rochars / byte-data

import endianness from 'endianness';

import utf8BufferSize from 'utf8-buffer-size';

import {pack as packUTF8, unpack as unpackUTF8} from 'utf8-buffer';

import NumberBuffer from './lib/number-buffer.js';

import {validateValueType} from './lib/validation.js';

/**

 * Read a string of UTF-8 characters from a byte buffer.

 * @param {!Uint8Array|!Array<number>} buffer A byte buffer.

 * @param {number=} index The buffer index to start reading.

 * @param {?number=} end The buffer index to stop reading.

 *   If end is null will read until the end of the buffer.

 * @return {string}

 */

export function unpackString(buffer, index=0, end=null) {

  return unpackUTF8(buffer, index, end);

}

/**

 * Write a string of UTF-8 characters as a byte buffer.

 * @param {string} str The string to pack.

 * @return {!Uint8Array} The buffer with the packed string written.

 */ 

export function packString(str) {

  /** @type {!Uint8Array} */

  let buffer = new Uint8Array(utf8BufferSize(str));

  packUTF8(str, buffer, 0);

  return buffer;

}

/**

 * Write a string of UTF-8 characters to a byte buffer.

 * @param {string} str The string to pack.

 * @param {!Uint8Array|!Array<number>} buffer The output buffer.

 * @param {number=} index The buffer index to start writing.

 *   Assumes zero if undefined.

 * @return {number} The next index to write in the buffer.

 */

export function packStringTo(str, buffer, index=0) {

  return packUTF8(str, buffer, index);

}

// Numbers

/**

 * Pack a number as a byte buffer.

 * @param {number} value The number.

 * @param {!Object} theType The type definition.

 * @return {!Array<number>} The packed value.

 * @throws {Error} If the type definition is not valid.

 * @throws {Error} If the value is not valid.

 */

export function pack(value, theType) {

  /** @type {!Array<number>} */

  let output = [];

  packTo(value, theType, output);

  return output;

}

/**

 * Pack a number to a byte buffer.

 * @param {number} value The value.

 * @param {!Object} theType The type definition.

 * @param {!Uint8Array|!Array<number>} buffer The output buffer.

 * @param {number=} index The buffer index to write. Assumes 0 if undefined.

 * @return {number} The next index to write.

 * @throws {Error} If the type definition is not valid.

 * @throws {Error} If the value is not valid.

 */

export function packTo(value, theType, buffer, index=0) {

  return packArrayTo([value], theType, buffer, index);

}

/**

 * Pack an array of numbers as a byte buffer.

 * @param {!Array<number>|!TypedArray} values The values.

 * @param {!Object} theType The type definition.

 * @return {!Array<number>} The packed values.

 * @throws {Error} If the type definition is not valid.

 * @throws {Error} If any of the values are not valid.

 */

export function packArray(values, theType) {

  /** @type {!Array<number>} */

  let output = [];

  packArrayTo(values, theType, output);

  return output;

}

/**

 * Pack a array of numbers to a byte buffer.

 * @param {!Array<number>|!TypedArray} values The value.

 * @param {!Object} theType The type definition.

 * @param {!Uint8Array|!Array<number>} buffer The output buffer.

 * @param {number=} index The buffer index to start writing.

 *   Assumes zero if undefined.

 * @return {number} The next index to write.

 * @throws {Error} If the type definition is not valid.

 * @throws {Error} If the value is not valid.

 */

export function packArrayTo(values, theType, buffer, index=0) {

  theType = theType || {};

  /** @type {NumberBuffer} */

  let packer = new NumberBuffer(

    theType.bits, theType.fp || theType.float, theType.signed);

  /** @type {number} */

  let offset = offset_(theType.bits);

  for (let i = 0, valuesLen = values.length; i < valuesLen; i++) {

    validateValueType(values[i]);

    /** @type {number} */

    let len = index + offset;

    while (index < len) {

      index = packer.pack(buffer, values[i], index);

    }

    swap_(theType.be, buffer, offset, index - offset, index);

  }

  return index;

}

/**

 * Unpack a number from a byte buffer.

 * @param {!Uint8Array|!Array<number>} buffer The byte buffer.

 * @param {!Object} theType The type definition.

 * @param {number=} index The buffer index to read. Assumes zero if undefined.

 * @return {number}

 * @throws {Error} If the type definition is not valid

 * @throws {Error} On bad buffer length.

 */

export function unpack(buffer, theType, index=0) {

  return unpackArray(

    buffer, theType, index, index + offset_(theType.bits), true)[0];

}

/**

 * Unpack an array of numbers from a byte buffer.

 * @param {!Uint8Array|!Array<number>} buffer The byte buffer.

 * @param {!Object} theType The type definition.

 * @param {number=} index The buffer index to start reading.

 *   Assumes zero if undefined.

 * @param {number=} end The buffer index to stop reading.

 *   Assumes the buffer length if undefined.

 * @param {boolean=} safe If set to false, extra bytes in the end of

 *   the array are ignored and input buffers with insufficient bytes will

 *   output a empty array. If safe is set to true the function

 *   will throw a 'Bad buffer length' error. Defaults to false.

 * @return {!Array<number>}

 * @throws {Error} If the type definition is not valid

 */

export function unpackArray(

    buffer, theType, index=0, end=buffer.length, safe=false) {

  /** @type {!Array<number>} */

  let output = [];

  unpackArrayTo(buffer, theType, output, index, end, safe);

  return output;

}

/**

 * Unpack a array of numbers to a typed array.

 * @param {!Uint8Array|!Array<number>} buffer The byte buffer.

 * @param {!Object} theType The type definition.

 * @param {!TypedArray|!Array<number>} output The output array.

 * @param {number=} start The buffer index to start reading.

 *   Assumes zero if undefined.

 * @param {number=} end The buffer index to stop reading.

 *   Assumes the buffer length if undefined.

 * @param {boolean=} safe If set to false, extra bytes in the end of

 *   the array are ignored and input buffers with insufficient bytes will

 *   write nothing to the output array. If safe is set to true the function

 *   will throw a 'Bad buffer length' error. Defaults to false.

 * @throws {Error} If the type definition is not valid

 */

export function unpackArrayTo(

    buffer, theType, output, start=0, end=buffer.length, safe=false) {

  theType = theType || {};

  /** @type {NumberBuffer} */

  let packer = new NumberBuffer(

    theType.bits, theType.fp || theType.float, theType.signed);

  /** @type {number} */

  let offset = offset_(theType.bits);

  /** @type {number} */

  let extra = (end - start) % offset;

  if (safe && (extra || buffer.length < offset)) {

    throw new Error('Bad buffer length');

  }

  end -= extra;

  swap_(theType.be, buffer, offset, start, end);

  for (let j = start, i = 0; j < end; j += offset, i++) {

    output[i] = packer.unpack(buffer, j);

  }

  swap_(theType.be, buffer, offset, start, end);

}

/**

 * Swap endianness in a slice of an array when flip == true.

 * @param {boolean} flip True if should swap endianness.

 * @param {!Uint8Array|!Array<number>} buffer The buffer.

 * @param {number} offset The number of bytes each value use.

 * @param {number} start The buffer index to start the swap.

 * @param {number} end The buffer index to end the swap.

 * @throws {Error} On bad buffer length for the swap.

 * @private

 */

function swap_(flip, buffer, offset, start, end) {

  if (flip) {

    endianness(buffer, offset, start, end);

  }

}

/**

 * Get the byte offset of a type based on its number of bits.

 * @param {number} bits The number of bits.

 * @private

 */

function offset_(bits) {

  return bits < 8 ? 1 : Math.ceil(bits / 8);

}