source/lib/byte_order.cpp

   1 /* Copyright (C) 2020 Wildfire Games.
   2  *
   3  * Permission is hereby granted, free of charge, to any person obtaining
   4  * a copy of this software and associated documentation files (the
   5  * "Software"), to deal in the Software without restriction, including
   6  * without limitation the rights to use, copy, modify, merge, publish,
   7  * distribute, sublicense, and/or sell copies of the Software, and to
   8  * permit persons to whom the Software is furnished to do so, subject to
   9  * the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included
  12  * in all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  15  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  16  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  17  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  18  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  19  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  20  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 /*
  24  * byte order (endianness) support routines.
  25  */
  26
  27 #include "precompiled.h"
  28 #include "lib/byte_order.h"
  29
  30 #include "lib/bits.h"
  31
  32 #include <cstring>
  33
  34 #ifndef swap16
  35 u16 swap16(const u16 x)
  36 {
  37         return (u16)(((x & 0xff) << 8) | (x >> 8));
  38 }
  39 #endif
  40
  41 #ifndef swap32
  42 u32 swap32(const u32 x)
  43 {
  44         return (x << 24) |
  45                 (x >> 24) |
  46                 ((x << 8) & 0x00ff0000) |
  47                 ((x >> 8) & 0x0000ff00);
  48 }
  49 #endif
  50
  51 #ifndef swap64
  52 u64 swap64(const u64 x)
  53 {
  54         const u32 lo = (u32)(x & 0xFFFFFFFF);
  55         const u32 hi = (u32)(x >> 32);
  56         u64 ret = swap32(lo);
  57         ret <<= 32;
  58         // careful: must shift var of type u64, not u32
  59         ret |= swap32(hi);
  60         return ret;
  61 }
  62 #endif
  63
  64
  65 //-----------------------------------------------------------------------------
  66
  67
  68 u16 read_le16(const void* p)
  69 {
  70         u16 n;
  71         memcpy(&n, p, sizeof(n));
  72         return to_le16(n);
  73 }
  74
  75 u32 read_le32(const void* p)
  76 {
  77         u32 n;
  78         memcpy(&n, p, sizeof(n));
  79         return to_le32(n);
  80 }
  81
  82 u64 read_le64(const void* p)
  83 {
  84         u64 n;
  85         memcpy(&n, p, sizeof(n));
  86         return to_le64(n);
  87 }
  88
  89
  90 u16 read_be16(const void* p)
  91 {
  92         u16 n;
  93         memcpy(&n, p, sizeof(n));
  94         return to_be16(n);
  95 }
  96
  97 u32 read_be32(const void* p)
  98 {
  99         u32 n;
 100         memcpy(&n, p, sizeof(n));
 101         return to_be32(n);
 102 }
 103
 104 u64 read_be64(const void* p)
 105 {
 106         u64 n;
 107         memcpy(&n, p, sizeof(n));
 108         return to_be64(n);
 109 }
 110
 111
 112 void write_le16(void* p, u16 x)
 113 {
 114         u16 n = to_le16(x);
 115         memcpy(p, &n, sizeof(n));
 116 }
 117
 118 void write_le32(void* p, u32 x)
 119 {
 120         u32 n = to_le32(x);
 121         memcpy(p, &n, sizeof(n));
 122 }
 123
 124 void write_le64(void* p, u64 x)
 125 {
 126         u64 n = to_le64(x);
 127         memcpy(p, &n, sizeof(n));
 128 }
 129
 130
 131 void write_be16(void* p, u16 x)
 132 {
 133         u16 n = to_be16(x);
 134         memcpy(p, &n, sizeof(n));
 135 }
 136
 137 void write_be32(void* p, u32 x)
 138 {
 139         u32 n = to_be32(x);
 140         memcpy(p, &n, sizeof(n));
 141 }
 142
 143 void write_be64(void* p, u64 x)
 144 {
 145         u64 n = to_be64(x);
 146         memcpy(p, &n, sizeof(n));
 147 }
 148
 149
 150 u64 movzx_le64(const u8* p, size_t size_bytes)
 151 {
 152         u64 number = 0;
 153         for(size_t i = 0; i < std::min(size_bytes, (size_t)8u); i++)
 154                 number |= ((u64)p[i]) << (i*8);
 155
 156         return number;
 157 }
 158
 159 u64 movzx_be64(const u8* p, size_t size_bytes)
 160 {
 161         u64 number = 0;
 162         for(size_t i = 0; i < std::min(size_bytes, (size_t)8u); i++)
 163         {
 164                 number <<= 8;
 165                 number |= p[i];
 166         }
 167
 168         return number;
 169 }
 170
 171
 172 static inline i64 SignExtend(u64 bits, size_t size_bytes)
 173 {
 174         // no point in sign-extending if >= 8 bytes were requested
 175         if(size_bytes < 8)
 176         {
 177                 const u64 sign_bit = Bit<u64>((size_bytes*8)-1);
 178
 179                 // number would be negative in the smaller type,
 180                 // so sign-extend, i.e. set all more significant bits.
 181                 if(bits & sign_bit)
 182                 {
 183                         const u64 valid_bit_mask = (sign_bit+sign_bit)-1;
 184                         bits |= ~valid_bit_mask;
 185                 }
 186         }
 187
 188         const i64 number = static_cast<i64>(bits);
 189         return number;
 190 }
 191
 192 i64 movsx_le64(const u8* p, size_t size_bytes)
 193 {
 194         const u64 number = movzx_le64(p, size_bytes);
 195         return SignExtend(number, size_bytes);
 196 }
 197
 198 i64 movsx_be64(const u8* p, size_t size_bytes)
 199 {
 200         const u64 number = movzx_be64(p, size_bytes);
 201         return SignExtend(number, size_bytes);
 202 }