libecb/ecb.h

/*
 * libecb - http://software.schmorp.de/pkg/libecb
 *
 * Copyright (©) 2009-2012 Marc Alexander Lehmann <libecb@schmorp.de>
 * Copyright (©) 2011 Emanuele Giaquinta
 * 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

/* 16 bits major, 16 bits minor */
#define ECB_VERSION 0x00010001

#ifdef _WIN32
  typedef   signed char   int8_t;
  typedef unsigned char  uint8_t;
  typedef   signed short  int16_t;
  typedef unsigned short uint16_t;
  typedef   signed int    int32_t;
  typedef unsigned int   uint32_t;
  #if __GNUC__
    typedef   signed long long int64_t;
    typedef unsigned long long uint64_t;
  #else /* _MSC_VER || __BORLANDC__ */
    typedef   signed __int64   int64_t;
    typedef unsigned __int64   uint64_t;
  #endif
  #ifdef _WIN64
    #define ECB_PTRSIZE 8
    typedef uint64_t uintptr_t;
    typedef  int64_t  intptr_t;
  #else
    #define ECB_PTRSIZE 4
    typedef uint32_t uintptr_t;
    typedef  int32_t  intptr_t;
  #endif
 typedef intptr_t ptrdiff_t;
#else
  #include <inttypes.h>
  #if UINTMAX_MAX > 0xffffffffU
    #define ECB_PTRSIZE 8
  #else
    #define ECB_PTRSIZE 4
  #endif
#endif

/* many compilers define _GNUC_ to some versions but then only implement
 * what their idiot authors think are the "more important" extensions,
 * causing enormous grief in return for some better fake benchmark numbers.
 * or so.
 * we try to detect these and simply assume they are not gcc - if they have
 * an issue with that they should have done it right in the first place.
 */
#ifndef ECB_GCC_VERSION
  #if !defined __GNUC_MINOR__ || defined __INTEL_COMPILER || defined __SUNPRO_C || defined __SUNPRO_CC || defined __llvm__ || defined __clang__
    #define ECB_GCC_VERSION(major,minor) 0
  #else
    #define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
  #endif
#endif

#define ECB_C     (__STDC__+0) /* this assumes that __STDC__ is either empty or a number */
#define ECB_C99   (__STDC_VERSION__ >= 199901L)
#define ECB_C11   (__STDC_VERSION__ >= 201112L)
#define ECB_CPP   (__cplusplus+0)
#define ECB_CPP98 (__cplusplus >= 199711L)
#define ECB_CPP11 (__cplusplus >= 201103L)

/*****************************************************************************/

/* ECB_NO_THREADS - ecb is not used by multiple threads, ever */
/* ECB_NO_SMP     - ecb might be used in multiple threads, but only on a single cpu */

#if ECB_NO_THREADS
# define ECB_NO_SMP 1
#endif

#if ECB_NO_SMP
  #define ECB_MEMORY_FENCE do { } while (0)
#endif

#ifndef ECB_MEMORY_FENCE
  #if ECB_C11 && !defined __STDC_NO_ATOMICS__
    /* we assume that these memory fences work on all variables/all memory accesses, */
    /* not just C11 atomics and atomic accesses */
    #include <stdatomic.h>
    #if 0
    #define ECB_MEMORY_FENCE         atomic_thread_fence (memory_order_acq_rel)
    #define ECB_MEMORY_FENCE_ACQUIRE atomic_thread_fence (memory_order_acquire)
    #define ECB_MEMORY_FENCE_RELEASE atomic_thread_fence (memory_order_release)
    #else
    /* the above *should* be enough in my book, but after experiences with gcc-4.7 */
    /* and clang, better play safe */
    #define ECB_MEMORY_FENCE         atomic_thread_fence (memory_order_seq_cst)
    #endif
  #endif
#endif

#ifndef ECB_MEMORY_FENCE
  #if ECB_GCC_VERSION(2,5) || defined __INTEL_COMPILER || (__llvm__ && __GNUC__) || __SUNPRO_C >= 0x5110 || __SUNPRO_CC >= 0x5110
    #if __i386 || __i386__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("lock; orb $0, -1(%%esp)" : : : "memory")
      #define ECB_MEMORY_FENCE_ACQUIRE ECB_MEMORY_FENCE /* non-lock xchg might be enough */
      #define ECB_MEMORY_FENCE_RELEASE do { } while (0) /* unlikely to change in future cpus */
    #elif __amd64 || __amd64__ || __x86_64 || __x86_64__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("mfence" : : : "memory")
      #define ECB_MEMORY_FENCE_ACQUIRE __asm__ __volatile__ ("lfence" : : : "memory")
      #define ECB_MEMORY_FENCE_RELEASE __asm__ __volatile__ ("sfence") /* play safe - not needed in any current cpu */
    #elif __powerpc__ || __ppc__ || __powerpc64__ || __ppc64__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("sync" : : : "memory")
    #elif defined __ARM_ARCH_6__  || defined __ARM_ARCH_6J__  \
       || defined __ARM_ARCH_6K__ || defined __ARM_ARCH_6ZK__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("mcr p15,0,%0,c7,c10,5" : : "r" (0) : "memory")
    #elif defined __ARM_ARCH_7__  || defined __ARM_ARCH_7A__  \
       || defined __ARM_ARCH_7M__ || defined __ARM_ARCH_7R__ 
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("dmb" : : : "memory")
    #elif __sparc || __sparc__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("membar #LoadStore | #LoadLoad | #StoreStore | #StoreLoad | " : : : "memory")
      #define ECB_MEMORY_FENCE_ACQUIRE __asm__ __volatile__ ("membar #LoadStore | #LoadLoad"                               : : : "memory")
      #define ECB_MEMORY_FENCE_RELEASE __asm__ __volatile__ ("membar #LoadStore |             #StoreStore")
    #elif defined __s390__ || defined __s390x__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("bcr 15,0" : : : "memory")
    #elif defined __mips__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("sync" : : : "memory")
    #elif defined __alpha__
      #define ECB_MEMORY_FENCE         __asm__ __volatile__ ("mb" : : : "memory")
    #endif
  #endif
#endif

#ifndef ECB_MEMORY_FENCE
  #if ECB_GCC_VERSION(4,7)
    /* unsolved mystery: ACQ_REL should be enough, but doesn't generate any code */
    /* which in turn actually breaks libev */
    #define ECB_MEMORY_FENCE         __atomic_thread_fence (__ATOMIC_SEQ_CST)
  #elif defined __clang && __has_feature (cxx_atomic)
    /* see above */
    #define ECB_MEMORY_FENCE         __c11_atomic_thread_fence (__ATOMIC_SEQ_CST)
  #elif ECB_GCC_VERSION(4,4) || defined __INTEL_COMPILER || defined __clang__
    #define ECB_MEMORY_FENCE         __sync_synchronize ()
    /*#define ECB_MEMORY_FENCE_ACQUIRE ({ char dummy = 0; __sync_lock_test_and_set (&dummy, 1); }) */
    /*#define ECB_MEMORY_FENCE_RELEASE ({ char dummy = 1; __sync_lock_release      (&dummy   ); }) */
  #elif _MSC_VER >= 1400 /* VC++ 2005 */
    #pragma intrinsic(_ReadBarrier,_WriteBarrier,_ReadWriteBarrier)
    #define ECB_MEMORY_FENCE         _ReadWriteBarrier ()
    #define ECB_MEMORY_FENCE_ACQUIRE _ReadWriteBarrier () /* according to msdn, _ReadBarrier is not a load fence */
    #define ECB_MEMORY_FENCE_RELEASE _WriteBarrier ()
  #elif defined _WIN32
    #include <WinNT.h>
    #define ECB_MEMORY_FENCE         MemoryBarrier () /* actually just xchg on x86... scary */
  #elif __SUNPRO_C >= 0x5110 || __SUNPRO_CC >= 0x5110
    #include <mbarrier.h>
    #define ECB_MEMORY_FENCE         __machine_rw_barrier ()
    #define ECB_MEMORY_FENCE_ACQUIRE __machine_r_barrier  ()
    #define ECB_MEMORY_FENCE_RELEASE __machine_w_barrier  ()
  #elif __xlC__
    #define ECB_MEMORY_FENCE         __sync ()
  #endif
#endif

#ifndef ECB_MEMORY_FENCE
  #if !ECB_AVOID_PTHREADS
    /*
     * if you get undefined symbol references to pthread_mutex_lock,
     * or failure to find pthread.h, then you should implement
     * the ECB_MEMORY_FENCE operations for your cpu/compiler
     * OR provide pthread.h and link against the posix thread library
     * of your system.
     */
    #include <pthread.h>
    #define ECB_NEEDS_PTHREADS 1
    #define ECB_MEMORY_FENCE_NEEDS_PTHREADS 1

    static pthread_mutex_t ecb_mf_lock = PTHREAD_MUTEX_INITIALIZER;
    #define ECB_MEMORY_FENCE do { pthread_mutex_lock (&ecb_mf_lock); pthread_mutex_unlock (&ecb_mf_lock); } while (0)
  #endif
#endif

#if !defined ECB_MEMORY_FENCE_ACQUIRE && defined ECB_MEMORY_FENCE
  #define ECB_MEMORY_FENCE_ACQUIRE ECB_MEMORY_FENCE
#endif

#if !defined ECB_MEMORY_FENCE_RELEASE && defined ECB_MEMORY_FENCE
  #define ECB_MEMORY_FENCE_RELEASE ECB_MEMORY_FENCE
#endif

/*****************************************************************************/

#if __cplusplus
  #define ecb_inline static inline
#elif ECB_GCC_VERSION(2,5)
  #define ecb_inline static __inline__
#elif ECB_C99
  #define ecb_inline static inline
#else
  #define ecb_inline static
#endif

#if ECB_GCC_VERSION(3,3)
  #define ecb_restrict __restrict__
#elif ECB_C99
  #define ecb_restrict restrict
#else
  #define ecb_restrict
#endif

typedef int ecb_bool;

#define ECB_CONCAT_(a, b) a ## b
#define ECB_CONCAT(a, b) ECB_CONCAT_(a, b)
#define ECB_STRINGIFY_(a) # a
#define ECB_STRINGIFY(a) ECB_STRINGIFY_(a)

#define ecb_function_ ecb_inline

#if ECB_GCC_VERSION(3,1)
  #define ecb_attribute(attrlist)        __attribute__(attrlist)
  #define ecb_is_constant(expr)          __builtin_constant_p (expr)
  #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(expr)          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_unused     ecb_attribute ((__unused__))
#define ecb_const      ecb_attribute ((__const__))
#define ecb_pure       ecb_attribute ((__pure__))

#if ECB_C11
  #define ecb_noreturn   _Noreturn
#else
  #define ecb_noreturn   ecb_attribute ((__noreturn__))
#endif

#if ECB_GCC_VERSION(4,3)
  #define ecb_artificial ecb_attribute ((__artificial__))
  #define ecb_hot        ecb_attribute ((__hot__))
  #define ecb_cold       ecb_attribute ((__cold__))
#else
  #define ecb_artificial
  #define ecb_hot
  #define ecb_cold
#endif

/* put around conditional expressions if you are very sure that the  */
/* expression is mostly true or mostly false. note that these return */
/* booleans, not the expression.                                     */
#define ecb_expect_false(expr) ecb_expect (!!(expr), 0)
#define ecb_expect_true(expr)  ecb_expect (!!(expr), 1)
/* for compatibility to the rest of the world */
#define ecb_likely(expr)   ecb_expect_true  (expr)
#define ecb_unlikely(expr) ecb_expect_false (expr)

/* count trailing zero bits and count # of one bits */
#if ECB_GCC_VERSION(3,4)
  /* we assume int == 32 bit, long == 32 or 64 bit and long long == 64 bit */
  #define ecb_ld32(x)      (__builtin_clz      (x) ^ 31)
  #define ecb_ld64(x)      (__builtin_clzll    (x) ^ 63)
  #define ecb_ctz32(x)      __builtin_ctz      (x)
  #define ecb_ctz64(x)      __builtin_ctzll    (x)
  #define ecb_popcount32(x) __builtin_popcount (x)
  /* no popcountll */
#else
  ecb_function_ int ecb_ctz32 (uint32_t x) ecb_const;
  ecb_function_ int
  ecb_ctz32 (uint32_t x)
  {
    int r = 0;

    x &= ~x + 1; /* this isolates the lowest bit */

#if ECB_branchless_on_i386
    r += !!(x & 0xaaaaaaaa) << 0;
    r += !!(x & 0xcccccccc) << 1;
    r += !!(x & 0xf0f0f0f0) << 2;
    r += !!(x & 0xff00ff00) << 3;
    r += !!(x & 0xffff0000) << 4;
#else
    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;
#endif

    return r;
  }

  ecb_function_ int ecb_ctz64 (uint64_t x) ecb_const;
  ecb_function_ int
  ecb_ctz64 (uint64_t x)
  {
    int shift = x & 0xffffffffU ? 0 : 32;
    return ecb_ctz32 (x >> shift) + shift;
  }

  ecb_function_ int ecb_popcount32 (uint32_t x) ecb_const;
  ecb_function_ int
  ecb_popcount32 (uint32_t x)
  {
    x -=  (x >> 1) & 0x55555555;
    x  = ((x >> 2) & 0x33333333) + (x & 0x33333333);
    x  = ((x >> 4) + x) & 0x0f0f0f0f;
    x *= 0x01010101;

    return x >> 24;
  }

  ecb_function_ int ecb_ld32 (uint32_t x) ecb_const;
  ecb_function_ int ecb_ld32 (uint32_t x)
  {
    int r = 0;

    if (x >> 16) { x >>= 16; r += 16; }
    if (x >>  8) { x >>=  8; r +=  8; }
    if (x >>  4) { x >>=  4; r +=  4; }
    if (x >>  2) { x >>=  2; r +=  2; }
    if (x >>  1) {           r +=  1; }

    return r;
  }

  ecb_function_ int ecb_ld64 (uint64_t x) ecb_const;
  ecb_function_ int ecb_ld64 (uint64_t x)
  {
    int r = 0;

    if (x >> 32) { x >>= 32; r += 32; }

    return r + ecb_ld32 (x);
  }
#endif

ecb_function_ ecb_bool ecb_is_pot32 (uint32_t x) ecb_const;
ecb_function_ ecb_bool ecb_is_pot32 (uint32_t x) { return !(x & (x - 1)); }
ecb_function_ ecb_bool ecb_is_pot64 (uint64_t x) ecb_const;
ecb_function_ ecb_bool ecb_is_pot64 (uint64_t x) { return !(x & (x - 1)); }

ecb_function_ uint8_t  ecb_bitrev8  (uint8_t  x) ecb_const;
ecb_function_ uint8_t  ecb_bitrev8  (uint8_t  x)
{
  return (  (x * 0x0802U & 0x22110U)
          | (x * 0x8020U & 0x88440U)) * 0x10101U >> 16; 
}

ecb_function_ uint16_t ecb_bitrev16 (uint16_t x) ecb_const;
ecb_function_ uint16_t ecb_bitrev16 (uint16_t x)
{
  x = ((x >>  1) &     0x5555) | ((x &     0x5555) <<  1);
  x = ((x >>  2) &     0x3333) | ((x &     0x3333) <<  2);
  x = ((x >>  4) &     0x0f0f) | ((x &     0x0f0f) <<  4);
  x = ( x >>  8              ) | ( x               <<  8);

  return x;
}

ecb_function_ uint32_t ecb_bitrev32 (uint32_t x) ecb_const;
ecb_function_ uint32_t ecb_bitrev32 (uint32_t x)
{
  x = ((x >>  1) & 0x55555555) | ((x & 0x55555555) <<  1);
  x = ((x >>  2) & 0x33333333) | ((x & 0x33333333) <<  2);
  x = ((x >>  4) & 0x0f0f0f0f) | ((x & 0x0f0f0f0f) <<  4);
  x = ((x >>  8) & 0x00ff00ff) | ((x & 0x00ff00ff) <<  8);
  x = ( x >> 16              ) | ( x               << 16);

  return x;
}

/* popcount64 is only available on 64 bit cpus as gcc builtin */
/* so for this version we are lazy */
ecb_function_ int ecb_popcount64 (uint64_t x) ecb_const;
ecb_function_ int
ecb_popcount64 (uint64_t x)
{
  return ecb_popcount32 (x) + ecb_popcount32 (x >> 32);
}

ecb_inline uint8_t  ecb_rotl8  (uint8_t  x, unsigned int count) ecb_const;
ecb_inline uint8_t  ecb_rotr8  (uint8_t  x, unsigned int count) ecb_const;
ecb_inline uint16_t ecb_rotl16 (uint16_t x, unsigned int count) ecb_const;
ecb_inline uint16_t ecb_rotr16 (uint16_t x, unsigned int count) ecb_const;
ecb_inline uint32_t ecb_rotl32 (uint32_t x, unsigned int count) ecb_const;
ecb_inline uint32_t ecb_rotr32 (uint32_t x, unsigned int count) ecb_const;
ecb_inline uint64_t ecb_rotl64 (uint64_t x, unsigned int count) ecb_const;
ecb_inline uint64_t ecb_rotr64 (uint64_t x, unsigned int count) ecb_const;

ecb_inline uint8_t  ecb_rotl8  (uint8_t  x, unsigned int count) { return (x >> ( 8 - count)) | (x << count); }
ecb_inline uint8_t  ecb_rotr8  (uint8_t  x, unsigned int count) { return (x << ( 8 - count)) | (x >> count); }
ecb_inline uint16_t ecb_rotl16 (uint16_t x, unsigned int count) { return (x >> (16 - count)) | (x << count); }
ecb_inline uint16_t ecb_rotr16 (uint16_t x, unsigned int count) { return (x << (16 - count)) | (x >> count); }
ecb_inline uint32_t ecb_rotl32 (uint32_t x, unsigned int count) { return (x >> (32 - count)) | (x << count); }
ecb_inline uint32_t ecb_rotr32 (uint32_t x, unsigned int count) { return (x << (32 - count)) | (x >> count); }
ecb_inline uint64_t ecb_rotl64 (uint64_t x, unsigned int count) { return (x >> (64 - count)) | (x << count); }
ecb_inline uint64_t ecb_rotr64 (uint64_t x, unsigned int count) { return (x << (64 - count)) | (x >> count); }

#if ECB_GCC_VERSION(4,3)
  #define ecb_bswap16(x) (__builtin_bswap32 (x) >> 16)
  #define ecb_bswap32(x)  __builtin_bswap32 (x)
  #define ecb_bswap64(x)  __builtin_bswap64 (x)
#else
  ecb_function_ uint16_t ecb_bswap16 (uint16_t x) ecb_const;
  ecb_function_ uint16_t
  ecb_bswap16 (uint16_t x)
  {
    return ecb_rotl16 (x, 8);
  }

  ecb_function_ uint32_t ecb_bswap32 (uint32_t x) ecb_const;
  ecb_function_ uint32_t
  ecb_bswap32 (uint32_t x)
  {
    return (((uint32_t)ecb_bswap16 (x)) << 16) | ecb_bswap16 (x >> 16);
  }

  ecb_function_ uint64_t ecb_bswap64 (uint64_t x) ecb_const;
  ecb_function_ uint64_t
  ecb_bswap64 (uint64_t x)
  {
    return (((uint64_t)ecb_bswap32 (x)) << 32) | ecb_bswap32 (x >> 32);
  }
#endif

#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_inline void ecb_unreachable (void) ecb_noreturn;
  ecb_inline void ecb_unreachable (void) { }
#endif

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

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

ecb_inline ecb_bool ecb_big_endian    (void) ecb_const;
ecb_inline ecb_bool ecb_big_endian    (void) { return ecb_byteorder_helper () == 0x11; }
ecb_inline ecb_bool ecb_little_endian (void) ecb_const;
ecb_inline ecb_bool ecb_little_endian (void) { return ecb_byteorder_helper () == 0x44; }

#if ECB_GCC_VERSION(3,0) || ECB_C99
  #define ecb_mod(m,n) ((m) % (n) + ((m) % (n) < 0 ? (n) : 0))
#else
  #define ecb_mod(m,n) ((m) < 0 ? ((n) - 1 - ((-1 - (m)) % (n))) : ((m) % (n)))
#endif

#if __cplusplus
  template<typename T>
  static inline T ecb_div_rd (T val, T div)
  {
    return val < 0 ? - ((-val + div - 1) / div) : (val          ) / div;
  }
  template<typename T>
  static inline T ecb_div_ru (T val, T div)
  {
    return val < 0 ? - ((-val          ) / div) : (val + div - 1) / div;
  }
#else
  #define ecb_div_rd(val,div) ((val) < 0 ? - ((-(val) + (div) - 1) / (div)) : ((val)            ) / (div))
  #define ecb_div_ru(val,div) ((val) < 0 ? - ((-(val)            ) / (div)) : ((val) + (div) - 1) / (div))
#endif

#if ecb_cplusplus_does_not_suck
  /* does not work for local types (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm) */
  template<typename T, int N>
  static inline int ecb_array_length (const T (&arr)[N])
  {
    return N;
  }
#else
  #define ecb_array_length(name) (sizeof (name) / sizeof (name [0]))
#endif

#endif

Revision:	1.93
Committed:	Tue May 29 19:10:50 2012 UTC (12 years, 1 month ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.92:	+15 -10 lines
Log Message:	* empty log message *
#	Content
1	/*
2	* libecb - http://software.schmorp.de/pkg/libecb
3	*
4	* Copyright (©) 2009-2012 Marc Alexander Lehmann <libecb@schmorp.de>
5	* Copyright (©) 2011 Emanuele Giaquinta
6	* All rights reserved.
7	*
8	* Redistribution and use in source and binary forms, with or without modifica-
9	* tion, are permitted provided that the following conditions are met:
10	*
11	* 1. Redistributions of source code must retain the above copyright notice,
12	* this list of conditions and the following disclaimer.
13	*
14	* 2. Redistributions in binary form must reproduce the above copyright
15	* notice, this list of conditions and the following disclaimer in the
16	* documentation and/or other materials provided with the distribution.
17	*
18	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
19	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
20	* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
21	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
22	* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
23	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
24	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
25	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
26	* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
27	* OF THE POSSIBILITY OF SUCH DAMAGE.
28	*/
29
30	#ifndef ECB_H
31	#define ECB_H
32
33	/* 16 bits major, 16 bits minor */
34	#define ECB_VERSION 0x00010001
35
36	#ifdef _WIN32
37	typedef signed char int8_t;
38	typedef unsigned char uint8_t;
39	typedef signed short int16_t;
40	typedef unsigned short uint16_t;
41	typedef signed int int32_t;
42	typedef unsigned int uint32_t;
43	#if __GNUC__
44	typedef signed long long int64_t;
45	typedef unsigned long long uint64_t;
46	#else /* _MSC_VER \|\| __BORLANDC__ */
47	typedef signed __int64 int64_t;
48	typedef unsigned __int64 uint64_t;
49	#endif
50	#ifdef _WIN64
51	#define ECB_PTRSIZE 8
52	typedef uint64_t uintptr_t;
53	typedef int64_t intptr_t;
54	#else
55	#define ECB_PTRSIZE 4
56	typedef uint32_t uintptr_t;
57	typedef int32_t intptr_t;
58	#endif
59	typedef intptr_t ptrdiff_t;
60	#else
61	#include <inttypes.h>
62	#if UINTMAX_MAX > 0xffffffffU
63	#define ECB_PTRSIZE 8
64	#else
65	#define ECB_PTRSIZE 4
66	#endif
67	#endif
68
69	/* many compilers define _GNUC_ to some versions but then only implement
70	* what their idiot authors think are the "more important" extensions,
71	* causing enormous grief in return for some better fake benchmark numbers.
72	* or so.
73	* we try to detect these and simply assume they are not gcc - if they have
74	* an issue with that they should have done it right in the first place.
75	*/
76	#ifndef ECB_GCC_VERSION
77	#if !defined __GNUC_MINOR__ \|\| defined __INTEL_COMPILER \|\| defined __SUNPRO_C \|\| defined __SUNPRO_CC \|\| defined __llvm__ \|\| defined __clang__
78	#define ECB_GCC_VERSION(major,minor) 0
79	#else
80	#define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) \|\| (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
81	#endif
82	#endif
83
84	#define ECB_C (__STDC__+0) /* this assumes that __STDC__ is either empty or a number */
85	#define ECB_C99 (__STDC_VERSION__ >= 199901L)
86	#define ECB_C11 (__STDC_VERSION__ >= 201112L)
87	#define ECB_CPP (__cplusplus+0)
88	#define ECB_CPP98 (__cplusplus >= 199711L)
89	#define ECB_CPP11 (__cplusplus >= 201103L)
90
91	/*****************************************************************************/
92
93	/* ECB_NO_THREADS - ecb is not used by multiple threads, ever */
94	/* ECB_NO_SMP - ecb might be used in multiple threads, but only on a single cpu */
95
96	#if ECB_NO_THREADS
97	# define ECB_NO_SMP 1
98	#endif
99
100	#if ECB_NO_SMP
101	#define ECB_MEMORY_FENCE do { } while (0)
102	#endif
103
104	#ifndef ECB_MEMORY_FENCE
105	#if ECB_C11 && !defined __STDC_NO_ATOMICS__
106	/* we assume that these memory fences work on all variables/all memory accesses, */
107	/* not just C11 atomics and atomic accesses */
108	#include <stdatomic.h>
109	#if 0
110	#define ECB_MEMORY_FENCE atomic_thread_fence (memory_order_acq_rel)
111	#define ECB_MEMORY_FENCE_ACQUIRE atomic_thread_fence (memory_order_acquire)
112	#define ECB_MEMORY_FENCE_RELEASE atomic_thread_fence (memory_order_release)
113	#else
114	/* the above should be enough in my book, but after experiences with gcc-4.7 */
115	/* and clang, better play safe */
116	#define ECB_MEMORY_FENCE atomic_thread_fence (memory_order_seq_cst)
117	#endif
118	#endif
119	#endif
120
121	#ifndef ECB_MEMORY_FENCE
122	#if ECB_GCC_VERSION(2,5) \|\| defined __INTEL_COMPILER \|\| (__llvm__ && __GNUC__) \|\| __SUNPRO_C >= 0x5110 \|\| __SUNPRO_CC >= 0x5110
123	#if __i386 \|\| __i386__
124	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("lock; orb $0, -1(%%esp)" : : : "memory")
125	#define ECB_MEMORY_FENCE_ACQUIRE ECB_MEMORY_FENCE /* non-lock xchg might be enough */
126	#define ECB_MEMORY_FENCE_RELEASE do { } while (0) /* unlikely to change in future cpus */
127	#elif __amd64 \|\| __amd64__ \|\| __x86_64 \|\| __x86_64__
128	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("mfence" : : : "memory")
129	#define ECB_MEMORY_FENCE_ACQUIRE __asm__ __volatile__ ("lfence" : : : "memory")
130	#define ECB_MEMORY_FENCE_RELEASE __asm__ __volatile__ ("sfence") /* play safe - not needed in any current cpu */
131	#elif __powerpc__ \|\| __ppc__ \|\| __powerpc64__ \|\| __ppc64__
132	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("sync" : : : "memory")
133	#elif defined __ARM_ARCH_6__ \|\| defined __ARM_ARCH_6J__ \
134	\|\| defined __ARM_ARCH_6K__ \|\| defined __ARM_ARCH_6ZK__
135	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("mcr p15,0,%0,c7,c10,5" : : "r" (0) : "memory")
136	#elif defined __ARM_ARCH_7__ \|\| defined __ARM_ARCH_7A__ \
137	\|\| defined __ARM_ARCH_7M__ \|\| defined __ARM_ARCH_7R__
138	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("dmb" : : : "memory")
139	#elif __sparc \|\| __sparc__
140	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("membar #LoadStore \| #LoadLoad \| #StoreStore \| #StoreLoad \| " : : : "memory")
141	#define ECB_MEMORY_FENCE_ACQUIRE __asm__ __volatile__ ("membar #LoadStore \| #LoadLoad" : : : "memory")
142	#define ECB_MEMORY_FENCE_RELEASE __asm__ __volatile__ ("membar #LoadStore \| #StoreStore")
143	#elif defined __s390__ \|\| defined __s390x__
144	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("bcr 15,0" : : : "memory")
145	#elif defined __mips__
146	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("sync" : : : "memory")
147	#elif defined __alpha__
148	#define ECB_MEMORY_FENCE __asm__ __volatile__ ("mb" : : : "memory")
149	#endif
150	#endif
151	#endif
152
153	#ifndef ECB_MEMORY_FENCE
154	#if ECB_GCC_VERSION(4,7)
155	/* unsolved mystery: ACQ_REL should be enough, but doesn't generate any code */
156	/* which in turn actually breaks libev */
157	#define ECB_MEMORY_FENCE __atomic_thread_fence (__ATOMIC_SEQ_CST)
158	#elif defined __clang && __has_feature (cxx_atomic)
159	/* see above */
160	#define ECB_MEMORY_FENCE __c11_atomic_thread_fence (__ATOMIC_SEQ_CST)
161	#elif ECB_GCC_VERSION(4,4) \|\| defined __INTEL_COMPILER \|\| defined __clang__
162	#define ECB_MEMORY_FENCE __sync_synchronize ()
163	/#define ECB_MEMORY_FENCE_ACQUIRE ({ char dummy = 0; __sync_lock_test_and_set (&dummy, 1); }) /
164	/#define ECB_MEMORY_FENCE_RELEASE ({ char dummy = 1; __sync_lock_release (&dummy ); }) /
165	#elif _MSC_VER >= 1400 /* VC++ 2005 */
166	#pragma intrinsic(_ReadBarrier,_WriteBarrier,_ReadWriteBarrier)
167	#define ECB_MEMORY_FENCE _ReadWriteBarrier ()
168	#define ECB_MEMORY_FENCE_ACQUIRE _ReadWriteBarrier () /* according to msdn, _ReadBarrier is not a load fence */
169	#define ECB_MEMORY_FENCE_RELEASE _WriteBarrier ()
170	#elif defined _WIN32
171	#include <WinNT.h>
172	#define ECB_MEMORY_FENCE MemoryBarrier () /* actually just xchg on x86... scary */
173	#elif __SUNPRO_C >= 0x5110 \|\| __SUNPRO_CC >= 0x5110
174	#include <mbarrier.h>
175	#define ECB_MEMORY_FENCE __machine_rw_barrier ()
176	#define ECB_MEMORY_FENCE_ACQUIRE __machine_r_barrier ()
177	#define ECB_MEMORY_FENCE_RELEASE __machine_w_barrier ()
178	#elif __xlC__
179	#define ECB_MEMORY_FENCE __sync ()
180	#endif
181	#endif
182
183	#ifndef ECB_MEMORY_FENCE
184	#if !ECB_AVOID_PTHREADS
185	/*
186	* if you get undefined symbol references to pthread_mutex_lock,
187	* or failure to find pthread.h, then you should implement
188	* the ECB_MEMORY_FENCE operations for your cpu/compiler
189	* OR provide pthread.h and link against the posix thread library
190	* of your system.
191	*/
192	#include <pthread.h>
193	#define ECB_NEEDS_PTHREADS 1
194	#define ECB_MEMORY_FENCE_NEEDS_PTHREADS 1
195
196	static pthread_mutex_t ecb_mf_lock = PTHREAD_MUTEX_INITIALIZER;
197	#define ECB_MEMORY_FENCE do { pthread_mutex_lock (&ecb_mf_lock); pthread_mutex_unlock (&ecb_mf_lock); } while (0)
198	#endif
199	#endif
200
201	#if !defined ECB_MEMORY_FENCE_ACQUIRE && defined ECB_MEMORY_FENCE
202	#define ECB_MEMORY_FENCE_ACQUIRE ECB_MEMORY_FENCE
203	#endif
204
205	#if !defined ECB_MEMORY_FENCE_RELEASE && defined ECB_MEMORY_FENCE
206	#define ECB_MEMORY_FENCE_RELEASE ECB_MEMORY_FENCE
207	#endif
208
209	/*****************************************************************************/
210
211	#if __cplusplus
212	#define ecb_inline static inline
213	#elif ECB_GCC_VERSION(2,5)
214	#define ecb_inline static __inline__
215	#elif ECB_C99
216	#define ecb_inline static inline
217	#else
218	#define ecb_inline static
219	#endif
220
221	#if ECB_GCC_VERSION(3,3)
222	#define ecb_restrict __restrict__
223	#elif ECB_C99
224	#define ecb_restrict restrict
225	#else
226	#define ecb_restrict
227	#endif
228
229	typedef int ecb_bool;
230
231	#define ECB_CONCAT_(a, b) a ## b
232	#define ECB_CONCAT(a, b) ECB_CONCAT_(a, b)
233	#define ECB_STRINGIFY_(a) # a
234	#define ECB_STRINGIFY(a) ECB_STRINGIFY_(a)
235
236	#define ecb_function_ ecb_inline
237
238	#if ECB_GCC_VERSION(3,1)
239	#define ecb_attribute(attrlist) __attribute__(attrlist)
240	#define ecb_is_constant(expr) __builtin_constant_p (expr)
241	#define ecb_expect(expr,value) __builtin_expect ((expr),(value))
242	#define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
243	#else
244	#define ecb_attribute(attrlist)
245	#define ecb_is_constant(expr) 0
246	#define ecb_expect(expr,value) (expr)
247	#define ecb_prefetch(addr,rw,locality)
248	#endif
249
250	/* no emulation for ecb_decltype */
251	#if ECB_GCC_VERSION(4,5)
252	#define ecb_decltype(x) __decltype(x)
253	#elif ECB_GCC_VERSION(3,0)
254	#define ecb_decltype(x) __typeof(x)
255	#endif
256
257	#define ecb_noinline ecb_attribute ((__noinline__))
258	#define ecb_unused ecb_attribute ((__unused__))
259	#define ecb_const ecb_attribute ((__const__))
260	#define ecb_pure ecb_attribute ((__pure__))
261
262	#if ECB_C11
263	#define ecb_noreturn _Noreturn
264	#else
265	#define ecb_noreturn ecb_attribute ((__noreturn__))
266	#endif
267
268	#if ECB_GCC_VERSION(4,3)
269	#define ecb_artificial ecb_attribute ((__artificial__))
270	#define ecb_hot ecb_attribute ((__hot__))
271	#define ecb_cold ecb_attribute ((__cold__))
272	#else
273	#define ecb_artificial
274	#define ecb_hot
275	#define ecb_cold
276	#endif
277
278	/* put around conditional expressions if you are very sure that the */
279	/* expression is mostly true or mostly false. note that these return */
280	/* booleans, not the expression. */
281	#define ecb_expect_false(expr) ecb_expect (!!(expr), 0)
282	#define ecb_expect_true(expr) ecb_expect (!!(expr), 1)
283	/* for compatibility to the rest of the world */
284	#define ecb_likely(expr) ecb_expect_true (expr)
285	#define ecb_unlikely(expr) ecb_expect_false (expr)
286
287	/* count trailing zero bits and count # of one bits */
288	#if ECB_GCC_VERSION(3,4)
289	/* we assume int == 32 bit, long == 32 or 64 bit and long long == 64 bit */
290	#define ecb_ld32(x) (__builtin_clz (x) ^ 31)
291	#define ecb_ld64(x) (__builtin_clzll (x) ^ 63)
292	#define ecb_ctz32(x) __builtin_ctz (x)
293	#define ecb_ctz64(x) __builtin_ctzll (x)
294	#define ecb_popcount32(x) __builtin_popcount (x)
295	/* no popcountll */
296	#else
297	ecb_function_ int ecb_ctz32 (uint32_t x) ecb_const;
298	ecb_function_ int
299	ecb_ctz32 (uint32_t x)
300	{
301	int r = 0;
302
303	x &= ~x + 1; /* this isolates the lowest bit */
304
305	#if ECB_branchless_on_i386
306	r += !!(x & 0xaaaaaaaa) << 0;
307	r += !!(x & 0xcccccccc) << 1;
308	r += !!(x & 0xf0f0f0f0) << 2;
309	r += !!(x & 0xff00ff00) << 3;
310	r += !!(x & 0xffff0000) << 4;
311	#else
312	if (x & 0xaaaaaaaa) r += 1;
313	if (x & 0xcccccccc) r += 2;
314	if (x & 0xf0f0f0f0) r += 4;
315	if (x & 0xff00ff00) r += 8;
316	if (x & 0xffff0000) r += 16;
317	#endif
318
319	return r;
320	}
321
322	ecb_function_ int ecb_ctz64 (uint64_t x) ecb_const;
323	ecb_function_ int
324	ecb_ctz64 (uint64_t x)
325	{
326	int shift = x & 0xffffffffU ? 0 : 32;
327	return ecb_ctz32 (x >> shift) + shift;
328	}
329
330	ecb_function_ int ecb_popcount32 (uint32_t x) ecb_const;
331	ecb_function_ int
332	ecb_popcount32 (uint32_t x)
333	{
334	x -= (x >> 1) & 0x55555555;
335	x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
336	x = ((x >> 4) + x) & 0x0f0f0f0f;
337	x *= 0x01010101;
338
339	return x >> 24;
340	}
341
342	ecb_function_ int ecb_ld32 (uint32_t x) ecb_const;
343	ecb_function_ int ecb_ld32 (uint32_t x)
344	{
345	int r = 0;
346
347	if (x >> 16) { x >>= 16; r += 16; }
348	if (x >> 8) { x >>= 8; r += 8; }
349	if (x >> 4) { x >>= 4; r += 4; }
350	if (x >> 2) { x >>= 2; r += 2; }
351	if (x >> 1) { r += 1; }
352
353	return r;
354	}
355
356	ecb_function_ int ecb_ld64 (uint64_t x) ecb_const;
357	ecb_function_ int ecb_ld64 (uint64_t x)
358	{
359	int r = 0;
360
361	if (x >> 32) { x >>= 32; r += 32; }
362
363	return r + ecb_ld32 (x);
364	}
365	#endif
366
367	ecb_function_ ecb_bool ecb_is_pot32 (uint32_t x) ecb_const;
368	ecb_function_ ecb_bool ecb_is_pot32 (uint32_t x) { return !(x & (x - 1)); }
369	ecb_function_ ecb_bool ecb_is_pot64 (uint64_t x) ecb_const;
370	ecb_function_ ecb_bool ecb_is_pot64 (uint64_t x) { return !(x & (x - 1)); }
371
372	ecb_function_ uint8_t ecb_bitrev8 (uint8_t x) ecb_const;
373	ecb_function_ uint8_t ecb_bitrev8 (uint8_t x)
374	{
375	return ( (x * 0x0802U & 0x22110U)
376	\| (x * 0x8020U & 0x88440U)) * 0x10101U >> 16;
377	}
378
379	ecb_function_ uint16_t ecb_bitrev16 (uint16_t x) ecb_const;
380	ecb_function_ uint16_t ecb_bitrev16 (uint16_t x)
381	{
382	x = ((x >> 1) & 0x5555) \| ((x & 0x5555) << 1);
383	x = ((x >> 2) & 0x3333) \| ((x & 0x3333) << 2);
384	x = ((x >> 4) & 0x0f0f) \| ((x & 0x0f0f) << 4);
385	x = ( x >> 8 ) \| ( x << 8);
386
387	return x;
388	}
389
390	ecb_function_ uint32_t ecb_bitrev32 (uint32_t x) ecb_const;
391	ecb_function_ uint32_t ecb_bitrev32 (uint32_t x)
392	{
393	x = ((x >> 1) & 0x55555555) \| ((x & 0x55555555) << 1);
394	x = ((x >> 2) & 0x33333333) \| ((x & 0x33333333) << 2);
395	x = ((x >> 4) & 0x0f0f0f0f) \| ((x & 0x0f0f0f0f) << 4);
396	x = ((x >> 8) & 0x00ff00ff) \| ((x & 0x00ff00ff) << 8);
397	x = ( x >> 16 ) \| ( x << 16);
398
399	return x;
400	}
401
402	/* popcount64 is only available on 64 bit cpus as gcc builtin */
403	/* so for this version we are lazy */
404	ecb_function_ int ecb_popcount64 (uint64_t x) ecb_const;
405	ecb_function_ int
406	ecb_popcount64 (uint64_t x)
407	{
408	return ecb_popcount32 (x) + ecb_popcount32 (x >> 32);
409	}
410
411	ecb_inline uint8_t ecb_rotl8 (uint8_t x, unsigned int count) ecb_const;
412	ecb_inline uint8_t ecb_rotr8 (uint8_t x, unsigned int count) ecb_const;
413	ecb_inline uint16_t ecb_rotl16 (uint16_t x, unsigned int count) ecb_const;
414	ecb_inline uint16_t ecb_rotr16 (uint16_t x, unsigned int count) ecb_const;
415	ecb_inline uint32_t ecb_rotl32 (uint32_t x, unsigned int count) ecb_const;
416	ecb_inline uint32_t ecb_rotr32 (uint32_t x, unsigned int count) ecb_const;
417	ecb_inline uint64_t ecb_rotl64 (uint64_t x, unsigned int count) ecb_const;
418	ecb_inline uint64_t ecb_rotr64 (uint64_t x, unsigned int count) ecb_const;
419
420	ecb_inline uint8_t ecb_rotl8 (uint8_t x, unsigned int count) { return (x >> ( 8 - count)) \| (x << count); }
421	ecb_inline uint8_t ecb_rotr8 (uint8_t x, unsigned int count) { return (x << ( 8 - count)) \| (x >> count); }
422	ecb_inline uint16_t ecb_rotl16 (uint16_t x, unsigned int count) { return (x >> (16 - count)) \| (x << count); }
423	ecb_inline uint16_t ecb_rotr16 (uint16_t x, unsigned int count) { return (x << (16 - count)) \| (x >> count); }
424	ecb_inline uint32_t ecb_rotl32 (uint32_t x, unsigned int count) { return (x >> (32 - count)) \| (x << count); }
425	ecb_inline uint32_t ecb_rotr32 (uint32_t x, unsigned int count) { return (x << (32 - count)) \| (x >> count); }
426	ecb_inline uint64_t ecb_rotl64 (uint64_t x, unsigned int count) { return (x >> (64 - count)) \| (x << count); }
427	ecb_inline uint64_t ecb_rotr64 (uint64_t x, unsigned int count) { return (x << (64 - count)) \| (x >> count); }
428
429	#if ECB_GCC_VERSION(4,3)
430	#define ecb_bswap16(x) (__builtin_bswap32 (x) >> 16)
431	#define ecb_bswap32(x) __builtin_bswap32 (x)
432	#define ecb_bswap64(x) __builtin_bswap64 (x)
433	#else
434	ecb_function_ uint16_t ecb_bswap16 (uint16_t x) ecb_const;
435	ecb_function_ uint16_t
436	ecb_bswap16 (uint16_t x)
437	{
438	return ecb_rotl16 (x, 8);
439	}
440
441	ecb_function_ uint32_t ecb_bswap32 (uint32_t x) ecb_const;
442	ecb_function_ uint32_t
443	ecb_bswap32 (uint32_t x)
444	{
445	return (((uint32_t)ecb_bswap16 (x)) << 16) \| ecb_bswap16 (x >> 16);
446	}
447
448	ecb_function_ uint64_t ecb_bswap64 (uint64_t x) ecb_const;
449	ecb_function_ uint64_t
450	ecb_bswap64 (uint64_t x)
451	{
452	return (((uint64_t)ecb_bswap32 (x)) << 32) \| ecb_bswap32 (x >> 32);
453	}
454	#endif
455
456	#if ECB_GCC_VERSION(4,5)
457	#define ecb_unreachable() __builtin_unreachable ()
458	#else
459	/* this seems to work fine, but gcc always emits a warning for it :/ */
460	ecb_inline void ecb_unreachable (void) ecb_noreturn;
461	ecb_inline void ecb_unreachable (void) { }
462	#endif
463
464	/* try to tell the compiler that some condition is definitely true */
465	#define ecb_assume(cond) do { if (!(cond)) ecb_unreachable (); } while (0)
466
467	ecb_inline unsigned char ecb_byteorder_helper (void) ecb_const;
468	ecb_inline unsigned char
469	ecb_byteorder_helper (void)
470	{
471	const uint32_t u = 0x11223344;
472	return (unsigned char )&u;
473	}
474
475	ecb_inline ecb_bool ecb_big_endian (void) ecb_const;
476	ecb_inline ecb_bool ecb_big_endian (void) { return ecb_byteorder_helper () == 0x11; }
477	ecb_inline ecb_bool ecb_little_endian (void) ecb_const;
478	ecb_inline ecb_bool ecb_little_endian (void) { return ecb_byteorder_helper () == 0x44; }
479
480	#if ECB_GCC_VERSION(3,0) \|\| ECB_C99
481	#define ecb_mod(m,n) ((m) % (n) + ((m) % (n) < 0 ? (n) : 0))
482	#else
483	#define ecb_mod(m,n) ((m) < 0 ? ((n) - 1 - ((-1 - (m)) % (n))) : ((m) % (n)))
484	#endif
485
486	#if __cplusplus
487	template<typename T>
488	static inline T ecb_div_rd (T val, T div)
489	{
490	return val < 0 ? - ((-val + div - 1) / div) : (val ) / div;
491	}
492	template<typename T>
493	static inline T ecb_div_ru (T val, T div)
494	{
495	return val < 0 ? - ((-val ) / div) : (val + div - 1) / div;
496	}
497	#else
498	#define ecb_div_rd(val,div) ((val) < 0 ? - ((-(val) + (div) - 1) / (div)) : ((val) ) / (div))
499	#define ecb_div_ru(val,div) ((val) < 0 ? - ((-(val) ) / (div)) : ((val) + (div) - 1) / (div))
500	#endif
501
502	#if ecb_cplusplus_does_not_suck
503	/* does not work for local types (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm) */
504	template<typename T, int N>
505	static inline int ecb_array_length (const T (&arr)[N])
506	{
507	return N;
508	}
509	#else
510	#define ecb_array_length(name) (sizeof (name) / sizeof (name [0]))
511	#endif
512
513	#endif
514