1  /*! ieee754. BSD-3-Clause License. Feross Aboukhadijeh <https://feross.org/opensource> */
 2  exports.read = function (buffer, offset, isLE, mLen, nBytes) {
 3    var e, m
 4    var eLen = (nBytes * 8) - mLen - 1
 5    var eMax = (1 << eLen) - 1
 6    var eBias = eMax >> 1
 7    var nBits = -7
 8    var i = isLE ? (nBytes - 1) : 0
 9    var d = isLE ? -1 : 1
10    var s = buffer[offset + i]
11  
12    i += d
13  
14    e = s & ((1 << (-nBits)) - 1)
15    s >>= (-nBits)
16    nBits += eLen
17    for (; nBits > 0; e = (e * 256) + buffer[offset + i], i += d, nBits -= 8) {}
18  
19    m = e & ((1 << (-nBits)) - 1)
20    e >>= (-nBits)
21    nBits += mLen
22    for (; nBits > 0; m = (m * 256) + buffer[offset + i], i += d, nBits -= 8) {}
23  
24    if (e === 0) {
25      e = 1 - eBias
26    } else if (e === eMax) {
27      return m ? NaN : ((s ? -1 : 1) * Infinity)
28    } else {
29      m = m + Math.pow(2, mLen)
30      e = e - eBias
31    }
32    return (s ? -1 : 1) * m * Math.pow(2, e - mLen)
33  }
34  
35  exports.write = function (buffer, value, offset, isLE, mLen, nBytes) {
36    var e, m, c
37    var eLen = (nBytes * 8) - mLen - 1
38    var eMax = (1 << eLen) - 1
39    var eBias = eMax >> 1
40    var rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0)
41    var i = isLE ? 0 : (nBytes - 1)
42    var d = isLE ? 1 : -1
43    var s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0
44  
45    value = Math.abs(value)
46  
47    if (isNaN(value) || value === Infinity) {
48      m = isNaN(value) ? 1 : 0
49      e = eMax
50    } else {
51      e = Math.floor(Math.log(value) / Math.LN2)
52      if (value * (c = Math.pow(2, -e)) < 1) {
53        e--
54        c *= 2
55      }
56      if (e + eBias >= 1) {
57        value += rt / c
58      } else {
59        value += rt * Math.pow(2, 1 - eBias)
60      }
61      if (value * c >= 2) {
62        e++
63        c /= 2
64      }
65  
66      if (e + eBias >= eMax) {
67        m = 0
68        e = eMax
69      } else if (e + eBias >= 1) {
70        m = ((value * c) - 1) * Math.pow(2, mLen)
71        e = e + eBias
72      } else {
73        m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen)
74        e = 0
75      }
76    }
77  
78    for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8) {}
79  
80    e = (e << mLen) | m
81    eLen += mLen
82    for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8) {}
83  
84    buffer[offset + i - d] |= s * 128
85  }