public float ReadHalf()
{
var encoded = ReadUInt16();
// Decode half float
// Based on numpy implementation (https://github.com/numpy/numpy/blob/984bc91367f9b525eadef14c48c759999bc4adfc/numpy/core/src/npymath/halffloat.c#L477)
uint decoded;
uint halfExponent = (encoded & 0x7c00u);
uint singleSign = (encoded & 0x8000u) << 16;
switch (halfExponent)
{
case 0x0000u: /* 0 or subnormal */
uint halfSign = (encoded & 0x03ffu);
if (halfSign == 0)
{
/* Signed zero */
decoded = singleSign;
}
else
{
/* Subnormal */
halfSign <<= 1;
while ((halfSign & 0x0400u) == 0)
{
halfSign <<= 1;
halfExponent++;
}
uint singleExponent = 127 - 15 - halfExponent << 23;
uint singleSig = (halfSign & 0x03ffu) << 13;
decoded = singleSign + singleExponent + singleSig;
}
break;
case 0x7c00u: /* inf or NaN */
/* All-ones exponent and a copy of the significand */
decoded = singleSign + 0x7f800000u + ((encoded & 0x03ffu) << 13);
break;
default: /* normalized */
/* Just need to adjust the exponent and shift */
decoded = singleSign + (((encoded & 0x7fffu) + 0x1c000u) << 13);
break;
}
return(UnsafeUtilities.ReinterpretCast <uint, float>(decoded));
}
// https://blog.fpmurphy.com/2008/12/half-precision-floating-point-format_14.html
private static ushort FloatToHalf(float value)
{
int i = UnsafeUtilities.ReinterpretCast <float, int>(value);
int s = (i >> 16) & 0x00008000; // sign
int e = ((i >> 23) & 0x000000ff) - (127 - 15); // exponent
int f = i & 0x007fffff; // fraction
// need to handle NaNs and Inf?
if (e <= 0)
{
if (e < -10)
{
if (s > 0) // handle -0.0
{
return(0x8000);
}
else
{
return(0);
}
}
f = (f | 0x00800000) >> (1 - e);
return(( ushort )(s | (f >> 13)));
}
else if (e == 0xff - (127 - 15))
{
if (f == 0) // Inf
{
return(( ushort )(s | 0x7c00));
}
else
{
// NAN
f >>= 13;
return(( ushort )(s | 0x7c00 | f | (f == 0 ? 1 : 0)));
}
}
else
{
if (e > 30) // Overflow
{
return(( ushort )(s | 0x7c00));
}
return(( ushort )(s | (e << 10) | (f >> 13)));
}
}