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