Merge with git+ssh://git.ucw.cz/projects/sherlock/GIT/sherlock.git

[libucw.git] / lib / hashfunc.h

diff --git a/lib/hashfunc.h b/lib/hashfunc.h
index d79e44ecfdaf695439a026496287ccab2e9ef76b..5f40c3d6783eb6c7346451a813170ca442347599 100644 (file)
--- a/lib/hashfunc.h
+++ b/lib/hashfunc.h
@@ -1,35 +1,43 @@
 /*
- *     Hyper-super-meta-alt-control-shift extra fast str_len() and hash_*()
- *     routines
+ *     UCW Library -- Hyper-super-meta-alt-control-shift extra fast
+ *     str_len() and hash_*() routines
  *
  *     (c) 2002, Robert Spalek <robert@ucw.cz>
+ *
+ *     This software may be freely distributed and used according to the terms
+ *     of the GNU Lesser General Public License.
  */
 
-#ifndef _SHERLOCK_HASHFUNC_H
-#define _SHERLOCK_HASHFUNC_H
+#ifndef _UCW_HASHFUNC_H
+#define _UCW_HASHFUNC_H
 
 #include "lib/lib.h"
 
-/* An equivalent of the Intel's rol instruction.  */
-#define        ROL(x, bits)    (((x) << (bits)) | ((x) >> (sizeof(uns)*8 - (bits))))
-
 /* The following functions need str to be aligned to uns.  */
-uns str_len_aligned(const byte *str) CONST;
-uns hash_string_aligned(const byte *str) CONST;
-uns hash_block_aligned(const byte *str, uns len) CONST;
+uns str_len_aligned(const byte *str) PURE;
+uns hash_string_aligned(const byte *str) PURE;
+uns hash_block_aligned(const byte *str, uns len) PURE;
 
 #ifdef CPU_ALLOW_UNALIGNED
 #define        str_len(str)            str_len_aligned(str)
 #define        hash_string(str)        hash_string_aligned(str)
 #define        hash_block(str, len)    hash_block_aligned(str, len)
 #else
-uns str_len(const byte *str) CONST;
-uns hash_string(const byte *str) CONST;
-uns hash_block(const byte *str, uns len) CONST;
+uns str_len(const byte *str) PURE;
+uns hash_string(const byte *str) PURE;
+uns hash_block(const byte *str, uns len) PURE;
 #endif
 
-uns hash_string_nocase(const byte *str) CONST;
+uns hash_string_nocase(const byte *str) PURE;
 
-static inline uns CONST hash_int(uns x) { return 6442450967*x; }
+/*
+ *  We hash integers by multiplying by a reasonably large prime with
+ *  few ones in its binary form (to gave the compiler the possibility
+ *  of using shifts and adds on architectures where multiplication
+ *  instructions are slow).
+ */
+static inline uns CONST hash_u32(uns x) { return 0x01008041*x; }
+static inline uns CONST hash_u64(u64 x) { return hash_u32((uns)x ^ (uns)(x >> 32)); }
+static inline uns CONST hash_pointer(void *x) { return ((sizeof(x) <= 4) ? hash_u32((uns)(uintptr_t)x) : hash_u64((u64)(uintptr_t)x)); }
 
 #endif