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/cvs/libecb/ecb.h
Revision: 1.4
Committed: Thu May 26 17:26:03 2011 UTC (13 years ago) by root
Content type: text/plain
Branch: MAIN
Changes since 1.3: +23 -16 lines
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# Content
1 /*
2 * libecb
3 *
4 * Copyright (©) 2009-2011 Marc Alexander Lehmann
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26 * OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #ifndef ECB_H
30 #define ECB_H
31
32 #define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
33
34 #ifndef __cplusplus
35 # if __STDC_VERSION__ >= 199901L
36 # define ECB_INLINE inline
37 typedef _Bool ecb_bool;
38 # else
39 # define ECB_INLINE inline /* yeah! */
40 typedef int ecb_bool;
41 # endif
42 #endif
43
44 #define ECB_HEADER_INLINE static ECB_INLINE
45
46 #if ECB_GCC_VERSION(3,1)
47 # define ecb_attribute(attrlist) __attribute__(attrlist)
48 # define ecb_is_constant(c) __builtin_constant_p (c)
49 # define ecb_expect(expr,value) __builtin_expect ((expr),(value))
50 # define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
51 #else
52 # define ecb_attribute(attrlist)
53 # define ecb_is_constant(c) 0
54 # define ecb_expect(expr,value) (expr)
55 # define ecb_prefetch(addr,rw,locality)
56 #endif
57
58 /* no emulation for ecb_decltype */
59 #if ECB_GCC_VERSION(4,5)
60 # define ecb_decltype(x) __decltype(x)
61 #elif ECB_GCC_VERSION(3,0)
62 # define ecb_decltype(x) typeof(x)
63 #endif
64
65 #define ecb_noinline ecb_attribute ((noinline))
66 #define ecb_noreturn ecb_attribute ((noreturn))
67 #define ecb_unused ecb_attribute ((unused))
68 #define ecb_const ecb_attribute ((const))
69 #define ecb_pure ecb_attribute ((pure))
70 #define ecb_hot ecb_attribute ((hot)) /* 4.3 */
71 #define ecb_cold ecb_attribute ((cold)) /* 4.3 */
72
73 #if ECB_GCC_VERSION(4,5)
74 # define ecb_unreachable() __builtin_unreachable ()
75 #else
76 /* this seems to work fine, but gcc always emits a warning for it :/ */
77 ECB_HEADER_INLINE void ecb_unreachable () ecb_attribute ((noreturn));
78 ECB_HEADER_INLINE void ecb_unreachable () { }
79 #endif
80
81 /* put into ifs if you are very sure that the expression */
82 /* is mostly true or mosty false. note that these return */
83 /* booleans, not the expression. */
84 #define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
85 #define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1)
86
87 /* try to tell the compiler that some condition is definitely true */
88 #define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)
89
90 /* count trailing zero bits and count # of one bits */
91 #if ECB_GCC_VERSION(3,4)
92 ECB_HEADER_INLINE int ecb_ctz32 (unsigned int x) { return __builtin_ctz (x); }
93 ECB_HEADER_INLINE int ecb_popcount32 (unsigned int x) { return __builtin_popcount (x); }
94 #else
95 ECB_HEADER_INLINE
96 ecb_ctz32 (unsigned int x) ecb_const
97 {
98 int r = 0;
99
100 x &= -x; /* this isolates the lowest bit */
101
102 if (x & 0xaaaaaaaa) r += 1;
103 if (x & 0xcccccccc) r += 2;
104 if (x & 0xf0f0f0f0) r += 4;
105 if (x & 0xff00ff00) r += 8;
106 if (x & 0xffff0000) r += 16;
107
108 return r;
109 }
110
111 ECB_HEADER_INLINE
112 ecb_popcount32 (unsigned int x) ecb_const
113 {
114 x -= (x >> 1) & 0x55555555;
115 x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
116 x = ((x >> 4) + x) & 0x0f0f0f0f;
117 x *= 0x01010101;
118
119 return x >> 24;
120 }
121 #endif
122
123 ECB_HEADER_INLINE unsigned char
124 ecb_byteorder_helper () ecb_const
125 {
126 const uint32_t u = 0x11223344;
127 return *(unsigned char *)&u;
128 }
129
130 ECB_HEADER_INLINE ecb_bool ecb_big_endian () ecb_const { return ecb_byteorder_helper () == 0x11; };
131 ECB_HEADER_INLINE ecb_bool ecb_little_endian () ecb_const { return ecb_byteorder_helper () == 0x44; };
132
133 #endif
134