summaryrefslogtreecommitdiff
path: root/src/macros.h
blob: c7621336bcd163e315717df0a2bfb456bc63efdf (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
/* $Id$ */

/** @file macros.h */

#ifndef MACROS_H
#define MACROS_H

#include "core/math_func.hpp"

/**
 * Fetch n bits from x, started at bit s.
 *
 * This function can be used to fetch n bits from the value x. The
 * s value set the startposition to read. The startposition is
 * count from the LSB and starts at 0. The result starts at a
 * LSB, as this isn't just an and-bitmask but also some
 * bit-shifting operations. GB(0xFF, 2, 1) will so
 * return 0x01 (0000 0001) instead of
 * 0x04 (0000 0100).
 *
 * @param x The value to read some bits.
 * @param s The startposition to read some bits.
 * @param n The number of bits to read.
 * @return The selected bits, aligned to a LSB.
 */
template<typename T> static inline uint GB(const T x, const uint8 s, const uint8 n)
{
	return (x >> s) & ((1U << n) - 1);
}

/** Set n bits from x starting at bit s to d
 *
 * This function sets n bits from x which started as bit s to the value of
 * d. The parameters x, s and n works the same as the parameters of
 * #GB. The result is saved in x again. Unused bits in the window
 * provided by n are set to 0 if the value of b isn't "big" enough.
 * This is not a bug, its a feature.
 *
 * @note Parameter x must be a variable as the result is saved there.
 * @note To avoid unexpecting results the value of b should not use more
 *       space as the provided space of n bits (log2)
 * @param x The variable to change some bits
 * @param s The startposition for the new bits
 * @param n The size/window for the new bits
 * @param d The actually new bits to save in the defined position.
 * @return The new value of x
 */
template<typename T, typename U> static inline T SB(T& x, const uint8 s, const uint8 n, const U d)
{
	x &= (T)(~(((1U << n) - 1) << s));
	x |= (T)(d << s);
	return x;
}

/** Add i to n bits of x starting at bit s.
 *
 * This add the value of i on n bits of x starting at bit s. The parameters x,
 * s, i are similar to #GB besides x must be a variable as the result are
 * saved there. An overflow does not affect the following bits of the given
 * bit window and is simply ignored.
 *
 * @note Parameter x must be a variable as the result is saved there.
 * @param x The variable to add some bits at some position
 * @param s The startposition of the addition
 * @param n The size/window for the addition
 * @param i The value to add at the given startposition in the given window.
 * @return The new value of x
 */
template<typename T, typename U> static inline T AB(T& x, const uint8 s, const uint8 n, const U i)
{
	const T mask = (T)(((1U << n) - 1) << s);
	x = (T)((x & ~mask) | ((x + (i << s)) & mask));
	return x;
}

/**
 * Checks if a bit in a value is set.
 *
 * This function checks if a bit inside a value is set or not.
 * The y value specific the position of the bit, started at the
 * LSB and count from 0.
 *
 * @param x The value to check
 * @param y The position of the bit to check, started from the LSB
 * @return True if the bit is set, false else.
 */
template<typename T> static inline bool HasBit(const T x, const uint8 y)
{
	return (x & ((T)1U << y)) != 0;
}

/**
 * Set a bit in a variable.
 *
 * This function sets a bit in a variable. The variable is changed
 * and the value is also returned. Parameter y defines the bit and
 * starts at the LSB with 0.
 *
 * @param x The variable to set a bit
 * @param y The bit position to set
 * @return The new value of the old value with the bit set
 */
template<typename T> static inline T SetBit(T& x, const uint8 y)
{
	return x = (T)(x | (T)(1U << y));
}

/**
 * Clears a bit in a variable.
 *
 * This function clears a bit in a variable. The variable is
 * changed and the value is also returned. Parameter y defines the bit
 * to clear and starts at the LSB with 0.
 *
 * @param x The variable to clear the bit
 * @param y The bit position to clear
 * @return The new value of the old value with the bit cleared
 */
template<typename T> static inline T ClrBit(T& x, const uint8 y)
{
	return x = (T)(x & ~((T)1U << y));
}

/**
 * Toggles a bit in a variable.
 *
 * This function toggles a bit in a variable. The variable is
 * changed and the value is also returned. Parameter y defines the bit
 * to toggle and starts at the LSB with 0.
 *
 * @param x The varliable to toggle the bit
 * @param y The bit position to toggle
 * @return The new value of the old value with the bit toggled
 */
template<typename T> static inline T ToggleBit(T& x, const uint8 y)
{
	return x = (T)(x ^ (T)(1U << y));
}


/* checking more bits. Maybe unneccessary, but easy to use */
/**
 * Check several bits in a value.
 *
 * This macro checks if a value contains at least one bit of an other
 * value.
 *
 * @param x The first value
 * @param y The second value
 * @return True if at least one bit is set in both values, false else.
 */
#define HASBITS(x, y) ((x) & (y))

/**
 * Sets several bits in a variable.
 *
 * This macro sets several bits in a variable. The bits to set are provided
 * by a value. The new value is also returned.
 *
 * @param x The variable to set some bits
 * @param y The value with set bits for setting them in the variable
 * @return The new value of x
 */
#define SETBITS(x, y) ((x) |= (y))

/**
 * Clears several bits in a variable.
 *
 * This macro clears several bits in a variable. The bits to clear are
 * provided by a value. The new value is also returned.
 *
 * @param x The variable to clear some bits
 * @param y The value with set bits for clearing them in the variable
 * @return The new value of x
 */
#define CLRBITS(x, y) ((x) &= ~(y))

#define GENERAL_SPRITE_COLOR(color) ((color) + PALETTE_RECOLOR_START)
#define PLAYER_SPRITE_COLOR(owner) (GENERAL_SPRITE_COLOR(_player_colors[owner]))

/**
 * Whether a sprite comes from the original graphics files or a new grf file
 * (either supplied by OpenTTD or supplied by the user).
 *
 * @param sprite The sprite to check
 * @return True if it is a new sprite, or false if it is original.
 */
#define IS_CUSTOM_SPRITE(sprite) ((sprite) >= SPR_SIGNALS_BASE)

extern const byte _ffb_64[64];

/**
 * Returns the first occure of a bit in a 6-bit value (from right).
 *
 * Returns the position of the first bit that is not zero, counted from the
 * LSB. Ie, 110100 returns 2, 000001 returns 0, etc. When x == 0 returns
 * 0.
 *
 * @param x The 6-bit value to check the first zero-bit
 * @return The first position of a bit started from the LSB or 0 if x is 0.
 */
#define FIND_FIRST_BIT(x) _ffb_64[(x)]

/**
 * Finds the position of the first bit in an integer.
 *
 * This function returns the position of the first bit set in the
 * integer. It does only check the bits of the bitmask
 * 0x3F3F (0011111100111111) and checks only the
 * bits of the bitmask 0x3F00 if and only if the
 * lower part 0x00FF is 0. This results the bits at 0x00C0 must
 * be also zero to check the bits at 0x3F00.
 *
 * @param value The value to check the first bits
 * @return The position of the first bit which is set
 * @see FIND_FIRST_BIT
 */
static inline int FindFirstBit2x64(int value)
{
	if ((value & 0xFF) == 0) {
		return FIND_FIRST_BIT((value >> 8) & 0x3F) + 8;
	} else {
		return FIND_FIRST_BIT(value & 0x3F);
	}
}

/**
 * Clear the first bit in an integer.
 *
 * This function returns a value where the first bit (from LSB)
 * is cleared.
 * So, 110100 returns 110000, 000001 returns 000000, etc.
 *
 * @param value The value to clear the first bit
 * @return The new value with the first bit cleared
 */
template<typename T> static inline T KillFirstBit(T value)
{
	return value &= (T)(value - 1);
}

/**
 * Counts the number of set bits in a variable.
 *
 * @param value the value to count the number of bits in.
 * @return the number of bits.
 */
template<typename T> static inline uint CountBits(T value)
{
	uint num;

	/* This loop is only called once for every bit set by clearing the lowest
	 * bit in each loop. The number of bits is therefore equal to the number of
	 * times the loop was called. It was found at the following website:
	 * http://graphics.stanford.edu/~seander/bithacks.html */

	for (num = 0; value != 0; num++) {
		value &= (T)(value - 1);
	}

	return num;
}

/**
 * Flips a coin with a given probability.
 *
 * This macro can be used to get true or false randomized according to a
 * given probability. The parameter a and b create a percent value with
 * (a/b). The macro returns true in (a/b) percent.
 *
 * @param a The numerator of the fraction
 * @param b The denominator of the fraction, must of course not be null
 * @return True in (a/b) percent
 */
#define CHANCE16(a, b) CHANCE16I(a, b, Random())

/**
 * Flips a coin with a given probability and saves the randomize-number in a variable.
 *
 * This macro uses the same parameters as the CHANCE16 marco. The third parameter
 * must be a variable the randomize-number from Random() is saved in.
 *
 * The low 16 bits of r will already be used and can therefor not be passed to
 * CHANCE16I. One can only send the high 16 bits to CHANCE16I.
 *
 * @param a The numerator of the fraction, see CHANCE16
 * @param b The denominator of the fraction, see CHANCE16
 * @param r The variable to save the randomize-number from Random()
 * @return True in (a/b) percent
 */
#define CHANCE16R(a, b, r) CHANCE16I(a, b, r = Random())

/**
 * Checks if a given randomize-number is below a given probability.
 *
 * This macro is used to check if the given probability by the fraction of (a/b)
 * is greater than low 16 bits of the given randomize-number v.
 *
 * Do not use this function twice on the same random 16 bits as it will yield
 * the same result. One can use a random number for two calls to CHANCE16I,
 * where one call sends the low 16 bits and the other the high 16 bits.
 *
 * @param a The numerator of the fraction, see CHANCE16
 * @param b The denominator of the fraction, see CHANCE16
 * @param r The given randomize-number
 * @return True if v is less or equals (a/b)
 */
static inline bool CHANCE16I(const uint a, const uint b, const uint32 r)
{
	return (uint16)r < (uint16)((65536 * a) / b);
}


#define for_each_bit(_i, _b)            \
	for (_i = 0; _b != 0; _i++, _b >>= 1) \
		if (_b & 1)


static inline uint16 ReadLE16Aligned(const void* x)
{
	return FROM_LE16(*(const uint16*)x);
}

static inline uint16 ReadLE16Unaligned(const void* x)
{
#ifdef OTTD_ALIGNMENT
	return ((const byte*)x)[0] | ((const byte*)x)[1] << 8;
#else
	return FROM_LE16(*(const uint16*)x);
#endif
}


/**
 * ROtate x Left by n
 *
 * @note Assumes a byte has 8 bits
 * @param x The value which we want to rotate
 * @param n The number how many we waht to rotate
 * @return A bit rotated number
 */
template<typename T> static inline T ROL(const T x, const uint8 n)
{
	return (T)(x << n | x >> (sizeof(x) * 8 - n));
}

/**
 * ROtate x Right by n
 *
 * @note Assumes a byte has 8 bits
 * @param x The value which we want to rotate
 * @param n The number how many we waht to rotate
 * @return A bit rotated number
 */
template<typename T> static inline T ROR(const T x, const uint8 n)
{
	return (T)(x >> n | x << (sizeof(x) * 8 - n));
}

/** return the largest value that can be entered in a variable.
 */
#define MAX_UVALUE(type) ((type)~(type)0)

#endif /* MACROS_H */