[nodejs]Buffer vs String

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\n
Host: foo.example.com\r\n
Content-Length: 5\r\n
Connection:keep-alive\r\n
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n
Cookie:connect.sid=OY2nKGqI3obs5lYee0JKTjhf.FDtbY1Jz5Ngw5So9Jv3MUetI5ITvrIfwgCkRw%2FcXUCk\r\n
User-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\n
q=bar

需求

获取Header中Host的值

Buffer版本

var SPACE = 0x20, // ' '
  COLON = 0x3a, // 58, :
  NEWLINE = 0x0a, // \n
  ENTER = 0x0d; // \r

exports.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.js
buffer_parse take: 1888 ms
string_parse take: 4948 ms

结论

Buffer比String快多了。