274 lines
7.3 KiB
C
274 lines
7.3 KiB
C
/*
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** $Id: lstring.c $
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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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#define lstring_c
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#define LUA_CORE
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#include "lprefix.h"
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#include <string.h>
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#include "lua.h"
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#include "ldebug.h"
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#include "ldo.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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/*
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** Maximum size for string table.
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*/
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#define MAXSTRTB cast_int(luaM_limitN(MAX_INT, TString*))
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/*
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** equality for long strings
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*/
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int luaS_eqlngstr (TString *a, TString *b) {
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size_t len = a->u.lnglen;
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lua_assert(a->tt == LUA_VLNGSTR && b->tt == LUA_VLNGSTR);
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return (a == b) || /* same instance or... */
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((len == b->u.lnglen) && /* equal length and ... */
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(memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */
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}
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unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
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unsigned int h = seed ^ cast_uint(l);
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for (; l > 0; l--)
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h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
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return h;
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}
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unsigned int luaS_hashlongstr (TString *ts) {
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lua_assert(ts->tt == LUA_VLNGSTR);
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if (ts->extra == 0) { /* no hash? */
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size_t len = ts->u.lnglen;
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ts->hash = luaS_hash(getstr(ts), len, ts->hash);
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ts->extra = 1; /* now it has its hash */
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}
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return ts->hash;
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}
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static void tablerehash (TString **vect, int osize, int nsize) {
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int i;
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for (i = osize; i < nsize; i++) /* clear new elements */
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vect[i] = NULL;
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for (i = 0; i < osize; i++) { /* rehash old part of the array */
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TString *p = vect[i];
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vect[i] = NULL;
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while (p) { /* for each string in the list */
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TString *hnext = p->u.hnext; /* save next */
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unsigned int h = lmod(p->hash, nsize); /* new position */
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p->u.hnext = vect[h]; /* chain it into array */
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vect[h] = p;
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p = hnext;
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}
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}
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}
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/*
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** Resize the string table. If allocation fails, keep the current size.
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** (This can degrade performance, but any non-zero size should work
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** correctly.)
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*/
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void luaS_resize (lua_State *L, int nsize) {
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stringtable *tb = &G(L)->strt;
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int osize = tb->size;
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TString **newvect;
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if (nsize < osize) /* shrinking table? */
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tablerehash(tb->hash, osize, nsize); /* depopulate shrinking part */
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newvect = luaM_reallocvector(L, tb->hash, osize, nsize, TString*);
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if (unlikely(newvect == NULL)) { /* reallocation failed? */
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if (nsize < osize) /* was it shrinking table? */
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tablerehash(tb->hash, nsize, osize); /* restore to original size */
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/* leave table as it was */
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}
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else { /* allocation succeeded */
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tb->hash = newvect;
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tb->size = nsize;
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if (nsize > osize)
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tablerehash(newvect, osize, nsize); /* rehash for new size */
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}
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}
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/*
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** Clear API string cache. (Entries cannot be empty, so fill them with
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** a non-collectable string.)
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*/
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void luaS_clearcache (global_State *g) {
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int i, j;
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for (i = 0; i < STRCACHE_N; i++)
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for (j = 0; j < STRCACHE_M; j++) {
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if (iswhite(g->strcache[i][j])) /* will entry be collected? */
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g->strcache[i][j] = g->memerrmsg; /* replace it with something fixed */
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}
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}
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/*
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** Initialize the string table and the string cache
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*/
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void luaS_init (lua_State *L) {
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global_State *g = G(L);
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int i, j;
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stringtable *tb = &G(L)->strt;
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tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
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tablerehash(tb->hash, 0, MINSTRTABSIZE); /* clear array */
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tb->size = MINSTRTABSIZE;
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/* pre-create memory-error message */
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g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
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luaC_fix(L, obj2gco(g->memerrmsg)); /* it should never be collected */
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for (i = 0; i < STRCACHE_N; i++) /* fill cache with valid strings */
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for (j = 0; j < STRCACHE_M; j++)
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g->strcache[i][j] = g->memerrmsg;
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}
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/*
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** creates a new string object
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*/
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static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
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TString *ts;
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GCObject *o;
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size_t totalsize; /* total size of TString object */
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totalsize = sizelstring(l);
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o = luaC_newobj(L, tag, totalsize);
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ts = gco2ts(o);
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ts->hash = h;
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ts->extra = 0;
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getstr(ts)[l] = '\0'; /* ending 0 */
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return ts;
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}
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TString *luaS_createlngstrobj (lua_State *L, size_t l) {
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TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
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ts->u.lnglen = l;
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return ts;
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}
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void luaS_remove (lua_State *L, TString *ts) {
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stringtable *tb = &G(L)->strt;
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TString **p = &tb->hash[lmod(ts->hash, tb->size)];
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while (*p != ts) /* find previous element */
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p = &(*p)->u.hnext;
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*p = (*p)->u.hnext; /* remove element from its list */
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tb->nuse--;
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}
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static void growstrtab (lua_State *L, stringtable *tb) {
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if (unlikely(tb->nuse == MAX_INT)) { /* too many strings? */
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luaC_fullgc(L, 1); /* try to free some... */
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if (tb->nuse == MAX_INT) /* still too many? */
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luaM_error(L); /* cannot even create a message... */
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}
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if (tb->size <= MAXSTRTB / 2) /* can grow string table? */
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luaS_resize(L, tb->size * 2);
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}
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/*
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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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TString *ts;
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global_State *g = G(L);
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stringtable *tb = &g->strt;
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unsigned int h = luaS_hash(str, l, g->seed);
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TString **list = &tb->hash[lmod(h, tb->size)];
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lua_assert(str != NULL); /* otherwise 'memcmp'/'memcpy' are undefined */
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for (ts = *list; ts != NULL; ts = ts->u.hnext) {
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if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
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/* found! */
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if (isdead(g, ts)) /* dead (but not collected yet)? */
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changewhite(ts); /* resurrect it */
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return ts;
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}
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}
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/* else must create a new string */
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if (tb->nuse >= tb->size) { /* need to grow string table? */
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growstrtab(L, tb);
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list = &tb->hash[lmod(h, tb->size)]; /* rehash with new size */
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}
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ts = createstrobj(L, l, LUA_VSHRSTR, h);
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memcpy(getstr(ts), str, l * sizeof(char));
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ts->shrlen = cast_byte(l);
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ts->u.hnext = *list;
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*list = ts;
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tb->nuse++;
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return ts;
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}
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/*
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** new string (with explicit length)
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*/
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TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
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if (l <= LUAI_MAXSHORTLEN) /* short string? */
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return internshrstr(L, str, l);
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else {
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TString *ts;
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if (unlikely(l >= (MAX_SIZE - sizeof(TString))/sizeof(char)))
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luaM_toobig(L);
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ts = luaS_createlngstrobj(L, l);
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memcpy(getstr(ts), str, l * sizeof(char));
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return ts;
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}
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}
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/*
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** Create or reuse a zero-terminated string, first checking in the
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** cache (using the string address as a key). The cache can contain
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** only zero-terminated strings, so it is safe to use 'strcmp' to
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** check hits.
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*/
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TString *luaS_new (lua_State *L, const char *str) {
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unsigned int i = point2uint(str) % STRCACHE_N; /* hash */
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int j;
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TString **p = G(L)->strcache[i];
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for (j = 0; j < STRCACHE_M; j++) {
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if (strcmp(str, getstr(p[j])) == 0) /* hit? */
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return p[j]; /* that is it */
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}
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/* normal route */
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for (j = STRCACHE_M - 1; j > 0; j--)
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p[j] = p[j - 1]; /* move out last element */
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/* new element is first in the list */
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p[0] = luaS_newlstr(L, str, strlen(str));
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return p[0];
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}
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Udata *luaS_newudata (lua_State *L, size_t s, int nuvalue) {
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Udata *u;
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int i;
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GCObject *o;
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if (unlikely(s > MAX_SIZE - udatamemoffset(nuvalue)))
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luaM_toobig(L);
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o = luaC_newobj(L, LUA_VUSERDATA, sizeudata(nuvalue, s));
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u = gco2u(o);
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u->len = s;
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u->nuvalue = nuvalue;
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u->metatable = NULL;
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for (i = 0; i < nuvalue; i++)
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setnilvalue(&u->uv[i].uv);
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return u;
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}
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