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comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/bit_operations.h @ 5:f762bf195c4b

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import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
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4:26cd8f1ef0b1 5:f762bf195c4b
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * bit_operations.h - Various bit level operations, such as bit reversal
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2006 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2, as
14 * published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: bit_operations.h,v 1.11 2006/11/28 15:37:03 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_BIT_OPERATIONS_H_)
31 #define _BIT_OPERATIONS_H_
32
33 #ifdef __cplusplus
34 extern "C" {
35 #endif
36
37 #if defined(__i386__) || defined(__x86_64__)
38 /*! \brief Find the bit position of the highest set bit in a word
39 \param bits The word to be searched
40 \return The bit number of the highest set bit, or -1 if the word is zero. */
41 static __inline__ int top_bit(unsigned int bits)
42 {
43 int res;
44
45 __asm__ (" xorl %[res],%[res];\n"
46 " decl %[res];\n"
47 " bsrl %[bits],%[res]\n"
48 : [res] "=&r" (res)
49 : [bits] "rm" (bits));
50 return res;
51 }
52 /*- End of function --------------------------------------------------------*/
53
54 /*! \brief Find the bit position of the lowest set bit in a word
55 \param bits The word to be searched
56 \return The bit number of the lowest set bit, or -1 if the word is zero. */
57 static __inline__ int bottom_bit(unsigned int bits)
58 {
59 int res;
60
61 __asm__ (" xorl %[res],%[res];\n"
62 " decl %[res];\n"
63 " bsfl %[bits],%[res]\n"
64 : [res] "=&r" (res)
65 : [bits] "rm" (bits));
66 return res;
67 }
68 /*- End of function --------------------------------------------------------*/
69 #else
70 static __inline__ int top_bit(unsigned int bits)
71 {
72 int i;
73
74 if (bits == 0)
75 return -1;
76 i = 0;
77 if (bits & 0xFFFF0000)
78 {
79 bits &= 0xFFFF0000;
80 i += 16;
81 }
82 if (bits & 0xFF00FF00)
83 {
84 bits &= 0xFF00FF00;
85 i += 8;
86 }
87 if (bits & 0xF0F0F0F0)
88 {
89 bits &= 0xF0F0F0F0;
90 i += 4;
91 }
92 if (bits & 0xCCCCCCCC)
93 {
94 bits &= 0xCCCCCCCC;
95 i += 2;
96 }
97 if (bits & 0xAAAAAAAA)
98 {
99 bits &= 0xAAAAAAAA;
100 i += 1;
101 }
102 return i;
103 }
104 /*- End of function --------------------------------------------------------*/
105
106 static __inline__ int bottom_bit(unsigned int bits)
107 {
108 int i;
109
110 if (bits == 0)
111 return -1;
112 i = 32;
113 if (bits & 0x0000FFFF)
114 {
115 bits &= 0x0000FFFF;
116 i -= 16;
117 }
118 if (bits & 0x00FF00FF)
119 {
120 bits &= 0x00FF00FF;
121 i -= 8;
122 }
123 if (bits & 0x0F0F0F0F)
124 {
125 bits &= 0x0F0F0F0F;
126 i -= 4;
127 }
128 if (bits & 0x33333333)
129 {
130 bits &= 0x33333333;
131 i -= 2;
132 }
133 if (bits & 0x55555555)
134 {
135 bits &= 0x55555555;
136 i -= 1;
137 }
138 return i;
139 }
140 /*- End of function --------------------------------------------------------*/
141 #endif
142
143 /*! \brief Bit reverse a byte.
144 \param data The byte to be reversed.
145 \return The bit reversed version of data. */
146 static __inline__ uint8_t bit_reverse8(uint8_t x)
147 {
148 #if defined(__i386__) || defined(__x86_64__)
149 /* If multiply is fast */
150 return ((x*0x0802U & 0x22110U) | (x*0x8020U & 0x88440U))*0x10101U >> 16;
151 #else
152 /* If multiply is slow, but we have a barrel shifter */
153 x = (x >> 4) | (x << 4);
154 x = ((x & 0xCC) >> 2) | ((x & 0x33) << 2);
155 return ((x & 0xAA) >> 1) | ((x & 0x55) << 1);
156 #endif
157 }
158 /*- End of function --------------------------------------------------------*/
159
160 /*! \brief Bit reverse a 16 bit word.
161 \param data The word to be reversed.
162 \return The bit reversed version of data. */
163 uint16_t bit_reverse16(uint16_t data);
164
165 /*! \brief Bit reverse a 32 bit word.
166 \param data The word to be reversed.
167 \return The bit reversed version of data. */
168 uint32_t bit_reverse32(uint32_t data);
169
170 /*! \brief Bit reverse each of the four bytes in a 32 bit word.
171 \param data The word to be reversed.
172 \return The bit reversed version of data. */
173 uint32_t bit_reverse_4bytes(uint32_t data);
174
175 /*! \brief Find the number of set bits in a 32 bit word.
176 \param x The word to be searched.
177 \return The number of set bits. */
178 int one_bits32(uint32_t x);
179
180 /*! \brief Create a mask as wide as the number in a 32 bit word.
181 \param x The word to be searched.
182 \return The mask. */
183 uint32_t make_mask32(uint32_t x);
184
185 /*! \brief Create a mask as wide as the number in a 16 bit word.
186 \param x The word to be searched.
187 \return The mask. */
188 uint16_t make_mask16(uint16_t x);
189
190 /*! \brief Find the least significant one in a word, and return a word
191 with just that bit set.
192 \param x The word to be searched.
193 \return The word with the single set bit. */
194 static __inline__ uint32_t least_significant_one32(uint32_t x)
195 {
196 return (x & (-(int32_t) x));
197 }
198 /*- End of function --------------------------------------------------------*/
199
200 /*! \brief Find the most significant one in a word, and return a word
201 with just that bit set.
202 \param x The word to be searched.
203 \return The word with the single set bit. */
204 static __inline__ uint32_t most_significant_one32(uint32_t x)
205 {
206 #if defined(__i386__) || defined(__x86_64__)
207 return 1 << top_bit(x);
208 #else
209 x = make_mask32(x);
210 return (x ^ (x >> 1));
211 #endif
212 }
213 /*- End of function --------------------------------------------------------*/
214
215 /*! \brief Find the parity of a byte.
216 \param x The byte to be checked.
217 \return 1 for odd, or 0 for even. */
218 static __inline__ int parity8(uint8_t x)
219 {
220 x = (x ^ (x >> 4)) & 0x0F;
221 return (0x6996 >> x) & 1;
222 }
223 /*- End of function --------------------------------------------------------*/
224
225 /*! \brief Find the parity of a 16 bit word.
226 \param x The word to be checked.
227 \return 1 for odd, or 0 for even. */
228 static __inline__ int parity16(uint16_t x)
229 {
230 x ^= (x >> 8);
231 x = (x ^ (x >> 4)) & 0x0F;
232 return (0x6996 >> x) & 1;
233 }
234 /*- End of function --------------------------------------------------------*/
235
236 /*! \brief Find the parity of a 32 bit word.
237 \param x The word to be checked.
238 \return 1 for odd, or 0 for even. */
239 static __inline__ int parity32(uint32_t x)
240 {
241 x ^= (x >> 16);
242 x ^= (x >> 8);
243 x = (x ^ (x >> 4)) & 0x0F;
244 return (0x6996 >> x) & 1;
245 }
246 /*- End of function --------------------------------------------------------*/
247
248 #ifdef __cplusplus
249 }
250 #endif
251
252 #endif
253 /*- End of file ------------------------------------------------------------*/

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