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96 lines
2.1 KiB
96 lines
2.1 KiB
"use strict"; |
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Object.defineProperty(exports, "__esModule", { |
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value: true |
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}); |
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exports.read = read; |
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exports.write = write; |
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function read(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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function write(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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