libecb/ecb.h

/*
 * libecb
 *
 * Copyright (©) 2009-2011 Marc Alexander Lehmann
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef ECB_H
#define ECB_H

#define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))

#define ECB_HEADER_INLINE static inline

#if ECB_GCC_VERSION(3,1)
# define ecb_attribute(attrlist)        __attribute__(attrlist)
# define ecb_is_constant(c)             __builtin_constant_p (c)
# define ecb_expect(expr,value)         __builtin_expect ((expr),(value))
# define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
#else
# define ecb_attribute(attrlist)
# define ecb_is_constant(c)             0
# define ecb_expect(expr,value)         (expr)
# define ecb_prefetch(addr,rw,locality)
#endif

/* no emulation for ecb_decltype */
#if ECB_GCC_VERSION(4,5)
# define ecb_decltype(x) __decltype(x)
#elif ECB_GCC_VERSION(3,0)
# define ecb_decltype(x) typeof(x)
#endif

#define ecb_noinline ecb_attribute ((noinline))
#define ecb_noreturn ecb_attribute ((noreturn))
#define ecb_unused   ecb_attribute ((unused))
#define ecb_const    ecb_attribute ((const))
#define ecb_pure     ecb_attribute ((pure))
#define ecb_hot      ecb_attribute ((hot))      // 4.3
#define ecb_cold     ecb_attribute ((cold))     // 4.3

#if ECB_GCC_VERSION(4,5)
# define ecb_unreachable() __builtin_unreachable ()
#else
 /* this seems to work fine, but gcc always emits a warning for it :/ */
 ECB_HEADER_INLINE void ecb_unreachable () ecb_attribute ((noreturn));
 ECB_HEADER_INLINE void ecb_unreachable () { }
#endif

/* put into ifs if you are very sure that the expression */
/* is mostly true or mosty false. note that these return */
/* booleans, not the expression. */
#define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
#define ecb_expect_true(expr)  ecb_expect ((expr) ? 1 : 0, 1)

/* try to tell the compiler that some condition is definitely true */
#define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)

/* count trailing zero bits and count # of one bits */
#if ECB_GCC_VERSION(3,4)
ECB_HEADER_INLINE int ecb_ctz      (unsigned int x) { return __builtin_ctz      (x); }
ECB_HEADER_INLINE int ecb_popcount (unsigned int x) { return __builtin_popcount (x); }
#else
ECB_HEADER_INLINE
ecb_ctz (unsigned int x) ecb_const
{
  int r = 0;

  x &= -x; // this isolates the lowest bit

  if (x & 0xaaaaaaaa) r +=  1;
  if (x & 0xcccccccc) r +=  2;
  if (x & 0xf0f0f0f0) r +=  4;
  if (x & 0xff00ff00) r +=  8;
  if (x & 0xffff0000) r += 16;

  return r;
}

ECB_HEADER_INLINE
ecb_popcount (unsigned int x) ecb_const
{
  x -=  (x >> 1) & 0x55555555;
  x  = ((x >> 2) & 0x33333333) + (x & 0x33333333);
  x  = ((x >> 4) + x) & 0x0f0f0f0f;
  x *= 0x01010101;

  return x >> 24;
}
#endif

ECB_HEADER_INLINE unsigned char
ecb_byteorder_helper () ecb_const
{
  const uint32_t u = 0x11223344;
  return *(unsigned char *)&u;
}

ECB_HEADER_INLINE bool ecb_big_endian    () ecb_const { return ecb_byteorder_helper () == 0x11; };
ECB_HEADER_INLINE bool ecb_network       () ecb_const { return big_endian ();                   };
ECB_HEADER_INLINE bool ecb_little_endian () ecb_const { return ecb_byteorder_helper () == 0x44; };
ECB_HEADER_INLINE bool ecb_vax           () ecb_const { return little_endian ();                };


#endif

Revision:	1.3
Committed:	Thu May 26 16:57:04 2011 UTC (13 years ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.2:	+29 -12 lines
Log Message:	* empty log message *
#	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	root	1.3	#define ECB_HEADER_INLINE static inline
35
36	root	1.1	#if ECB_GCC_VERSION(3,1)
37			# define ecb_attribute(attrlist) __attribute__(attrlist)
38			# define ecb_is_constant(c) __builtin_constant_p (c)
39			# define ecb_expect(expr,value) __builtin_expect ((expr),(value))
40			# define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
41			#else
42			# define ecb_attribute(attrlist)
43			# define ecb_is_constant(c) 0
44			# define ecb_expect(expr,value) (expr)
45			# define ecb_prefetch(addr,rw,locality)
46			#endif
47
48	root	1.2	/* no emulation for ecb_decltype */
49	root	1.1	#if ECB_GCC_VERSION(4,5)
50			# define ecb_decltype(x) __decltype(x)
51			#elif ECB_GCC_VERSION(3,0)
52			# define ecb_decltype(x) typeof(x)
53			#endif
54
55			#define ecb_noinline ecb_attribute ((noinline))
56			#define ecb_noreturn ecb_attribute ((noreturn))
57			#define ecb_unused ecb_attribute ((unused))
58			#define ecb_const ecb_attribute ((const))
59			#define ecb_pure ecb_attribute ((pure))
60			#define ecb_hot ecb_attribute ((hot)) // 4.3
61			#define ecb_cold ecb_attribute ((cold)) // 4.3
62
63			#if ECB_GCC_VERSION(4,5)
64			# define ecb_unreachable() __builtin_unreachable ()
65			#else
66	root	1.3	/* this seems to work fine, but gcc always emits a warning for it :/ */
67			ECB_HEADER_INLINE void ecb_unreachable () ecb_attribute ((noreturn));
68			ECB_HEADER_INLINE void ecb_unreachable () { }
69	root	1.1	#endif
70
71	root	1.3	/* put into ifs if you are very sure that the expression */
72			/* is mostly true or mosty false. note that these return */
73			/* booleans, not the expression. */
74	root	1.1	#define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
75			#define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1)
76
77	root	1.3	/* try to tell the compiler that some condition is definitely true */
78	root	1.1	#define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)
79
80	root	1.3	/* count trailing zero bits and count # of one bits */
81	root	1.1	#if ECB_GCC_VERSION(3,4)
82	root	1.3	ECB_HEADER_INLINE int ecb_ctz (unsigned int x) { return __builtin_ctz (x); }
83			ECB_HEADER_INLINE int ecb_popcount (unsigned int x) { return __builtin_popcount (x); }
84	root	1.1	#else
85	root	1.3	ECB_HEADER_INLINE
86			ecb_ctz (unsigned int x) ecb_const
87	root	1.1	{
88			int r = 0;
89
90			x &= -x; // this isolates the lowest bit
91
92			if (x & 0xaaaaaaaa) r += 1;
93			if (x & 0xcccccccc) r += 2;
94			if (x & 0xf0f0f0f0) r += 4;
95			if (x & 0xff00ff00) r += 8;
96			if (x & 0xffff0000) r += 16;
97
98			return r;
99			}
100
101	root	1.3	ECB_HEADER_INLINE
102			ecb_popcount (unsigned int x) ecb_const
103	root	1.1	{
104			x -= (x >> 1) & 0x55555555;
105			x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
106			x = ((x >> 4) + x) & 0x0f0f0f0f;
107			x *= 0x01010101;
108
109			return x >> 24;
110			}
111			#endif
112
113	root	1.3	ECB_HEADER_INLINE unsigned char
114			ecb_byteorder_helper () ecb_const
115			{
116			const uint32_t u = 0x11223344;
117			return (unsigned char )&u;
118			}
119
120			ECB_HEADER_INLINE bool ecb_big_endian () ecb_const { return ecb_byteorder_helper () == 0x11; };
121			ECB_HEADER_INLINE bool ecb_network () ecb_const { return big_endian (); };
122			ECB_HEADER_INLINE bool ecb_little_endian () ecb_const { return ecb_byteorder_helper () == 0x44; };
123			ECB_HEADER_INLINE bool ecb_vax () ecb_const { return little_endian (); };
124
125
126	root	1.1	#endif
127