node. js buffer (buffer)

The JavaScript language itself has only a string data type and no binary data type.

However, when processing a TCP stream or file stream, you must use the binary data. Therefore, in node. js, a buffer class is defined that is used to create a buffer that is dedicated to storing the binary data.

In node. js, the Buffer class is the core library that is published with the Node kernel. The buffer library provides a way for node. JS to store the raw data, allowing node. js to process the binary data, possibly using the buffer library whenever data moved in the I/O operation needs to be handled in node. js. 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 the V8 heap memory.

Create a Buffer class

The Node Buffer class can be created in several ways.

Method 1

Create a Buffer instance with a length of 10 bytes:

var=newBuffer(ten);     

Method 2

Creates a Buffer instance from the given array:

var=newBuffer([ten, +, +, +]);   

Method 3

Create a Buffer instance with a string:

var=newBuffer("aaaaaa","Utf-8");       

Utf-8 is the default encoding method, and it also supports the following encodings: "ASCII", "UTF8", "Utf16le", "UCS2", "base64" and "hex".

Write buffer syntax

The syntax for writing to the Node buffer is as follows:

BUF.  Write(string[, offset[, length]][, encoding])   

Parameters

The parameters are described as follows:

• String-writes the buffer to the strings.

• offset -the index value at which the buffer begins writing, by default, 0.

• length -the number of bytes written, default is Buffer.length

• encoding -the encoding used. The default is ' UTF8 '.

return value

Returns the actual write size. If the buffer space is insufficient, only a partial string is written.

Instance

=NewBuffer(n);  = buf.  Write("aaaaaaa");  Console.  Log("number of bytes written:"+ len);            

Execute the above code and the output is:

$node main.  JS Write bytes  : 7

Read data syntax from buffer

The syntax for reading the Node buffer data is as follows:

BUF.  ToString([encoding[, start[,end]])      

Parameters

The parameters are described as follows:

• encoding -the encoding used. The default is ' UTF8 '.

• Start -Specifies the index position at which to start reading, which defaults to 0.

• End-the ending position, which defaults to the end of the buffer.

return value

Decodes the buffer data and returns a string using the specified encoding.

Instance

Buf= New Buffer(26);For (VarI= 0 ;I< 26 ;I++) {Buf[I] =I+ 97;}Console.Log(Buf.Tostring(' ASCII ')); Output: ABCDEFGHIJKLMNOPQRSTUVWXYZConsole.Log(Buf.Tostring(' ASCII ',0,5)); //output: Abcdeconsole. ( Buf. Tostring ( ' UTF8 ' ,0,< Span class= "lit" >5 //output: Abcdeconsole. ( Buf. Tostring (undefined,0 , 5 //using ' UTF8 ' encoding and output: ABCDE          

Execute the above code and the output is:

$ node main.  JSABCDEFGHIJKLMNOPQRSTUVWXYZABCDEABCDEABCDE 

Convert Buffer to JSON object syntax

The function syntax for converting Node Buffer to a JSON object is formatted as follows:

BUF.  ToJSON()  

return value

Returns a JSON object.

Instance

var=newBuffer(' node. js ');  var= buf.  ToJSON(buf);  Console.  Log(json);                

Execute the above code, the output is? You can try the results.

Buffer Merge Syntax

The syntax for the Node buffer merge is as follows:

Buffer.  Concat(list[, totallength])      

Parameters

The parameters are described as follows:

• List-the array of Buffer objects used for merging.

• totallength -Specifies the total length of the merged buffer object.

return value

Returns a new Buffer object with multiple members merged.

Instance

VarBuffer1= New Buffer(' Node Tutorial ');var Buffer2 = new buffer ( ' AAAAA ' var Buffer3 = buffer< Span class= "pun". concat ([buffer1, Buffer2console. +. Tostring              

Execute the above code and the output is:

Content: node tutorial aaaaa  

Buffer comparison Syntax

The function syntax for node Buffer comparison is shown below, which was introduced in the node. JS v0.12.2 Version:

BUF.  Compare(otherbuffer);    

Parameters

The parameters are described as follows:

• Otherbuffer -another Buffer object compared to the buf object.

return value

Returns a number that represents buf before, after, or the same as Otherbuffer .

Instance

VarBuffer1= New Buffer(' ABC ');VarBuffer2= New Buffer(' ABCD ');VarResult=Buffer1.Compare(Buffer2);If(Result< 0) {Console.Log(Buffer1+ In +Buffer2+ Before);}Else If(Result== 0){Consolelog (buffer1 +  + Buffer2 +   "Same" }else { Consolelog (buffer1 +  " + Buffer2 +   "               /span>                

Execute the above code and the output is:

ABC   before ABCD 

Copy buffer syntax

The Node buffer copy syntax is as follows:

BUF.  Copy(targetbuffer[, targetstart[, sourcestart[, sourceend]]) 

Parameters

The parameters are described as follows:

• Targetbuffer -The Buffer object to copy.

• Targetstart -number, optional, default: 0

• Sourcestart -number, optional, default: 0

• sourceend -number, optional, default: Buffer.length

return value

no return value.

Instance

VarBuffer1= New buffer ( ' ABC ' //copy a buffer var Buffer2 =  new buffer ( 3); buffer1.buffer2. Log ( "Buffer2 content:"  +  Buffer2.              

Execute the above code and the output is:

Buffer2 content: ABC 

Buffer clipping

The Node buffer clipping syntax is as follows:

BUF.  Slice([start[,end]])      

Parameters

The parameters are described as follows:

• Start -number, optional, default: 0

• End -number, optional, default: Buffer.length

return value

Returns a new buffer that points to the same piece of memory as the old buffer, but cuts from the index start to end.

Instance

Var Buffer1 = new buffer ( ' Runoob ' //cut buffer var Buffer2 =< Span class= "PLN" > Buffer1.0,2. Log ( "Buffer2 content:"  +  Buffer2.              

Execute the above code and the output is:

Buffer2 content: ru 

Buffer length Syntax

The Node buffer length calculation syntax is as follows:

BUF.  Length;  

return value

Returns the memory length occupied by the Buffer object.

Instance

var=newBuffer(' aaaaaa ');  Buffer length console.  Log("buffer length:"+ buffer. ) Length);                

Execute the above code and the output is:

Buffer length: 6

node. js buffer (buffer)