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more efficient hash for numbers in IEEE754 machines

This commit is contained in:
Roberto Ierusalimschy 2010-12-23 13:38:28 -02:00
parent 551b076f1c
commit 0b3f4e254e
1 changed files with 10 additions and 9 deletions
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17
llimits.h
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@ -1,5 +1,5 @@
/*
** $Id: llimits.h,v 1.84 2010/11/08 16:33:20 roberto Exp roberto $
** $Id: llimits.h,v 1.85 2010/12/10 13:40:22 roberto Exp roberto $
** Limits, basic types, and some other `installation-dependent' definitions
** See Copyright Notice in lua.h
*/
@ -174,6 +174,9 @@ typedef lu_int32 Instruction;
** lua_number2integer is a macro to convert lua_Number to lua_Integer.
** lua_number2unsigned is a macro to convert a lua_Number to a lua_Unsigned.
** lua_unsigned2number is a macro to convert a lua_Unsigned to a lua_Number.
** luai_hashnum is a macro to hash a lua_Number value into an integer.
** The hash must be deterministic and give reasonable values for
** both small and large values (outside the range of integers).
*/
#if defined(MS_ASMTRICK) /* { */
@ -204,6 +207,10 @@ union luai_Cast { double l_d; LUA_INT32 l_p[2]; };
volatile union luai_Cast u; u.l_d = (n) + 6755399441055744.0; \
(i) = (t)u.l_p[LUA_IEEEENDIAN]; }
#define luai_hashnum(i,n) \
{ volatile union luai_Cast u; u.l_d = (n) + 1.0; /* avoid -0 */ \
(i) = u.l_p[0] + u.l_p[1]; } /* add double bits for his hash */
#define lua_number2int(i,n) lua_number2int32(i, n, int)
#define lua_number2integer(i,n) lua_number2int32(i, n, lua_Integer)
#define lua_number2unsigned(i,n) lua_number2int32(i, n, lua_Unsigned)
@ -242,14 +249,8 @@ union luai_Cast { double l_d; LUA_INT32 l_p[2]; };
#endif
/*
** luai_hashnum is a macro do hash a lua_Number value into an integer.
** The hash must be deterministic and give reasonable values for
** both small and large values (outside the range of integers).
** It is used only in ltable.c.
*/
#if !defined(luai_hashnum) /* { */
#if defined(ltable_c) && !defined(luai_hashnum) /* { */
#include <float.h>
#include <math.h>