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 #include "SkFloatBits.h" #include "SkMath.h" /****************************************************************************** SkFloatBits_toInt[Floor, Round, Ceil] are identical except for what they do right before they return ... >> exp; Floor - adds nothing Round - adds 1 << (exp - 1) Ceil - adds (1 << exp) - 1 Floor and Cast are very similar, but Cast applies its sign after all other computations on value. Also, Cast does not need to check for negative zero, as that value (0x80000000) "does the right thing" for Ceil. Note that it doesn't for Floor/Round/Ceil, hence the explicit check. ******************************************************************************/ #define EXP_BIAS (127+23) #define MATISSA_MAGIC_BIG (1 << 23) static inline int unpack_exp(uint32_t packed) { return (packed << 1 >> 24); } #if 0 // the ARM compiler generates an extra BIC, so I use the dirty version instead static inline int unpack_matissa(uint32_t packed) { // we could mask with 0x7FFFFF, but that is harder for ARM to encode return (packed & ~0xFF000000) | MATISSA_MAGIC_BIG; } #endif // returns the low 24-bits, so we need to OR in the magic_bit afterwards static inline int unpack_matissa_dirty(uint32_t packed) { return packed & ~0xFF000000; } // same as (int)float int32_t SkFloatBits_toIntCast(int32_t packed) { int exp = unpack_exp(packed) - EXP_BIAS; int value = unpack_matissa_dirty(packed) | MATISSA_MAGIC_BIG; if (exp >= 0) { if (exp > 7) { // overflow value = SK_MaxS32; } else { value <<= exp; } } else { exp = -exp; if (exp > 25) { // underflow exp = 25; } value >>= exp; } return SkApplySign(value, SkExtractSign(packed)); } // same as (int)floor(float) int32_t SkFloatBits_toIntFloor(int32_t packed) { // curse you negative 0 if ((packed << 1) == 0) { return 0; } int exp = unpack_exp(packed) - EXP_BIAS; int value = unpack_matissa_dirty(packed) | MATISSA_MAGIC_BIG; if (exp >= 0) { if (exp > 7) { // overflow value = SK_MaxS32; } else { value <<= exp; } // apply the sign after we check for overflow return SkApplySign(value, SkExtractSign(packed)); } else { // apply the sign before we right-shift value = SkApplySign(value, SkExtractSign(packed)); exp = -exp; if (exp > 25) { // underflow exp = 25; } // int add = 0; return value >> exp; } } // same as (int)floor(float + 0.5) int32_t SkFloatBits_toIntRound(int32_t packed) { // curse you negative 0 if ((packed << 1) == 0) { return 0; } int exp = unpack_exp(packed) - EXP_BIAS; int value = unpack_matissa_dirty(packed) | MATISSA_MAGIC_BIG; if (exp >= 0) { if (exp > 7) { // overflow value = SK_MaxS32; } else { value <<= exp; } // apply the sign after we check for overflow return SkApplySign(value, SkExtractSign(packed)); } else { // apply the sign before we right-shift value = SkApplySign(value, SkExtractSign(packed)); exp = -exp; if (exp > 25) { // underflow exp = 25; } int add = 1 << (exp - 1); return (value + add) >> exp; } } // same as (int)ceil(float) int32_t SkFloatBits_toIntCeil(int32_t packed) { // curse you negative 0 if ((packed << 1) == 0) { return 0; } int exp = unpack_exp(packed) - EXP_BIAS; int value = unpack_matissa_dirty(packed) | MATISSA_MAGIC_BIG; if (exp >= 0) { if (exp > 7) { // overflow value = SK_MaxS32; } else { value <<= exp; } // apply the sign after we check for overflow return SkApplySign(value, SkExtractSign(packed)); } else { // apply the sign before we right-shift value = SkApplySign(value, SkExtractSign(packed)); exp = -exp; if (exp > 25) { // underflow exp = 25; } int add = (1 << exp) - 1; return (value + add) >> exp; } } float SkFloatBits_intToFloatNative(int x); float SkFloatBits_intToFloatNative(int x) { return x; } float SkIntToFloatCast(int32_t value) { if (0 == value) { return 0; } int shift = EXP_BIAS; // record the sign and make value positive int sign = SkExtractSign(value); value = SkApplySign(value, sign); if (value >> 24) { // value is too big (has more than 24 bits set) int bias = 8 - SkCLZ(value); SkDebugf("value = %d, bias = %d\n", value, bias); SkASSERT(bias > 0 && bias < 8); value >>= bias; // need to round? shift += bias; } else { int zeros = SkCLZ(value << 8); SkASSERT(zeros >= 0 && zeros <= 23); value <<= zeros; shift -= zeros; } // now value is left-aligned to 24 bits SkASSERT((value >> 23) == 1); SkASSERT(shift >= 0 && shift <= 255); SkFloatIntUnion data; data.fSignBitInt = (sign << 31) | (shift << 23) | (value & ~MATISSA_MAGIC_BIG); return data.fFloat; } float SkIntToFloatCast_NoOverflowCheck(int32_t value) { if (0 == value) { return 0; } int shift = EXP_BIAS; // record the sign and make value positive int sign = SkExtractSign(value); value = SkApplySign(value, sign); int zeros = SkCLZ(value << 8); value <<= zeros; shift -= zeros; SkFloatIntUnion data; data.fSignBitInt = (sign << 31) | (shift << 23) | (value & ~MATISSA_MAGIC_BIG); return data.fFloat; }