lib/float/index.js

"use strict";

module.exports = factory(factory);

/**
 * Reads / writes floats / doubles from / to buffers.
 * @name util.float
 * @namespace
 */

/**
 * Writes a 32 bit float to a buffer using little endian byte order.
 * @name util.float.writeFloatLE
 * @function
 * @param {number} val Value to write
 * @param {Uint8Array} buf Target buffer
 * @param {number} pos Target buffer offset
 * @returns {undefined}
 */

/**
 * Writes a 32 bit float to a buffer using big endian byte order.
 * @name util.float.writeFloatBE
 * @function
 * @param {number} val Value to write
 * @param {Uint8Array} buf Target buffer
 * @param {number} pos Target buffer offset
 * @returns {undefined}
 */

/**
 * Reads a 32 bit float from a buffer using little endian byte order.
 * @name util.float.readFloatLE
 * @function
 * @param {Uint8Array} buf Source buffer
 * @param {number} pos Source buffer offset
 * @returns {number} Value read
 */

/**
 * Reads a 32 bit float from a buffer using big endian byte order.
 * @name util.float.readFloatBE
 * @function
 * @param {Uint8Array} buf Source buffer
 * @param {number} pos Source buffer offset
 * @returns {number} Value read
 */

/**
 * Writes a 64 bit double to a buffer using little endian byte order.
 * @name util.float.writeDoubleLE
 * @function
 * @param {number} val Value to write
 * @param {Uint8Array} buf Target buffer
 * @param {number} pos Target buffer offset
 * @returns {undefined}
 */

/**
 * Writes a 64 bit double to a buffer using big endian byte order.
 * @name util.float.writeDoubleBE
 * @function
 * @param {number} val Value to write
 * @param {Uint8Array} buf Target buffer
 * @param {number} pos Target buffer offset
 * @returns {undefined}
 */

/**
 * Reads a 64 bit double from a buffer using little endian byte order.
 * @name util.float.readDoubleLE
 * @function
 * @param {Uint8Array} buf Source buffer
 * @param {number} pos Source buffer offset
 * @returns {number} Value read
 */

/**
 * Reads a 64 bit double from a buffer using big endian byte order.
 * @name util.float.readDoubleBE
 * @function
 * @param {Uint8Array} buf Source buffer
 * @param {number} pos Source buffer offset
 * @returns {number} Value read
 */

// Factory function for the purpose of node-based testing in modified global environments
function factory(exports) {

    // float: typed array
    if (typeof Float32Array !== "undefined") (function() {

        var f32 = new Float32Array([ -0 ]),
            f8b = new Uint8Array(f32.buffer),
            le  = f8b[3] === 128;

        function writeFloat_f32_cpy(val, buf, pos) {
            f32[0] = val;
            buf[pos    ] = f8b[0];
            buf[pos + 1] = f8b[1];
            buf[pos + 2] = f8b[2];
            buf[pos + 3] = f8b[3];
        }

        function writeFloat_f32_rev(val, buf, pos) {
            f32[0] = val;
            buf[pos    ] = f8b[3];
            buf[pos + 1] = f8b[2];
            buf[pos + 2] = f8b[1];
            buf[pos + 3] = f8b[0];
        }

        /* istanbul ignore next */
        exports.writeFloatLE = le ? writeFloat_f32_cpy : writeFloat_f32_rev;
        /* istanbul ignore next */
        exports.writeFloatBE = le ? writeFloat_f32_rev : writeFloat_f32_cpy;

        function readFloat_f32_cpy(buf, pos) {
            f8b[0] = buf[pos    ];
            f8b[1] = buf[pos + 1];
            f8b[2] = buf[pos + 2];
            f8b[3] = buf[pos + 3];
            return f32[0];
        }

        function readFloat_f32_rev(buf, pos) {
            f8b[3] = buf[pos    ];
            f8b[2] = buf[pos + 1];
            f8b[1] = buf[pos + 2];
            f8b[0] = buf[pos + 3];
            return f32[0];
        }

        /* istanbul ignore next */
        exports.readFloatLE = le ? readFloat_f32_cpy : readFloat_f32_rev;
        /* istanbul ignore next */
        exports.readFloatBE = le ? readFloat_f32_rev : readFloat_f32_cpy;

    // float: ieee754
    })(); else (function() {

        function writeFloat_ieee754(writeUint, val, buf, pos) {
            var sign = val < 0 ? 1 : 0;
            if (sign)
                val = -val;
            if (val === 0)
                writeUint(1 / val > 0 ? /* positive */ 0 : /* negative 0 */ 2147483648, buf, pos);
            else if (isNaN(val))
                writeUint(2143289344, buf, pos);
            else if (val > 3.4028234663852886e+38) // +-Infinity
                writeUint((sign << 31 | 2139095040) >>> 0, buf, pos);
            else if (val < 1.1754943508222875e-38) // denormal
                writeUint((sign << 31 | Math.round(val / 1.401298464324817e-45)) >>> 0, buf, pos);
            else {
                var exponent = Math.floor(Math.log(val) / Math.LN2),
                    mantissa = Math.round(val * Math.pow(2, -exponent) * 8388608) & 8388607;
                writeUint((sign << 31 | exponent + 127 << 23 | mantissa) >>> 0, buf, pos);
            }
        }

        exports.writeFloatLE = writeFloat_ieee754.bind(null, writeUintLE);
        exports.writeFloatBE = writeFloat_ieee754.bind(null, writeUintBE);

        function readFloat_ieee754(readUint, buf, pos) {
            var uint = readUint(buf, pos),
                sign = (uint >> 31) * 2 + 1,
                exponent = uint >>> 23 & 255,
                mantissa = uint & 8388607;
            return exponent === 255
                ? mantissa
                ? NaN
                : sign * Infinity
                : exponent === 0 // denormal
                ? sign * 1.401298464324817e-45 * mantissa
                : sign * Math.pow(2, exponent - 150) * (mantissa + 8388608);
        }

        exports.readFloatLE = readFloat_ieee754.bind(null, readUintLE);
        exports.readFloatBE = readFloat_ieee754.bind(null, readUintBE);

    })();

    // double: typed array
    if (typeof Float64Array !== "undefined") (function() {

        var f64 = new Float64Array([-0]),
            f8b = new Uint8Array(f64.buffer),
            le  = f8b[7] === 128;

        function writeDouble_f64_cpy(val, buf, pos) {
            f64[0] = val;
            buf[pos    ] = f8b[0];
            buf[pos + 1] = f8b[1];
            buf[pos + 2] = f8b[2];
            buf[pos + 3] = f8b[3];
            buf[pos + 4] = f8b[4];
            buf[pos + 5] = f8b[5];
            buf[pos + 6] = f8b[6];
            buf[pos + 7] = f8b[7];
        }

        function writeDouble_f64_rev(val, buf, pos) {
            f64[0] = val;
            buf[pos    ] = f8b[7];
            buf[pos + 1] = f8b[6];
            buf[pos + 2] = f8b[5];
            buf[pos + 3] = f8b[4];
            buf[pos + 4] = f8b[3];
            buf[pos + 5] = f8b[2];
            buf[pos + 6] = f8b[1];
            buf[pos + 7] = f8b[0];
        }

        /* istanbul ignore next */
        exports.writeDoubleLE = le ? writeDouble_f64_cpy : writeDouble_f64_rev;
        /* istanbul ignore next */
        exports.writeDoubleBE = le ? writeDouble_f64_rev : writeDouble_f64_cpy;

        function readDouble_f64_cpy(buf, pos) {
            f8b[0] = buf[pos    ];
            f8b[1] = buf[pos + 1];
            f8b[2] = buf[pos + 2];
            f8b[3] = buf[pos + 3];
            f8b[4] = buf[pos + 4];
            f8b[5] = buf[pos + 5];
            f8b[6] = buf[pos + 6];
            f8b[7] = buf[pos + 7];
            return f64[0];
        }

        function readDouble_f64_rev(buf, pos) {
            f8b[7] = buf[pos    ];
            f8b[6] = buf[pos + 1];
            f8b[5] = buf[pos + 2];
            f8b[4] = buf[pos + 3];
            f8b[3] = buf[pos + 4];
            f8b[2] = buf[pos + 5];
            f8b[1] = buf[pos + 6];
            f8b[0] = buf[pos + 7];
            return f64[0];
        }

        /* istanbul ignore next */
        exports.readDoubleLE = le ? readDouble_f64_cpy : readDouble_f64_rev;
        /* istanbul ignore next */
        exports.readDoubleBE = le ? readDouble_f64_rev : readDouble_f64_cpy;

    // double: ieee754
    })(); else (function() {

        function writeDouble_ieee754(writeUint, off0, off1, val, buf, pos) {
            var sign = val < 0 ? 1 : 0;
            if (sign)
                val = -val;
            if (val === 0) {
                writeUint(0, buf, pos + off0);
                writeUint(1 / val > 0 ? /* positive */ 0 : /* negative 0 */ 2147483648, buf, pos + off1);
            } else if (isNaN(val)) {
                writeUint(0, buf, pos + off0);
                writeUint(2146959360, buf, pos + off1);
            } else if (val > 1.7976931348623157e+308) { // +-Infinity
                writeUint(0, buf, pos + off0);
                writeUint((sign << 31 | 2146435072) >>> 0, buf, pos + off1);
            } else {
                var mantissa;
                if (val < 2.2250738585072014e-308) { // denormal
                    mantissa = val / 5e-324;
                    writeUint(mantissa >>> 0, buf, pos + off0);
                    writeUint((sign << 31 | mantissa / 4294967296) >>> 0, buf, pos + off1);
                } else {
                    var exponent = Math.floor(Math.log(val) / Math.LN2);
                    if (exponent === 1024)
                        exponent = 1023;
                    mantissa = val * Math.pow(2, -exponent);
                    writeUint(mantissa * 4503599627370496 >>> 0, buf, pos + off0);
                    writeUint((sign << 31 | exponent + 1023 << 20 | mantissa * 1048576 & 1048575) >>> 0, buf, pos + off1);
                }
            }
        }

        exports.writeDoubleLE = writeDouble_ieee754.bind(null, writeUintLE, 0, 4);
        exports.writeDoubleBE = writeDouble_ieee754.bind(null, writeUintBE, 4, 0);

        function readDouble_ieee754(readUint, off0, off1, buf, pos) {
            var lo = readUint(buf, pos + off0),
                hi = readUint(buf, pos + off1);
            var sign = (hi >> 31) * 2 + 1,
                exponent = hi >>> 20 & 2047,
                mantissa = 4294967296 * (hi & 1048575) + lo;
            return exponent === 2047
                ? mantissa
                ? NaN
                : sign * Infinity
                : exponent === 0 // denormal
                ? sign * 5e-324 * mantissa
                : sign * Math.pow(2, exponent - 1075) * (mantissa + 4503599627370496);
        }

        exports.readDoubleLE = readDouble_ieee754.bind(null, readUintLE, 0, 4);
        exports.readDoubleBE = readDouble_ieee754.bind(null, readUintBE, 4, 0);

    })();

    return exports;
}

// uint helpers

function writeUintLE(val, buf, pos) {
    buf[pos    ] =  val        & 255;
    buf[pos + 1] =  val >>> 8  & 255;
    buf[pos + 2] =  val >>> 16 & 255;
    buf[pos + 3] =  val >>> 24;
}

function writeUintBE(val, buf, pos) {
    buf[pos    ] =  val >>> 24;
    buf[pos + 1] =  val >>> 16 & 255;
    buf[pos + 2] =  val >>> 8  & 255;
    buf[pos + 3] =  val        & 255;
}

function readUintLE(buf, pos) {
    return (buf[pos    ]
          | buf[pos + 1] << 8
          | buf[pos + 2] << 16
          | buf[pos + 3] << 24) >>> 0;
}

function readUintBE(buf, pos) {
    return (buf[pos    ] << 24
          | buf[pos + 1] << 16
          | buf[pos + 2] << 8
          | buf[pos + 3]) >>> 0;
}