@petamoriken/float16/lib/_util/converter.cjs

IEEE 754 half-precision floating-point for JavaScript

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.convertToNumber = convertToNumber;
exports.roundToFloat16 = roundToFloat16;
exports.roundToFloat16Bits = roundToFloat16Bits;
var _primordials = require("./primordials.cjs");
const INVERSE_OF_EPSILON = 1 / _primordials.EPSILON;
function roundTiesToEven(num) {
  return num + INVERSE_OF_EPSILON - INVERSE_OF_EPSILON;
}
const FLOAT16_MIN_VALUE = 6.103515625e-05;
const FLOAT16_MAX_VALUE = 65504;
const FLOAT16_EPSILON = 0.0009765625;
const FLOAT16_EPSILON_MULTIPLIED_BY_FLOAT16_MIN_VALUE = FLOAT16_EPSILON * FLOAT16_MIN_VALUE;
const FLOAT16_EPSILON_DEVIDED_BY_EPSILON = FLOAT16_EPSILON * INVERSE_OF_EPSILON;
function roundToFloat16(num) {
  const number = +num;
  if (!(0, _primordials.NumberIsFinite)(number) || number === 0) {
    return number;
  }
  const sign = number > 0 ? 1 : -1;
  const absolute = (0, _primordials.MathAbs)(number);
  if (absolute < FLOAT16_MIN_VALUE) {
    return sign * roundTiesToEven(absolute / FLOAT16_EPSILON_MULTIPLIED_BY_FLOAT16_MIN_VALUE) * FLOAT16_EPSILON_MULTIPLIED_BY_FLOAT16_MIN_VALUE;
  }
  const temp = (1 + FLOAT16_EPSILON_DEVIDED_BY_EPSILON) * absolute;
  const result = temp - (temp - absolute);
  if (result > FLOAT16_MAX_VALUE || (0, _primordials.NumberIsNaN)(result)) {
    return sign * Infinity;
  }
  return sign * result;
}
const buffer = new _primordials.NativeArrayBuffer(4);
const floatView = new _primordials.NativeFloat32Array(buffer);
const uint32View = new _primordials.NativeUint32Array(buffer);
const baseTable = new _primordials.NativeUint16Array(512);
const shiftTable = new _primordials.NativeUint8Array(512);
for (let i = 0; i < 256; ++i) {
  const e = i - 127;
  if (e < -24) {
    baseTable[i] = 0x0000;
    baseTable[i | 0x100] = 0x8000;
    shiftTable[i] = 24;
    shiftTable[i | 0x100] = 24;
  } else if (e < -14) {
    baseTable[i] = 0x0400 >> -e - 14;
    baseTable[i | 0x100] = 0x0400 >> -e - 14 | 0x8000;
    shiftTable[i] = -e - 1;
    shiftTable[i | 0x100] = -e - 1;
  } else if (e <= 15) {
    baseTable[i] = e + 15 << 10;
    baseTable[i | 0x100] = e + 15 << 10 | 0x8000;
    shiftTable[i] = 13;
    shiftTable[i | 0x100] = 13;
  } else if (e < 128) {
    baseTable[i] = 0x7c00;
    baseTable[i | 0x100] = 0xfc00;
    shiftTable[i] = 24;
    shiftTable[i | 0x100] = 24;
  } else {
    baseTable[i] = 0x7c00;
    baseTable[i | 0x100] = 0xfc00;
    shiftTable[i] = 13;
    shiftTable[i | 0x100] = 13;
  }
}
function roundToFloat16Bits(num) {
  floatView[0] = roundToFloat16(num);
  const f = uint32View[0];
  const e = f >> 23 & 0x1ff;
  return baseTable[e] + ((f & 0x007fffff) >> shiftTable[e]);
}
const mantissaTable = new _primordials.NativeUint32Array(2048);
for (let i = 1; i < 1024; ++i) {
  let m = i << 13;
  let e = 0;
  while ((m & 0x00800000) === 0) {
    m <<= 1;
    e -= 0x00800000;
  }
  m &= ~0x00800000;
  e += 0x38800000;
  mantissaTable[i] = m | e;
}
for (let i = 1024; i < 2048; ++i) {
  mantissaTable[i] = 0x38000000 + (i - 1024 << 13);
}
const exponentTable = new _primordials.NativeUint32Array(64);
for (let i = 1; i < 31; ++i) {
  exponentTable[i] = i << 23;
}
exponentTable[31] = 0x47800000;
exponentTable[32] = 0x80000000;
for (let i = 33; i < 63; ++i) {
  exponentTable[i] = 0x80000000 + (i - 32 << 23);
}
exponentTable[63] = 0xc7800000;
const offsetTable = new _primordials.NativeUint16Array(64);
for (let i = 1; i < 64; ++i) {
  if (i !== 32) {
    offsetTable[i] = 1024;
  }
}
function convertToNumber(float16bits) {
  const i = float16bits >> 10;
  uint32View[0] = mantissaTable[offsetTable[i] + (float16bits & 0x3ff)] + exponentTable[i];
  return floatView[0];
}