233 lines
6.6 KiB
C
233 lines
6.6 KiB
C
/*
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* Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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/* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J.
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* Available here: http://www.opengl-redbook.com/appendices/
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* The algorithm in the book contains a bug though, which is fixed in the code
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* below.
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*/
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#define UF11(e, m) ((e << 6) | (m))
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#define UF11_EXPONENT_BIAS 15
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#define UF11_EXPONENT_BITS 0x1F
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#define UF11_EXPONENT_SHIFT 6
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#define UF11_MANTISSA_BITS 0x3F
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#define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT)
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#define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)
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#define UF10(e, m) ((e << 5) | (m))
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#define UF10_EXPONENT_BIAS 15
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#define UF10_EXPONENT_BITS 0x1F
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#define UF10_EXPONENT_SHIFT 5
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#define UF10_MANTISSA_BITS 0x1F
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#define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT)
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#define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)
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#define F32_INFINITY 0x7f800000
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static INLINE unsigned f32_to_uf11(float val)
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{
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union {
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float f;
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uint32_t ui;
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} f32 = {val};
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uint16_t uf11 = 0;
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/* Decode little-endian 32-bit floating-point value */
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int sign = (f32.ui >> 16) & 0x8000;
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/* Map exponent to the range [-127,128] */
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int exponent = ((f32.ui >> 23) & 0xff) - 127;
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int mantissa = f32.ui & 0x007fffff;
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if (exponent == 128) { /* Infinity or NaN */
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/* From the GL_EXT_packed_float spec:
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*
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* "Additionally: negative infinity is converted to zero; positive
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* infinity is converted to positive infinity; and both positive and
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* negative NaN are converted to positive NaN."
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*/
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uf11 = UF11_MAX_EXPONENT;
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if (mantissa) {
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uf11 |= 1; /* NaN */
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} else {
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if (sign)
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uf11 = 0; /* 0.0 */
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}
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} else if (sign) {
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return 0;
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} else if (val > 65024.0f) {
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/* From the GL_EXT_packed_float spec:
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*
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* "Likewise, finite positive values greater than 65024 (the maximum
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* finite representable unsigned 11-bit floating-point value) are
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* converted to 65024."
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*/
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uf11 = UF11(30, 63);
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}
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else if (exponent > -15) { /* Representable value */
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exponent += UF11_EXPONENT_BIAS;
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mantissa >>= UF11_MANTISSA_SHIFT;
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uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa;
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}
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return uf11;
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}
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static INLINE float uf11_to_f32(uint16_t val)
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{
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union {
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float f;
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uint32_t ui;
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} f32;
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int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
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int mantissa = (val & 0x003f);
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f32.f = 0.0;
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if (exponent == 0) {
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if (mantissa != 0) {
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const float scale = 1.0 / (1 << 20);
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f32.f = scale * mantissa;
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}
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}
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else if (exponent == 31) {
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f32.ui = F32_INFINITY | mantissa;
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}
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else {
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float scale, decimal;
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exponent -= 15;
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if (exponent < 0) {
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scale = 1.0f / (1 << -exponent);
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}
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else {
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scale = (float) (1 << exponent);
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}
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decimal = 1.0f + (float) mantissa / 64;
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f32.f = scale * decimal;
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}
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return f32.f;
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}
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static INLINE unsigned f32_to_uf10(float val)
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{
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union {
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float f;
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uint32_t ui;
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} f32 = {val};
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uint16_t uf10 = 0;
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/* Decode little-endian 32-bit floating-point value */
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int sign = (f32.ui >> 16) & 0x8000;
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/* Map exponent to the range [-127,128] */
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int exponent = ((f32.ui >> 23) & 0xff) - 127;
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int mantissa = f32.ui & 0x007fffff;
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if (exponent == 128) {
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/* From the GL_EXT_packed_float spec:
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*
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* "Additionally: negative infinity is converted to zero; positive
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* infinity is converted to positive infinity; and both positive and
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* negative NaN are converted to positive NaN."
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*/
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uf10 = UF10_MAX_EXPONENT;
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if (mantissa) {
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uf10 |= 1; /* NaN */
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} else {
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if (sign)
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uf10 = 0; /* 0.0 */
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}
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} else if (sign) {
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return 0;
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} else if (val > 64512.0f) { /* Overflow - flush to Infinity */
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/* From the GL_EXT_packed_float spec:
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*
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* "Likewise, finite positive values greater than 64512 (the maximum
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* finite representable unsigned 10-bit floating-point value) are
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* converted to 64512."
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*/
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uf10 = UF10(30, 31);
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}
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else if (exponent > -15) { /* Representable value */
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exponent += UF10_EXPONENT_BIAS;
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mantissa >>= UF10_MANTISSA_SHIFT;
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uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa;
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}
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return uf10;
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}
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static INLINE float uf10_to_f32(uint16_t val)
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{
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union {
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float f;
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uint32_t ui;
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} f32;
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int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
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int mantissa = (val & 0x001f);
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f32.f = 0.0;
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if (exponent == 0) {
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if (mantissa != 0) {
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const float scale = 1.0 / (1 << 20);
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f32.f = scale * mantissa;
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}
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}
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else if (exponent == 31) {
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f32.ui = F32_INFINITY | mantissa;
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}
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else {
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float scale, decimal;
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exponent -= 15;
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if (exponent < 0) {
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scale = 1.0f / (1 << -exponent);
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}
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else {
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scale = (float) (1 << exponent);
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}
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decimal = 1.0f + (float) mantissa / 32;
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f32.f = scale * decimal;
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}
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return f32.f;
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}
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static INLINE unsigned float3_to_r11g11b10f(const float rgb[3])
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{
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return ( f32_to_uf11(rgb[0]) & 0x7ff) |
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((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
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((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
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}
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static INLINE void r11g11b10f_to_float3(unsigned rgb, float retval[3])
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{
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retval[0] = uf11_to_f32( rgb & 0x7ff);
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retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
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retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);
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}
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