This article describes the usage of buffer buffers in the basic nodejs. Share it for your reference, as follows:
JavaScript Language itselfOnly string data types, no binary data types. However, when processing streams like TCP or file streams, binary data must be used. Therefore, in , a Buffer class is defined, which is used to create a cache area that specifically stores binary data. In , the Buffer class is a core library released with the Node kernel. The Buffer library brings a way to store raw data, allowing the processing of binary data whenever it needs to be inWhen processing data moved during I/O operations, it is possible to use the Buffer library. The raw data is stored in an instance of the Buffer class. A Buffer is similar to an array of integers, but it corresponds to a piece of raw memory outside of V8 heap memory.
Create a buffer class
1. Create a buffer instance with a specified byte length
var buffer = new Buffer(10); //Create a buffer instance with a length of 10 bytes
2. Create a buffer instance through an array
var buffer = new Buffer([10,20,30,40,50]);
3. Create a buffer instance through a string
var buffer = new Buffer('','utf-8');
//utf-8 is the default encoding method. In addition, the following encodings can be specified: "ascii", "utf8", "utf16le", "ucs2", "base64" and "hex"
Buffer length
grammar:
;
Return value:
Returns the length of memory occupied by the Buffer object.
Example:
var buffer = new Buffer('');
// Buffer length("buffer length: " + ); //buffer length: 14
Write to the buffer
grammar:
(string[, offset][, length][, encoding])
parameter:
- string: A string written to the buffer.
- offset: The index value that the buffer starts to write, defaults to 0.
-
length: The number of bytes written, default is
-
encoding: The encoding used. Default is '
utf8' 。
Return value:
Returns the actual size (number type). If the buffer space is insufficient, only part of the string will be written.
Example:
buf = new Buffer(256);
len = ("");
("Written bytes: "+ len); //Written bytes: 14
Read data from the buffer
grammar:
([encoding][, start][, end])
parameter:
- encoding: The encoding used, default is utf-8
- start: Specify the index position to start reading, default is 0
- end: Specify the end position of the read, default to the end of the buffer
Return value:
Decode the buffer data and return the string using the specified encoding
Example:
buf = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf[i] = i + 97;
}
( ('ascii')); // Output: abcdefghijklmnopqrstuvwxyz( ('ascii',0,5)); // Output: abcde( ('utf8',0,5)); // Output: abcde( (undefined,0,5)); // Use 'utf8' to encode and output: abcde
Convert buffer object to json object
grammar:
toJSON()method
Return value:
json object
Example:
var buf = new Buffer('');
var json = (buf);
(json); //[ 119, 119, 119, 46, 103, 111, 111, 103, 108, 101, 46, 99, 111, 109 ]
Buffer merge
grammar:
(list[, totalLength])
parameter:
- list: A list of arrays of Buffer objects used for merge.
- totalLength: Specifies the total length of the merged Buffer object.
Return value:
Returns a new Buffer object that is merged with multiple members.
Example:
var buf1 = new Buffer("Google URL:");
var buf2 = new Buffer("");
var buf3 = ([buf1,buf2]);
('buf1's content is:'+()); //The content of buf1 is: Google URL:('buf2's content is:'+()); //The content of buf2 is:('buf3's content is:'+()); //The content of buf3 is: Google URL:
Buffer copy
grammar:
(targetBuffer[, targetStart][, sourceStart][, sourceEnd])
parameter:
The parameters are described as follows:
- targetBuffer- Buffer object to copy.
- targetStart- Number, optional, default: 0
- sourceStart- Number, optional, default: 0
-
sourceEnd- Number, optional, default:
Return value:
No return value.
Example:
var buf1 = new Buffer('ABC');
// Copy a buffervar buf2 = new Buffer(2);
var buf3 = new Buffer(3);
var buf4 = new Buffer(5);
var buf5 = new Buffer('abcdef');
(buf2);
(buf3);
(buf4);
(buf5);
("buf2 content: " + ()); //buf2 content: AB
("buf3 content: " + ()); //buf3 content: ABC
("buf4 content: " + ()); //buf4 content: ABC has opened up a lot of memory, so I'll get a bunch of weird symbols here("buf5 content: " + ()); //buf5 content: ABCdef
Buffer clipping
grammar:
([start][, end])
parameter:
The parameters are described as follows:
- start- Number, optional, default: 0
-
end- Number, optional, default:
Return value:
Returns a new buffer pointing to the same memory as the old buffer, but cuts from the index start to end.
Example:
var buffer1 = new Buffer('runoob');
// Cut buffervar buffer2 = (0,2);
("buffer2 content: " + ()); //buffer2 content: ru
I hope this article will be helpful to everyone's nodejs programming.