aaac7fed
 liuqimichale
add
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exports.read = function (buffer, offset, isLE, mLen, nBytes) {
var e, m
var eLen = (nBytes * 8) - mLen - 1
var eMax = (1 << eLen) - 1
var eBias = eMax >> 1
var nBits = -7
var i = isLE ? (nBytes - 1) : 0
var d = isLE ? -1 : 1
var s = buffer[offset + i]
i += d
e = s & ((1 << (-nBits)) - 1)
s >>= (-nBits)
nBits += eLen
for (; nBits > 0; e = (e * 256) + buffer[offset + i], i += d, nBits -= 8) {}
m = e & ((1 << (-nBits)) - 1)
e >>= (-nBits)
nBits += mLen
for (; nBits > 0; m = (m * 256) + buffer[offset + i], i += d, nBits -= 8) {}
if (e === 0) {
e = 1 - eBias
} else if (e === eMax) {
return m ? NaN : ((s ? -1 : 1) * Infinity)
} else {
m = m + Math.pow(2, mLen)
e = e - eBias
}
return (s ? -1 : 1) * m * Math.pow(2, e - mLen)
}
exports.write = function (buffer, value, offset, isLE, mLen, nBytes) {
var e, m, c
var eLen = (nBytes * 8) - mLen - 1
var eMax = (1 << eLen) - 1
var eBias = eMax >> 1
var rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0)
var i = isLE ? 0 : (nBytes - 1)
var d = isLE ? 1 : -1
var s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0
value = Math.abs(value)
if (isNaN(value) || value === Infinity) {
m = isNaN(value) ? 1 : 0
e = eMax
} else {
e = Math.floor(Math.log(value) / Math.LN2)
if (value * (c = Math.pow(2, -e)) < 1) {
e--
c *= 2
}
if (e + eBias >= 1) {
value += rt / c
} else {
value += rt * Math.pow(2, 1 - eBias)
}
if (value * c >= 2) {
e++
c /= 2
}
if (e + eBias >= eMax) {
m = 0
e = eMax
} else if (e + eBias >= 1) {
m = ((value * c) - 1) * Math.pow(2, mLen)
e = e + eBias
} else {
m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen)
e = 0
}
}
for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8) {}
e = (e << mLen) | m
eLen += mLen
for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8) {}
buffer[offset + i - d] |= s * 128
}
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