Correct stitching of Node.js practical code segment Buffer_node.js

For beginners Node.js Framework developers, may think that the buffer module is easier to learn, the importance is not so prominent. In fact, the buffer module in file I/O and network I/O application is very wide, its processing binary performance than ordinary string performance is much higher, the importance is important. Let's use a routine to show the reader the process of stitching using the Buf.concat () method.

This example ch04.buffer-concat.js the main code as follows:

/** 
 * ch04.buffer-concat.js * * 
console.info ("------  buffer concat vs String concat------"); 
Console.info (); 
/** 
 * Define variable 
 * @type {buffer} 
/var buf = new Buffer ("This is buffer concat test!"); 
var str = "This is String concat test!"; 
/** 
 * Start record time 
 * 
/Console.time ("Buffer concat test!"); 
var list = []; 
var len = 100000 * buf.length; 
for (var i=0; i<100000; i++) { 
  list.push (BUF); 
  Len + + buf.length; 
} 
/** 
 * Buffer Object stitching 
 / 
var s1 = buffer.concat (list, Len). toString (); 
Console.timeend ("Buffer concat test!"); 
Console.info (); 
Console.time ("string concat test!"); 
var list = []; 
for (var i=100000; i>=0; i--) { 
  list.push (str); 
} 
/** 
 * String Object stitching 
 * @type {string} 
 * 
/var s2 = list.join (""); 
Console.timeend ("string concat test!"); 
/** * End Record time * 
/Console.info (); 
Console.info ("------  Buffer concat vs String concat------");

"Code Analysis"

The 10th line of code defines a buffer object, the variable named buf, and initializes a string data ("Thisis Buffer concat test!" The 11th line of code defines a string variable, str, and initializes a string data ("Thisis string concat test!" From line 15th to line 26th, the Console.time () and Console.timeend () methods are used to complete a period of time interval records; the 16th to 21st line of code defines an array variable list[], The array variable is initialized with the BUF variable, and the 25th line of code in the list[] array is spliced back into a buffer object by the Buffer.concat (List,len) method, about Buffer.concat (List,len) The syntax for the method is described below:

Syntax:buffer.concat (List,[totallength])
Parameter Description:

List{array}: array type, buffer array, used to be connected
totallength:{Number} type, first parameter buffer the total size of the array object

The method returns a buffer object that holds the concatenation of all the buffer objects in the incoming buffer array, if the passed-in array has no content, or if the Totallength parameter is 0, it returns a zero-length buffer ; If there is only one item in the array, the first item is returned, and if there are more than one item in the array, a new instance of the buffer object is created; If the totallength argument is not supplied, the read is computed from the buffer array. However, an additional loop is added to compute the length, so providing a clear totallength parameter will make the Buffer.concat () method perform faster;

The results shown in the diagram show that the Buffer.concat (List,len) method for stitching is 48ms.

Buffer Object Splicing function

Note: The 2nd parameter of the BUFFER.CONCAT (list, [Totallength]) method is Totallength special, where the totallength is not the sum of the size of the buffer instance in the array.

The above is the second practical node.js Code section, I hope to help you learn.