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      1 /*
      2  * Copyright 2006 The Android Open Source Project
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkEndian_DEFINED
      9 #define SkEndian_DEFINED
     10 
     11 #include "SkTypes.h"
     12 
     13 /** \file SkEndian.h
     14 
     15     Macros and helper functions for handling 16 and 32 bit values in
     16     big and little endian formats.
     17 */
     18 
     19 #if defined(SK_CPU_LENDIAN) && defined(SK_CPU_BENDIAN)
     20     #error "can't have both LENDIAN and BENDIAN defined"
     21 #endif
     22 
     23 #if !defined(SK_CPU_LENDIAN) && !defined(SK_CPU_BENDIAN)
     24     #error "need either LENDIAN or BENDIAN defined"
     25 #endif
     26 
     27 /** Swap the two bytes in the low 16bits of the parameters.
     28     e.g. 0x1234 -> 0x3412
     29 */
     30 static inline uint16_t SkEndianSwap16(uint16_t value) {
     31     return static_cast<uint16_t>((value >> 8) | (value << 8));
     32 }
     33 
     34 template<uint16_t N> struct SkTEndianSwap16 {
     35     static const uint16_t value = static_cast<uint16_t>((N >> 8) | ((N & 0xFF) << 8));
     36 };
     37 
     38 /** Vector version of SkEndianSwap16(), which swaps the
     39     low two bytes of each value in the array.
     40 */
     41 static inline void SkEndianSwap16s(uint16_t array[], int count) {
     42     SkASSERT(count == 0 || array != nullptr);
     43 
     44     while (--count >= 0) {
     45         *array = SkEndianSwap16(*array);
     46         array += 1;
     47     }
     48 }
     49 
     50 /** Reverse all 4 bytes in a 32bit value.
     51     e.g. 0x12345678 -> 0x78563412
     52 */
     53 static constexpr uint32_t SkEndianSwap32(uint32_t value) {
     54     return ((value & 0xFF) << 24) |
     55            ((value & 0xFF00) << 8) |
     56            ((value & 0xFF0000) >> 8) |
     57             (value >> 24);
     58 }
     59 
     60 template<uint32_t N> struct SkTEndianSwap32 {
     61     static const uint32_t value = ((N & 0xFF) << 24) |
     62                                   ((N & 0xFF00) << 8) |
     63                                   ((N & 0xFF0000) >> 8) |
     64                                   (N >> 24);
     65 };
     66 
     67 /** Vector version of SkEndianSwap32(), which swaps the
     68     bytes of each value in the array.
     69 */
     70 static inline void SkEndianSwap32s(uint32_t array[], int count) {
     71     SkASSERT(count == 0 || array != nullptr);
     72 
     73     while (--count >= 0) {
     74         *array = SkEndianSwap32(*array);
     75         array += 1;
     76     }
     77 }
     78 
     79 /** Reverse all 8 bytes in a 64bit value.
     80     e.g. 0x1122334455667788 -> 0x8877665544332211
     81 */
     82 static inline uint64_t SkEndianSwap64(uint64_t value) {
     83     return (((value & 0x00000000000000FFULL) << (8*7)) |
     84             ((value & 0x000000000000FF00ULL) << (8*5)) |
     85             ((value & 0x0000000000FF0000ULL) << (8*3)) |
     86             ((value & 0x00000000FF000000ULL) << (8*1)) |
     87             ((value & 0x000000FF00000000ULL) >> (8*1)) |
     88             ((value & 0x0000FF0000000000ULL) >> (8*3)) |
     89             ((value & 0x00FF000000000000ULL) >> (8*5)) |
     90             ((value)                         >> (8*7)));
     91 }
     92 template<uint64_t N> struct SkTEndianSwap64 {
     93     static const uint64_t value = (((N & 0x00000000000000FFULL) << (8*7)) |
     94                                    ((N & 0x000000000000FF00ULL) << (8*5)) |
     95                                    ((N & 0x0000000000FF0000ULL) << (8*3)) |
     96                                    ((N & 0x00000000FF000000ULL) << (8*1)) |
     97                                    ((N & 0x000000FF00000000ULL) >> (8*1)) |
     98                                    ((N & 0x0000FF0000000000ULL) >> (8*3)) |
     99                                    ((N & 0x00FF000000000000ULL) >> (8*5)) |
    100                                    ((N)                         >> (8*7)));
    101 };
    102 
    103 /** Vector version of SkEndianSwap64(), which swaps the
    104     bytes of each value in the array.
    105 */
    106 static inline void SkEndianSwap64s(uint64_t array[], int count) {
    107     SkASSERT(count == 0 || array != nullptr);
    108 
    109     while (--count >= 0) {
    110         *array = SkEndianSwap64(*array);
    111         array += 1;
    112     }
    113 }
    114 
    115 #ifdef SK_CPU_LENDIAN
    116     #define SkEndian_SwapBE16(n)    SkEndianSwap16(n)
    117     #define SkEndian_SwapBE32(n)    SkEndianSwap32(n)
    118     #define SkEndian_SwapBE64(n)    SkEndianSwap64(n)
    119     #define SkEndian_SwapLE16(n)    (n)
    120     #define SkEndian_SwapLE32(n)    (n)
    121     #define SkEndian_SwapLE64(n)    (n)
    122 
    123     #define SkTEndian_SwapBE16(n)    SkTEndianSwap16<n>::value
    124     #define SkTEndian_SwapBE32(n)    SkTEndianSwap32<n>::value
    125     #define SkTEndian_SwapBE64(n)    SkTEndianSwap64<n>::value
    126     #define SkTEndian_SwapLE16(n)    (n)
    127     #define SkTEndian_SwapLE32(n)    (n)
    128     #define SkTEndian_SwapLE64(n)    (n)
    129 #else   // SK_CPU_BENDIAN
    130     #define SkEndian_SwapBE16(n)    (n)
    131     #define SkEndian_SwapBE32(n)    (n)
    132     #define SkEndian_SwapBE64(n)    (n)
    133     #define SkEndian_SwapLE16(n)    SkEndianSwap16(n)
    134     #define SkEndian_SwapLE32(n)    SkEndianSwap32(n)
    135     #define SkEndian_SwapLE64(n)    SkEndianSwap64(n)
    136 
    137     #define SkTEndian_SwapBE16(n)    (n)
    138     #define SkTEndian_SwapBE32(n)    (n)
    139     #define SkTEndian_SwapBE64(n)    (n)
    140     #define SkTEndian_SwapLE16(n)    SkTEndianSwap16<n>::value
    141     #define SkTEndian_SwapLE32(n)    SkTEndianSwap32<n>::value
    142     #define SkTEndian_SwapLE64(n)    SkTEndianSwap64<n>::value
    143 #endif
    144 
    145 // When a bytestream is embedded in a 32-bit word, how far we need to
    146 // shift the word to extract each byte from the low 8 bits by anding with 0xff.
    147 #ifdef SK_CPU_LENDIAN
    148     #define SkEndian_Byte0Shift 0
    149     #define SkEndian_Byte1Shift 8
    150     #define SkEndian_Byte2Shift 16
    151     #define SkEndian_Byte3Shift 24
    152 #else   // SK_CPU_BENDIAN
    153     #define SkEndian_Byte0Shift 24
    154     #define SkEndian_Byte1Shift 16
    155     #define SkEndian_Byte2Shift 8
    156     #define SkEndian_Byte3Shift 0
    157 #endif
    158 
    159 
    160 #if defined(SK_UINT8_BITFIELD_LENDIAN) && defined(SK_UINT8_BITFIELD_BENDIAN)
    161     #error "can't have both bitfield LENDIAN and BENDIAN defined"
    162 #endif
    163 
    164 #if !defined(SK_UINT8_BITFIELD_LENDIAN) && !defined(SK_UINT8_BITFIELD_BENDIAN)
    165     #ifdef SK_CPU_LENDIAN
    166         #define SK_UINT8_BITFIELD_LENDIAN
    167     #else
    168         #define SK_UINT8_BITFIELD_BENDIAN
    169     #endif
    170 #endif
    171 
    172 #ifdef SK_UINT8_BITFIELD_LENDIAN
    173     #define SK_UINT8_BITFIELD(f0, f1, f2, f3, f4, f5, f6, f7) \
    174         SK_OT_BYTE f0 : 1; \
    175         SK_OT_BYTE f1 : 1; \
    176         SK_OT_BYTE f2 : 1; \
    177         SK_OT_BYTE f3 : 1; \
    178         SK_OT_BYTE f4 : 1; \
    179         SK_OT_BYTE f5 : 1; \
    180         SK_OT_BYTE f6 : 1; \
    181         SK_OT_BYTE f7 : 1;
    182 #else
    183     #define SK_UINT8_BITFIELD(f0, f1, f2, f3, f4, f5, f6, f7) \
    184         SK_OT_BYTE f7 : 1; \
    185         SK_OT_BYTE f6 : 1; \
    186         SK_OT_BYTE f5 : 1; \
    187         SK_OT_BYTE f4 : 1; \
    188         SK_OT_BYTE f3 : 1; \
    189         SK_OT_BYTE f2 : 1; \
    190         SK_OT_BYTE f1 : 1; \
    191         SK_OT_BYTE f0 : 1;
    192 #endif
    193 
    194 #endif
    195