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85 lines
2.1 KiB
85 lines
2.1 KiB
/*! ieee754. BSD-3-Clause License. Feross Aboukhadijeh <https://feross.org/opensource> */ |
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exports.read = function (buffer, offset, isLE, mLen, nBytes) { |
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var e, m |
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var eLen = (nBytes * 8) - mLen - 1 |
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var eMax = (1 << eLen) - 1 |
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var eBias = eMax >> 1 |
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var nBits = -7 |
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var i = isLE ? (nBytes - 1) : 0 |
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var d = isLE ? -1 : 1 |
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var s = buffer[offset + i] |
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i += d |
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e = s & ((1 << (-nBits)) - 1) |
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s >>= (-nBits) |
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nBits += eLen |
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for (; nBits > 0; e = (e * 256) + buffer[offset + i], i += d, nBits -= 8) {} |
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m = e & ((1 << (-nBits)) - 1) |
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e >>= (-nBits) |
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nBits += mLen |
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for (; nBits > 0; m = (m * 256) + buffer[offset + i], i += d, nBits -= 8) {} |
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if (e === 0) { |
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e = 1 - eBias |
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} else if (e === eMax) { |
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return m ? NaN : ((s ? -1 : 1) * Infinity) |
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} else { |
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m = m + Math.pow(2, mLen) |
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e = e - eBias |
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} |
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return (s ? -1 : 1) * m * Math.pow(2, e - mLen) |
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} |
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exports.write = function (buffer, value, offset, isLE, mLen, nBytes) { |
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var e, m, c |
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var eLen = (nBytes * 8) - mLen - 1 |
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var eMax = (1 << eLen) - 1 |
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var eBias = eMax >> 1 |
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var rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0) |
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var i = isLE ? 0 : (nBytes - 1) |
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var d = isLE ? 1 : -1 |
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var s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0 |
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value = Math.abs(value) |
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if (isNaN(value) || value === Infinity) { |
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m = isNaN(value) ? 1 : 0 |
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e = eMax |
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} else { |
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e = Math.floor(Math.log(value) / Math.LN2) |
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if (value * (c = Math.pow(2, -e)) < 1) { |
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e-- |
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c *= 2 |
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} |
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if (e + eBias >= 1) { |
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value += rt / c |
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} else { |
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value += rt * Math.pow(2, 1 - eBias) |
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} |
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if (value * c >= 2) { |
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e++ |
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c /= 2 |
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} |
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if (e + eBias >= eMax) { |
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m = 0 |
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e = eMax |
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} else if (e + eBias >= 1) { |
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m = ((value * c) - 1) * Math.pow(2, mLen) |
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e = e + eBias |
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} else { |
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m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen) |
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e = 0 |
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} |
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} |
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for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8) {} |
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e = (e << mLen) | m |
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eLen += mLen |
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for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8) {} |
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buffer[offset + i - d] |= s * 128 |
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}
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