疑问
按nodejs官方的文档说明，使用Buffer操作字节流通常会比转化成String要高效。
实际情况全都是这样的吗？本文通过一个简单的解析HTTP Request Header实例来解开此疑问。HTTP Request Header Demo
POST /foo HTTP/1.1\r\nHost: foo.example.com\r\nContent-Length: 5\r\nConnection:keep-alive\r\nAccept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\nCookie:connect.sid=OY2nKGqI3obs5lYee0JKTjhf.FDtbY1Jz5Ngw5So9Jv3MUetI5ITvrIfwgCkRw%2FcXUCk\r\nUser-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.41 Safari/535.7\r\n\r\nq=bar
需求
获取Header中Host的值
Buffer版本
var SPACE = 0x20, // ' ' COLON = 0x3a, // 58, : NEWLINE = 0x0a, // \n ENTER = 0x0d; // \rexports.parse = function parse(data) { var line_start = 0, len = data.length; for(var i = 0 ; i < len; i++) { // Host: xxx.abc.com if(data[i] === COLON) { var key = data.toString('ascii', line_start, i).toLowerCase(); i++; // skip ':' if(key === 'host') { var value_start = i; while(i < len) { if(data[i] === ENTER) { return data.toString('ascii', value_start, i).trim().toLowerCase(); } i++; } } } else if(data[i] === ENTER && data[i+1] === NEWLINE) { i += 2; line_start = i; if(data[i] === ENTER && data[i+1] === NEWLINE) { // \r\n\r\n return 'Host header not found'; } } } return null;}; String版本
exports.parse = function parse(data) { var lines = data.toString('ascii').split("\n"); var cut, name, host; for (var i = 0, len = lines.length; i < len; i++) { cut = lines[i].split(':'); name = cut[0]; if (name === 'Host') { if (cut[1] === undefined) { return 'Host header not found'; } host = cut[1].trim().toLowerCase(); return host; } } return null;}; 测试脚本
var buffer_parse = require('./string-buffer-benchmark-parse-header-buffer').parse , string_parse = require('./string-buffer-benchmark-parse-header-string').parse;var data = new Buffer('POST /foo HTTP/1.1\r\nHost: foo.example.com\r\nContent-Length: 5\r\nConnection:keep-alive\r\nAccept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\nCookie:connect.sid=OY2nKGqI3obs5lYee0JKTjhf.FDtbY1Jz5Ngw5So9Jv3MUetI5ITvrIfwgCkRw%2FcXUCk\r\nUser-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.41 Safari/535.7\r\n\r\nq=bar');//console.log(buffer_parse(data));//console.log(string_parse(data), data.length);var n = 1000000;var start = new Date();for(var i = 0; i < n; i++) { buffer_parse(data);}console.log('buffer_parse take: ' + (new Date() - start) + ' ms');start = new Date();for(var i = 0; i < n; i++) { string_parse(data);}console.log('string_parse take: ' + (new Date() - start) + ' ms'); 测试结果
$ node string-buffer-benchmark.jsbuffer_parse take: 1888 msstring_parse take: 4948 ms
结论
Buffer比String快多了。