[Python-checkins] cpython (3.2): Consolidate the occurrances of the prime used as the multiplier when hashing

[gregory.p.smith]

http://hg.python.org/cpython/rev/050c07b31192
changeset:   74415:050c07b31192
branch:      3.2
parent:      74411:70c46599fb0e
user:        Gregory P. Smith <greg at krypto.org>
date:        Sat Jan 14 15:31:34 2012 -0800
summary:
  Consolidate the occurrances of the prime used as the multiplier when hashing
to a single #define instead of having several copies in several files.

This excludes the Modules/ tree (datetime and expat both have a copy
for their own purposes with no need for it to be the same).

files:
  Include/pyport.h        |  5 ++++-
  Objects/bytesobject.c   |  2 +-
  Objects/tupleobject.c   |  2 +-
  Objects/unicodeobject.c |  2 +-
  4 files changed, 7 insertions(+), 4 deletions(-)


diff --git a/Include/pyport.h b/Include/pyport.h
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -131,6 +131,9 @@
 #endif
 #endif
 
+/* Prime multiplier used in string and various other hashes. */
+#define _PyHASH_MULTIPLIER 1000003  /* 0xf4243 */
+
 /* Parameters used for the numeric hash implementation.  See notes for
    _PyHash_Double in Objects/object.c.  Numeric hashes are based on
    reduction modulo the prime 2**_PyHASH_BITS - 1. */
@@ -143,7 +146,7 @@
 #define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
 #define _PyHASH_INF 314159
 #define _PyHASH_NAN 0
-#define _PyHASH_IMAG 1000003UL
+#define _PyHASH_IMAG _PyHASH_MULTIPLIER
 
 /* uintptr_t is the C9X name for an unsigned integral type such that a
  * legitimate void* can be cast to uintptr_t and then back to void* again
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -881,7 +881,7 @@
     p = (unsigned char *) a->ob_sval;
     x = *p << 7;
     while (--len >= 0)
-        x = (1000003*x) ^ *p++;
+        x = (_PyHASH_MULTIPLIER*x) ^ *p++;
     x ^= Py_SIZE(a);
     if (x == -1)
         x = -2;
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -315,7 +315,7 @@
     register Py_hash_t x, y;
     register Py_ssize_t len = Py_SIZE(v);
     register PyObject **p;
-    Py_hash_t mult = 1000003L;
+    Py_hash_t mult = _PyHASH_MULTIPLIER;
     x = 0x345678L;
     p = v->ob_item;
     while (--len >= 0) {
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -7666,7 +7666,7 @@
     p = self->str;
     x = *p << 7;
     while (--len >= 0)
-        x = (1000003*x) ^ *p++;
+        x = (_PyHASH_MULTIPLIER*x) ^ *p++;
     x ^= Py_SIZE(self);
     if (x == -1)
         x = -2;

-- 
Repository URL: http://hg.python.org/cpython