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export function read(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) | |
} | |
export function write(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 | |
} | |