[wasm] Add a JavaScript utility to make it easier to build WASM modules from JavaScript.

test/mjsunit/wasm/wasm-module-builder.js

Index: test/mjsunit/wasm/wasm-module-builder.js
diff --git a/test/mjsunit/wasm/wasm-module-builder.js b/test/mjsunit/wasm/wasm-module-builder.js
new file mode 100644
index 0000000000000000000000000000000000000000..0aae6d9eaec08a0dd636cc8c401a49929ba38706
--- /dev/null
+++ b/test/mjsunit/wasm/wasm-module-builder.js
@@ -0,0 +1,311 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function StringRef(string) {
+    this.pos = -1;
+    this.string = string;
+}
+
+function DataRef(data) {
+    this.pos = -1;
+    this.data = data;
+}
+
+function WasmFunctionBuilder(name, sig_index) {
+    this.name = name;
+    this.sig_index = sig_index;
+    this.exports = [];
+}
+
+WasmFunctionBuilder.prototype.exportAs = function(name) {
+    this.exports.push(name);
+    return this;
+}
+
+WasmFunctionBuilder.prototype.addBody = function(body) {
+    this.body = body;
+    return this;
+}
+
+WasmFunctionBuilder.prototype.addLocals = function(locals) {
+    this.locals = locals;
+    return this;
+}
+
+function WasmModuleBuilder() {
+    this.signatures = [];
+    this.imports = [];
+    this.functions = [];
+    this.exports = [];
+    this.function_table = [];
+    this.data_segments = [];
+    return this;
+}
+
+WasmModuleBuilder.prototype.addMemory = function(min, max, exp) {
+    this.memory = {min: min, max: max, exp: exp};
+    return this;
+}
+
+// Add a signature; format is [rettype, param0, param1, ...]
+WasmModuleBuilder.prototype.addSignature = function(sig) {
+    // TODO: canonicalize signatures?
+    this.signatures.push(sig);
+    return this.signatures.length - 1;
+}
+
+WasmModuleBuilder.prototype.addFunction = function(name, sig) {
+    var sig_index = (typeof sig) == "number" ? sig : this.addSignature(sig);
+    var func = new WasmFunctionBuilder(name, sig_index);
+    func.index = this.functions.length;
+    this.functions.push(func);
+    return func;
+}
+
+WasmModuleBuilder.prototype.addImport = function(name, sig) {
+    var sig_index = (typeof sig) == "number" ? sig : this.addSignature(sig);
+    this.imports.push({name: name, sig_index: sig_index});
+    return this.imports.length - 1;
+}
+
+WasmModuleBuilder.prototype.addDataSegment = function(addr, data, init) {
+    this.data_segments.push({addr: addr, data: data, init: init});
+    return this.data_segments.length - 1;
+}
+
+WasmModuleBuilder.prototype.appendToFunctionTable = function(array) {
+    this.function_table = this.function_table.concat(array);
+    return this;
+}
+
+function emit_u8(bytes, val) {
+    bytes.push(val & 0xff);
+}
+
+function emit_u16(bytes, val) {
+    bytes.push(val & 0xff);
+    bytes.push((val >> 8) & 0xff);
+}
+
+function emit_u32(bytes, val) {
+    bytes.push(val & 0xff);
+    bytes.push((val >> 8) & 0xff);
+    bytes.push((val >> 16) & 0xff);
+    bytes.push((val >> 24) & 0xff);
+}
+
+function emit_string(bytes, string) {
+    bytes.push(new StringRef(string));
+    bytes.push(0);
+    bytes.push(0);
+    bytes.push(0);
+}
+
+function emit_data_ref(bytes, string) {
+    bytes.push(new DataRef(string));
+    bytes.push(0);
+    bytes.push(0);
+    bytes.push(0);
+}
+
+function emit_varint(bytes, val) {
+    while (true) {
+        var v = val & 0xff;
+        val = val >>> 7;
+        if (val == 0) {
+            bytes.push(v);
+            break;
+        }
+        bytes.push(v | 0x80);
+    }
+}
+
+WasmModuleBuilder.prototype.toArray = function(debug) {
+    // Add header bytes
+    var bytes = [];
+    bytes = bytes.concat([kWasmH0, kWasmH1, kWasmH2, kWasmH3,
+                          kWasmV0, kWasmV1, kWasmV2, kWasmV3]);
+
+    // Add memory section
+    if (this.memory != undefined) {
+        if (debug) print("emitting memory @ " + bytes.length);
+        emit_u8(bytes, kDeclMemory);
+        emit_varint(bytes, this.memory.min);
+        emit_varint(bytes, this.memory.max);
+        emit_u8(bytes, this.memory.exp ? 1 : 0);
+    }
+
+    // Add signatures section
+    if (this.signatures.length > 0) {
+        if (debug) print("emitting signatures @ " + bytes.length);
+        emit_u8(bytes, kDeclSignatures);
+        emit_varint(bytes, this.signatures.length);
+        for (sig of this.signatures) {
+            var params = sig.length - 1;
+            emit_u8(bytes, params);
+            for (var j = 0; j < sig.length; j++) {
+                emit_u8(bytes, sig[j]);
+            }
+        }
+    }
+
+    // Add imports section
+    if (this.imports.length > 0) {
+        if (debug) print("emitting imports @ " + bytes.length);
+        emit_u8(bytes, kDeclImportTable);
+        emit_varint(bytes, this.imports.length);
+        for (imp of this.imports) {
+            emit_u16(bytes, imp.sig_index);
+            emit_string(bytes, "");
+            emit_string(bytes, imp.name);
+        }
+    }
+
+    // Add functions section
+    var names = false;
+    var exports = 0;
+    if (this.functions.length > 0) {
+        if (debug) print("emitting functions @ " + bytes.length);
+        emit_u8(bytes, kDeclFunctions);
+        emit_varint(bytes, this.functions.length);
+        var index = 0;
+        for (func of this.functions) {
+            var flags = 0;
+            var hasName = func.name != undefined && func.name.length > 0;
+            names = names || hasName;
+            if (hasName) flags |= kDeclFunctionName;
+            if (func.locals != undefined) flags |= kDeclFunctionLocals;
+            exports += func.exports.length;
+
+            emit_u8(bytes, flags);
+            emit_u16(bytes, func.sig_index);
+
+            if (hasName) {
+                emit_string(bytes, func.name);
+            }
+            if (func.locals != undefined) {
+                emit_u16(bytes, func.locals.i32_count);
+                emit_u16(bytes, func.locals.i64_count);
+                emit_u16(bytes, func.locals.f32_count);
+                emit_u16(bytes, func.locals.f64_count);
+            }
+            emit_u16(bytes, func.body.length);
+            for (var i = 0; i < func.body.length; i++) {
+                emit_u8(bytes, func.body[i]);
+            }
+
+            index++;
+        }
+    }
+
+    if (this.function_table.length > 0) {
+        if (debug) print("emitting function table @ " + bytes.length);
+        emit_u8(bytes, kDeclFunctionTable);
+        emit_varint(bytes, this.function_table.length);
+        for (index of this.function_table) {
+            emit_u16(bytes, index);
+        }
+    }
+
+    if (exports > 0) {
+        if (debug) print("emitting exports @ " + bytes.length);
+        emit_u8(bytes, kDeclExportTable);
+        emit_varint(bytes, exports);
+        for (func of this.functions) {
+            for (exp of func.exports) {
+                emit_u16(bytes, func.index);
+                emit_string(bytes, exp);
+            }
+        }
+    }
+
+    if (this.data_segments.length > 0) {
+        if (debug) print("emitting data segments @ " + bytes.length);
+        emit_u8(bytes, kDeclDataSegments);
+        emit_varint(bytes, this.data_segments.length);
+        for (seg of this.data_segments) {
+            emit_u32(bytes, seg.addr);
+            emit_data_ref(bytes, seg.data);
+            emit_u32(bytes, seg.data.length);
+            emit_u8(bytes, seg.init ? 1 : 0);
+        }
+    }
+
+    // End the module.
+    if (debug) print("emitting end @ " + bytes.length);
+    emit_u8(bytes, kDeclEnd);
+
+    // Collect references and canonicalize strings.
+    var strings = new Object();
+    var data_segments = [];
+    var count = 0;
+    for (var i = 0; i < bytes.length; i++) {
+        var b = bytes[i];
+        if (b instanceof StringRef) {
+            count++;
+            var prev = strings[b.string];
+            if (prev) {
+                bytes[i] = prev;
+            } else {
+                strings[b.string] = b;
+            }
+        }
+        if (b instanceof DataRef) {
+            data_segments.push(b);
+            count++;
+        }
+    }
+
+    if (count > 0) {
+        // Emit strings.
+        if (debug) print("emitting strings @ " + bytes.length);
+        for (str in strings) {
+            var ref = strings[str];
+            if (!(ref instanceof StringRef)) continue;
+            if (debug) print("  \"" + str + "\" @ " + bytes.length);
+            ref.pos = bytes.length;
+            for (var i = 0; i < str.length; i++) {
+                emit_u8(bytes, str.charCodeAt(i));
+            }
+            emit_u8(bytes, 0);  // null terminator.
+        }
+        // Emit data.
+        if (debug) print("emitting data @ " + bytes.length);
+        for (ref of data_segments) {
+            ref.pos = bytes.length;
+            for (var i = 0; i < ref.data.length; i++) {
+                emit_u8(bytes, ref.data[i]);
+            }
+        }
+        // Update references to strings and data.
+        for (var i = 0; i < bytes.length; i++) {
+            var b = bytes[i];
+            if (b instanceof StringRef || b instanceof DataRef) {
+                bytes[i] = b.pos & 0xFF;
+                bytes[i + 1] = (b.pos >> 8) & 0xFF;
+                bytes[i + 2] = (b.pos >> 16) & 0xFF;
+                bytes[i + 3] = (b.pos >> 24) & 0xFF;
+            }
+        }
+    }
+
+    return bytes;
+}
+
+WasmModuleBuilder.prototype.toBuffer = function(debug) {
+    var bytes = this.toArray(debug);
+    var buffer = new ArrayBuffer(bytes.length);
+    var view = new Uint8Array(buffer);
+    for (var i = 0; i < bytes.length; i++) {
+        var val = bytes[i];
+        if ((typeof val) == "string") val = val.charCodeAt(0);
+        view[i] = val | 0;
+    }
+    return buffer;
+}
+
+WasmModuleBuilder.prototype.instantiate = function(ffi) {
+    var buffer = this.toBuffer();
+    return _WASMEXP_.instantiateModule(buffer, ffi);
+}