This article will give you an in-depth understanding of Buffer (buffer) in Node.js. It will introduce various ways to create the Buffer class, methods of writing to the buffer, etc. I hope it will be useful to everyone. Helped!
#The JavaScript language itself only has string data types, not binary data types.
But when processing streams like TCP or file streams, binary data must be used. Therefore, in Node.js, a Buffer class is defined, which is used to create a buffer area specifically for storing binary data.
In Node.js, the Buffer class is a core library released with the Node kernel. The Buffer library brings a method of storing raw data to Node.js, allowing Node.js to process binary data. Whenever you need to process data moved during I/O operations in Node.js, it is possible to use the Buffer library .
The original data is stored in an instance of the Buffer class.
A Buffer is similar to an integer array, but it corresponds to a piece of original memory outside the V8 heap memory.
The Node Buffer class can be created in a variety of ways.
Method 1
Create a Buffer instance with a length of 10 bytes:
var buf = new Buffer(10);
Method 2
Create a Buffer instance from the given array:
var buf = new Buffer([10, 20, 30, 40, 50]);
Method 3
Create a Buffer instance from a string:
var buf = new Buffer("bianchengsanmei", "utf-8");utf-8 is the default encoding, and it also supports the following encodings: "ascii", "utf8", "utf16le", "ucs2", "base64" and "hex".
Syntax
The syntax for writing Node buffer is as follows:
buf.write(string[, offset[, length]][, encoding])
Parameters
The parameters are described as follows:
Return value
Returns the actual written size. If there is insufficient buffer space, only part of the string will be written.
Example
buf = new Buffer(256);
len = buf.write("bi");
len = buf.write("bianchengsanmei");
console.log("写入字节数 : "+ len);Execute the above code, the output result is:
$node main.js 写入字节数 : 15
Syntax
The syntax for reading Node buffer data is as follows:
buf.toString([encoding[,start[,end]]])
Parameters
The parameters are described as follows:
encoding - the encoding to use. Defaults to 'utf8' .
start - Specifies the index position to start reading, default is 0.
end - End position, defaults to the end of the buffer.
Return Value
Decode the buffer data and return a string using the specified encoding.
Example
buf = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf[i] = i + 97;
}
console.log( buf.toString('ascii')); // 输出: abcdefghijklmnopqrstuvwxyz
console.log( buf.toString('ascii',0,5)); // 输出: abcde
console.log( buf.toString('utf8',0,5)); // 输出: abcde
console.log( buf.toString(undefined,0,5)); // 使用 'utf8' 编码, 并输出: abcdeExecute the above code, the output result is:
$ node main.js abcdefghijklmnopqrstuvwxyz abcde abcde abcde
Syntax
The function syntax format for converting Node Buffer to JSON object is as follows:
buf.toJSON()
Return value
Returns JSON object.
Example
var buf = new Buffer('bianchengsanmei'); var json = buf.toJSON(buf); console.log(json);
Execute the above code, the output result is:
{
type: 'Buffer',
data: [
98, 105, 97, 110, 99, 104, 101, 110, 103, 115, 97, 110, 109, 101, 105
]
}Syntax
The syntax of Node buffer merging is as follows:
Buffer.concat(list[, totalLength])
Parameters
The parameters are described as follows:
Return value
Returns a new Buffer object that combines multiple members.
Example
var buffer1 = new Buffer('编程三昧 ');
var buffer2 = new Buffer('bi');
var buffer2 = new Buffer('bianchengsanmei');
var buffer3 = Buffer.concat([buffer1,buffer2]);
console.log("buffer3 内容: " + buffer3.toString());Execute the above code, the output result is:
buffer3 内容: 编程三昧 bianchengsanmei
Syntax
The function syntax of Node Buffer comparison is as follows. This method was introduced in Node.js v0.12.2 version:
buf.compare(otherBuffer);
Parameters
Parameters The description is as follows:
Return Value
Returns a number indicating that buf is before, after, or the same as otherBuffer.
Example
var buffer1 = new Buffer('ABC');
var buffer2 = new Buffer('ABCD');
var result = buffer1.compare(buffer2);
if(result < 0) {
console.log(buffer1 + " 在 " + buffer2 + "之前");
}else if(result == 0){
console.log(buffer1 + " 与 " + buffer2 + "相同");
}else {
console.log(buffer1 + " 在 " + buffer2 + "之后");
}Execute the above code, the output result is:
ABC在ABCD之前
Syntax
Node buffer copy syntax is as follows:
buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])
Parameters
The parameters are described as follows:
Return value
No return value.
Example
var buffer1 = new Buffer('ABC');
// 拷贝一个缓冲区
var buffer2 = new Buffer(3);
buffer1.copy(buffer2);
console.log("buffer2 content: " + buffer2.toString());Execute the above code, the output result is:
buffer2 content: ABC
Node 缓冲区裁剪语法如下所示：
buf.slice([start[, end]])
参数
参数描述如下：
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。
实例
var buffer1 = new Buffer('youj');
// 剪切缓冲区
var buffer2 = buffer1.slice(0,2);
console.log("buffer2 content: " + buffer2.toString());执行以上代码，输出结果为：
buffer2 content: yo
语法 Node 缓冲区长度计算语法如下所示：
buf.length;
返回值
返回 Buffer 对象所占据的内存长度。
实例
var buffer = new Buffer('bianchengsanmei');
// 缓冲区长度
console.log("buffer length: " + buffer.length);执行以上代码，输出结果为：
buffer length: 15
~
~本文完，感谢阅读！
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