change in string table: string table is now independent of GC lists; all
strings live in 'normal' GC lists
This commit is contained in:
Roberto Ierusalimschy
140
lstring.c
140
lstring.c
@@ -1,5 +1,5 @@
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/*
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** $Id: lstring.c,v 2.27 2013/06/19 14:27:00 roberto Exp roberto $
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** $Id: lstring.c,v 2.28 2013/08/05 16:58:28 roberto Exp roberto $
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** String table (keeps all strings handled by Lua)
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** See Copyright Notice in lua.h
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*/
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@@ -12,12 +12,21 @@
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#include "lua.h"
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#include "ldebug.h"
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#include "lmem.h"
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#include "lobject.h"
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#include "lstate.h"
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#include "lstring.h"
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/* mark for vacant places in hash table */
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#define VACANTK cast(TString *, cast(size_t, -1))
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/* second hash (for double hash) */
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#define h2(h1,hash,size) lmod(h1 + ((hash % 31) | 1), size)
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/*
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** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to
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** compute its hash
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@@ -64,30 +73,27 @@ unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
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void luaS_resize (lua_State *L, int newsize) {
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int i;
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stringtable *tb = &G(L)->strt;
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/* cannot resize while GC is traversing strings */
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luaC_runtilstate(L, ~bitmask(GCSsweepstring));
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if (newsize > tb->size) {
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luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
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for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL;
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}
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TString **oldhash = tb->hash;
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int oldsize = tb->size;
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tb->hash = luaM_newvector(L, newsize, TString *);
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tb->size = newsize;
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/* keep load factor below 75% */
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tb->empty = newsize/2 + newsize/4 - tb->nuse;
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for (i = 0; i < newsize; i++) tb->hash[i] = NULL;
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tb->nuse = 0;
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/* rehash */
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for (i=0; i<tb->size; i++) {
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GCObject *p = tb->hash[i];
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tb->hash[i] = NULL;
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while (p) { /* for each node in the list */
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GCObject *next = gch(p)->next; /* save next */
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unsigned int h = lmod(gco2ts(p)->hash, newsize); /* new position */
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gch(p)->next = tb->hash[h]; /* chain it */
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tb->hash[h] = p;
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p = next;
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for (i = 0; i < oldsize; i++) {
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TString *ts = oldhash[i];
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if (ts != NULL && ts != VACANTK) {
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unsigned int hash = ts->tsv.hash;
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int h1 = lmod(hash, tb->size);
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while (tb->hash[h1] != NULL)
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h1 = h2(h1, hash, tb->size);
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tb->hash[h1] = ts;
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tb->nuse++;
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}
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}
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if (newsize < tb->size) {
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/* shrinking slice must be empty */
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lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
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luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
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}
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tb->size = newsize;
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luaM_freearray(L, oldhash, oldsize);
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}
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@@ -95,11 +101,11 @@ void luaS_resize (lua_State *L, int newsize) {
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** creates a new string object
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*/
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static TString *createstrobj (lua_State *L, const char *str, size_t l,
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int tag, unsigned int h, GCObject **list) {
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int tag, unsigned int h) {
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TString *ts;
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size_t totalsize; /* total size of TString object */
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totalsize = sizeof(TString) + ((l + 1) * sizeof(char));
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ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts;
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ts = &luaC_newobj(L, tag, totalsize, NULL, 0)->ts;
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ts->tsv.len = l;
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ts->tsv.hash = h;
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ts->tsv.extra = 0;
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@@ -109,20 +115,33 @@ static TString *createstrobj (lua_State *L, const char *str, size_t l,
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}
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/*
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** creates a new short string, inserting it into string table
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*/
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static TString *newshrstr (lua_State *L, const char *str, size_t l,
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unsigned int h) {
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GCObject **list; /* (pointer to) list where it will be inserted */
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static void rehash (lua_State *L, stringtable *tb) {
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int newsize;
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if (tb->nuse < tb->size / 2) { /* using less than half the size? */
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if (tb->nuse < tb->size / 4) /* using less than half of that? */
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newsize = tb->size / 2; /* shrink table */
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else
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newsize = tb->size; /* keep size (but reorganize table) */
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}
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else { /* table must grow */
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if (tb->size >= MAX_INT/2)
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luaG_runerror(L, "string-table overflow: too many strings");
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newsize = tb->size * 2;
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}
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luaS_resize(L, newsize);
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}
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LUAI_FUNC void luaS_remove (lua_State *L, TString *ts) {
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stringtable *tb = &G(L)->strt;
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TString *s;
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if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
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luaS_resize(L, tb->size*2); /* too crowded */
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list = &tb->hash[lmod(h, tb->size)];
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s = createstrobj(L, str, l, LUA_TSHRSTR, h, list);
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tb->nuse++;
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return s;
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unsigned int hash = ts->tsv.hash;
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int h1 = lmod(hash, tb->size);
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while (tb->hash[h1] != ts) {
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lua_assert(tb->hash[h1] != NULL);
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h1 = h2(h1, hash, tb->size);
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}
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tb->hash[h1] = VACANTK;
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tb->nuse--;
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}
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@@ -130,22 +149,39 @@ static TString *newshrstr (lua_State *L, const char *str, size_t l,
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** checks whether short string exists and reuses it or creates a new one
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*/
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static TString *internshrstr (lua_State *L, const char *str, size_t l) {
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GCObject *o;
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global_State *g = G(L);
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unsigned int h = luaS_hash(str, l, g->seed);
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for (o = g->strt.hash[lmod(h, g->strt.size)];
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o != NULL;
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o = gch(o)->next) {
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TString *ts = rawgco2ts(o);
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if (h == ts->tsv.hash &&
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l == ts->tsv.len &&
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(memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
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if (isdead(G(L), o)) /* string is dead (but was not collected yet)? */
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changewhite(o); /* resurrect it */
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return ts;
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TString *ts;
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unsigned int hash = luaS_hash(str, l, G(L)->seed);
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stringtable *tb = &G(L)->strt;
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int vacant = -1;
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int h1;
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if (tb->empty <= 0)
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rehash(L, tb);
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h1 = lmod(hash, tb->size); /* previous call can changed 'size' */
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while ((ts = tb->hash[h1]) != NULL) { /* search the string in hash table */
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if (ts == VACANTK) {
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if (vacant < 0) vacant = h1; /* keep track of a vacant place */
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}
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else if (l == ts->tsv.len &&
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(memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
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/* found! */
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if (isdead(G(L), obj2gco(ts))) /* dead (but was not collected yet)? */
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changewhite(obj2gco(ts)); /* resurrect it */
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if (vacant >= 0) { /* is there a better place for this string? */
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tb->hash[vacant] = ts; /* move it up the line */
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tb->hash[h1] = VACANTK;
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}
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return ts; /* found */
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}
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h1 = h2(h1, hash, tb->size);
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}
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return newshrstr(L, str, l, h); /* not found; create a new string */
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ts = createstrobj(L, str, l, LUA_TSHRSTR, hash);
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tb->nuse++;
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if (vacant < 0) /* found no vacant place? */
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tb->empty--; /* will have to use the empty place */
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else
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h1 = vacant; /* insert string into vacant place */
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tb->hash[h1] = ts;
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return ts;
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}
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@@ -158,7 +194,7 @@ TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
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else {
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if (l + 1 > (MAX_SIZE - sizeof(TString))/sizeof(char))
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luaM_toobig(L);
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return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL);
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return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed);
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}
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}
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