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https://github.com/libretro/scummvm.git
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cdd27ca943
This is a better solution for the gcc aliasing problem that happens when aliasing a struct onto something else. What happens is that the compiler assumes no aliasing can happen when -O2 and -O3 are activated, and a call to READ_UINT32() followed by WRITE_UINT32() and another READ_UINT32() will be optimized to return the original read value instead of re-reading. svn-id: r52480
413 lines
12 KiB
C
413 lines
12 KiB
C
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*
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*/
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#ifndef COMMON_ENDIAN_H
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#define COMMON_ENDIAN_H
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#include "common/scummsys.h"
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/**
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* \file endian.h
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* Endian conversion and byteswap conversion functions or macros
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*
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* SWAP_BYTES_??(a) - inverse byte order
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* SWAP_CONSTANT_??(a) - inverse byte order, implemented as macro.
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* Use with compiletime-constants only, the result will be a compiletime-constant aswell.
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* Unlike most other functions these can be used for eg. switch-case labels
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*
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* READ_UINT??(a) - read native value from pointer a
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* READ_??_UINT??(a) - read LE/BE value from pointer a and convert it to native
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* WRITE_??_UINT??(a, v) - write native value v to pointer a with LE/BE encoding
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* TO_??_??(a) - convert native value v to LE/BE
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* FROM_??_??(a) - convert LE/BE value v to native
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* CONSTANT_??_??(a) - convert LE/BE value v to native, implemented as macro.
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* Use with compiletime-constants only, the result will be a compiletime-constant aswell.
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* Unlike most other functions these can be used for eg. switch-case labels
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*/
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// Sanity check
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#if !defined(SCUMM_LITTLE_ENDIAN) && !defined(SCUMM_BIG_ENDIAN)
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# error No endianness defined
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#endif
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#define SWAP_CONSTANT_32(a) \
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((uint32)((((a) >> 24) & 0x00FF) | \
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(((a) >> 8) & 0xFF00) | \
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(((a) & 0xFF00) << 8) | \
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(((a) & 0x00FF) << 24) ))
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#define SWAP_CONSTANT_16(a) \
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((uint16)((((a) >> 8) & 0x00FF) | \
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(((a) << 8) & 0xFF00) ))
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/**
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* Swap the bytes in a 32 bit word in order to convert LE encoded data to BE
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* and vice versa.
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*/
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// machine/compiler-specific variants come first, fallback last
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// Test for GCC and if the target has the MIPS rel.2 instructions (we know the psp does)
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#if defined(__GNUC__) && (defined(__psp__) || defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS64R2))
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FORCEINLINE uint32 SWAP_BYTES_32(const uint32 a) {
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if (__builtin_constant_p(a)) {
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return SWAP_CONSTANT_32(a);
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} else {
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uint32 result;
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# if defined(__psp__)
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// use special allegrex instruction
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__asm__ ("wsbw %0,%1" : "=r" (result) : "r" (a));
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# else
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__asm__ ("wsbh %0,%1\n"
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"rotr %0,%0,16" : "=r" (result) : "r" (a));
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# endif
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return result;
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}
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}
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// Test for GCC >= 4.3.0 as this version added the bswap builtin
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#elif defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
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FORCEINLINE uint32 SWAP_BYTES_32(uint32 a) {
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return __builtin_bswap32(a);
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}
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// test for MSVC 7 or newer
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#elif defined(_MSC_VER) && _MSC_VER >= 1300
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FORCEINLINE uint32 SWAP_BYTES_32(uint32 a) {
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return _byteswap_ulong(a);
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}
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// generic fallback
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#else
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inline uint32 SWAP_BYTES_32(uint32 a) {
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const uint16 low = (uint16)a, high = (uint16)(a >> 16);
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return ((uint32)(uint16)((low >> 8) | (low << 8)) << 16)
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| (uint16)((high >> 8) | (high << 8));
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}
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#endif
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/**
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* Swap the bytes in a 16 bit word in order to convert LE encoded data to BE
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* and vice versa.
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*/
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// compilerspecific variants come first, fallback last
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// Test for GCC and if the target has the MIPS rel.2 instructions (we know the psp does)
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#if defined(__GNUC__) && (defined(__psp__) || defined(_MIPS_ARCH_MIPS32R2) || defined(_MIPS_ARCH_MIPS64R2))
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FORCEINLINE uint16 SWAP_BYTES_16(const uint16 a) {
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if (__builtin_constant_p(a)) {
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return SWAP_CONSTANT_16(a);
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} else {
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uint16 result;
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__asm__ ("wsbh %0,%1" : "=r" (result) : "r" (a));
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return result;
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}
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}
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#else
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inline uint16 SWAP_BYTES_16(const uint16 a) {
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return (a >> 8) | (a << 8);
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}
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#endif
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/**
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* A wrapper macro used around four character constants, like 'DATA', to
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* ensure portability. Typical usage: MKID_BE('DATA').
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*
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* Why is this necessary? The C/C++ standard does not define the endianess to
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* be used for character constants. Hence if one uses multi-byte character
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* constants, a potential portability problem opens up.
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*
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* Fortunately, a semi-standard has been established: On almost all systems
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* and compilers, multi-byte character constants are encoded using the big
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* endian convention (probably in analogy to the encoding of string constants).
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* Still some systems differ. This is why we provide the MKID_BE macro. If
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* you wrap your four character constants with it, the result will always be
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* BE encoded, even on systems which differ from the default BE encoding.
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*
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* For the latter systems we provide the INVERSE_MKID override.
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*/
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#if defined(INVERSE_MKID)
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#define MKID_BE(a) SWAP_CONSTANT_32(a)
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#else
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# define MKID_BE(a) ((uint32)(a))
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#endif
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// Functions for reading/writing native Integers,
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// this transparently handles the need for alignment
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#if !defined(SCUMM_NEED_ALIGNMENT)
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FORCEINLINE uint16 READ_UINT16(const void *ptr) {
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return *(const uint16 *)(ptr);
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}
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FORCEINLINE uint32 READ_UINT32(const void *ptr) {
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return *(const uint32 *)(ptr);
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}
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FORCEINLINE void WRITE_UINT16(void *ptr, uint16 value) {
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*(uint16 *)(ptr) = value;
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}
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FORCEINLINE void WRITE_UINT32(void *ptr, uint32 value) {
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*(uint32 *)(ptr) = value;
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}
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// test for GCC >= 4.0. these implementations will automatically use CPU-specific
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// instructions for unaligned data when they are available (eg. MIPS)
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#elif defined(__GNUC__) && (__GNUC__ >= 4)
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FORCEINLINE uint16 READ_UINT16(const void *ptr) {
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struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
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return ((const Unaligned16 *)ptr)->val;
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}
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FORCEINLINE uint32 READ_UINT32(const void *ptr) {
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struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
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return ((const Unaligned32 *)ptr)->val;
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}
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FORCEINLINE void WRITE_UINT16(void *ptr, uint16 value) {
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struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
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((Unaligned16 *)ptr)->val = value;
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}
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FORCEINLINE void WRITE_UINT32(void *ptr, uint32 value) {
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struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
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((Unaligned32 *)ptr)->val = value;
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}
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// use software fallback by loading each byte explicitely
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#else
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# if defined(SCUMM_LITTLE_ENDIAN)
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inline uint16 READ_UINT16(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[1] << 8) | b[0];
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}
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inline uint32 READ_UINT32(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | (b[0]);
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}
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inline void WRITE_UINT16(void *ptr, uint16 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 0);
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b[1] = (uint8)(value >> 8);
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}
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inline void WRITE_UINT32(void *ptr, uint32 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 0);
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b[1] = (uint8)(value >> 8);
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b[2] = (uint8)(value >> 16);
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b[3] = (uint8)(value >> 24);
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}
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# elif defined(SCUMM_BIG_ENDIAN)
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inline uint16 READ_UINT16(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[0] << 8) | b[1];
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}
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inline uint32 READ_UINT32(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | (b[3]);
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}
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inline void WRITE_UINT16(void *ptr, uint16 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 8);
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b[1] = (uint8)(value >> 0);
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}
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inline void WRITE_UINT32(void *ptr, uint32 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 24);
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b[1] = (uint8)(value >> 16);
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b[2] = (uint8)(value >> 8);
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b[3] = (uint8)(value >> 0);
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}
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# endif
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#endif
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// Map Funtions for reading/writing BE/LE integers depending on native endianess
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#if defined(SCUMM_LITTLE_ENDIAN)
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#define READ_LE_UINT16(a) READ_UINT16(a)
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#define READ_LE_UINT32(a) READ_UINT32(a)
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#define WRITE_LE_UINT16(a, v) WRITE_UINT16(a, v)
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#define WRITE_LE_UINT32(a, v) WRITE_UINT32(a, v)
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#define FROM_LE_32(a) ((uint32)(a))
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#define FROM_LE_16(a) ((uint16)(a))
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#define FROM_BE_32(a) SWAP_BYTES_32(a)
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#define FROM_BE_16(a) SWAP_BYTES_16(a)
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#define TO_LE_32(a) ((uint32)(a))
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#define TO_LE_16(a) ((uint16)(a))
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#define TO_BE_32(a) SWAP_BYTES_32(a)
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#define TO_BE_16(a) SWAP_BYTES_16(a)
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#define CONSTANT_LE_32(a) ((uint32)(a))
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#define CONSTANT_LE_16(a) ((uint16)(a))
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#define CONSTANT_BE_32(a) SWAP_CONSTANT_32(a)
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#define CONSTANT_BE_16(a) SWAP_CONSTANT_16(a)
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// if the unaligned load and the byteswap take alot instructions its better to directly read and invert
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# if defined(SCUMM_NEED_ALIGNMENT) && !defined(__mips__)
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inline uint16 READ_BE_UINT16(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[0] << 8) | b[1];
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}
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inline uint32 READ_BE_UINT32(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | (b[3]);
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}
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inline void WRITE_BE_UINT16(void *ptr, uint16 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 8);
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b[1] = (uint8)(value >> 0);
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}
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inline void WRITE_BE_UINT32(void *ptr, uint32 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 24);
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b[1] = (uint8)(value >> 16);
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b[2] = (uint8)(value >> 8);
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b[3] = (uint8)(value >> 0);
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}
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# else
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inline uint16 READ_BE_UINT16(const void *ptr) {
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return SWAP_BYTES_16(READ_UINT16(ptr));
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}
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inline uint32 READ_BE_UINT32(const void *ptr) {
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return SWAP_BYTES_32(READ_UINT32(ptr));
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}
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inline void WRITE_BE_UINT16(void *ptr, uint16 value) {
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WRITE_UINT16(ptr, SWAP_BYTES_16(value));
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}
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inline void WRITE_BE_UINT32(void *ptr, uint32 value) {
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WRITE_UINT32(ptr, SWAP_BYTES_32(value));
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}
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# endif // if defined(SCUMM_NEED_ALIGNMENT)
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#elif defined(SCUMM_BIG_ENDIAN)
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#define MKID_BE(a) ((uint32)(a))
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#define READ_BE_UINT16(a) READ_UINT16(a)
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#define READ_BE_UINT32(a) READ_UINT32(a)
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#define WRITE_BE_UINT16(a, v) WRITE_UINT16(a, v)
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#define WRITE_BE_UINT32(a, v) WRITE_UINT32(a, v)
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#define FROM_LE_32(a) SWAP_BYTES_32(a)
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#define FROM_LE_16(a) SWAP_BYTES_16(a)
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#define FROM_BE_32(a) ((uint32)(a))
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#define FROM_BE_16(a) ((uint16)(a))
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#define TO_LE_32(a) SWAP_BYTES_32(a)
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#define TO_LE_16(a) SWAP_BYTES_16(a)
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#define TO_BE_32(a) ((uint32)(a))
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#define TO_BE_16(a) ((uint16)(a))
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#define CONSTANT_LE_32(a) SWAP_CONSTANT_32(a)
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#define CONSTANT_LE_16(a) SWAP_CONSTANT_16(a)
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#define CONSTANT_BE_32(a) ((uint32)(a))
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#define CONSTANT_BE_16(a) ((uint16)(a))
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// if the unaligned load and the byteswap take alot instructions its better to directly read and invert
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# if defined(SCUMM_NEED_ALIGNMENT) && !defined(__mips__)
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inline uint16 READ_LE_UINT16(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[1] << 8) | b[0];
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}
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inline uint32 READ_LE_UINT32(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | (b[0]);
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}
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inline void WRITE_LE_UINT16(void *ptr, uint16 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 0);
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b[1] = (uint8)(value >> 8);
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}
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inline void WRITE_LE_UINT32(void *ptr, uint32 value) {
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uint8 *b = (uint8 *)ptr;
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b[0] = (uint8)(value >> 0);
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b[1] = (uint8)(value >> 8);
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b[2] = (uint8)(value >> 16);
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b[3] = (uint8)(value >> 24);
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}
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# else
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inline uint16 READ_LE_UINT16(const void *ptr) {
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return SWAP_BYTES_16(READ_UINT16(ptr));
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}
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inline uint32 READ_LE_UINT32(const void *ptr) {
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return SWAP_BYTES_32(READ_UINT32(ptr));
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}
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inline void WRITE_LE_UINT16(void *ptr, uint16 value) {
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WRITE_UINT16(ptr, SWAP_BYTES_16(value));
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}
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inline void WRITE_LE_UINT32(void *ptr, uint32 value) {
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WRITE_UINT32(ptr, SWAP_BYTES_32(value));
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}
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# endif // if defined(SCUMM_NEED_ALIGNMENT)
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#endif // if defined(SCUMM_LITTLE_ENDIAN)
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inline uint32 READ_LE_UINT24(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[2] << 16) | (b[1] << 8) | (b[0]);
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}
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inline uint32 READ_BE_UINT24(const void *ptr) {
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const uint8 *b = (const uint8 *)ptr;
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return (b[0] << 16) | (b[1] << 8) | (b[2]);
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}
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#endif
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