commit 146508b28e942fbfed5eedc6965857be558e9c57
parent d103312661d4d2428516924658154df09b3168a4
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 20 Nov 2015 10:29:54 -0200
randomness in pivot for 'table.sort' done by a macro (easier to change)
Diffstat:
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/ltablib.c b/ltablib.c
@@ -1,5 +1,5 @@
/*
-** $Id: ltablib.c,v 1.84 2015/11/06 16:07:14 roberto Exp roberto $
+** $Id: ltablib.c,v 1.85 2015/11/12 18:07:25 roberto Exp roberto $
** Library for Table Manipulation
** See Copyright Notice in lua.h
*/
@@ -12,7 +12,6 @@
#include <limits.h>
#include <stddef.h>
-#include <time.h>
#include "lua.h"
@@ -24,10 +23,10 @@
** Operations that an object must define to mimic a table
** (some functions only need some of them)
*/
-#define TAB_R 1
-#define TAB_W 2
-#define TAB_L 4
-#define TAB_RW (TAB_R | TAB_W)
+#define TAB_R 1 /* read */
+#define TAB_W 2 /* write */
+#define TAB_L 4 /* length */
+#define TAB_RW (TAB_R | TAB_W) /* read/write */
#define aux_getn(L,n,w) (checktab(L, n, (w) | TAB_L), luaL_len(L, n))
@@ -51,7 +50,7 @@ static void checktab (lua_State *L, int arg, int what) {
(!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&
(!(what & TAB_L) || checkfield(L, "__len", ++n))) {
lua_pop(L, n); /* pop metatable and tested metamethods */
-}
+ }
else
luaL_argerror(L, arg, "table expected"); /* force an error */
}
@@ -295,8 +294,12 @@ static int partition (lua_State *L, int lo, int up) {
/*
** Choose a "random" pivot in the middle part of the interval [lo, up].
-** Use 'time' and 'clock' as sources of "randomness".
+** (If you don't want/need this "randomness", (lo+up)/2 is an excelent
+** choice.)
*/
+#if !defined(l_sortpivot)
+/* Use 'time' and 'clock' as sources of "randomness" */
+#include <time.h>
static int choosePivot (int lo, int up) {
unsigned int t = (unsigned int)(unsigned long)time(NULL); /* time */
unsigned int c = (unsigned int)(unsigned long)clock(); /* clock */
@@ -306,11 +309,14 @@ static int choosePivot (int lo, int up) {
return (int)p;
}
+#define l_sortpivot(lo,up) choosePivot(lo,up)
+#endif
+
static void auxsort (lua_State *L, int lo, int up) {
while (lo < up) { /* loop for tail recursion */
- int p;
- /* sort elements 'lo', '(lo + up)/2' and 'up' */
+ int p; /* Pivot index */
+ /* sort elements 'lo', 'p', and 'up' */
lua_geti(L, 1, lo);
lua_geti(L, 1, up);
if (sort_comp(L, -1, -2)) /* a[up] < a[lo]? */
@@ -322,7 +328,7 @@ static void auxsort (lua_State *L, int lo, int up) {
if (up - lo < 100) /* small interval? */
p = (lo + up)/2; /* middle element is a good pivot */
else /* for larger intervals, it is worth a random pivot */
- p = choosePivot(lo, up);
+ p = l_sortpivot(lo, up);
lua_geti(L, 1, p);
lua_geti(L, 1, lo);
if (sort_comp(L, -2, -1)) /* a[p] < a[lo]? */