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IoT.js-API-Buffer.md

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IoT.js provides Buffer to compensate the lack of pure Javascript's capability of manipulating binary data, Javascript string is only suitable for Unicode string. Buffer allows you to handle sequence of binary data in Javascript world.

Class: Buffer

Buffer class is a global type. you can create a buffer object in several way.

Constructor

new Buffer(size)

  • size: Number

Allocate a new buffer of size bytes.

new Buffer(buffer)

  • buffer: Buffer

Allocate a new buffer copied from given buffer.

new Buffer(str)

  • str: String

Allocate a new buffer containing given str.

Class Methods

Buffer.byteLength(string[, encoding])

  • string: String
  • encoding: String
  • Return: Number

Returns actual byte length of string encoded by encoding. UTF-8 encoding is by default. Note that it may be different from String.prototype.length since that returns the number of characters in a string.

Buffer.concat(list)

  • list: Array of Buffer
  • Return: Buffer

Returns a Buffer concatenating all the Buffers in the list.

Buffer.isBuffer(obj)

  • obj: Object

Test if obj is a Buffer.

Instance of Buffer

Once you get buffer object in some way, you can handle the buffer using the following API:

Properties

buf.length

  • Number

The capacity of buffer in bytes. Note that the value of length is not necessarily the same to the size of contents.

Methods

buf.equals(otherBuffer)

  • otherBuffer: Buffer
  • Return: Bool

Returns whether this and otherBuffer have the same bytes.

buf.compare(otherBuffer)

  • otherBuffer: Buffer
  • Return: Number

Returns a number indicating which buffer comes first between this and otherBuffer when lexicographically sorted.

buf.write(string[,offset[,length]])

  • string: String - data to be written to buffer
  • offset: Number, Default: 0 - start position of buffer for writing.
  • length: Number, Default: buffer.length - offset - total length to be written.
  • Return: Number - total number of bytes written.

Writes string to buffer starting from offset. Returns total number of bytes written to the buffer.

buf.toString([,start[,end]])

  • start: Number, Default: 0
  • end: Number, Default: buffer.length
  • Return: String

Returns a string from buffer.

buf.copy(targetBuffer[,targetStart[,sourceStart[,sourceEnd]]])

  • targetBuffer: Buffer
  • targetStart: Number, Default: 0
  • sourceStart: Number, Default: 0
  • sourceEnd: Number, Default: buf.length

buf.slice([start[,end]])

  • start: Number, Default: `0
  • end: Number, Default: buf.length
  • Return: Buffer

Returns new buffer containing the same bytes of original buffer cropped by the given indices.

Copies data from buf[sourceStart..sourceEnd-1] to targetBuffer[targetStart..].