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92 lines
2.6 KiB
92 lines
2.6 KiB
/*
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* Copyright 2008 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkFloatBits_DEFINED
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#define SkFloatBits_DEFINED
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#include "include/core/SkTypes.h"
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#include "include/private/SkSafe_math.h"
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#include <float.h>
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/** Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement
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int. This also converts -0 (0x80000000) to 0. Doing this to a float allows
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it to be compared using normal C operators (<, <=, etc.)
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*/
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static inline int32_t SkSignBitTo2sCompliment(int32_t x) {
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if (x < 0) {
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x &= 0x7FFFFFFF;
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x = -x;
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}
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return x;
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}
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/** Convert a 2s compliment int to a sign-bit (i.e. int interpreted as float).
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This undoes the result of SkSignBitTo2sCompliment().
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*/
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static inline int32_t Sk2sComplimentToSignBit(int32_t x) {
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int sign = x >> 31;
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// make x positive
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x = (x ^ sign) - sign;
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// set the sign bit as needed
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x |= SkLeftShift(sign, 31);
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return x;
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}
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union SkFloatIntUnion {
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float fFloat;
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int32_t fSignBitInt;
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};
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// Helper to see a float as its bit pattern (w/o aliasing warnings)
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static inline int32_t SkFloat2Bits(float x) {
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SkFloatIntUnion data;
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data.fFloat = x;
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return data.fSignBitInt;
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}
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// Helper to see a bit pattern as a float (w/o aliasing warnings)
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static inline float SkBits2Float(int32_t floatAsBits) {
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SkFloatIntUnion data;
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data.fSignBitInt = floatAsBits;
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return data.fFloat;
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}
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constexpr int32_t gFloatBits_exponent_mask = 0x7F800000;
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constexpr int32_t gFloatBits_matissa_mask = 0x007FFFFF;
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static inline bool SkFloatBits_IsFinite(int32_t bits) {
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return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask;
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}
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static inline bool SkFloatBits_IsInf(int32_t bits) {
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return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) &&
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(bits & gFloatBits_matissa_mask) == 0;
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}
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/** Return the float as a 2s compliment int. Just to be used to compare floats
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to each other or against positive float-bit-constants (like 0). This does
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not return the int equivalent of the float, just something cheaper for
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compares-only.
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*/
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static inline int32_t SkFloatAs2sCompliment(float x) {
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return SkSignBitTo2sCompliment(SkFloat2Bits(x));
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}
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/** Return the 2s compliment int as a float. This undos the result of
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SkFloatAs2sCompliment
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*/
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static inline float Sk2sComplimentAsFloat(int32_t x) {
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return SkBits2Float(Sk2sComplimentToSignBit(x));
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}
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// Scalar wrappers for float-bit routines
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#define SkScalarAs2sCompliment(x) SkFloatAs2sCompliment(x)
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#endif
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