Node.js Buffer applies what you learn

Learning points:

Write to buffer

Read data from buffer

Convert Buffer to JSON object

Merge buffers

Copy buffer

Buffer clipping

Buffer length

Node.js Buffer (buffer)

This class is used Create a buffer area specifically to store binary data

Create the Buffer class

Create a Buffer instance with a length of 10 bytes

[code]var buffer = new Buffer(10);

Create a Buffer instance from the given array

[code]var buffer = new Buffer([10, 20, 30, 40]);

Create a Buffer instance through a string

[code]var buffer = new Buffer('光明大神棍的博客', 'utf-8');

Write to the buffer

[code]buffer.write(string[, offset, length, encoding])
参数
    string   必填 要输入缓冲区的字符串
    offset   可选 缓冲区开始写入的索引值，默认为 0 
    length   可选 写入的字节数，默认为 buffer.length
    encoding 可选 使用的编码。默认为 'utf8' 
返回值：
    实际写入的大小。如果 buffer 空间不足， 则只会写入部分字符串

Case: buffer.js

[code]var buffer = new Buffer(100);
var len = buffer.write('http://www.lamport.me/club');
console.log('事件输入的字符：' + len);

Read data from buffer

[code]buffer.toString([ending, start, end])
参数
    encoding - 使用的编码。默认为 'utf8' 。
    start - 指定开始读取的索引位置，默认为 0。
    end - 结束位置，默认为缓冲区的末尾。
返回值
    解码缓冲区数据并以指定编码返回字符串

Case: buffer2.js

[code]var buffer = new Buffer(26);
for (var i = 0; i < 26; i++) {
    buffer[i] = i + 97;
}
console.log(buffer.toString(&#39;ascii&#39;));
console.log(buffer.toString(&#39;ascii&#39;, 0, 4));
console.log(buffer.toString(&#39;utf8&#39;, 0, 4));
console.log(buffer.toString(undefined, 0, 4));

Convert Buffer to JSON object

toJSON(buffer)

Case: buffer3.js

[code]var buffer = new Buffer('http://www.lamport.me/club');
var data =buffer.toJSON(buffer);
console.log(data);

Merge buffer

[code]Buffer.concat(list[, totalLength])
参数
    list - 用于合并的 Buffer 对象数组列表。
    totalLength - 指定合并后Buffer对象的总长度。

Case: buffer4.js

[code]var bf1 = new Buffer("Hello ");
var bf2 = new Buffer("World");
var bf3 = Buffer.concat([bf1, bf2]);
console.log(bf3.toString());

##Copy buffer

[code]buf.copy(targetBuffer[, targetStart[, sourceStart[, sourceEnd]]])
参数
    targetBuffer - 要拷贝的 Buffer 对象。
    targetStart - 数字, 可选, 默认: 0
    sourceStart - 数字, 可选, 默认: 0
    sourceEnd - 数字, 可选, 默认: buffer.length
返回值
    没有返回值。

Case: buffer5.js

[code]var buffer1 = new Buffer('ABC');
var buffer2 = new Buffer(3);
buffer1.copy(buffer2);
console.log(buffer2.toString());

Buffer clipping

[code]buf.slice([start[, end]])
参数
    start - 数字, 可选, 默认: 0
    end - 数字, 可选, 默认: buffer.length
返回值
    返回一个新的缓冲区，它和旧缓冲区指向同一块内存，但是从索引 start 到 end 的位置剪切。

Example: buffer6.js

[code]var buffer = new Buffer("ABCD");
var buffer2 = buffer.slice(0, 2);
console.log(buffer2.toString());

Buffer length

[code]buf.length;
返回值
    返回 Buffer 对象所占据的内存长度。

Example:buffer7.js

[code]var buffer = new Buffer("abcd");
console.log(buffer.length);

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