rochars / byte-data

 * byte-data

 * Readable data to and from byte buffers.

 * Copyright (c) 2017 Rafael da Silva Rocha.

 * https://github.com/rochars/byte-data

 *

 */

let toBytes = require("../src/to-bytes");

let fromBytes = require("../src/from-bytes");

let helpers = require("../src/helpers");

/**

 * Turn a number or 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.

 * @return {!Array<number>|!Array<string>}

 */

function pack(value, type, base=10) {

    let theType = helpers.getType(type, base, true);

    value = theType.char ? value.slice(0, type.bits / 8) : value;

    return toBytes.toBytes(helpers.turnToArray(value), theType);

}

/**

 * Turn a byte buffer into a readable value.

 * @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.

 * @return {number|string}

 */

function unpack(buffer, type, base=10) {

    return fromBytes.fromBytes(buffer, helpers.getType(type, base, true));

}

/**

 * Turn a array of numbers 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.

 * @return {!Array<number>|!Array<string>}

 */

function packArray(values, type, base=10) {

    return toBytes.toBytes(values, helpers.getType(type, base, false));

}

/**

 * Turn a byte array into a sequence of readable values.

 * @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.

 * @return {!Array<number>|string}

 */

function unpackArray(buffer, type, base=10) {

    return fromBytes.fromBytes(buffer, helpers.getType(type, base, false));

}

/**

 * 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) {

    let found = "";

    for (let i = 0; i < buffer.length; i++) {

        found = unpack(

            buffer.slice(i, i + text.length + 1),

            {"bits": text.length * 8, "char": true});

        if (found == text) {

            return i;

        }

    }

    return -1;

}

/**

 * 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.

 * @return {!Array<number>|!Array<string>}

 */

function packStruct(struct, def, base=10) {

    if (struct.length < def.length) {

        return [];

    }

    let bytes = [];

    for (let i = 0; i < def.length; i++) {

        bytes = bytes.concat(pack(struct[i], def[i], base));

    }

    return bytes;

}

/**

 * Turn a byte buffer into a structure.

 * 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.

 * @return {Array}

 */

function unpackStruct(buffer, def, base=10) {

    if (buffer.length < getStructBits(def)) {

        return [];

    }

    let struct = [];

    let i = 0;

    let j = 0;

    while (i < def.length) {

        let bits = def[i].bits < 8 ? 1 : def[i].bits / 8;

        struct = struct.concat(

                unpack(buffer.slice(j, j + bits), def[i], base)

            );

        j += bits;

        i++;

    }

    return struct;

}

module.exports.pack = pack;

module.exports.findString = findString;

module.exports.unpack = unpack;

module.exports.packArray = packArray;

module.exports.unpackArray = unpackArray;

module.exports.unpackStruct = unpackStruct;

module.exports.packStruct = packStruct;