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avoid unnecessary call to log2 on too large indices

This commit is contained in:
Roberto Ierusalimschy 2003-04-28 10:31:46 -03:00
parent 17149b7d43
commit 943c82b376
1 changed files with 14 additions and 10 deletions
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24
ltable.c
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@ -1,5 +1,5 @@
/* /*
** $Id: ltable.c,v 1.131 2003/03/24 14:18:42 roberto Exp roberto $ ** $Id: ltable.c,v 1.132 2003/04/03 13:35:34 roberto Exp roberto $
** Lua tables (hash) ** Lua tables (hash)
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -45,9 +45,7 @@
#define MAXBITS (BITS_INT-2) #define MAXBITS (BITS_INT-2)
#endif #endif
/* check whether `x' < 2^MAXBITS */ #define MAXASIZE (1 << MAXBITS)
#define toobig(x) ((((x)-1) >> MAXBITS) != 0)
/* function to convert a lua_Number to int (with any rounding method) */ /* function to convert a lua_Number to int (with any rounding method) */
#ifndef lua_number2int #ifndef lua_number2int
@ -116,11 +114,13 @@ Node *luaH_mainposition (const Table *t, const TObject *key) {
** returns the index for `key' if `key' is an appropriate key to live in ** returns the index for `key' if `key' is an appropriate key to live in
** the array part of the table, -1 otherwise. ** the array part of the table, -1 otherwise.
*/ */
static int arrayindex (const TObject *key) { static int arrayindex (const TObject *key, lua_Number lim) {
if (ttisnumber(key)) { if (ttisnumber(key)) {
lua_Number n = nvalue(key);
int k; int k;
lua_number2int(k, (nvalue(key))); if (n <= 0 || n > lim) return -1; /* out of range? */
if (cast(lua_Number, k) == nvalue(key) && k >= 1 && !toobig(k)) lua_number2int(k, n);
if (cast(lua_Number, k) == nvalue(key))
return k; return k;
} }
return -1; /* `key' did not match some condition */ return -1; /* `key' did not match some condition */
@ -135,8 +135,8 @@ static int arrayindex (const TObject *key) {
static int luaH_index (lua_State *L, Table *t, StkId key) { static int luaH_index (lua_State *L, Table *t, StkId key) {
int i; int i;
if (ttisnil(key)) return -1; /* first iteration */ if (ttisnil(key)) return -1; /* first iteration */
i = arrayindex(key); i = arrayindex(key, t->sizearray);
if (0 <= i && i <= t->sizearray) { /* is `key' inside array part? */ if (0 <= i) { /* is `key' inside array part? */
return i-1; /* yes; that's the index (corrected to C) */ return i-1; /* yes; that's the index (corrected to C) */
} }
else { else {
@ -202,6 +202,7 @@ static void numuse (const Table *t, int *narray, int *nhash) {
int nums[MAXBITS+1]; int nums[MAXBITS+1];
int i, lg; int i, lg;
int totaluse = 0; int totaluse = 0;
lua_Number sizelimit; /* an upper bound for the array size */
/* count elements in array part */ /* count elements in array part */
for (i=0, lg=0; lg<=MAXBITS; lg++) { /* for each slice [2^(lg-1) to 2^lg) */ for (i=0, lg=0; lg<=MAXBITS; lg++) { /* for each slice [2^(lg-1) to 2^lg) */
int ttlg = twoto(lg); /* 2^lg */ int ttlg = twoto(lg); /* 2^lg */
@ -221,10 +222,13 @@ static void numuse (const Table *t, int *narray, int *nhash) {
*narray = totaluse; /* all previous uses were in array part */ *narray = totaluse; /* all previous uses were in array part */
/* count elements in hash part */ /* count elements in hash part */
i = sizenode(t); i = sizenode(t);
/* array part cannot be larger than twice the maximum number of elements */
sizelimit = cast(lua_Number, totaluse + i) * 2;
if (sizelimit >= MAXASIZE) sizelimit = MAXASIZE;
while (i--) { while (i--) {
Node *n = &t->node[i]; Node *n = &t->node[i];
if (!ttisnil(gval(n))) { if (!ttisnil(gval(n))) {
int k = arrayindex(gkey(n)); int k = arrayindex(gkey(n), sizelimit);
if (k >= 0) { /* is `key' an appropriate array index? */ if (k >= 0) { /* is `key' an appropriate array index? */
nums[luaO_log2(k-1)+1]++; /* count as such */ nums[luaO_log2(k-1)+1]++; /* count as such */
(*narray)++; (*narray)++;