FloatParser.packFloatBits_ - Code Metrics - Inspection of "Update docs with v11.0" - rochars/wavefile - Measure and Improve Code Quality continuously with Scrutinizer

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by Rafael S.

created 2020-01-30 04:04 UTC

FloatParser.packFloatBits_ B

↳ Parent: FloatParser

Complexity

Conditions

Size

Total Lines	31
Code Lines	19

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	6
eloc	19
dl	0
loc	31
rs	8.5166
c	0
b	0
f	0

/*
 * Copyright (c) 2018-2019 Rafael da Silva Rocha.
 * Copyright (c) 2013 DeNA Co., Ltd.
 * Copyright (c) 2010, Linden Research, Inc
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 */

/**
 * @fileoverview Encode and decode IEEE 754 floating point numbers.
 * @see https://github.com/rochars/byte-data
 * @see https://github.com/rochars/wavefile
 * @see https://bitbucket.org/lindenlab/llsd/raw/7d2646cd3f9b4c806e73aebc4b32bd81e4047fdc/js/typedarray.js
 * @see https://github.com/kazuho/ieee754.js/blob/master/ieee754.js
 */

/**
 * A class to encode and decode IEEE 754 floating-point numbers.
 */
export class FloatParser {

  /**
   * Pack a IEEE 754 floating point number.
   * @param {number} ebits The exponent bits.
   * @param {number} fbits The fraction bits.
   */
  constructor(ebits, fbits) {
    /**
     * @type {number}
     */
    this.offset = Math.ceil((ebits + fbits) / 8);
    /**
     * @type {number}
     * @private
     */
    this.ebits = ebits;
    /**
     * @type {number}
     * @private
     */
    this.fbits = fbits;
    /**
     * @type {number}
     * @private
     */
    this.bias = (1 << (ebits - 1)) - 1;
    /**
     * @type {number}
     * @private
     */
    this.biasP2 = Math.pow(2, this.bias + 1);
    /**
     * @type {number}
     * @private
     */
    this.ebitsFbits = (ebits + fbits);
    /**
     * @type {number}
     * @private
     */
    this.fbias = Math.pow(2, -(8 * this.offset - 1 - ebits));
  }

  /**
   * Pack a IEEE 754 floating point number.
   * @param {!Uint8Array|!Array<number>} buffer The buffer.
   * @param {number} num The number.
   * @param {number} index The index to write on the buffer.
   * @return {number} The next index to write on the buffer.
   */
  pack(buffer, num, index) {
    // Round overflows
    if (Math.abs(num) > this.biasP2 - (this.ebitsFbits * 2)) {
      num = num < 0 ? -Infinity : Infinity;
    }
    /**
     * sign, need this to handle negative zero
     * @see http://cwestblog.com/2014/02/25/javascript-testing-for-negative-zero/
     * @type {number}
     */
    let sign = (((num = +num) || 1 / num) < 0) ? 1 : num < 0 ? 1 : 0;
    num = Math.abs(num);
    /** @type {number} */
    let exp = Math.min(Math.floor(Math.log(num) / Math.LN2), 1023);
    /** @type {number} */
    let fraction = roundToEven(num / Math.pow(2, exp) * Math.pow(2, this.fbits));
    // NaN
    if (num !== num) {
      fraction = Math.pow(2, this.fbits - 1);
      exp = (1 << this.ebits) - 1;
    // Number
    } else if (num !== 0) {
      if (num >= Math.pow(2, 1 - this.bias)) {
        if (fraction / Math.pow(2, this.fbits) >= 2) {
          exp = exp + 1;
          fraction = 1;
        }
        // Overflow
        if (exp > this.bias) {
          exp = (1 << this.ebits) - 1;
          fraction = 0;
        } else {
          exp = exp + this.bias;
          fraction = roundToEven(fraction) - Math.pow(2, this.fbits);
        }
      } else {
        fraction = roundToEven(num / Math.pow(2, 1 - this.bias - this.fbits));
        exp = 0;
      } 
    }
    return this.packFloatBits_(buffer, index, sign, exp, fraction);
  }

  /**
   * Unpack a IEEE 754 floating point number.
   * Derived from IEEE754 by DeNA Co., Ltd., MIT License. 
   * Adapted to handle NaN. Should port the solution to the original repo.
   * @param {!Uint8Array|!Array<number>} buffer The buffer.
   * @param {number} index The index to read from the buffer.
   * @return {number} The floating point number.
   */
  unpack(buffer, index) {
    /** @type {number} */
    let eMax = (1 << this.ebits) - 1;
    /** @type {number} */
    let significand;
    /** @type {string} */
    let leftBits = "";
    for (let i = this.offset - 1; i >= 0 ; i--) {
      /** @type {string} */
      let t = buffer[i + index].toString(2);
      leftBits += "00000000".substring(t.length) + t;
    }
    /** @type {number} */
    let sign = leftBits.charAt(0) == "1" ? -1 : 1;
    leftBits = leftBits.substring(1);
    /** @type {number} */
    let exponent = parseInt(leftBits.substring(0, this.ebits), 2);
    leftBits = leftBits.substring(this.ebits);
    if (exponent == eMax) {
      if (parseInt(leftBits, 2) !== 0) {
        return NaN;
      }
      return sign * Infinity;  
    } else if (exponent === 0) {
      exponent += 1;
      significand = parseInt(leftBits, 2);
    } else {
      significand = parseInt("1" + leftBits, 2);
    }
    return sign * significand * this.fbias * Math.pow(2, exponent - this.bias);
  }

  /**
   * Pack a IEEE754 from its sign, exponent and fraction bits
   * and place it in a byte buffer.
   * @param {!Uint8Array|!Array<number>} buffer The byte buffer to write to.
   * @param {number} index The buffer index to write.
   * @param {number} sign The sign.
   * @param {number} exp the exponent.
   * @param {number} fraction The fraction.
   * @return {number}
   * @private
   */
  packFloatBits_(buffer, index, sign, exp, fraction) {
    /** @type {!Array<number>} */
    let bits = [];
    // the sign
    bits.push(sign);
    // the exponent
    for (let i = this.ebits; i > 0; i -= 1) {
      bits[i] = (exp % 2 ? 1 : 0);
      exp = Math.floor(exp / 2);
    }
    // the fraction
    let len = bits.length;
    for (let i = this.fbits; i > 0; i -= 1) {
      bits[len + i] = (fraction % 2 ? 1 : 0);
      fraction = Math.floor(fraction / 2);
    }
    // pack as bytes
    /** @type {string} */
    let str = bits.join('');
    /** @type {number} */
    let offset = this.offset + index - 1;
    /** @type {number} */
    let k = index;
    while (offset >= index) {
      buffer[offset] = parseInt(str.substring(0, 8), 2);
      str = str.substring(8);
      offset--;
      k++;
    }
    return k;
  }
}

/**
 * Round a number to its nearest even value.
 * @param {number} n The number.
 * @return {number}
 * @private
 */
function roundToEven(n) {
  /** @type {number} */
  let w = Math.floor(n);
  let f = n - w;
  if (f < 0.5) {
    return w;
  }
  if (f > 0.5) {
    return w + 1;
  }
  return w % 2 ? w + 1 : w;
}


1			/*
2			* Copyright (c) 2018-2019 Rafael da Silva Rocha.
3			* Copyright (c) 2013 DeNA Co., Ltd.
4			* Copyright (c) 2010, Linden Research, Inc
5			*
6			* Permission is hereby granted, free of charge, to any person obtaining
7			* a copy of this software and associated documentation files (the
8			* "Software"), to deal in the Software without restriction, including
9			* without limitation the rights to use, copy, modify, merge, publish,
10			* distribute, sublicense, and/or sell copies of the Software, and to
11			* permit persons to whom the Software is furnished to do so, subject to
12			* the following conditions:
13			*
14			* The above copyright notice and this permission notice shall be
15			* included in all copies or substantial portions of the Software.
16			*
17			* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18			* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19			* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20			* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
21			* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
22			* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
23			* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24			*
25			*/
26
27			/**
28			* @fileoverview Encode and decode IEEE 754 floating point numbers.
29			* @see https://github.com/rochars/byte-data
30			* @see https://github.com/rochars/wavefile
31			* @see https://bitbucket.org/lindenlab/llsd/raw/7d2646cd3f9b4c806e73aebc4b32bd81e4047fdc/js/typedarray.js
32			* @see https://github.com/kazuho/ieee754.js/blob/master/ieee754.js
33			*/
34
35			/**
36			* A class to encode and decode IEEE 754 floating-point numbers.
37			*/
38			export class FloatParser {
39
40			/**
41			* Pack a IEEE 754 floating point number.
42			* @param {number} ebits The exponent bits.
43			* @param {number} fbits The fraction bits.
44			*/
45			constructor(ebits, fbits) {
46			/**
47			* @type {number}
48			*/
49			this.offset = Math.ceil((ebits + fbits) / 8);
50			/**
51			* @type {number}
52			* @private
53			*/
54			this.ebits = ebits;
55			/**
56			* @type {number}
57			* @private
58			*/
59			this.fbits = fbits;
60			/**
61			* @type {number}
62			* @private
63			*/
64			this.bias = (1 << (ebits - 1)) - 1;
65			/**
66			* @type {number}
67			* @private
68			*/
69			this.biasP2 = Math.pow(2, this.bias + 1);
70			/**
71			* @type {number}
72			* @private
73			*/
74			this.ebitsFbits = (ebits + fbits);
75			/**
76			* @type {number}
77			* @private
78			*/
79			this.fbias = Math.pow(2, -(8 * this.offset - 1 - ebits));
80			}
81
82			/**
83			* Pack a IEEE 754 floating point number.
84			* @param {!Uint8Array\|!Array<number>} buffer The buffer.
85			* @param {number} num The number.
86			* @param {number} index The index to write on the buffer.
87			* @return {number} The next index to write on the buffer.
88			*/
89			pack(buffer, num, index) {
90			// Round overflows
91			if (Math.abs(num) > this.biasP2 - (this.ebitsFbits * 2)) {
92			num = num < 0 ? -Infinity : Infinity;
93			}
94			/**
95			* sign, need this to handle negative zero
96			* @see http://cwestblog.com/2014/02/25/javascript-testing-for-negative-zero/
97			* @type {number}
98			*/
99			let sign = (((num = +num) \|\| 1 / num) < 0) ? 1 : num < 0 ? 1 : 0;
100			num = Math.abs(num);
101			/** @type {number} */
102			let exp = Math.min(Math.floor(Math.log(num) / Math.LN2), 1023);
103			/** @type {number} */
104			let fraction = roundToEven(num / Math.pow(2, exp) * Math.pow(2, this.fbits));
105			// NaN
106			if (num !== num) {
107			fraction = Math.pow(2, this.fbits - 1);
108			exp = (1 << this.ebits) - 1;
109			// Number
110			} else if (num !== 0) {
111			if (num >= Math.pow(2, 1 - this.bias)) {
112			if (fraction / Math.pow(2, this.fbits) >= 2) {
113			exp = exp + 1;
114			fraction = 1;
115			}
116			// Overflow
117			if (exp > this.bias) {
118			exp = (1 << this.ebits) - 1;
119			fraction = 0;
120			} else {
121			exp = exp + this.bias;
122			fraction = roundToEven(fraction) - Math.pow(2, this.fbits);
123			}
124			} else {
125			fraction = roundToEven(num / Math.pow(2, 1 - this.bias - this.fbits));
126			exp = 0;
127			}
128			}
129			return this.packFloatBits_(buffer, index, sign, exp, fraction);
130			}
131
132			/**
133			* Unpack a IEEE 754 floating point number.
134			* Derived from IEEE754 by DeNA Co., Ltd., MIT License.
135			* Adapted to handle NaN. Should port the solution to the original repo.
136			* @param {!Uint8Array\|!Array<number>} buffer The buffer.
137			* @param {number} index The index to read from the buffer.
138			* @return {number} The floating point number.
139			*/
140			unpack(buffer, index) {
141			/** @type {number} */
142			let eMax = (1 << this.ebits) - 1;
143			/** @type {number} */
144			let significand;
145			/** @type {string} */
146			let leftBits = "";
147			for (let i = this.offset - 1; i >= 0 ; i--) {
148			/** @type {string} */
149			let t = buffer[i + index].toString(2);
150			leftBits += "00000000".substring(t.length) + t;
151			}
152			/** @type {number} */
153			let sign = leftBits.charAt(0) == "1" ? -1 : 1;
154			leftBits = leftBits.substring(1);
155			/** @type {number} */
156			let exponent = parseInt(leftBits.substring(0, this.ebits), 2);
157			leftBits = leftBits.substring(this.ebits);
158			if (exponent == eMax) {
159			if (parseInt(leftBits, 2) !== 0) {
160			return NaN;
161			}
162			return sign * Infinity;
163			} else if (exponent === 0) {
164			exponent += 1;
165			significand = parseInt(leftBits, 2);
166			} else {
167			significand = parseInt("1" + leftBits, 2);
168			}
169			return sign * significand * this.fbias * Math.pow(2, exponent - this.bias);
170			}
171
172			/**
173			* Pack a IEEE754 from its sign, exponent and fraction bits
174			* and place it in a byte buffer.
175			* @param {!Uint8Array\|!Array<number>} buffer The byte buffer to write to.
176			* @param {number} index The buffer index to write.
177			* @param {number} sign The sign.
178			* @param {number} exp the exponent.
179			* @param {number} fraction The fraction.
180			* @return {number}
181			* @private
182			*/
183			packFloatBits_(buffer, index, sign, exp, fraction) {
184			/** @type {!Array<number>} */
185			let bits = [];
186			// the sign
187			bits.push(sign);
188			// the exponent
189			for (let i = this.ebits; i > 0; i -= 1) {
190			bits[i] = (exp % 2 ? 1 : 0);
191			exp = Math.floor(exp / 2);
192			}
193			// the fraction
194			let len = bits.length;
195			for (let i = this.fbits; i > 0; i -= 1) {
196			bits[len + i] = (fraction % 2 ? 1 : 0);
197			fraction = Math.floor(fraction / 2);
198			}
199			// pack as bytes
200			/** @type {string} */
201			let str = bits.join('');
202			/** @type {number} */
203			let offset = this.offset + index - 1;
204			/** @type {number} */
205			let k = index;
206			while (offset >= index) {
207			buffer[offset] = parseInt(str.substring(0, 8), 2);
208			str = str.substring(8);
209			offset--;
210			k++;
211			}
212			return k;
213			}
214			}
215
216			/**
217			* Round a number to its nearest even value.
218			* @param {number} n The number.
219			* @return {number}
220			* @private
221			*/
222			function roundToEven(n) {
223			/** @type {number} */
224			let w = Math.floor(n);
225			let f = n - w;
226			if (f < 0.5) {
227			return w;
228			}
229			if (f > 0.5) {
230			return w + 1;
231			}
232			return w % 2 ? w + 1 : w;
233			}
234

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