = wasmtime_func_call(wasm_ctx, &fib.of.func, params, 1, results, 1, &trap);
 assert(results[0].kind == WASMTIME_I32);

 sqlite3_result_int(context, results[0].of.i32);
}

int main(void) {
 sqlite3 *db;
 sqlite3_stmt *stmt;
 
 sqlite3_open("/tmp/srn.db", &db);

 if (!db) {
  printf("Failed to open DB\n");
  return 1;
 }

    sqlite3_create_function(db, "fib_but_wasm", 1, SQLITE_UTF8, NULL, &fib_but_wasm, NULL, NULL);

 sqlite3_prepare_v2(db, "select id, fib_but_wasm(id) from t", -1, &stmt, NULL);
 
 printf("Results:\n");
 while (sqlite3_step(stmt) != SQLITE_DONE) {
  assert(sqlite3_column_count(stmt) == 2);
  assert(sqlite3_column_type(stmt, 0) == SQLITE_INTEGER);
  assert(sqlite3_column_type(stmt, 1) == SQLITE_INTEGER);
  printf("\tfib(%d) = %d\n", sqlite3_column_int(stmt, 0), sqlite3_column_int(stmt, 1));
 }
 sqlite3_finalize(stmt);
 sqlite3_close(db);

 return 0;
}