// SQLite WASM example for mcp-v8
//
// This script is designed to run inside mcp-v8 with the SQLite WASM module
// pre-loaded via:
//
// mcp-v8 --stateless --wasm-module sqlite=examples/sqlite-wasm/sqlite3.wasm
//
// The compiled WebAssembly.Module is available as the global `__wasm_sqlite`.
// Because the module has WASI imports, it is NOT auto-instantiated — we
// provide the imports ourselves and instantiate it manually.
// ── WASI stubs ──────────────────────────────────────────────────────────
// SQLite compiled with Emscripten STANDALONE_WASM imports a handful of
// WASI functions. For an in-memory-only database none of these need real
// implementations — simple stubs are sufficient.
var wasiStubs = {
// fd_close(fd) -> errno
fd_close: function () { return 0; },
// fd_fdstat_get(fd, buf) -> errno
fd_fdstat_get: function () { return 0; },
// fd_seek(fd, offset_lo, offset_hi, whence, newoffset_ptr) -> errno
fd_seek: function () { return 0; },
// fd_write(fd, iovs, iovs_len, nwritten_ptr) -> errno
fd_write: function (fd, iovs, iovsLen, nwrittenPtr) {
// Silently discard output (used by sqlite3_log / fprintf)
var view = new DataView(memory.buffer);
var totalWritten = 0;
for (var i = 0; i < iovsLen; i++) {
var len = view.getUint32(iovs + i * 8 + 4, true);
totalWritten += len;
}
view.setUint32(nwrittenPtr, totalWritten, true);
return 0;
},
// fd_read(fd, iovs, iovs_len, nread_ptr) -> errno
fd_read: function () { return 0; },
// environ_get(environ, environ_buf) -> errno
environ_get: function () { return 0; },
// environ_sizes_get(count_ptr, buf_size_ptr) -> errno
environ_sizes_get: function (countPtr, bufSizePtr) {
var view = new DataView(memory.buffer);
view.setUint32(countPtr, 0, true);
view.setUint32(bufSizePtr, 0, true);
return 0;
},
// proc_exit(code) — should never be called
proc_exit: function () {},
// clock_time_get(id, precision, time_ptr) -> errno
clock_time_get: function (id, precLo, precHi, timePtr) {
var view = new DataView(memory.buffer);
view.setBigUint64(timePtr, BigInt(0), true);
return 0;
},
};
// ── Instantiate the WASM module ─────────────────────────────────────────
var memory; // will be set from the module's exported memory
// Build import object dynamically — enumerate the module's imports and
// provide stubs for anything not explicitly handled above. This makes
// the example resilient to different Emscripten versions which may add
// or remove WASI / env imports.
var knownImports = {
wasi_snapshot_preview1: wasiStubs,
env: {
emscripten_notify_memory_growth: function () {},
},
};
var moduleImports = WebAssembly.Module.imports(__wasm_sqlite);
var importObject = {};
for (var i = 0; i < moduleImports.length; i++) {
var imp = moduleImports[i];
if (!importObject[imp.module]) {
importObject[imp.module] = {};
}
// Use the known stub if available, otherwise provide a no-op.
var known = knownImports[imp.module];
if (known && known[imp.name] !== undefined) {
importObject[imp.module][imp.name] = known[imp.name];
} else if (imp.kind === "function") {
importObject[imp.module][imp.name] = function () { return 0; };
}
}
var instance = new WebAssembly.Instance(__wasm_sqlite, importObject);
var exports = instance.exports;
memory = exports.memory;
// ── Low-level helpers ───────────────────────────────────────────────────
// These translate between JS strings and WASM linear memory.
function encodeString(str) {
var bytes = [];
for (var i = 0; i < str.length; i++) {
var c = str.charCodeAt(i);
if (c < 0x80) {
bytes.push(c);
} else if (c < 0x800) {
bytes.push(0xc0 | (c >> 6));
bytes.push(0x80 | (c & 0x3f));
} else if (c >= 0xd800 && c <= 0xdbff) {
// surrogate pair
var hi = c;
var lo = str.charCodeAt(++i);
var cp = ((hi - 0xd800) << 10) + (lo - 0xdc00) + 0x10000;
bytes.push(0xf0 | (cp >> 18));
bytes.push(0x80 | ((cp >> 12) & 0x3f));
bytes.push(0x80 | ((cp >> 6) & 0x3f));
bytes.push(0x80 | (cp & 0x3f));
} else {
bytes.push(0xe0 | (c >> 12));
bytes.push(0x80 | ((c >> 6) & 0x3f));
bytes.push(0x80 | (c & 0x3f));
}
}
bytes.push(0); // null terminator
return bytes;
}
function allocString(str) {
var bytes = encodeString(str);
var ptr = exports.malloc(bytes.length);
if (ptr === 0) throw new Error("malloc failed");
var view = new Uint8Array(memory.buffer);
for (var j = 0; j < bytes.length; j++) view[ptr + j] = bytes[j];
return ptr;
}
function readCString(ptr) {
if (ptr === 0) return null;
var view = new Uint8Array(memory.buffer);
var end = ptr;
while (view[end] !== 0) end++;
var bytes = view.slice(ptr, end);
// Decode UTF-8
var result = "";
var i = 0;
while (i < bytes.length) {
var b = bytes[i];
if (b < 0x80) {
result += String.fromCharCode(b);
i++;
} else if (b < 0xe0) {
result += String.fromCharCode(((b & 0x1f) << 6) | (bytes[i + 1] & 0x3f));
i += 2;
} else if (b < 0xf0) {
result += String.fromCharCode(
((b & 0x0f) << 12) | ((bytes[i + 1] & 0x3f) << 6) | (bytes[i + 2] & 0x3f)
);
i += 3;
} else {
var cp =
((b & 0x07) << 18) |
((bytes[i + 1] & 0x3f) << 12) |
((bytes[i + 2] & 0x3f) << 6) |
(bytes[i + 3] & 0x3f);
cp -= 0x10000;
result += String.fromCharCode(0xd800 + (cp >> 10), 0xdc00 + (cp & 0x3ff));
i += 4;
}
}
return result;
}
// ── SQLite wrapper ──────────────────────────────────────────────────────
var SQLITE_OK = 0;
var SQLITE_ROW = 100;
var SQLITE_DONE = 101;
// Column type constants
var SQLITE_INTEGER = 1;
var SQLITE_FLOAT = 2;
var SQLITE_TEXT = 3;
var SQLITE_BLOB = 4;
var SQLITE_NULL = 5;
function SQLite() {
// Allocate a pointer-sized slot for sqlite3_open's output parameter
this._dbPtrPtr = exports.malloc(4);
var namePtr = allocString(":memory:");
var rc = exports.sqlite3_open(namePtr, this._dbPtrPtr);
exports.free(namePtr);
if (rc !== SQLITE_OK) {
throw new Error("sqlite3_open failed: " + rc);
}
var view = new DataView(memory.buffer);
this._db = view.getUint32(this._dbPtrPtr, true);
}
SQLite.prototype.errmsg = function () {
var ptr = exports.sqlite3_errmsg(this._db);
return readCString(ptr);
};
SQLite.prototype.exec = function (sql) {
var sqlPtr = allocString(sql);
var rc = exports.sqlite3_exec(this._db, sqlPtr, 0, 0, 0);
exports.free(sqlPtr);
if (rc !== SQLITE_OK) {
throw new Error("sqlite3_exec error (" + rc + "): " + this.errmsg());
}
};
SQLite.prototype.query = function (sql) {
var sqlPtr = allocString(sql);
var stmtPtrPtr = exports.malloc(4);
var rc = exports.sqlite3_prepare_v2(this._db, sqlPtr, -1, stmtPtrPtr, 0);
exports.free(sqlPtr);
if (rc !== SQLITE_OK) {
exports.free(stmtPtrPtr);
throw new Error("sqlite3_prepare_v2 error (" + rc + "): " + this.errmsg());
}
var view = new DataView(memory.buffer);
var stmt = view.getUint32(stmtPtrPtr, true);
exports.free(stmtPtrPtr);
var colCount = exports.sqlite3_column_count(stmt);
// Read column names
var columns = [];
for (var c = 0; c < colCount; c++) {
var namePtr = exports.sqlite3_column_name(stmt, c);
columns.push(readCString(namePtr));
}
// Read rows
var rows = [];
while (true) {
rc = exports.sqlite3_step(stmt);
if (rc === SQLITE_DONE) break;
if (rc !== SQLITE_ROW) {
exports.sqlite3_finalize(stmt);
throw new Error("sqlite3_step error (" + rc + "): " + this.errmsg());
}
var row = {};
for (var c = 0; c < colCount; c++) {
var colType = exports.sqlite3_column_type(stmt, c);
var name = columns[c];
if (colType === SQLITE_NULL) {
row[name] = null;
} else if (colType === SQLITE_INTEGER) {
row[name] = exports.sqlite3_column_int(stmt, c);
} else if (colType === SQLITE_FLOAT) {
row[name] = exports.sqlite3_column_double(stmt, c);
} else {
// TEXT or BLOB — read as string
var textPtr = exports.sqlite3_column_text(stmt, c);
row[name] = readCString(textPtr);
}
}
rows.push(row);
}
exports.sqlite3_finalize(stmt);
return { columns: columns, rows: rows };
};
SQLite.prototype.changes = function () {
return exports.sqlite3_changes(this._db);
};
SQLite.prototype.lastInsertRowId = function () {
return exports.sqlite3_last_insert_rowid(this._db);
};
SQLite.prototype.close = function () {
if (this._db) {
exports.sqlite3_close(this._db);
exports.free(this._dbPtrPtr);
this._db = 0;
}
};
// ── Demo ────────────────────────────────────────────────────────────────
var db = new SQLite();
// Create a table
db.exec("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, email TEXT, age INTEGER)");
// Insert data
db.exec("INSERT INTO users (name, email, age) VALUES ('Alice', 'alice@example.com', 30)");
db.exec("INSERT INTO users (name, email, age) VALUES ('Bob', 'bob@example.com', 25)");
db.exec("INSERT INTO users (name, email, age) VALUES ('Charlie', 'charlie@example.com', 35)");
// Query data
var result = db.query("SELECT * FROM users ORDER BY age");
// Aggregate query
var stats = db.query("SELECT COUNT(*) as count, AVG(age) as avg_age FROM users");
db.close();
JSON.stringify({ users: result.rows, stats: stats.rows[0] });
