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/*

 * Copyright (C) 2011 Marek Olšák 

 *

 * 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 AUTHORS OR COPYRIGHT HOLDERS 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.

 */

/* Copied from EXT_texture_shared_exponent and edited. */

#ifndef RGB9E5_H

#define RGB9E5_H

#include 

#include 

#define RGB9E5_EXPONENT_BITS          5

#define RGB9E5_MANTISSA_BITS          9

#define RGB9E5_EXP_BIAS               15

#define RGB9E5_MAX_VALID_BIASED_EXP   31

#define MAX_RGB9E5_EXP               (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS)

#define RGB9E5_MANTISSA_VALUES       (1<

#define MAX_RGB9E5_MANTISSA          (RGB9E5_MANTISSA_VALUES-1)

#define MAX_RGB9E5                   (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<

#define EPSILON_RGB9E5               ((1.0/RGB9E5_MANTISSA_VALUES) / (1<

typedef union {

   unsigned int raw;

   float value;

   struct {

#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)

      unsigned int negative:1;

      unsigned int biasedexponent:8;

      unsigned int mantissa:23;

#else

      unsigned int mantissa:23;

      unsigned int biasedexponent:8;

      unsigned int negative:1;

#endif

   } field;

} float754;

typedef union {

   unsigned int raw;

   struct {

#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)

      unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;

      unsigned int b:RGB9E5_MANTISSA_BITS;

      unsigned int g:RGB9E5_MANTISSA_BITS;

      unsigned int r:RGB9E5_MANTISSA_BITS;

#else

      unsigned int r:RGB9E5_MANTISSA_BITS;

      unsigned int g:RGB9E5_MANTISSA_BITS;

      unsigned int b:RGB9E5_MANTISSA_BITS;

      unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;

#endif

   } field;

} rgb9e5;

static INLINE float rgb9e5_ClampRange(float x)

{

   if (x > 0.0) {

      if (x >= MAX_RGB9E5) {

         return MAX_RGB9E5;

      } else {

         return x;

      }

   } else {

      /* NaN gets here too since comparisons with NaN always fail! */

      return 0.0;

   }

}

/* Ok, FloorLog2 is not correct for the denorm and zero values, but we

   are going to do a max of this value with the minimum rgb9e5 exponent

   that will hide these problem cases. */

static INLINE int rgb9e5_FloorLog2(float x)

{

   float754 f;

   f.value = x;

   return (f.field.biasedexponent - 127);

}

static INLINE unsigned float3_to_rgb9e5(const float rgb[3])

{

   rgb9e5 retval;

   float maxrgb;

   int rm, gm, bm;

   float rc, gc, bc;

   int exp_shared, maxm;

   double denom;

   rc = rgb9e5_ClampRange(rgb[0]);

   gc = rgb9e5_ClampRange(rgb[1]);

   bc = rgb9e5_ClampRange(rgb[2]);

   maxrgb = MAX3(rc, gc, bc);

   exp_shared = MAX2(-RGB9E5_EXP_BIAS-1, rgb9e5_FloorLog2(maxrgb)) + 1 + RGB9E5_EXP_BIAS;

   assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);

   assert(exp_shared >= 0);

   /* This pow function could be replaced by a table. */

   denom = pow(2, exp_shared - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS);

   maxm = (int) floor(maxrgb / denom + 0.5);

   if (maxm == MAX_RGB9E5_MANTISSA+1) {

      denom *= 2;

      exp_shared += 1;

      assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);

   } else {

      assert(maxm <= MAX_RGB9E5_MANTISSA);

   }

   rm = (int) floor(rc / denom + 0.5);

   gm = (int) floor(gc / denom + 0.5);

   bm = (int) floor(bc / denom + 0.5);

   assert(rm <= MAX_RGB9E5_MANTISSA);

   assert(gm <= MAX_RGB9E5_MANTISSA);

   assert(bm <= MAX_RGB9E5_MANTISSA);

   assert(rm >= 0);

   assert(gm >= 0);

   assert(bm >= 0);

   retval.field.r = rm;

   retval.field.g = gm;

   retval.field.b = bm;

   retval.field.biasedexponent = exp_shared;

   return retval.raw;

}

static INLINE void rgb9e5_to_float3(unsigned rgb, float retval[3])

{

   rgb9e5 v;

   int exponent;

   float scale;

   v.raw = rgb;

   exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;

   scale = (float) pow(2, exponent);

   retval[0] = v.field.r * scale;

   retval[1] = v.field.g * scale;

   retval[2] = v.field.b * scale;

}

#endif