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using unsigned int (instead of int) in 'table.sort' to avoid overflows 

(when computing the pivot and in original table size)
This commit is contained in:
Roberto Ierusalimschy 2015-11-23 09:17:31 -02:00
parent dc9ac5b8c2
commit c231a5e2b6
1 changed files with 23 additions and 17 deletions
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40
ltablib.c
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@ -1,5 +1,5 @@
/* /*
** $Id: ltablib.c,v 1.86 2015/11/20 12:30:20 roberto Exp roberto $ ** $Id: ltablib.c,v 1.87 2015/11/23 11:09:27 roberto Exp roberto $
** Library for Table Manipulation ** Library for Table Manipulation
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -230,7 +230,7 @@ static int unpack (lua_State *L) {
** ======================================================= ** =======================================================
*/ */
static void set2 (lua_State *L, int i, int j) { static void set2 (lua_State *L, unsigned int i, unsigned int j) {
lua_seti(L, 1, i); lua_seti(L, 1, i);
lua_seti(L, 1, j); lua_seti(L, 1, j);
} }
@ -258,9 +258,10 @@ static int sort_comp (lua_State *L, int a, int b) {
** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up] ** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]
** returns 'i'. ** returns 'i'.
*/ */
static int partition (lua_State *L, int lo, int up) { static unsigned int partition (lua_State *L, unsigned int lo,
int i = lo; /* will be incremented before first use */ unsigned int up) {
int j = up - 1; /* will be decremented before first use */ unsigned int i = lo; /* will be incremented before first use */
unsigned int j = up - 1; /* will be decremented before first use */
/* loop invariant: a[lo .. i] <= P <= a[j .. up] */ /* loop invariant: a[lo .. i] <= P <= a[j .. up] */
for (;;) { for (;;) {
/* next loop: repeat ++i while a[i] < P */ /* next loop: repeat ++i while a[i] < P */
@ -292,28 +293,30 @@ static int partition (lua_State *L, int lo, int up) {
/* /*
** Choose a "random" pivot in the middle part of the interval [lo, up]. ** Choose a "random" pivot in the middle part of the interval [lo, up].
** (If you don't want/need this "randomness", (lo+up)/2 is an excelent ** (If you don't want/need this "randomness", (lo+up)/2 is an excellent
** choice.) ** choice.)
*/ */
#if !defined(l_sortpivot) #if !defined(l_sortpivot)
/* Use 'time' and 'clock' as sources of "randomness" */ /* Use 'time' and 'clock' as sources of "randomness" */
#include <time.h> #include <time.h>
static int choosePivot (int lo, int up) {
static unsigned int choosePivot (unsigned int lo, unsigned int up) {
unsigned int t = (unsigned int)(unsigned long)time(NULL); /* time */ unsigned int t = (unsigned int)(unsigned long)time(NULL); /* time */
unsigned int c = (unsigned int)(unsigned long)clock(); /* clock */ unsigned int c = (unsigned int)(unsigned long)clock(); /* clock */
unsigned int r4 = (unsigned int)(up - lo) / 4u; /* range/4 */ unsigned int r4 = (unsigned int)(up - lo) / 4u; /* range/4 */
unsigned int p = (c + t) % (r4 * 2) + (lo + r4); unsigned int p = (c + t) % (r4 * 2) + (lo + r4);
lua_assert(lo + r4 <= p && p <= up - r4); lua_assert(lo + r4 <= p && p <= up - r4);
return (int)p; return p;
} }
#define l_sortpivot(lo,up) choosePivot(lo,up) #define l_sortpivot(lo,up) choosePivot(lo,up)
#endif #endif
static void auxsort (lua_State *L, int lo, int up) { static void auxsort (lua_State *L, unsigned int lo, unsigned int up) {
while (lo < up) { /* loop for tail recursion */ while (lo < up) { /* loop for tail recursion */
int p; /* Pivot index */ unsigned int p; /* Pivot index */
/* sort elements 'lo', 'p', and 'up' */ /* sort elements 'lo', 'p', and 'up' */
lua_geti(L, 1, lo); lua_geti(L, 1, lo);
lua_geti(L, 1, up); lua_geti(L, 1, up);
@ -323,7 +326,7 @@ static void auxsort (lua_State *L, int lo, int up) {
lua_pop(L, 2); /* remove both values */ lua_pop(L, 2); /* remove both values */
if (up - lo == 1) /* only 2 elements? */ if (up - lo == 1) /* only 2 elements? */
return; /* already sorted */ return; /* already sorted */
if (up - lo < 100) /* small interval? */ if (up - lo < 100u) /* small interval? */
p = (lo + up)/2; /* middle element is a good pivot */ p = (lo + up)/2; /* middle element is a good pivot */
else /* for larger intervals, it is worth a random pivot */ else /* for larger intervals, it is worth a random pivot */
p = l_sortpivot(lo, up); p = l_sortpivot(lo, up);
@ -360,12 +363,15 @@ static void auxsort (lua_State *L, int lo, int up) {
static int sort (lua_State *L) { static int sort (lua_State *L) {
int n = (int)aux_getn(L, 1, TAB_RW); lua_Integer n = aux_getn(L, 1, TAB_RW);
luaL_checkstack(L, 50, ""); /* assume array is smaller than 2^50 */ if (n > 1) { /* non-trivial interval? */
if (!lua_isnoneornil(L, 2)) /* is there a 2nd argument? */ luaL_argcheck(L, n < INT_MAX, 1, "array too big");
luaL_checktype(L, 2, LUA_TFUNCTION); luaL_checkstack(L, 40, ""); /* assume array is smaller than 2^40 */
lua_settop(L, 2); /* make sure there are two arguments */ if (!lua_isnoneornil(L, 2)) /* is there a 2nd argument? */
auxsort(L, 1, n); luaL_checktype(L, 2, LUA_TFUNCTION); /* must be a function */
lua_settop(L, 2); /* make sure there are two arguments */
auxsort(L, 1, (unsigned int)n);
}
return 0; return 0;
} }