Package Exports

byte-data

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Readme

byte-data

Readable data to and from byte buffers.
Copyright (c) 2017 Rafael da Silva Rocha.
https://github.com/rochars/byte-data

For Node and the browser
Less than 3KB minified + compressed, less than 8KB minified
Tested against Python's struct module
Pack and unpack single values, arrays and structs

Support:

char
booleans
2-bit integers (signed/unsigned)
4-bit integers (signed/unsigned)
8-bit integers (signed/unsigned)
16-bit integers (signed/unsigned)
16-bit half-precision floating point numbers
24-bit integers (signed/unsigned)
32-bit integers (signed/unsigned)
32-bit single-precision floating point numbers
40-bit integers (signed/unsigned)
48-bit integers (signed/unsigned)
64-bit double-precision floating point numbers
little-endian and big-endian
strings of fixed and variable length

Install

npm install byte-data

Example

let byteData = require('byte-data');

// Pack a float32 number, output bytes to hex
byteData.pack(2.1474836, byteData.float32, 16),
//["5f","70","09","40"]

// Pack an array of uInt16 numbers, output to base 10 (default)
byteData.packArray([65535, 0], byteData.uInt16)
// [255, 255, 0, 0]);

// Pack an array of int32 numbers, output to base 10 (default)
byteData.packArray([-2147483648, 2147483647], byteData.int32),
//[0, 0, 0, 128, 255, 255, 255, 127]

// unpack an array of uInt16 numbers from bytes represented as hex values
byteData.unpackArray(["ff", "ff", "00", "00"], byteData.uInt16, 16),
// [65535, 0]

Interface

/**
 * Turn a number or fixed-length string into a byte buffer.
 * @param {number|string} value The value.
 * @param {Object} type One of the available types.
 * @param {number} base The base of the output. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {!Array<number>|!Array<string>}
 */
function pack(value, type, base=10) {}

/**
 * Turn a byte buffer into a number or a fixed-length string.
 * @param {!Array<number>|!Array<string>|Uint8Array} buffer An array of bytes.
 * @param {Object} type One of the available types.
 * @param {number} base The base of the input. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {number|string}
 */
function unpack(buffer, type, base=10) {}

/**
 * Turn a array of numbers or a string into a byte buffer.
 * @param {!Array<number>|string} values The values.
 * @param {Object} type One of the available types.
 * @param {number} base The base of the output. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {!Array<number>|!Array<string>}
 */
function packArray(values, type, base=10) {}

/**
 * Turn a byte buffer into a array of numbers or a string.
 * @param {!Array<number>|!Array<string>|Uint8Array} buffer The byte array.
 * @param {Object} type One of the available types.
 * @param {number} base The base of the input. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {!Array<number>|string}
 */
function unpackArray(buffer, type, base=10) {}

/**
 * Turn a struct into a byte buffer.
 * A struct is an array of values of not necessarily the same type.
 * @param {Array} struct The struct values.
 * @param {!Array<Object>} def The struct type definition.
 * @param {number} base The base of the output. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {!Array<number>|!Array<string>}
 */
function packStruct(struct, def, base=10) {}

/**
 * Turn a byte buffer into a struct.
 * A struct is an array of values of not necessarily the same type.
 * @param {!Array<number>|!Array<string>|Uint8Array} buffer The byte buffer.
 * @param {!Array<Object>} def The struct type definition.
 * @param {number} base The base of the input. Optional. Default is 10.
 *      Possible values are 2, 10 or 16.
 * @return {Array}
 */
function unpackStruct(buffer, def, base=10) {}

/**
 * Find and return the start index of some string.
 * Return -1 if the string is not found.
 * @param {!Array<number>|Uint8Array} buffer A byte buffer.
 * @param {string} text Some string to look for.
 * @return {number} The start index of the first occurrence, -1 if not found
 */
function findString(buffer, text) {}

Standard types

chr
fourCC
bool
int2
uInt2
int4
uInt4
int8
uInt8

little-endian

int16
uInt16
float16
int24
uInt24
int32
uInt32
float32
int40
uInt40
int48
uInt48
float64

big-endian:

int16BE
uInt16BE
float16BE
int24BE
uInt24BE
int32BE
uInt32BE
float32BE
int40BE
uInt40BE
int48BE
uInt48BE
float64BE

byteData.pack(value, byteData.float16);

Structs

You must define a struct to use packStruct() and unpackStruct(). A struct is a array os values of not necessarily the same type.

Packing a struct

// Define a struct:
let structDef = [
    byteData.fourCC,
    byteData.uInt32,
    byteData.uInt16
];

// The struct data:
let struct = [
    "abcd",
    4294967295,
    65535
]

// Pack the struct:
console.log(byteData.packStruct(struct, structDef));
// [97,98,99,100,255,255,255,255,255,255]

Unpacking a struct

// Define a struct:
let structDef = [
    byteData.fourCC,
    byteData.uInt32,
    byteData.uInt16
];

// The byte buffer:
let buffer = [97,98,99,100,255,255,255,255,255,255];

// Unpack the struct:
console.log(byteData.unpackStruct(buffer, structDef));
// ["abcd", 4294967295, 65535]

Overflow

Integer values will be truncated according to the bit depth of the type. There is no overflow or underflow check for floating-point values.

// Values in the correct range
byteData.pack(254, uInt8); // [254]
byteData.pack(255, uInt8); // [255]

// Overflow
byteData.pack(300, uInt8); // [255]

// Underflow
byteData.pack(-1, uInt8); // [0]

Floating-point numbers

Floating-point numbers are based on the IEEE 754 standard.

16-bit floating-point numbers may show precision differences when compared to other implementations.

LICENSE

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.