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117 lines
3.7 KiB
JavaScript
117 lines
3.7 KiB
JavaScript
// Copyright (c) 2008, Fair Oaks Labs, Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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//
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// * Neither the name of Fair Oaks Labs, Inc. nor the names of its contributors
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// may be used to endorse or promote products derived from this software
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// without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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//
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// Modifications to writeIEEE754 to support negative zeroes made by Brian White
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exports.readIEEE754 = function(buffer, offset, isBE, mLen, nBytes) {
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var e, m,
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eLen = nBytes * 8 - mLen - 1,
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eMax = (1 << eLen) - 1,
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eBias = eMax >> 1,
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nBits = -7,
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i = isBE ? 0 : (nBytes - 1),
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d = isBE ? 1 : -1,
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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.writeIEEE754 = function(buffer, value, offset, isBE, mLen, nBytes) {
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var e, m, c,
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eLen = nBytes * 8 - mLen - 1,
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eMax = (1 << eLen) - 1,
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eBias = eMax >> 1,
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rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0),
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i = isBE ? (nBytes - 1) : 0,
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d = isBE ? -1 : 1,
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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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