util/numbers.h

   1 /* $Id$ */
   2
   3 #ifndef HED__UTIL_NUMBERS_H
   4 #define HED__UTIL_NUMBERS_H
   5
   6 /*
   7  * Bilbo was going to be eleventy-one, 111, a rather curious number and a very
   8  * respectable age for a hobbit (the Old Took himself had only reached 130);
   9  * and Frodo was going to be thirty-three, 33, an important number: the date
  10  * of his 'coming of age'.
  11  */
  12
  13 /* Maximal values of off_t and uoff_t.
  14  * uoff_t is unsigned, while off_t is signed; in 2's complement
  15  * arithmetic, this means that UOFF_MAX is all 1's, and OFF_MAX
  16  * has only the highest bit clear.
  17  */
  18 #define UOFF_MAX (~(hed_uoff_t)(0))
  19 #define OFF_MAX (hed_off_t)(UOFF_MAX >> 1)
  20
  21 /* The biggest possible integer type. */
  22 typedef BINT_TYPE bint;
  23 typedef unsigned BINT_TYPE ubint;
  24
  25 /* Minimax. */
  26 static bint min(const bint a, const bint b);
  27 static bint max(const bint a, const bint b);
  28
  29 /* Find the highest bit. */
  30 static int bitsize(ubint x);
  31
  32
  33
  34 /**** Inline functions and such. */
  35
  36 static inline bint
  37 min(const bint a, const bint b)
  38 {
  39         return a < b ? a : b;
  40 }
  41
  42 static inline bint
  43 max(const bint a, const bint b)
  44 {
  45         return a > b ? a : b;
  46 }
  47
  48 static inline int
  49 bitsize(ubint x)
  50 {
  51         int r = 0;
  52         /* FIXME: only up to 64bits */
  53         if (x & 0xffffffff00000000ULL) { x >>= 32; r += 32; }
  54         if (x & 0x00000000ffff0000ULL) { x >>= 16; r += 16; }
  55         if (x & 0x000000000000ff00ULL) { x >>=  8; r +=  8; }
  56         if (x & 0x00000000000000f0ULL) { x >>=  4; r +=  4; }
  57         if (x & 0x000000000000000cULL) { x >>=  2; r +=  2; }
  58         if (x & 0x0000000000000002ULL) {           r +=  1; }
  59         return r;
  60 }
  61
  62 /**** Endianity. */
  63
  64 /* Returns 1 if running on a little-endian architecture.
  65  * Hopefully, this will be always optimized to a constant expression.
  66  */
  67 static inline int
  68 arch_little_endian(void)
  69 {
  70         union {
  71                 long x;
  72                 char c;
  73         } u = { 1 };
  74         return u.c;
  75 }
  76
  77 #endif