v8/test/mjsunit/wasm/wasm-module-builder.js

// 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.exportFunc = function() {
  this.exports.push(this.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 = [];
    this.explicit = [];
    return this;
}

WasmModuleBuilder.prototype.addStart = function(start_index) {
    this.start_index = start_index;
}

WasmModuleBuilder.prototype.addMemory = function(min, max, exp) {
    this.memory = {min: min, max: max, exp: exp};
    return this;
}

WasmModuleBuilder.prototype.addExplicitSection = function(bytes) {
  this.explicit.push(bytes);
  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.addImportWithModule = function(module, name, sig) {
  var sig_index = (typeof sig) == "number" ? sig : this.addSignature(sig);
  this.imports.push({module: module, name: name, sig_index: sig_index});
  return this.imports.length - 1;
}

WasmModuleBuilder.prototype.addImport = function(name, sig) {
  var sig_index = (typeof sig) == "number" ? sig : this.addSignature(sig);
  this.imports.push({module: name, name: undefined, 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_varint(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_varint(bytes, imp.sig_index);
            emit_string(bytes, imp.module);
            if (imp.name == undefined) {
              emit_u32(bytes, 0);
            } else {
              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;
            exports += func.exports.length;

            emit_u8(bytes, flags);
            emit_u16(bytes, func.sig_index);

            if (hasName) emit_string(bytes, func.name);

            // Function body length will be patched later.
            var length_pos = bytes.length;
            emit_u16(bytes, 0);

            var local_decls = [];
            var l = func.locals;
            if (l != undefined) {
              var local_decls_count = 0;
              if (l.i32_count > 0) {
                local_decls.push({count: l.i32_count, type: kAstI32});
              }
              if (l.i64_count > 0) {
                local_decls.push({count: l.i64_count, type: kAstI64});
              }
              if (l.f32_count > 0) {
                local_decls.push({count: l.f32_count, type: kAstF32});
              }
              if (l.f64_count > 0) {
                local_decls.push({count: l.f64_count, type: kAstF64});
              }
            }
            emit_varint(bytes, local_decls.length);
            for (decl of local_decls) {
              emit_varint(bytes, decl.count);
              emit_u8(bytes, decl.type);
            }

            for (var i = 0; i < func.body.length; i++) {
                emit_u8(bytes, func.body[i]);
            }
            var length = bytes.length - length_pos - 2;
            bytes[length_pos] = length & 0xff;
            bytes[length_pos + 1] = (length >> 8) & 0xff;

            index++;
        }
    }

    // Add start function section.
    if (this.start_index != undefined) {
        if (debug) print("emitting start function @ " + bytes.length);
      emit_u8(bytes, kDeclStartFunction);
      emit_varint(bytes, this.start_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_varint(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_varint(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);
        }
    }

    // Emit any explicitly added sections
    for (exp of this.explicit) {
        if (debug) print("emitting explicit @ " + bytes.length);
        for (var i = 0; i < exp.length; i++) {
            emit_u8(bytes, exp[i]);
        }
    }

    // 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, memory) {
    var buffer = this.toBuffer();
    if (memory != undefined) {
      return Wasm.instantiateModule(buffer, ffi, memory);
    } else {
      return Wasm.instantiateModule(buffer, ffi);
    }
}