FastBinaryEncoding/projects/JavaScript/proto/ieee754.js at main · chronoxor/FastBinaryEncoding · GitHub

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//------------------------------------------------------------------------------
// Automatically generated by the Fast Binary Encoding compiler, do not modify!
// https://github.com/chronoxor/FastBinaryEncoding
// Source: FBE
// FBE version: 1.15.0.0
//------------------------------------------------------------------------------

/* eslint-disable prefer-const,no-loss-of-precision */
'use strict'

/**
 * Read float/double value from the given buffer
 * @param {!Buffer|!Uint8Array} buffer Buffer to read
 * @param {!number} offset Buffer offset
 * @param {!boolean} isLE Little endian flag
 * @param {!number} mLen Value length (float = 23; double = 52)
 * @param {!number} nBytes Value size in bytes (float = 4; double = 8)
 * @returns {!number} Float/Double value
 */
let ieee754read = function (buffer, offset, isLE, mLen, nBytes) {
  let e, m
  let eLen = (nBytes * 8) - mLen - 1
  let eMax = (1 << eLen) - 1
  let eBias = eMax >> 1
  let nBits = -7
  let i = isLE ? (nBytes - 1) : 0
  let d = isLE ? -1 : 1
  let s = buffer[offset + i]

  i += d

  e = s & ((1 << (-nBits)) - 1)
  s >>= (-nBits)
  nBits += eLen
  for (; nBits > 0; e = (e * 256) + buffer[offset + i], i += d, nBits -= 8);

  m = e & ((1 << (-nBits)) - 1)
  e >>= (-nBits)
  nBits += mLen
  for (; nBits > 0; m = (m * 256) + buffer[offset + i], i += d, nBits -= 8);

  if (e === 0) {
    e = 1 - eBias
  } else if (e === eMax) {
    return m ? NaN : ((s ? -1 : 1) * Infinity)
  } else {
    m = m + Math.pow(2, mLen)
    e = e - eBias
  }
  return (s ? -1 : 1) * m * Math.pow(2, e - mLen)
}

exports.ieee754read = ieee754read

/**
 * Write float/double value into the given buffer
 * @param {!Buffer|!Uint8Array} buffer Buffer to write
 * @param {!number} offset Buffer offset
 * @param {!number} value Value to write
 * @param {!boolean} isLE Little endian flag
 * @param {!number} mLen Value length (float = 23; double = 52)
 * @param {!number} nBytes Value size in bytes (float = 4; double = 8)
 */
let ieee754write = function (buffer, offset, value, isLE, mLen, nBytes) {
  let e, m, c
  let eLen = (nBytes * 8) - mLen - 1
  let eMax = (1 << eLen) - 1
  let eBias = eMax >> 1
  let rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0)
  let i = isLE ? 0 : (nBytes - 1)
  let d = isLE ? 1 : -1
  let s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0

  value = Math.abs(value)

  if (isNaN(value) || value === Infinity) {
    m = isNaN(value) ? 1 : 0
    e = eMax
  } else {
    e = Math.floor(Math.log(value) / Math.LN2)
    if (value * (c = Math.pow(2, -e)) < 1) {
      e--
      c *= 2
    }
    if (e + eBias >= 1) {
      value += rt / c
    } else {
      value += rt * Math.pow(2, 1 - eBias)
    }
    if (value * c >= 2) {
      e++
      c /= 2
    }

    if (e + eBias >= eMax) {
      m = 0
      e = eMax
    } else if (e + eBias >= 1) {
      m = ((value * c) - 1) * Math.pow(2, mLen)
      e = e + eBias
    } else {
      m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen)
      e = 0
    }
  }

  for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8);

  e = (e << mLen) | m
  eLen += mLen
  for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8);

  buffer[offset + i - d] |= s * 128
}

exports.ieee754write = ieee754write