aboutsummaryrefslogtreecommitdiff
path: root/common/endian.h
blob: 1760dc74b2473a869960d7bbdc55022babcb3a3c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
/* 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.
 *
 */

#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 GCC_ATLEAST(4, 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) ((uint32)((a3) | ((a2) << 8) | ((a1) << 16) | ((a0) << 24)))

// Functions for reading/writing native integers.
// They also transparently handle the need for alignment.

// Test for GCC >= 4.0. These implementations will automatically use
// CPU-specific instructions for unaligned data when they are available (eg.
// MIPS). See also this email thread on scummvm-devel for details:
// <http://thread.gmane.org/gmane.games.devel.scummvm/8063>
//
// Moreover, we activate this code for GCC >= 3.3 but *only* if unaligned access
// is allowed.
#if GCC_ATLEAST(4, 0) || (GCC_ATLEAST(3, 3) && !defined(SCUMM_NEED_ALIGNMENT))

	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;
	}

#elif !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;
	}


// 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