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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMathPriv_DEFINED
#define SkMathPriv_DEFINED
#include "SkMath.h"
/** Returns -1 if n < 0, else returns 0
*/
#define SkExtractSign(n) ((int32_t)(n) >> 31)
/** If sign == -1, returns -n, else sign must be 0, and returns n.
Typically used in conjunction with SkExtractSign().
*/
static inline int32_t SkApplySign(int32_t n, int32_t sign) {
SkASSERT(sign == 0 || sign == -1);
return (n ^ sign) - sign;
}
/** Return x with the sign of y */
static inline int32_t SkCopySign32(int32_t x, int32_t y) {
return SkApplySign(x, SkExtractSign(x ^ y));
}
/** Given a positive value and a positive max, return the value
pinned against max.
Note: only works as long as max - value doesn't wrap around
@return max if value >= max, else value
*/
static inline unsigned SkClampUMax(unsigned value, unsigned max) {
#ifdef SK_CPU_HAS_CONDITIONAL_INSTR
if (value > max) {
value = max;
}
return value;
#else
int diff = max - value;
// clear diff if diff is positive
diff &= diff >> 31;
return value + diff;
#endif
}
/** Computes the 64bit product of a * b, and then shifts the answer down by
shift bits, returning the low 32bits. shift must be [0..63]
e.g. to perform a fixedmul, call SkMulShift(a, b, 16)
*/
int32_t SkMulShift(int32_t a, int32_t b, unsigned shift);
/** Return the integer cube root of value, with a bias of bitBias
*/
int32_t SkCubeRootBits(int32_t value, int bitBias);
///////////////////////////////////////////////////////////////////////////////
/** Return a*b/255, truncating away any fractional bits. Only valid if both
a and b are 0..255
*/
static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) {
SkASSERT((uint8_t)a == a);
SkASSERT((uint8_t)b == b);
unsigned prod = SkMulS16(a, b) + 1;
return (prod + (prod >> 8)) >> 8;
}
/** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if
both a and b are 0..255. The expected result equals (a * b + 254) / 255.
*/
static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) {
SkASSERT((uint8_t)a == a);
SkASSERT((uint8_t)b == b);
unsigned prod = SkMulS16(a, b) + 255;
return (prod + (prod >> 8)) >> 8;
}
/** Just the rounding step in SkDiv255Round: round(value / 255)
*/
static inline unsigned SkDiv255Round(unsigned prod) {
prod += 128;
return (prod + (prod >> 8)) >> 8;
}
#endif
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