latest sources commit

deps/mysqllite/include/internal/my_bit.h

@@ -0,0 +1,105 @@
+#ifndef MY_BIT_INCLUDED
+#define MY_BIT_INCLUDED
+
+/*
+  Some useful bit functions
+*/
+
+C_MODE_START
+
+extern const char _my_bits_nbits[256];
+extern const uchar _my_bits_reverse_table[256];
+
+/*
+  Find smallest X in 2^X >= value
+  This can be used to divide a number with value by doing a shift instead
+*/
+
+static inline uint my_bit_log2(ulong value)
+{
+  uint bit;
+  for (bit=0 ; value > 1 ; value>>=1, bit++) ;
+  return bit;
+}
+
+static inline uint my_count_bits(ulonglong v)
+{
+#if SIZEOF_LONG_LONG > 4
+  /* The following code is a bit faster on 16 bit machines than if we would
+     only shift v */
+  ulong v2=(ulong) (v >> 32);
+  return (uint) (uchar) (_my_bits_nbits[(uchar)  v] +
+                         _my_bits_nbits[(uchar) (v >> 8)] +
+                         _my_bits_nbits[(uchar) (v >> 16)] +
+                         _my_bits_nbits[(uchar) (v >> 24)] +
+                         _my_bits_nbits[(uchar) (v2)] +
+                         _my_bits_nbits[(uchar) (v2 >> 8)] +
+                         _my_bits_nbits[(uchar) (v2 >> 16)] +
+                         _my_bits_nbits[(uchar) (v2 >> 24)]);
+#else
+  return (uint) (uchar) (_my_bits_nbits[(uchar)  v] +
+                         _my_bits_nbits[(uchar) (v >> 8)] +
+                         _my_bits_nbits[(uchar) (v >> 16)] +
+                         _my_bits_nbits[(uchar) (v >> 24)]);
+#endif
+}
+
+static inline uint my_count_bits_ushort(ushort v)
+{
+  return _my_bits_nbits[v];
+}
+
+
+/*
+  Next highest power of two
+
+  SYNOPSIS
+    my_round_up_to_next_power()
+    v		Value to check
+
+  RETURN
+    Next or equal power of 2
+    Note: 0 will return 0
+
+  NOTES
+    Algorithm by Sean Anderson, according to:
+    http://graphics.stanford.edu/~seander/bithacks.html
+    (Orignal code public domain)
+
+    Comments shows how this works with 01100000000000000000000000001011
+*/
+
+static inline uint32 my_round_up_to_next_power(uint32 v)
+{
+  v--;			/* 01100000000000000000000000001010 */
+  v|= v >> 1;		/* 01110000000000000000000000001111 */
+  v|= v >> 2;		/* 01111100000000000000000000001111 */
+  v|= v >> 4;		/* 01111111110000000000000000001111 */
+  v|= v >> 8;		/* 01111111111111111100000000001111 */
+  v|= v >> 16;		/* 01111111111111111111111111111111 */
+  return v+1;		/* 10000000000000000000000000000000 */
+}
+
+static inline uint32 my_clear_highest_bit(uint32 v)
+{
+  uint32 w=v >> 1;
+  w|= w >> 1;
+  w|= w >> 2;
+  w|= w >> 4;
+  w|= w >> 8;
+  w|= w >> 16;
+  return v & w;
+}
+
+static inline uint32 my_reverse_bits(uint32 key)
+{
+  return
+    (_my_bits_reverse_table[ key      & 255] << 24) |
+    (_my_bits_reverse_table[(key>> 8) & 255] << 16) |
+    (_my_bits_reverse_table[(key>>16) & 255] <<  8) |
+     _my_bits_reverse_table[(key>>24)      ];
+}
+
+C_MODE_END
+
+#endif /* MY_BIT_INCLUDED */