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/cvs/libecb/ecb.h
Revision: 1.2
Committed: Thu May 26 16:46:48 2011 UTC (13 years ago) by root
Content type: text/plain
Branch: MAIN
Changes since 1.1: +2 -1 lines
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# User Rev Content
1 root 1.1 /*
2     * libecb
3     *
4 root 1.2 * Copyright (©) 2009-2011 Marc Alexander Lehmann
5 root 1.1 * 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     #if ECB_GCC_VERSION(3,1)
35     # define ecb_attribute(attrlist) __attribute__(attrlist)
36     # define ecb_is_constant(c) __builtin_constant_p (c)
37     # define ecb_expect(expr,value) __builtin_expect ((expr),(value))
38     # define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
39     #else
40     # define ecb_attribute(attrlist)
41     # define ecb_is_constant(c) 0
42     # define ecb_expect(expr,value) (expr)
43     # define ecb_prefetch(addr,rw,locality)
44     #endif
45    
46 root 1.2 /* no emulation for ecb_decltype */
47 root 1.1 #if ECB_GCC_VERSION(4,5)
48     # define ecb_decltype(x) __decltype(x)
49     #elif ECB_GCC_VERSION(3,0)
50     # define ecb_decltype(x) typeof(x)
51     #endif
52    
53     #define ecb_noinline ecb_attribute ((noinline))
54     #define ecb_noreturn ecb_attribute ((noreturn))
55     #define ecb_unused ecb_attribute ((unused))
56     #define ecb_const ecb_attribute ((const))
57     #define ecb_pure ecb_attribute ((pure))
58     #define ecb_hot ecb_attribute ((hot)) // 4.3
59     #define ecb_cold ecb_attribute ((cold)) // 4.3
60    
61     #if ECB_GCC_VERSION(4,5)
62     # define ecb_unreachable() __builtin_unreachable ()
63     #else
64     // this seems to work fine, but gcc always emits a warning for it :/
65     static inline void ecb_unreachable () ecb_attribute ((noreturn));
66     static inline void ecb_unreachable () { }
67     #endif
68    
69     // put into ifs if you are very sure that the expression
70     // is mostly true or mosty false. note that these return
71     // booleans, not the expression.
72     #define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
73     #define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1)
74    
75     // try to tell the compiler that some condition is definitely true
76     #define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)
77    
78     // count trailing zero bits and count # of one bits
79     #if ECB_GCC_VERSION(3,4)
80     static inline int ecb_ctz (unsigned int x) { return __builtin_ctz (x); }
81     static inline int ecb_popcount (unsigned int x) { return __builtin_popcount (x); }
82     #else
83     static int ecb_ctz (unsigned int x) ecb_const
84     {
85     int r = 0;
86    
87     x &= -x; // this isolates the lowest bit
88    
89     if (x & 0xaaaaaaaa) r += 1;
90     if (x & 0xcccccccc) r += 2;
91     if (x & 0xf0f0f0f0) r += 4;
92     if (x & 0xff00ff00) r += 8;
93     if (x & 0xffff0000) r += 16;
94    
95     return r;
96     }
97    
98     static int ecb_popcount (unsigned int x) ecb_const
99     {
100     x -= (x >> 1) & 0x55555555;
101     x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
102     x = ((x >> 4) + x) & 0x0f0f0f0f;
103     x *= 0x01010101;
104    
105     return x >> 24;
106     }
107     #endif
108    
109     #endif
110