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/* ScummVM - Scumm Interpreter
* Copyright (C) 2001 Ludvig Strigeus
* Copyright (C) 2001-2006 The ScummVM project
*
* 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"
//
// Endian conversion functions, macros etc., follow from here!
//
/**
* Swap the bytes in a 32 bit word in order to convert LE encoded data to BE
* and vice versa.
*/
FORCEINLINE uint32 SWAP_BYTES_32(uint32 a) {
return ((a >> 24) & 0x000000FF) |
((a >> 8) & 0x0000FF00) |
((a << 8) & 0x00FF0000) |
((a << 24) & 0xFF000000);
}
/**
* Swap the bytes in a 16 bit word in order to convert LE encoded data to BE
* and vice versa.
*/
FORCEINLINE uint16 SWAP_BYTES_16(uint16 a) {
return ((a >> 8) & 0x00FF) + ((a << 8) & 0xFF00);
}
/**
* A wrapper macro used around four character constants, like 'DATA', to
* ensure portability. Typical usage: MKID_BE('DATA').
*
* 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.
*
* Fortunately, a semi-standard has been established: On almost all systems
* and compilers, multi-byte character constants are encoded using the big
* endian convention (probably in analogy to the encoding of string constants).
* Still some systems differ. This is why we provide the MKID_BE macro. If
* you wrap your four character constants with it, the result will always be
* BE encoded, even on systems which differ from the default BE encoding.
*
* For the latter systems we provide the INVERSE_MKID override.
*/
#if defined(INVERSE_MKID)
#define MKID_BE(a) ((uint32) \
(((a) >> 24) & 0x000000FF) | \
(((a) >> 8) & 0x0000FF00) | \
(((a) << 8) & 0x00FF0000) | \
(((a) << 24) & 0xFF000000))
#else
# define MKID_BE(a) ((uint32)(a))
#endif
#if defined(SCUMM_LITTLE_ENDIAN)
#define READ_UINT16(a) READ_LE_UINT16(a)
#define READ_UINT32(a) READ_LE_UINT32(a)
#define WRITE_UINT16(a, v) WRITE_LE_UINT16(a, v)
#define WRITE_UINT32(a, v) WRITE_LE_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)
#elif defined(SCUMM_BIG_ENDIAN)
#define MKID(a) ((uint32)(a))
#define MKID_BE(a) ((uint32)(a))
#define READ_UINT16(a) READ_BE_UINT16(a)
#define READ_UINT32(a) READ_BE_UINT32(a)
#define WRITE_UINT16(a, v) WRITE_BE_UINT16(a, v)
#define WRITE_UINT32(a, v) WRITE_BE_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))
#else
#error No endianness defined
#endif
#if defined(SCUMM_NEED_ALIGNMENT) || defined(SCUMM_BIG_ENDIAN)
FORCEINLINE uint16 READ_LE_UINT16(const void *ptr) {
const byte *b = (const byte *)ptr;
return (b[1] << 8) + b[0];
}
FORCEINLINE uint32 READ_LE_UINT32(const void *ptr) {
const byte *b = (const byte *)ptr;
return (b[3] << 24) + (b[2] << 16) + (b[1] << 8) + (b[0]);
}
FORCEINLINE void WRITE_LE_UINT16(void *ptr, uint16 value) {
byte *b = (byte *)ptr;
b[0] = (byte)(value >> 0);
b[1] = (byte)(value >> 8);
}
FORCEINLINE void WRITE_LE_UINT32(void *ptr, uint32 value) {
byte *b = (byte *)ptr;
b[0] = (byte)(value >> 0);
b[1] = (byte)(value >> 8);
b[2] = (byte)(value >> 16);
b[3] = (byte)(value >> 24);
}
#else
FORCEINLINE uint16 READ_LE_UINT16(const void *ptr) {
return *(const uint16 *)(ptr);
}
FORCEINLINE uint32 READ_LE_UINT32(const void *ptr) {
return *(const uint32 *)(ptr);
}
FORCEINLINE void WRITE_LE_UINT16(void *ptr, uint16 value) {
*(uint16 *)(ptr) = value;
}
FORCEINLINE void WRITE_LE_UINT32(void *ptr, uint32 value) {
*(uint32 *)(ptr) = value;
}
#endif
#if defined(SCUMM_NEED_ALIGNMENT) || defined(SCUMM_LITTLE_ENDIAN)
FORCEINLINE uint16 READ_BE_UINT16(const void *ptr) {
const byte *b = (const byte *)ptr;
return (b[0] << 8) + b[1];
}
FORCEINLINE uint32 READ_BE_UINT32(const void *ptr) {
const byte *b = (const byte*)ptr;
return (b[0] << 24) + (b[1] << 16) + (b[2] << 8) + (b[3]);
}
FORCEINLINE void WRITE_BE_UINT16(void *ptr, uint16 value) {
byte *b = (byte *)ptr;
b[0] = (byte)(value >> 8);
b[1] = (byte)(value >> 0);
}
FORCEINLINE void WRITE_BE_UINT32(void *ptr, uint32 value) {
byte *b = (byte *)ptr;
b[0] = (byte)(value >> 24);
b[1] = (byte)(value >> 16);
b[2] = (byte)(value >> 8);
b[3] = (byte)(value >> 0);
}
#else
FORCEINLINE uint16 READ_BE_UINT16(const void *ptr) {
return *(const uint16 *)(ptr);
}
FORCEINLINE uint32 READ_BE_UINT32(const void *ptr) {
return *(const uint32 *)(ptr);
}
FORCEINLINE void WRITE_BE_UINT16(void *ptr, uint16 value) {
*(uint16 *)(ptr) = value;
}
FORCEINLINE void WRITE_BE_UINT32(void *ptr, uint32 value) {
*(uint32 *)(ptr) = value;
}
#endif
FORCEINLINE uint32 READ_LE_UINT24(const void *ptr) {
const byte *b = (const byte *)ptr;
return (b[2] << 16) + (b[1] << 8) + (b[0]);
}
FORCEINLINE uint32 READ_BE_UINT24(const void *ptr) {
const byte *b = (const byte*)ptr;
return (b[0] << 16) + (b[1] << 8) + (b[2]);
}
#endif
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