bool ParseProgram(ParseInfo* info, Isolate* isolate) {// .../*** 生成一个Parser实例* 调用内部方法启动转换*/Parser parser(info);FunctionLiteral* result = nullptr;/*** 转换AST后将结果赋值给ParseInfo的literal_*/result = parser.ParseProgram(isolate, info);info->set_literal(result);// ...return (result != nullptr);
}

FunctionLiteral* Parser::ParseProgram(Isolate* isolate, ParseInfo* info) {// .../*** scanner_为Parser类的一个私有属性* 这里仅仅进行初始化*/scanner_.Initialize();FunctionLiteral* result = DoParseProgram(isolate, info);// ...return result;
}

bool ParseProgram(ParseInfo* info, Isolate* isolate) {// .../*** 1、info->script()返回的是字符串的描述信息 source是Local<String>类型的源字符串* 2、ScannerStream是scanner-character-streams头文件的类 内部方法均为静态类型 可以直接调用* 3、返回的具体类型根据String类型不同而不同 但是由于均继承于Utf16CharacterStream 所以直接用父类接*/Handle<String> source(String::cast(info->script()->source()), isolate);std::unique_ptr<Utf16CharacterStream> stream(ScannerStream::For(isolate, source));info->set_character_stream(std::move(stream));// ...
}/*** 有四种特殊的String类型 分别new不同的子类* ScannerStream::For(isolate, data, 0, data->length());*/
Utf16CharacterStream* ScannerStream::For(Isolate* isolate, Handle<String> data, int start_pos, int end_pos) {size_t start_offset = 0;// ...if (data->IsSeqOneByteString()) {return new BufferedCharacterStream<OnHeapStream>(static_cast<size_t>(start_pos), Handle<SeqOneByteString>::cast(data),start_offset, static_cast<size_t>(end_pos));}
}

/*** Scanner类* 跟Utf16CharacterStream一个文件*/
class V8_EXPORT_PRIVATE Scanner {public:// 返回next_的token类型Token::Value peek() const { return next().token; }// 返回current_的位置信息const Location& location() const { return current().location; }private:// 当前字符的Unicode编码 -1表示结尾(typedef int32_t uc32)
    uc32 c0_;TokenDesc* current_;    // desc for current token (as returned by Next())TokenDesc* next_;       // desc for next token (one token look-ahead)TokenDesc* next_next_;  // desc for the token after next (after PeakAhead())// 从Handle<String>转换后的类型 负责执行解析的实际类Utf16CharacterStream* const source_;
}

/*** 词法结构体* 每一个TokenDesc代表单独一段词法*/
struct TokenDesc {/*** 词法所在位置* 该结构体比较简单 就不展开了 两个值代表起始、结束位置* 例如sample中 "'Hello' + ' World'" 'Hello'会被解析为TOKEN::STRING location为{0, 7}*/Location location = {0, 0};/*** 字符串词法相关*/LiteralBuffer literal_chars;LiteralBuffer raw_literal_chars;/*** 词法的枚举类型* 例如 '(' 是 TOKEN::LPAREN '===' 是 TOKEN::EQ_STRICT* 所有类型可见token.h*/Token::Value token = Token::UNINITIALIZED;MessageTemplate invalid_template_escape_message = MessageTemplate::kNone;Location invalid_template_escape_location;// 小整数uint32_t smi_value_ = 0;bool after_line_terminator = false;
}