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/**************************************************************************
*
* Copyright 2010 Luca Barbieri
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
**************************************************************************/
#ifndef U_HALF_H
#define U_HALF_H
#ifdef __cplusplus
extern "C" {
#endif
union fi {
float f;
int32_t i;
uint32_t ui;
};
/*
* References for float <-> half conversions
*
* http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
* https://gist.github.com/2156668
* https://gist.github.com/2144712
*/
static inline uint16_t
util_float_to_half(float f)
{
uint32_t sign_mask = 0x80000000;
uint32_t round_mask = ~0xfff;
uint32_t f32inf = 0xff << 23;
uint32_t f16inf = 0x1f << 23;
uint32_t sign;
union fi magic;
union fi f32;
uint16_t f16;
magic.ui = 0xf << 23;
f32.f = f;
/* Sign */
sign = f32.ui & sign_mask;
f32.ui ^= sign;
if (f32.ui == f32inf) {
/* Inf */
f16 = 0x7c00;
} else if (f32.ui > f32inf) {
/* NaN */
f16 = 0x7e00;
} else {
/* Number */
f32.ui &= round_mask;
f32.f *= magic.f;
f32.ui -= round_mask;
/*
* Clamp to max finite value if overflowed.
* OpenGL has completely undefined rounding behavior for float to
* half-float conversions, and this matches what is mandated for float
* to fp11/fp10, which recommend round-to-nearest-finite too.
* (d3d10 is deeply unhappy about flushing such values to infinity, and
* while it also mandates round-to-zero it doesn't care nearly as much
* about that.)
*/
if (f32.ui > f16inf)
f32.ui = f16inf - 1;
f16 = f32.ui >> 13;
}
/* Sign */
f16 |= sign >> 16;
return f16;
}
static inline float
util_half_to_float(uint16_t f16)
{
union fi infnan;
union fi magic;
union fi f32;
infnan.ui = 0x8f << 23;
infnan.f = 65536.0f;
magic.ui = 0xef << 23;
/* Exponent / Mantissa */
f32.ui = (f16 & 0x7fff) << 13;
/* Adjust */
f32.f *= magic.f;
/* Inf / NaN */
if (f32.f >= infnan.f)
f32.ui |= 0xff << 23;
/* Sign */
f32.ui |= (f16 & 0x8000) << 16;
return f32.f;
}
#ifdef __cplusplus
}
#endif
#endif /* U_HALF_H */
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