commit b077b20206bf90a4d5cb683d8c63595f2af48756
parent 3cf340f676aea0d2f4a1135bf9aebc979f93d30a
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Tue, 12 Dec 2017 09:52:08 -0200
back to reallocation when resizing the string table.
(Not a good idea to explicitly allocate new memory when shrinking
something.)
Diffstat:
M | lstring.c | | | 90 | +++++++++++++++++++++++++++++++++++++++++++++++++++++--------------------------- |
1 file changed, 60 insertions(+), 30 deletions(-)
diff --git a/lstring.c b/lstring.c
@@ -1,5 +1,5 @@
/*
-** $Id: lstring.c,v 2.59 2017/12/07 18:59:52 roberto Exp roberto $
+** $Id: lstring.c,v 2.60 2017/12/08 17:28:25 roberto Exp roberto $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/
@@ -69,31 +69,47 @@ unsigned int luaS_hashlongstr (TString *ts) {
}
-/*
-** Resize the string table. If allocation fails, keep the current size.
-** (This can degrade performance, but any size should work correctly.)
-*/
-void luaS_resize (lua_State *L, int newsize) {
+static void rehash (TString **vect, int osize, int nsize) {
int i;
- TString **newhash = luaM_newvector(L, newsize, TString *);
- stringtable *tb = &G(L)->strt;
- if (newhash == NULL) /* allocation failed? */
- return; /* leave hash as it is */
- for (i = 0; i < newsize; i++) /* initialize new hash array */
- newhash[i] = NULL;
- for (i = 0; i < tb->size; i++) { /* rehash all elements into new array */
- TString *p = tb->hash[i];
+ for (i = osize; i < nsize; i++) /* clear new elements */
+ vect[i] = NULL;
+ for (i = 0; i < osize; i++) { /* rehash old part of the array */
+ TString *p = vect[i];
+ vect[i] = NULL;
while (p) { /* for each string in the list */
TString *hnext = p->u.hnext; /* save next */
- unsigned int h = lmod(p->hash, newsize); /* new position */
- p->u.hnext = newhash[h]; /* chain it into new array */
- newhash[h] = p;
+ unsigned int h = lmod(p->hash, nsize); /* new position */
+ p->u.hnext = vect[h]; /* chain it into array */
+ vect[h] = p;
p = hnext;
}
}
- luaM_freearray(L, tb->hash, tb->size); /* free old array */
- tb->hash = newhash;
- tb->size = newsize;
+}
+
+
+/*
+** Resize the string table. If allocation fails, keep the current size.
+** (This can degrade performance, but any non-zero size should work
+** correctly.)
+*/
+void luaS_resize (lua_State *L, int nsize) {
+ stringtable *tb = &G(L)->strt;
+ int osize = tb->size;
+ TString **newvect;
+ if (nsize < osize) /* shrinking table? */
+ rehash(tb->hash, osize, nsize); /* remove elements from shrinking part */
+ newvect = luaM_reallocvector(L, tb->hash, osize, nsize, TString*);
+ if (newvect == NULL) { /* reallocation failed? */
+ if (nsize < osize) /* was it shrinking table? */
+ rehash(tb->hash, nsize, osize); /* restore to original size */
+ /* leave table as it was */
+ }
+ else { /* allocation succeeded */
+ tb->hash = newvect;
+ tb->size = nsize;
+ if (nsize > osize)
+ rehash(newvect, osize, nsize); /* rehash for new size */
+ }
}
@@ -118,7 +134,10 @@ void luaS_init (lua_State *L) {
global_State *g = G(L);
int i, j;
TString *memerrmsg;
- luaS_resize(L, MINSTRTABSIZE); /* initial size of string table */
+ stringtable *tb = &G(L)->strt;
+ tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
+ rehash(tb->hash, 0, MINSTRTABSIZE); /* clear array */
+ tb->size = MINSTRTABSIZE;
/* pre-create memory-error message */
memerrmsg = luaS_newliteral(L, MEMERRMSG);
luaC_fix(L, obj2gco(memerrmsg)); /* it should never be collected */
@@ -165,35 +184,46 @@ void luaS_remove (lua_State *L, TString *ts) {
}
+static void growstrtab (lua_State *L, stringtable *tb) {
+ if (tb->nuse == MAX_INT) { /* too many strings? */
+ luaC_fullgc(L, 1); /* try to free some... */
+ if (tb->nuse == MAX_INT) /* still too many? */
+ luaM_error(L); /* cannot even create a message... */
+ }
+ if (tb->size <= MAXSTRTB / 2) /* can grow string table? */
+ luaS_resize(L, tb->size * 2);
+}
+
+
/*
-** checks whether short string exists and reuses it or creates a new one
+** Checks whether short string exists and reuses it or creates a new one.
*/
static TString *internshrstr (lua_State *L, const char *str, size_t l) {
TString *ts;
global_State *g = G(L);
+ stringtable *tb = &g->strt;
unsigned int h = luaS_hash(str, l, g->seed);
- TString **list = &g->strt.hash[lmod(h, g->strt.size)];
+ TString **list = &tb->hash[lmod(h, tb->size)];
lua_assert(str != NULL); /* otherwise 'memcmp'/'memcpy' are undefined */
for (ts = *list; ts != NULL; ts = ts->u.hnext) {
- if (l == ts->shrlen &&
- (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
+ if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
/* found! */
if (isdead(g, ts)) /* dead (but not collected yet)? */
changewhite(ts); /* resurrect it */
return ts;
}
}
- if (g->strt.nuse >= g->strt.size &&
- g->strt.size <= MAXSTRTB / 2) {
- luaS_resize(L, g->strt.size * 2);
- list = &g->strt.hash[lmod(h, g->strt.size)]; /* recompute with new size */
+ /* else must create a new string */
+ if (tb->nuse >= tb->size) { /* need to grow string table? */
+ growstrtab(L, tb);
+ list = &tb->hash[lmod(h, tb->size)]; /* rehash with new size */
}
ts = createstrobj(L, l, LUA_TSHRSTR, h);
memcpy(getstr(ts), str, l * sizeof(char));
ts->shrlen = cast_byte(l);
ts->u.hnext = *list;
*list = ts;
- g->strt.nuse++;
+ tb->nuse++;
return ts;
}