XRTLibrary-BufferUtilities

Introduction

This library provides following buffer utilities:

• Buffer fetcher (fetch several bytes synchronously from a Buffer object).
• Blocked buffer fetcher (fetch several bytes synchronously from a Buffer array).
• Buffer merger (merge a buffer array into one).

Installation

To install this package, you can use NPM by typing following command:

npm install xrtlibrary-bufferutilities --save

Then you can import this library in your JavaScript code:

const XRTLibBufferUtilities = require("xrtlibrary-bufferutilities");

API

(Class) BufferFetcher

Buffer fetcher.

new BufferFetcher(buffer)

Construct a new object.

Parameter(s):

• buffer (Buffer): The buffer.

fetcher.isEnd()

Get whether the cursor reached the end.

Return value:

• (Boolean) True if ended.

fetcher.reset()

Reset the cursor.

fetcher.fetch()

Fetch one byte.

Exception(s):

• BufferFetcher.EndOfStreamError: Raised if the stream was already ended.

Return value:

• (Number) The byte.

Example:

let fetcher = new XRTLibBufferUtilities.BufferFetcher(
    Buffer.from([10, 9, 8, 7])
);
while (!fetcher.isEnd()) {
    console.log(fetcher.fetch());
}
//  Output:
//    10
//    9
//    8
//    7

fetcher.fetchTo(output)

Fetch bytes to output buffer.

Parameter(s):

• output (Buffer): The output buffer.

Return value:

• (Number) The count of copied bytes.

Example:

let fetcher = new XRTLibBufferUtilities.BufferFetcher(
    Buffer.from([1, 2, 3, 4])
);
while (!fetcher.isEnd()) {
    let output = Buffer.alloc(2);
    fetcher.fetchTo(output);
    console.log(output);
}
//  Output:
//    <Buffer 01 02>
//    <Buffer 03 04>

fetcher.fetchToWithStart(output, outputStart)

Fetch bytes to output buffer (with start position).

Parameter(s):

• output (Buffer): The output buffer.
• outputStart (Number): The start position of the output buffer.

Return value:

• (Number) The count of copied bytes.

fetcher.fetchAll()

Fetch all bytes.

Return value:

• (Buffer): The bytes.

Example:

let fetcher = new XRTLibBufferUtilities.BufferFetcher(
    Buffer.from([1, 2, 3, 4])
);
console.log(fetcher.fetch());
console.log(fetcher.fetchAll());
//  Output:
//    1
//    <Buffer 02 03 04>

fetcher.fetchBytes(count)

Fetch specific bytes.

Parameter(s):

• count (Number): The bytes count.

Return value:

• (Buffer) The bytes.

fetcher.skip(steps)

Skip specific bytes.

Parameter(s):

• steps (Number): The count of bytes to be skipped.

Return value:

• (Number): The count of skipped bytes.

Example:

let fetcher = new XRTLibBufferUtilities.BufferFetcher(
    Buffer.from([1, 2, 3, 4])
);
console.log(fetcher.fetch());
fetcher.skip(2);
console.log(fetcher.fetch());
//  Output:
//    1
//    4

fetcher.getRemainingCount()

Get the count of remaining bytes.

Return value:

• (Number): The count.

fetcher.reinitialize(newBuffer)

Parameter(s):

• newBuffer (Buffer): New buffer.

(Class) BufferFetcher.Error

Buffer fetcher error.

Extend(s):

• Error

(Class) BufferFetcher.EndOfStreamError

Buffer fetcher end of stream error.

Extend(s):

• BufferFetcher.Error

(Class) BlockBufferFetcher

Block buffer fetcher.

new BlockBufferFetcher(blocks)

Construct a new object.

Parameter(s):

• blocks (Buffer[]): The buffer blocks.

blockfetcher.isEnd()

Get whether the cursor reached the end.

Return value:

• (Boolean) True if ended.

blockfetcher.reset()

Reset the cursor.

blockfetcher.fetch()

Fetch one byte.

Exception(s):

• BlockBufferFetcher.EndOfStreamError: Raised if the stream was already ended.

Return value:

• (Number) The byte.

blockfetcher.fetchTo(output)

Fetch bytes to output buffer.

Parameter(s):

• output (Buffer): The output buffer.

Return value:

• (Number) The count of copied bytes.

blockfetcher.fetchAll()

Fetch all bytes.

Return value:

• (Buffer) The bytes.

blockfetcher.fetchAllAsBlocks([outBytesCount = new OutputParameter()])

Fetch all remaining bytes as blocks (faster).

Parameter(s):

• outBytesCount (OutputParameter): (Optional, Out) The size of output buffer blocks.

Return value:

• (Buffer[]) The blocks.

blockfetcher.fetchBytes(count)

Fetch specific bytes.

Parameter(s):

• count (Number): The bytes count.

Return value:

• (Buffer) The bytes.

blockfetcher.fetchBytesAsBlocks(count)

Fetch specific bytes as blocks.

Warning(s):

• This method has been deprecated (but still usable).
• Use blockfetcher.fetchBytesAsBlocks2() instead.

Parameter(s):

• count (Number): The bytes count.

Return value:

• (Object) The fetch result.
  • buffers (Buffer[]): The buffer array.
  • length (Number): The length of bytes fetched.

blockfetcher.fetchBytesAsBlocks2(count, [outBytesCount = new OutputParameter()])

Fetch specific bytes as blocks.

Parameter(s):

• count (Number): The bytes count.
• outBytesCount (OutputParameter): (Optional, Out) The size of output buffer blocks.

Return value:

• (Buffer[]) The buffer blocks.

blockfetcher.skip(steps)

Skip specific bytes.

Parameter(s):

• steps (Number): The count of bytes to be skipped.

Return value:

• (Number) The count of skipped bytes.

blockfetcher.reinitialize(newBlocks)

Reinitialize the object.

Parameter(s):

• newBlocks (Buffer[]): New blocks.

(Class) BlockBufferFetcher.Error

Block buffer fetcher error.

Extend(s):

• Error

(Class) BlockBufferFetcher.EndOfStreamError

Block buffer fetcher end of stream error.

Extend(s):

• BlockBufferFetcher.Error

(Class) BufferMerger

Buffer merger.

new BufferMerger()

Construct a new object.

merger.push(data)

Push a buffer.

Parameter(s):

• data (Buffer): The buffer.

merger.merge()

Merge pushed buffers.

Return value:

• (Buffer) The concatencated buffer.

merger.reset()

Clear pushed buffers.

(Class) BufferEmitter

Buffer emitter.

Extend(s):

• BufferMerger

new BufferEmitter()

Construct a new object.

emitter.writeUInt8(value)

Write an 8-bit unsigned integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeInt8(value)

Write an 8-bit signed integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeUInt16LE(value)

Write an 16-bit little endian unsigned integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeUInt16BE(value)

Write an 16-bit big endian unsigned integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeInt16LE(value)

Write an 16-bit little endian signed integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeInt16BE(value)

Write an 16-bit big endian signed integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeUInt32LE(value)

Write an 32-bit little endian unsigned integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeUInt32BE(value)

Write an 32-bit big endian unsigned integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeInt32LE(value)

Write an 32-bit little endian signed integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeInt32BE(value)

Write an 32-bit big endian signed integer.

Parameter(s):

• value (Number): The integer value.

emitter.writeUIntLE(value, byteLength)

Write an custom byte length little endian unsigned integer.

Parameter(s):

• value (Number): The integer value.
• byteLength (Number): The byte size.

emitter.writeUIntBE(value, byteLength)

Write an custom byte length big endian unsigned integer.

Parameter(s):

• value (Number): The integer value.
• byteLength (Number): The byte size.

emitter.writeIntLE(value, byteLength)

Write an custom byte length little endian signed integer.

Parameter(s):

• value (Number): The integer value.
• byteLength (Number): The byte size.

emitter.writeIntBE(value, byteLength)

Write an custom byte length big endian signed integer.

Parameter(s):

• value (Number): The integer value.
• byteLength (Number): The byte size.

emitter.writeFloatLE(value)

Write a little-endian float.

Parameter(s):

• value (Number): The float value.

emitter.writeFloatBE(value)

Write a big-endian float.

Parameter(s):

• value (Number): The float value.

emitter.writeDoubleLE(value)

Write a little-endian double.

Parameter(s):

• value (Number): The float value.

emitter.writeDoubleBE(value)

Write a big-endian double.

Parameter(s):

• value (Number): The float value.

MergeBufferBlocks(blocks)

Merge buffer blocks to one buffer.

Parameter(s):

• blocks (Buffer[]): The blocks to be concatencated.

Return value:

• (Buffer) The concatencated buffer.