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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 */
SkEndianSwap16(uint16_t value)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 */
SkEndianSwap16s(uint16_t array[],int count)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 */
SkEndianSwap32(uint32_t value)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 */
SkEndianSwap32s(uint32_t array[],int count)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 */
SkEndianSwap64(uint64_t value)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 */
SkEndianSwap64s(uint64_t array[],int count)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