@mediafish/buffer-operator v0.1.2
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); // => trueAPI
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