拼接buffer

buffer.js

var chunks = [];  
var size = 0;  
res.on('data', function (chunk) {  
  chunks.push(chunk);  
  size += chunk.length;  
});  
res.on('end', function () {  
  var data = null;  
  switch(chunks.length) {  
    case 0: data = new Buffer(0);  
      break;  
    case 1: data = chunks[0];  
      break;  
    default:  
      data = new Buffer(size);  
      for (var i = 0, pos = 0, l = chunks.length; i < l; i++) {  
        var chunk = chunks[i];  
        chunk.copy(data, pos);  
        pos += chunk.length;  
      }  
      break;  
  }  
});