Mercurial > projects > ldc
comparison druntime/src/common/core/bitmanip.d @ 1458:e0b2d67cfe7c
Added druntime (this should be removed once it works).
author | Robert Clipsham <robert@octarineparrot.com> |
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date | Tue, 02 Jun 2009 17:43:06 +0100 |
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1 /** | |
2 * This module contains a collection of bit-level operations. | |
3 * | |
4 * Copyright: Copyright (c) 2005-2008, The D Runtime Project | |
5 * License: BSD Style, see LICENSE | |
6 * Authors: Walter Bright, Don Clugston, Sean Kelly | |
7 */ | |
8 module core.bitmanip; | |
9 | |
10 | |
11 version( DDoc ) | |
12 { | |
13 /** | |
14 * Scans the bits in v starting with bit 0, looking | |
15 * for the first set bit. | |
16 * Returns: | |
17 * The bit number of the first bit set. | |
18 * The return value is undefined if v is zero. | |
19 */ | |
20 int bsf( uint v ); | |
21 | |
22 | |
23 /** | |
24 * Scans the bits in v from the most significant bit | |
25 * to the least significant bit, looking | |
26 * for the first set bit. | |
27 * Returns: | |
28 * The bit number of the first bit set. | |
29 * The return value is undefined if v is zero. | |
30 * Example: | |
31 * --- | |
32 * import core.bitmanip; | |
33 * | |
34 * int main() | |
35 * { | |
36 * uint v; | |
37 * int x; | |
38 * | |
39 * v = 0x21; | |
40 * x = bsf(v); | |
41 * printf("bsf(x%x) = %d\n", v, x); | |
42 * x = bsr(v); | |
43 * printf("bsr(x%x) = %d\n", v, x); | |
44 * return 0; | |
45 * } | |
46 * --- | |
47 * Output: | |
48 * bsf(x21) = 0<br> | |
49 * bsr(x21) = 5 | |
50 */ | |
51 int bsr( uint v ); | |
52 | |
53 | |
54 /** | |
55 * Tests the bit. | |
56 */ | |
57 int bt( uint* p, uint bitnum ); | |
58 | |
59 | |
60 /** | |
61 * Tests and complements the bit. | |
62 */ | |
63 int btc( uint* p, uint bitnum ); | |
64 | |
65 | |
66 /** | |
67 * Tests and resets (sets to 0) the bit. | |
68 */ | |
69 int btr( uint* p, uint bitnum ); | |
70 | |
71 | |
72 /** | |
73 * Tests and sets the bit. | |
74 * Params: | |
75 * p = a non-NULL pointer to an array of uints. | |
76 * index = a bit number, starting with bit 0 of p[0], | |
77 * and progressing. It addresses bits like the expression: | |
78 --- | |
79 p[index / (uint.sizeof*8)] & (1 << (index & ((uint.sizeof*8) - 1))) | |
80 --- | |
81 * Returns: | |
82 * A non-zero value if the bit was set, and a zero | |
83 * if it was clear. | |
84 * | |
85 * Example: | |
86 * --- | |
87 import core.bitmanip; | |
88 | |
89 int main() | |
90 { | |
91 uint array[2]; | |
92 | |
93 array[0] = 2; | |
94 array[1] = 0x100; | |
95 | |
96 printf("btc(array, 35) = %d\n", <b>btc</b>(array, 35)); | |
97 printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]); | |
98 | |
99 printf("btc(array, 35) = %d\n", <b>btc</b>(array, 35)); | |
100 printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]); | |
101 | |
102 printf("bts(array, 35) = %d\n", <b>bts</b>(array, 35)); | |
103 printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]); | |
104 | |
105 printf("btr(array, 35) = %d\n", <b>btr</b>(array, 35)); | |
106 printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]); | |
107 | |
108 printf("bt(array, 1) = %d\n", <b>bt</b>(array, 1)); | |
109 printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]); | |
110 | |
111 return 0; | |
112 } | |
113 * --- | |
114 * Output: | |
115 <pre> | |
116 btc(array, 35) = 0 | |
117 array = [0]:x2, [1]:x108 | |
118 btc(array, 35) = -1 | |
119 array = [0]:x2, [1]:x100 | |
120 bts(array, 35) = 0 | |
121 array = [0]:x2, [1]:x108 | |
122 btr(array, 35) = -1 | |
123 array = [0]:x2, [1]:x100 | |
124 bt(array, 1) = -1 | |
125 array = [0]:x2, [1]:x100 | |
126 </pre> | |
127 */ | |
128 int bts( uint* p, uint bitnum ); | |
129 | |
130 | |
131 /** | |
132 * Swaps bytes in a 4 byte uint end-to-end, i.e. byte 0 becomes | |
133 * byte 3, byte 1 becomes byte 2, byte 2 becomes byte 1, byte 3 | |
134 * becomes byte 0. | |
135 */ | |
136 uint bswap( uint v ); | |
137 | |
138 | |
139 /** | |
140 * Reads I/O port at port_address. | |
141 */ | |
142 ubyte inp( uint port_address ); | |
143 | |
144 | |
145 /** | |
146 * ditto | |
147 */ | |
148 ushort inpw( uint port_address ); | |
149 | |
150 | |
151 /** | |
152 * ditto | |
153 */ | |
154 uint inpl( uint port_address ); | |
155 | |
156 | |
157 /** | |
158 * Writes and returns value to I/O port at port_address. | |
159 */ | |
160 ubyte outp( uint port_address, ubyte value ); | |
161 | |
162 | |
163 /** | |
164 * ditto | |
165 */ | |
166 ushort outpw( uint port_address, ushort value ); | |
167 | |
168 | |
169 /** | |
170 * ditto | |
171 */ | |
172 uint outpl( uint port_address, uint value ); | |
173 } | |
174 else | |
175 { | |
176 public import std.intrinsic; | |
177 } | |
178 | |
179 | |
180 /** | |
181 * Calculates the number of set bits in a 32-bit integer. | |
182 */ | |
183 int popcnt( uint x ) | |
184 { | |
185 // Avoid branches, and the potential for cache misses which | |
186 // could be incurred with a table lookup. | |
187 | |
188 // We need to mask alternate bits to prevent the | |
189 // sum from overflowing. | |
190 // add neighbouring bits. Each bit is 0 or 1. | |
191 x = x - ((x>>1) & 0x5555_5555); | |
192 // now each two bits of x is a number 00,01 or 10. | |
193 // now add neighbouring pairs | |
194 x = ((x&0xCCCC_CCCC)>>2) + (x&0x3333_3333); | |
195 // now each nibble holds 0000-0100. Adding them won't | |
196 // overflow any more, so we don't need to mask any more | |
197 | |
198 // Now add the nibbles, then the bytes, then the words | |
199 // We still need to mask to prevent double-counting. | |
200 // Note that if we used a rotate instead of a shift, we | |
201 // wouldn't need the masks, and could just divide the sum | |
202 // by 8 to account for the double-counting. | |
203 // On some CPUs, it may be faster to perform a multiply. | |
204 | |
205 x += (x>>4); | |
206 x &= 0x0F0F_0F0F; | |
207 x += (x>>8); | |
208 x &= 0x00FF_00FF; | |
209 x += (x>>16); | |
210 x &= 0xFFFF; | |
211 return x; | |
212 } | |
213 | |
214 | |
215 debug( UnitTest ) | |
216 { | |
217 unittest | |
218 { | |
219 assert( popcnt( 0 ) == 0 ); | |
220 assert( popcnt( 7 ) == 3 ); | |
221 assert( popcnt( 0xAA )== 4 ); | |
222 assert( popcnt( 0x8421_1248 ) == 8 ); | |
223 assert( popcnt( 0xFFFF_FFFF ) == 32 ); | |
224 assert( popcnt( 0xCCCC_CCCC ) == 16 ); | |
225 assert( popcnt( 0x7777_7777 ) == 24 ); | |
226 } | |
227 } | |
228 | |
229 | |
230 /** | |
231 * Reverses the order of bits in a 32-bit integer. | |
232 */ | |
233 uint bitswap( uint x ) | |
234 { | |
235 | |
236 version( D_InlineAsm_X86 ) | |
237 { | |
238 asm | |
239 { | |
240 // Author: Tiago Gasiba. | |
241 mov EDX, EAX; | |
242 shr EAX, 1; | |
243 and EDX, 0x5555_5555; | |
244 and EAX, 0x5555_5555; | |
245 shl EDX, 1; | |
246 or EAX, EDX; | |
247 mov EDX, EAX; | |
248 shr EAX, 2; | |
249 and EDX, 0x3333_3333; | |
250 and EAX, 0x3333_3333; | |
251 shl EDX, 2; | |
252 or EAX, EDX; | |
253 mov EDX, EAX; | |
254 shr EAX, 4; | |
255 and EDX, 0x0f0f_0f0f; | |
256 and EAX, 0x0f0f_0f0f; | |
257 shl EDX, 4; | |
258 or EAX, EDX; | |
259 bswap EAX; | |
260 } | |
261 } | |
262 else | |
263 { | |
264 // swap odd and even bits | |
265 x = ((x >> 1) & 0x5555_5555) | ((x & 0x5555_5555) << 1); | |
266 // swap consecutive pairs | |
267 x = ((x >> 2) & 0x3333_3333) | ((x & 0x3333_3333) << 2); | |
268 // swap nibbles | |
269 x = ((x >> 4) & 0x0F0F_0F0F) | ((x & 0x0F0F_0F0F) << 4); | |
270 // swap bytes | |
271 x = ((x >> 8) & 0x00FF_00FF) | ((x & 0x00FF_00FF) << 8); | |
272 // swap 2-byte long pairs | |
273 x = ( x >> 16 ) | ( x << 16); | |
274 return x; | |
275 | |
276 } | |
277 } | |
278 | |
279 | |
280 debug( UnitTest ) | |
281 { | |
282 unittest | |
283 { | |
284 assert( bitswap( 0x8000_0100 ) == 0x0080_0001 ); | |
285 } | |
286 } |