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scummvm/common/endian.h
Max Horn 0ce2ca4e00 COMMON: Replace MKID_BE by MKTAG 
MKID_BE relied on unspecified behavior of the C++ compiler,
and as such was always a bit unsafe. The new MKTAG macro
is slightly less elegant, but does no longer depend on the
behavior of the compiler.
Inspired by FFmpeg, which has an almost identical macro.
2011-04-12 16:53:15 +02:00

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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* $URL$
* $Id$
*
*/
#ifndef COMMON_ENDIAN_H
#define COMMON_ENDIAN_H
#include "common/scummsys.h"
/**
* \file endian.h
* Endian conversion and byteswap conversion functions or macros
*
* SWAP_BYTES_??(a) - inverse byte order
* SWAP_CONSTANT_??(a) - inverse byte order, implemented as macro.
* Use with compiletime-constants only, the result will be a compiletime-constant aswell.
* Unlike most other functions these can be used for eg. switch-case labels
*
* READ_UINT??(a) - read native value from pointer a
* READ_??_UINT??(a) - read LE/BE value from pointer a and convert it to native
* WRITE_??_UINT??(a, v) - write native value v to pointer a with LE/BE encoding
* TO_??_??(a) - convert native value v to LE/BE
* FROM_??_??(a) - convert LE/BE value v to native
* CONSTANT_??_??(a) - convert LE/BE value v to native, implemented as macro.
* Use with compiletime-constants only, the result will be a compiletime-constant aswell.
* Unlike most other functions these can be used for eg. switch-case labels
*/
// Sanity check
#if !defined(SCUMM_LITTLE_ENDIAN) && !defined(SCUMM_BIG_ENDIAN)
# error No endianness defined
#endif
#define SWAP_CONSTANT_32(a) \
((uint32)((((a) >> 24) & 0x00FF) | \
(((a) >> 8) & 0xFF00) | \
(((a) & 0xFF00) << 8) | \
(((a) & 0x00FF) << 24) ))
#define SWAP_CONSTANT_16(a) \
((uint16)((((a) >> 8) & 0x00FF) | \
(((a) << 8) & 0xFF00) ))
/**
* Swap the bytes in a 32 bit word in order to convert LE encoded data to BE
* and vice versa.
*/
// machine/compiler-specific variants come first, fallback last
// Test for GCC and if the target has the MIPS rel.2 instructions (we know the psp does)
#if defined(__GNUC__) && (defined(__psp__) || defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS64R2))
FORCEINLINE uint32 SWAP_BYTES_32(const uint32 a) {
if (__builtin_constant_p(a)) {
return SWAP_CONSTANT_32(a);
} else {
uint32 result;
# if defined(__psp__)
// use special allegrex instruction
__asm__ ("wsbw %0,%1" : "=r" (result) : "r" (a));
# else
__asm__ ("wsbh %0,%1\n"
"rotr %0,%0,16" : "=r" (result) : "r" (a));
# endif
return result;
}
}
// Test for GCC >= 4.3.0 as this version added the bswap builtin
#elif defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
FORCEINLINE uint32 SWAP_BYTES_32(uint32 a) {
return __builtin_bswap32(a);
}
// test for MSVC 7 or newer
#elif defined(_MSC_VER) && _MSC_VER >= 1300
FORCEINLINE uint32 SWAP_BYTES_32(uint32 a) {
return _byteswap_ulong(a);
}
// generic fallback
#else
inline uint32 SWAP_BYTES_32(uint32 a) {
const uint16 low = (uint16)a, high = (uint16)(a >> 16);
return ((uint32)(uint16)((low >> 8) | (low << 8)) << 16)
| (uint16)((high >> 8) | (high << 8));
}
#endif
/**
* Swap the bytes in a 16 bit word in order to convert LE encoded data to BE
* and vice versa.
*/
// compilerspecific variants come first, fallback last
// Test for GCC and if the target has the MIPS rel.2 instructions (we know the psp does)
#if defined(__GNUC__) && (defined(__psp__) || defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS64R2))
FORCEINLINE uint16 SWAP_BYTES_16(const uint16 a) {
if (__builtin_constant_p(a)) {
return SWAP_CONSTANT_16(a);
} else {
uint16 result;
__asm__ ("wsbh %0,%1" : "=r" (result) : "r" (a));
return result;
}
}
#else
inline uint16 SWAP_BYTES_16(const uint16 a) {
return (a >> 8) | (a << 8);
}
#endif
/**
* A wrapper macro used around four character constants, like 'DATA', to
* ensure portability. Typical usage: MKTAG('D','A','T','A').
*
* Why is this necessary? The C/C++ standard does not define the endianess to
* be used for character constants. Hence if one uses multi-byte character
* constants, a potential portability problem opens up.
*/
#define MKTAG(a0,a1,a2,a3) ((a0) | ((a1) << 8) | ((a2) << 16) | ((a3) << 24))
// Functions for reading/writing native Integers,
// this transparently handles the need for alignment
#if !defined(SCUMM_NEED_ALIGNMENT)
FORCEINLINE uint16 READ_UINT16(const void *ptr) {
return *(const uint16 *)(ptr);
}
FORCEINLINE uint32 READ_UINT32(const void *ptr) {
return *(const uint32 *)(ptr);
}
FORCEINLINE void WRITE_UINT16(void *ptr, uint16 value) {
*(uint16 *)(ptr) = value;
}
FORCEINLINE void WRITE_UINT32(void *ptr, uint32 value) {
*(uint32 *)(ptr) = value;
}
// test for GCC >= 4.0. these implementations will automatically use CPU-specific
// instructions for unaligned data when they are available (eg. MIPS)
#elif defined(__GNUC__) && (__GNUC__ >= 4)
FORCEINLINE uint16 READ_UINT16(const void *ptr) {
struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
return ((const Unaligned16 *)ptr)->val;
}
FORCEINLINE uint32 READ_UINT32(const void *ptr) {
struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
return ((const Unaligned32 *)ptr)->val;
}
FORCEINLINE void WRITE_UINT16(void *ptr, uint16 value) {
struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
((Unaligned16 *)ptr)->val = value;
}
FORCEINLINE void WRITE_UINT32(void *ptr, uint32 value) {
struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
((Unaligned32 *)ptr)->val = value;
}
// use software fallback by loading each byte explicitely
#else
# if defined(SCUMM_LITTLE_ENDIAN)
inline uint16 READ_UINT16(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[1] << 8) | b[0];
}
inline uint32 READ_UINT32(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | (b[0]);
}
inline void WRITE_UINT16(void *ptr, uint16 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 0);
b[1] = (uint8)(value >> 8);
}
inline void WRITE_UINT32(void *ptr, uint32 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 0);
b[1] = (uint8)(value >> 8);
b[2] = (uint8)(value >> 16);
b[3] = (uint8)(value >> 24);
}
# elif defined(SCUMM_BIG_ENDIAN)
inline uint16 READ_UINT16(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[0] << 8) | b[1];
}
inline uint32 READ_UINT32(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | (b[3]);
}
inline void WRITE_UINT16(void *ptr, uint16 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 8);
b[1] = (uint8)(value >> 0);
}
inline void WRITE_UINT32(void *ptr, uint32 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 24);
b[1] = (uint8)(value >> 16);
b[2] = (uint8)(value >> 8);
b[3] = (uint8)(value >> 0);
}
# endif
#endif
// Map Funtions for reading/writing BE/LE integers depending on native endianess
#if defined(SCUMM_LITTLE_ENDIAN)
#define READ_LE_UINT16(a) READ_UINT16(a)
#define READ_LE_UINT32(a) READ_UINT32(a)
#define WRITE_LE_UINT16(a, v) WRITE_UINT16(a, v)
#define WRITE_LE_UINT32(a, v) WRITE_UINT32(a, v)
#define FROM_LE_32(a) ((uint32)(a))
#define FROM_LE_16(a) ((uint16)(a))
#define FROM_BE_32(a) SWAP_BYTES_32(a)
#define FROM_BE_16(a) SWAP_BYTES_16(a)
#define TO_LE_32(a) ((uint32)(a))
#define TO_LE_16(a) ((uint16)(a))
#define TO_BE_32(a) SWAP_BYTES_32(a)
#define TO_BE_16(a) SWAP_BYTES_16(a)
#define CONSTANT_LE_32(a) ((uint32)(a))
#define CONSTANT_LE_16(a) ((uint16)(a))
#define CONSTANT_BE_32(a) SWAP_CONSTANT_32(a)
#define CONSTANT_BE_16(a) SWAP_CONSTANT_16(a)
// if the unaligned load and the byteswap take alot instructions its better to directly read and invert
# if defined(SCUMM_NEED_ALIGNMENT) && !defined(__mips__)
inline uint16 READ_BE_UINT16(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[0] << 8) | b[1];
}
inline uint32 READ_BE_UINT32(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | (b[3]);
}
inline void WRITE_BE_UINT16(void *ptr, uint16 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 8);
b[1] = (uint8)(value >> 0);
}
inline void WRITE_BE_UINT32(void *ptr, uint32 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 24);
b[1] = (uint8)(value >> 16);
b[2] = (uint8)(value >> 8);
b[3] = (uint8)(value >> 0);
}
# else
inline uint16 READ_BE_UINT16(const void *ptr) {
return SWAP_BYTES_16(READ_UINT16(ptr));
}
inline uint32 READ_BE_UINT32(const void *ptr) {
return SWAP_BYTES_32(READ_UINT32(ptr));
}
inline void WRITE_BE_UINT16(void *ptr, uint16 value) {
WRITE_UINT16(ptr, SWAP_BYTES_16(value));
}
inline void WRITE_BE_UINT32(void *ptr, uint32 value) {
WRITE_UINT32(ptr, SWAP_BYTES_32(value));
}
# endif // if defined(SCUMM_NEED_ALIGNMENT)
#elif defined(SCUMM_BIG_ENDIAN)
#define READ_BE_UINT16(a) READ_UINT16(a)
#define READ_BE_UINT32(a) READ_UINT32(a)
#define WRITE_BE_UINT16(a, v) WRITE_UINT16(a, v)
#define WRITE_BE_UINT32(a, v) WRITE_UINT32(a, v)
#define FROM_LE_32(a) SWAP_BYTES_32(a)
#define FROM_LE_16(a) SWAP_BYTES_16(a)
#define FROM_BE_32(a) ((uint32)(a))
#define FROM_BE_16(a) ((uint16)(a))
#define TO_LE_32(a) SWAP_BYTES_32(a)
#define TO_LE_16(a) SWAP_BYTES_16(a)
#define TO_BE_32(a) ((uint32)(a))
#define TO_BE_16(a) ((uint16)(a))
#define CONSTANT_LE_32(a) SWAP_CONSTANT_32(a)
#define CONSTANT_LE_16(a) SWAP_CONSTANT_16(a)
#define CONSTANT_BE_32(a) ((uint32)(a))
#define CONSTANT_BE_16(a) ((uint16)(a))
// if the unaligned load and the byteswap take alot instructions its better to directly read and invert
# if defined(SCUMM_NEED_ALIGNMENT) && !defined(__mips__)
inline uint16 READ_LE_UINT16(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[1] << 8) | b[0];
}
inline uint32 READ_LE_UINT32(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | (b[0]);
}
inline void WRITE_LE_UINT16(void *ptr, uint16 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 0);
b[1] = (uint8)(value >> 8);
}
inline void WRITE_LE_UINT32(void *ptr, uint32 value) {
uint8 *b = (uint8 *)ptr;
b[0] = (uint8)(value >> 0);
b[1] = (uint8)(value >> 8);
b[2] = (uint8)(value >> 16);
b[3] = (uint8)(value >> 24);
}
# else
inline uint16 READ_LE_UINT16(const void *ptr) {
return SWAP_BYTES_16(READ_UINT16(ptr));
}
inline uint32 READ_LE_UINT32(const void *ptr) {
return SWAP_BYTES_32(READ_UINT32(ptr));
}
inline void WRITE_LE_UINT16(void *ptr, uint16 value) {
WRITE_UINT16(ptr, SWAP_BYTES_16(value));
}
inline void WRITE_LE_UINT32(void *ptr, uint32 value) {
WRITE_UINT32(ptr, SWAP_BYTES_32(value));
}
# endif // if defined(SCUMM_NEED_ALIGNMENT)
#endif // if defined(SCUMM_LITTLE_ENDIAN)
inline uint32 READ_LE_UINT24(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[2] << 16) | (b[1] << 8) | (b[0]);
}
inline uint32 READ_BE_UINT24(const void *ptr) {
const uint8 *b = (const uint8 *)ptr;
return (b[0] << 16) | (b[1] << 8) | (b[2]);
}
#endif
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