1 // Copyright (c) 2012 The WebM project authors. All Rights Reserved. 2 // 3 // Use of this source code is governed by a BSD-style license 4 // that can be found in the LICENSE file in the root of the source 5 // tree. An additional intellectual property rights grant can be found 6 // in the file PATENTS. All contributing project authors may 7 // be found in the AUTHORS file in the root of the source tree. 8 9 #include "common/webm_endian.h" 10 11 #include <stdint.h> 12 13 namespace { 14 15 // Swaps unsigned 32 bit values to big endian if needed. Returns |value| 16 // unmodified if architecture is big endian. Returns swapped bytes of |value| 17 // if architecture is little endian. Returns 0 otherwise. swap32_check_little_endian(uint32_t value)18uint32_t swap32_check_little_endian(uint32_t value) { 19 // Check endianness. 20 union { 21 uint32_t val32; 22 uint8_t c[4]; 23 } check; 24 check.val32 = 0x01234567U; 25 26 // Check for big endian. 27 if (check.c[3] == 0x67) 28 return value; 29 30 // Check for not little endian. 31 if (check.c[0] != 0x67) 32 return 0; 33 34 return value << 24 | ((value << 8) & 0x0000FF00U) | 35 ((value >> 8) & 0x00FF0000U) | value >> 24; 36 } 37 38 // Swaps unsigned 64 bit values to big endian if needed. Returns |value| 39 // unmodified if architecture is big endian. Returns swapped bytes of |value| 40 // if architecture is little endian. Returns 0 otherwise. swap64_check_little_endian(uint64_t value)41uint64_t swap64_check_little_endian(uint64_t value) { 42 // Check endianness. 43 union { 44 uint64_t val64; 45 uint8_t c[8]; 46 } check; 47 check.val64 = 0x0123456789ABCDEFULL; 48 49 // Check for big endian. 50 if (check.c[7] == 0xEF) 51 return value; 52 53 // Check for not little endian. 54 if (check.c[0] != 0xEF) 55 return 0; 56 57 return value << 56 | ((value << 40) & 0x00FF000000000000ULL) | 58 ((value << 24) & 0x0000FF0000000000ULL) | 59 ((value << 8) & 0x000000FF00000000ULL) | 60 ((value >> 8) & 0x00000000FF000000ULL) | 61 ((value >> 24) & 0x0000000000FF0000ULL) | 62 ((value >> 40) & 0x000000000000FF00ULL) | value >> 56; 63 } 64 65 } // namespace 66 67 namespace libwebm { 68 host_to_bigendian(uint32_t value)69uint32_t host_to_bigendian(uint32_t value) { 70 return swap32_check_little_endian(value); 71 } 72 bigendian_to_host(uint32_t value)73uint32_t bigendian_to_host(uint32_t value) { 74 return swap32_check_little_endian(value); 75 } 76 host_to_bigendian(uint64_t value)77uint64_t host_to_bigendian(uint64_t value) { 78 return swap64_check_little_endian(value); 79 } 80 bigendian_to_host(uint64_t value)81uint64_t bigendian_to_host(uint64_t value) { 82 return swap64_check_little_endian(value); 83 } 84 85 } // namespace libwebm 86