michael@0: /*
michael@0:  * Copyright 2012 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef SkMathPriv_DEFINED
michael@0: #define SkMathPriv_DEFINED
michael@0: 
michael@0: #include "SkMath.h"
michael@0: 
michael@0: /** Returns -1 if n < 0, else returns 0
michael@0:  */
michael@0: #define SkExtractSign(n)    ((int32_t)(n) >> 31)
michael@0: 
michael@0: /** If sign == -1, returns -n, else sign must be 0, and returns n.
michael@0:  Typically used in conjunction with SkExtractSign().
michael@0:  */
michael@0: static inline int32_t SkApplySign(int32_t n, int32_t sign) {
michael@0:     SkASSERT(sign == 0 || sign == -1);
michael@0:     return (n ^ sign) - sign;
michael@0: }
michael@0: 
michael@0: /** Return x with the sign of y */
michael@0: static inline int32_t SkCopySign32(int32_t x, int32_t y) {
michael@0:     return SkApplySign(x, SkExtractSign(x ^ y));
michael@0: }
michael@0: 
michael@0: /** Given a positive value and a positive max, return the value
michael@0:  pinned against max.
michael@0:  Note: only works as long as max - value doesn't wrap around
michael@0:  @return max if value >= max, else value
michael@0:  */
michael@0: static inline unsigned SkClampUMax(unsigned value, unsigned max) {
michael@0:     if (value > max) {
michael@0:         value = max;
michael@0:     }
michael@0:     return value;
michael@0: }
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: /** Return a*b/255, truncating away any fractional bits. Only valid if both
michael@0:  a and b are 0..255
michael@0:  */
michael@0: static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
michael@0:     SkASSERT((uint8_t)a == a);
michael@0:     SkASSERT((uint8_t)b == b);
michael@0:     unsigned prod = SkMulS16(a, b) + 1;
michael@0:     return (prod + (prod >> 8)) >> 8;
michael@0: }
michael@0: 
michael@0: /** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if
michael@0:  both a and b are 0..255. The expected result equals (a * b + 254) / 255.
michael@0:  */
michael@0: static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
michael@0:     SkASSERT((uint8_t)a == a);
michael@0:     SkASSERT((uint8_t)b == b);
michael@0:     unsigned prod = SkMulS16(a, b) + 255;
michael@0:     return (prod + (prod >> 8)) >> 8;
michael@0: }
michael@0: 
michael@0: /** Just the rounding step in SkDiv255Round: round(value / 255)
michael@0:  */
michael@0: static inline unsigned SkDiv255Round(unsigned prod) {
michael@0:     prod += 128;
michael@0:     return (prod + (prod >> 8)) >> 8;
michael@0: }
michael@0: 
michael@0: #endif