Line data    Source code

       1             : /*
       2             : ** $Id: lstring.c,v 2.56.1.1 2017/04/19 17:20:42 roberto Exp $
       3             : ** String table (keeps all strings handled by Lua)
       4             : ** See Copyright Notice in lua.h
       5             : */
       6             : 
       7             : #define lstring_c
       8             : #define LUA_CORE
       9             : 
      10             : #include "lprefix.h"
      11             : 
      12             : 
      13             : #include <string.h>
      14             : 
      15             : #include "lua.h"
      16             : 
      17             : #include "ldebug.h"
      18             : #include "ldo.h"
      19             : #include "lmem.h"
      20             : #include "lobject.h"
      21             : #include "lstate.h"
      22             : #include "lstring.h"
      23             : 
      24             : 
      25             : #define MEMERRMSG       "not enough mem, increase SCR_HEAP_SIZE"
      26             : 
      27             : 
      28             : /*
      29             : ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to
      30             : ** compute its hash
      31             : */
      32             : #if !defined(LUAI_HASHLIMIT)
      33             : #define LUAI_HASHLIMIT          5
      34             : #endif
      35             : 
      36             : 
      37             : /*
      38             : ** equality for long strings
      39             : */
      40         273 : int luaS_eqlngstr (TString *a, TString *b) {
      41         273 :   size_t len = a->u.lnglen;
      42             :   lua_assert(a->tt == LUA_TLNGSTR && b->tt == LUA_TLNGSTR);
      43         302 :   return (a == b) ||  /* same instance or... */
      44          29 :     ((len == b->u.lnglen) &&  /* equal length and ... */
      45          18 :      (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
      46             : }
      47             : 
      48             : 
      49      155897 : unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
      50      155897 :   unsigned int h = seed ^ cast(unsigned int, l);
      51      155897 :   size_t step = (l >> LUAI_HASHLIMIT) + 1;
      52     1313147 :   for (; l >= step; l -= step)
      53     1157250 :     h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
      54      155897 :   return h;
      55             : }
      56             : 
      57             : 
      58        1323 : unsigned int luaS_hashlongstr (TString *ts) {
      59             :   lua_assert(ts->tt == LUA_TLNGSTR);
      60        1323 :   if (ts->extra == 0) {  /* no hash? */
      61         268 :     ts->hash = luaS_hash(getstr(ts), ts->u.lnglen, ts->hash);
      62         268 :     ts->extra = 1;  /* now it has its hash */
      63             :   }
      64        1323 :   return ts->hash;
      65             : }
      66             : 
      67             : 
      68             : /*
      69             : ** resizes the string table
      70             : */
      71         244 : void luaS_resize (lua_State *L, int newsize) {
      72             :   int i;
      73         244 :   stringtable *tb = &G(L)->strt;
      74         244 :   if (newsize > tb->size) {  /* grow table if needed */
      75         243 :     luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
      76       44275 :     for (i = tb->size; i < newsize; i++)
      77       44032 :       tb->hash[i] = NULL;
      78             :   }
      79       32884 :   for (i = 0; i < tb->size; i++) {  /* rehash */
      80       32640 :     TString *p = tb->hash[i];
      81       32640 :     tb->hash[i] = NULL;
      82       64410 :     while (p) {  /* for each node in the list */
      83       31770 :       TString *hnext = p->u.hnext;  /* save next */
      84       31770 :       unsigned int h = lmod(p->hash, newsize);  /* new position */
      85       31770 :       p->u.hnext = tb->hash[h];  /* chain it */
      86       31770 :       tb->hash[h] = p;
      87       31770 :       p = hnext;
      88             :     }
      89             :   }
      90         244 :   if (newsize < tb->size) {  /* shrink table if needed */
      91             :     /* vanishing slice should be empty */
      92             :     lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
      93           1 :     luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
      94             :   }
      95         244 :   tb->size = newsize;
      96         244 : }
      97             : 
      98             : 
      99             : /*
     100             : ** Clear API string cache. (Entries cannot be empty, so fill them with
     101             : ** a non-collectable string.)
     102             : */
     103       90640 : void luaS_clearcache (global_State *g) {
     104             :   int i, j;
     105     4894560 :   for (i = 0; i < STRCACHE_N; i++)
     106    14411760 :     for (j = 0; j < STRCACHE_M; j++) {
     107     9607840 :     if (iswhite(g->strcache[i][j]))  /* will entry be collected? */
     108         654 :       g->strcache[i][j] = g->memerrmsg;  /* replace it with something fixed */
     109             :     }
     110       90640 : }
     111             : 
     112             : 
     113             : /*
     114             : ** Initialize the string table and the string cache
     115             : */
     116          97 : void luaS_init (lua_State *L) {
     117          97 :   global_State *g = G(L);
     118             :   int i, j;
     119          97 :   luaS_resize(L, MINSTRTABSIZE);  /* initial size of string table */
     120             :   /* pre-create memory-error message */
     121          97 :   g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
     122          97 :   luaC_fix(L, obj2gco(g->memerrmsg));  /* it should never be collected */
     123        5238 :   for (i = 0; i < STRCACHE_N; i++)  /* fill cache with valid strings */
     124       15423 :     for (j = 0; j < STRCACHE_M; j++)
     125       10282 :       g->strcache[i][j] = g->memerrmsg;
     126          97 : }
     127             : 
     128             : 
     129             : 
     130             : /*
     131             : ** creates a new string object
     132             : */
     133       54906 : static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
     134             :   TString *ts;
     135             :   GCObject *o;
     136             :   size_t totalsize;  /* total size of TString object */
     137       54906 :   totalsize = sizelstring(l);
     138       54906 :   o = luaC_newobj(L, tag, totalsize);
     139       54906 :   ts = gco2ts(o);
     140       54906 :   ts->hash = h;
     141       54906 :   ts->extra = 0;
     142             : #pragma GCC diagnostic push
     143             : #if defined(__GNUC__) &&  __GNUC__ >= 10
     144             : #pragma GCC diagnostic ignored "-Wstringop-overflow"
     145             : #endif
     146       54906 :   getstr(ts)[l] = '\0';  /* ending 0 */
     147             : #pragma GCC diagnostic pop
     148       54906 :   return ts;
     149             : }
     150             : 
     151             : 
     152        1648 : TString *luaS_createlngstrobj (lua_State *L, size_t l) {
     153        1648 :   TString *ts = createstrobj(L, l, LUA_TLNGSTR, G(L)->seed);
     154        1648 :   ts->u.lnglen = l;
     155        1648 :   return ts;
     156             : }
     157             : 
     158             : 
     159       41038 : void luaS_remove (lua_State *L, TString *ts) {
     160       41038 :   stringtable *tb = &G(L)->strt;
     161       41038 :   TString **p = &tb->hash[lmod(ts->hash, tb->size)];
     162       43827 :   while (*p != ts)  /* find previous element */
     163        2789 :     p = &(*p)->u.hnext;
     164       41038 :   *p = (*p)->u.hnext;  /* remove element from its list */
     165       41038 :   tb->nuse--;
     166       41038 : }
     167             : 
     168             : 
     169             : /*
     170             : ** checks whether short string exists and reuses it or creates a new one
     171             : */
     172      155532 : static TString *internshrstr (lua_State *L, const char *str, size_t l) {
     173             :   TString *ts;
     174      155532 :   global_State *g = G(L);
     175      155532 :   unsigned int h = luaS_hash(str, l, g->seed);
     176      155532 :   TString **list = &g->strt.hash[lmod(h, g->strt.size)];
     177             :   lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
     178      215715 :   for (ts = *list; ts != NULL; ts = ts->u.hnext) {
     179      162457 :     if (l == ts->shrlen &&
     180      107231 :         (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
     181             :       /* found! */
     182      102274 :       if (isdead(g, ts))  /* dead (but not collected yet)? */
     183           0 :         changewhite(ts);  /* resurrect it */
     184      102274 :       return ts;
     185             :     }
     186             :   }
     187       53258 :   if (g->strt.nuse >= g->strt.size && g->strt.size <= MAX_INT/2) {
     188         146 :     luaS_resize(L, g->strt.size * 2);
     189         146 :     list = &g->strt.hash[lmod(h, g->strt.size)];  /* recompute with new size */
     190             :   }
     191       53258 :   ts = createstrobj(L, l, LUA_TSHRSTR, h);
     192       53258 :   memcpy(getstr(ts), str, l * sizeof(char));
     193       53258 :   ts->shrlen = cast_byte(l);
     194       53258 :   ts->u.hnext = *list;
     195       53258 :   *list = ts;
     196       53258 :   g->strt.nuse++;
     197       53258 :   return ts;
     198             : }
     199             : 
     200             : 
     201             : /*
     202             : ** new string (with explicit length)
     203             : */
     204      156937 : TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
     205      156937 :   if (l <= LUAI_MAXSHORTLEN)  /* short string? */
     206      155532 :     return internshrstr(L, str, l);
     207             :   else {
     208             :     TString *ts;
     209        1405 :     if (l >= (MAX_SIZE - sizeof(TString))/sizeof(char))
     210           0 :       luaM_toobig(L);
     211        1405 :     ts = luaS_createlngstrobj(L, l);
     212        1405 :     memcpy(getstr(ts), str, l * sizeof(char));
     213        1405 :     return ts;
     214             :   }
     215             : }
     216             : 
     217             : 
     218             : /*
     219             : ** Create or reuse a zero-terminated string, first checking in the
     220             : ** cache (using the string address as a key). The cache can contain
     221             : ** only zero-terminated strings, so it is safe to use 'strcmp' to
     222             : ** check hits.
     223             : */
     224     4122171 : TString *luaS_new (lua_State *L, const char *str) {
     225     4122171 :   unsigned int i = point2uint(str) % STRCACHE_N;  /* hash */
     226             :   int j;
     227     4122171 :   TString **p = G(L)->strcache[i];
     228     4731349 :   for (j = 0; j < STRCACHE_M; j++) {
     229     4715902 :     if (strcmp(str, getstr(p[j])) == 0)  /* hit? */
     230     4106724 :       return p[j];  /* that is it */
     231             :   }
     232             :   /* normal route */
     233       30894 :   for (j = STRCACHE_M - 1; j > 0; j--)
     234       15447 :     p[j] = p[j - 1];  /* move out last element */
     235             :   /* new element is first in the list */
     236       15447 :   p[0] = luaS_newlstr(L, str, strlen(str));
     237       15447 :   return p[0];
     238             : }
     239             : 
     240             : 
     241      902229 : Udata *luaS_newudata (lua_State *L, size_t s) {
     242             :   Udata *u;
     243             :   GCObject *o;
     244      902229 :   if (s > MAX_SIZE - sizeof(Udata))
     245           0 :     luaM_toobig(L);
     246      902229 :   o = luaC_newobj(L, LUA_TUSERDATA, sizeludata(s));
     247      902229 :   u = gco2u(o);
     248      902229 :   u->len = s;
     249      902229 :   u->metatable = NULL;
     250      902229 :   setuservalue(L, u, luaO_nilobject);
     251      902229 :   return u;
     252             : }
     253             :