@mediafish/buffer-operator

buffer-operator

Provides JS functions to read/write a byte buffer (both node's Buffer and Uint8Array)

Install

Usage

const {reader, writer} = require('@mediafish/buffer-operator');

const buffer = Buffer.from([0xFF, 0xFF, 0xFF, 0x61, 0x62, 0x63]);
// Or use Uint8Array
const buffer = Uint8Array.from([0xFF, 0xFF, 0xFF, 0x61, 0x62, 0x63]);

let offset, value;
[offset, value] = reader.readNumber(buffer, 0, 1); // Specify offset and length
// offset => 1
// value => 255
[offset, value] = reader.readNumber(buffer, offset, 2, true); // signed = true
// offset => 3
// value => -1
[offset, value] = reader.readString(buffer, offset, 3);
// offset => 6
// value => 'abc'

const dest = Buffer.alloc(6);
// Or use Uint8Array
const dest = new Uint8Array(6);

offset = writer.writeNumber(255, dest, 0, 1);
// offset => 1
offset = writer.writeNumber(-1, dest, offset, 2);
// offset => 3
offset = writer.writeString('abc', dest, offset, 3);
// offset => 6
dest.equals(buffer); // => true

API

reader.readNumber(buffer, offset[, length, signed])

Read an integer from the buffer

params

Name	Type	Required	Default	Description
buffer	Buffer or Uint8Array	Yes	N/A	The buffer from which the data is read
offset	number	Yes	N/A	An integer to specify the position within the buffer
length	number	No	4	An integer to specify how many bytes to read
signed	boolean	No	false	Set true to read a negative number

return value

An array containing the following pair of values

Index	Type	Description
[0]	number	An integer to indicate the position from which the next data should be read
[1]	number	The read value

reader.readString(buffer, offset[, length, nullTerminated])

Read a string from the buffer

params

Name	Type	Required	Default	Description
buffer	Buffer or Uint8Array	Yes	N/A	The buffer from which the data is read
offset	number	Yes	N/A	An integer to specify the position within the buffer
length	number	No	buffer.length - offset	An integer to specify how many bytes to read
nullTerminated	boolean	No	false	Set true to stop reading when encountering zero

return value

An array containing the following pair of values

Index	Type	Description
[0]	number	An integer to indicate the position from which the next data should be read
[1]	string	The read value

reader.subBuffer(buffer, offset[, length])

Create a sub buffer from the original one.

params

Name	Type	Required	Default	Description
buffer	Buffer or Uint8Array	Yes	N/A	The buffer from which the sub buffer is extracted
offset	number	Yes	N/A	An integer to specify the position within the original buffer
length	number	No	buffer.length - offset	An integer to specify how many bytes to extract

return value

The created sub buffer

reader.setOptions(obj)

Updates the option values

params

Name	Type	Required	Default	Description
obj	Object	Yes	{}	An object holding option values which will be used to overwrite the internal option values.

supported options

Name	Type	Default	Description
strictMode	boolean	false	If true, the function throws an error when the method invocations failed. If false, the function just logs the error and continues to run.

reader.getOptions()

Retrieves the current option values

return value

A cloned object containing the current option values

writer.writeNumber(value, buffer, offset[, length])

Write an integer to the buffer

params

Name	Type	Required	Default	Description
value	number	Yes	N/A	The value to be written to the buffer
buffer	Buffer or Uint8Array	Yes	N/A	The buffer to which the data is written
offset	number	Yes	N/A	An integer to specify the position within the buffer
length	number	No	4	An integer to specify how many bytes to write

return value

An integer to indicate the position to which the next data should be written

writer.writeString(value, buffer, offset[, length])

Write a string to the buffer

params

Name	Type	Required	Default	Description
value	string	Yes	N/A	The value to be written to the buffer
buffer	Buffer or Uint8Array	Yes	N/A	The buffer to which the data is written
offset	number	Yes	N/A	An integer to specify the position within the buffer
length	number	No	undefined	An integer to specify how many bytes to write. If not specified, the data is written until the end of the buffer

return value

An integer to indicate the position to which the next data should be written

writer.copyBuffer(src, srcOffset, dst, dstOffset[, length])

Copy data from the src buffer to dst buffer

params

Name	Type	Required	Default	Description
src	Buffer or Uint8Array	Yes	N/A	The source buffer from which the data is copied
srcOffset	number	Yes	N/A	An integer to specify the position within the source buffer
dst	Buffer or Uint8Array	Yes	N/A	The destination buffer to which the data is copied
dstOffset	number	Yes	N/A	An integer to specify the position within the destination buffer
length	number	No	src.length - srcOffset	An integer to specify how many bytes to copy.

return value

An integer to indicate the position within the dst buffer to which the next data should be written