nanocoat/lib/3rdparty/lua/lstring.c

   1 /*
   2 ** $Id: lstring.c $
   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 /*
  26 ** Maximum size for string table.
  27 */
  28 #define MAXSTRTB        cast_int(luaM_limitN(MAX_INT, TString*))
  29
  30
  31 /*
  32 ** equality for long strings
  33 */
  34 int luaS_eqlngstr (TString *a, TString *b) {
  35   size_t len = a->u.lnglen;
  36   lua_assert(a->tt == LUA_VLNGSTR && b->tt == LUA_VLNGSTR);
  37   return (a == b) ||  /* same instance or... */
  38     ((len == b->u.lnglen) &&  /* equal length and ... */
  39      (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
  40 }
  41
  42
  43 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
  44   unsigned int h = seed ^ cast_uint(l);
  45   for (; l > 0; l--)
  46     h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
  47   return h;
  48 }
  49
  50
  51 unsigned int luaS_hashlongstr (TString *ts) {
  52   lua_assert(ts->tt == LUA_VLNGSTR);
  53   if (ts->extra == 0) {  /* no hash? */
  54     size_t len = ts->u.lnglen;
  55     ts->hash = luaS_hash(getstr(ts), len, ts->hash);
  56     ts->extra = 1;  /* now it has its hash */
  57   }
  58   return ts->hash;
  59 }
  60
  61
  62 static void tablerehash (TString **vect, int osize, int nsize) {
  63   int i;
  64   for (i = osize; i < nsize; i++)  /* clear new elements */
  65     vect[i] = NULL;
  66   for (i = 0; i < osize; i++) {  /* rehash old part of the array */
  67     TString *p = vect[i];
  68     vect[i] = NULL;
  69     while (p) {  /* for each string in the list */
  70       TString *hnext = p->u.hnext;  /* save next */
  71       unsigned int h = lmod(p->hash, nsize);  /* new position */
  72       p->u.hnext = vect[h];  /* chain it into array */
  73       vect[h] = p;
  74       p = hnext;
  75     }
  76   }
  77 }
  78
  79
  80 /*
  81 ** Resize the string table. If allocation fails, keep the current size.
  82 ** (This can degrade performance, but any non-zero size should work
  83 ** correctly.)
  84 */
  85 void luaS_resize (lua_State *L, int nsize) {
  86   stringtable *tb = &G(L)->strt;
  87   int osize = tb->size;
  88   TString **newvect;
  89   if (nsize < osize)  /* shrinking table? */
  90     tablerehash(tb->hash, osize, nsize);  /* depopulate shrinking part */
  91   newvect = luaM_reallocvector(L, tb->hash, osize, nsize, TString*);
  92   if (l_unlikely(newvect == NULL)) {  /* reallocation failed? */
  93     if (nsize < osize)  /* was it shrinking table? */
  94       tablerehash(tb->hash, nsize, osize);  /* restore to original size */
  95     /* leave table as it was */
  96   }
  97   else {  /* allocation succeeded */
  98     tb->hash = newvect;
  99     tb->size = nsize;
 100     if (nsize > osize)
 101       tablerehash(newvect, osize, nsize);  /* rehash for new size */
 102   }
 103 }
 104
 105
 106 /*
 107 ** Clear API string cache. (Entries cannot be empty, so fill them with
 108 ** a non-collectable string.)
 109 */
 110 void luaS_clearcache (global_State *g) {
 111   int i, j;
 112   for (i = 0; i < STRCACHE_N; i++)
 113     for (j = 0; j < STRCACHE_M; j++) {
 114       if (iswhite(g->strcache[i][j]))  /* will entry be collected? */
 115         g->strcache[i][j] = g->memerrmsg;  /* replace it with something fixed */
 116     }
 117 }
 118
 119
 120 /*
 121 ** Initialize the string table and the string cache
 122 */
 123 void luaS_init (lua_State *L) {
 124   global_State *g = G(L);
 125   int i, j;
 126   stringtable *tb = &G(L)->strt;
 127   tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
 128   tablerehash(tb->hash, 0, MINSTRTABSIZE);  /* clear array */
 129   tb->size = MINSTRTABSIZE;
 130   /* pre-create memory-error message */
 131   g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
 132   luaC_fix(L, obj2gco(g->memerrmsg));  /* it should never be collected */
 133   for (i = 0; i < STRCACHE_N; i++)  /* fill cache with valid strings */
 134     for (j = 0; j < STRCACHE_M; j++)
 135       g->strcache[i][j] = g->memerrmsg;
 136 }
 137
 138
 139
 140 /*
 141 ** creates a new string object
 142 */
 143 static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
 144   TString *ts;
 145   GCObject *o;
 146   size_t totalsize;  /* total size of TString object */
 147   totalsize = sizelstring(l);
 148   o = luaC_newobj(L, tag, totalsize);
 149   ts = gco2ts(o);
 150   ts->hash = h;
 151   ts->extra = 0;
 152   getstr(ts)[l] = '\0';  /* ending 0 */
 153   return ts;
 154 }
 155
 156
 157 TString *luaS_createlngstrobj (lua_State *L, size_t l) {
 158   TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
 159   ts->u.lnglen = l;
 160   return ts;
 161 }
 162
 163
 164 void luaS_remove (lua_State *L, TString *ts) {
 165   stringtable *tb = &G(L)->strt;
 166   TString **p = &tb->hash[lmod(ts->hash, tb->size)];
 167   while (*p != ts)  /* find previous element */
 168     p = &(*p)->u.hnext;
 169   *p = (*p)->u.hnext;  /* remove element from its list */
 170   tb->nuse--;
 171 }
 172
 173
 174 static void growstrtab (lua_State *L, stringtable *tb) {
 175   if (l_unlikely(tb->nuse == MAX_INT)) {  /* too many strings? */
 176     luaC_fullgc(L, 1);  /* try to free some... */
 177     if (tb->nuse == MAX_INT)  /* still too many? */
 178       luaM_error(L);  /* cannot even create a message... */
 179   }
 180   if (tb->size <= MAXSTRTB / 2)  /* can grow string table? */
 181     luaS_resize(L, tb->size * 2);
 182 }
 183
 184
 185 /*
 186 ** Checks whether short string exists and reuses it or creates a new one.
 187 */
 188 static TString *internshrstr (lua_State *L, const char *str, size_t l) {
 189   TString *ts;
 190   global_State *g = G(L);
 191   stringtable *tb = &g->strt;
 192   unsigned int h = luaS_hash(str, l, g->seed);
 193   TString **list = &tb->hash[lmod(h, tb->size)];
 194   lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
 195   for (ts = *list; ts != NULL; ts = ts->u.hnext) {
 196     if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
 197       /* found! */
 198       if (isdead(g, ts))  /* dead (but not collected yet)? */
 199         changewhite(ts);  /* resurrect it */
 200       return ts;
 201     }
 202   }
 203   /* else must create a new string */
 204   if (tb->nuse >= tb->size) {  /* need to grow string table? */
 205     growstrtab(L, tb);
 206     list = &tb->hash[lmod(h, tb->size)];  /* rehash with new size */
 207   }
 208   ts = createstrobj(L, l, LUA_VSHRSTR, h);
 209   memcpy(getstr(ts), str, l * sizeof(char));
 210   ts->shrlen = cast_byte(l);
 211   ts->u.hnext = *list;
 212   *list = ts;
 213   tb->nuse++;
 214   return ts;
 215 }
 216
 217
 218 /*
 219 ** new string (with explicit length)
 220 */
 221 TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
 222   if (l <= LUAI_MAXSHORTLEN)  /* short string? */
 223     return internshrstr(L, str, l);
 224   else {
 225     TString *ts;
 226     if (l_unlikely(l >= (MAX_SIZE - sizeof(TString))/sizeof(char)))
 227       luaM_toobig(L);
 228     ts = luaS_createlngstrobj(L, l);
 229     memcpy(getstr(ts), str, l * sizeof(char));
 230     return ts;
 231   }
 232 }
 233
 234
 235 /*
 236 ** Create or reuse a zero-terminated string, first checking in the
 237 ** cache (using the string address as a key). The cache can contain
 238 ** only zero-terminated strings, so it is safe to use 'strcmp' to
 239 ** check hits.
 240 */
 241 TString *luaS_new (lua_State *L, const char *str) {
 242   unsigned int i = point2uint(str) % STRCACHE_N;  /* hash */
 243   int j;
 244   TString **p = G(L)->strcache[i];
 245   for (j = 0; j < STRCACHE_M; j++) {
 246     if (strcmp(str, getstr(p[j])) == 0)  /* hit? */
 247       return p[j];  /* that is it */
 248   }
 249   /* normal route */
 250   for (j = STRCACHE_M - 1; j > 0; j--)
 251     p[j] = p[j - 1];  /* move out last element */
 252   /* new element is first in the list */
 253   p[0] = luaS_newlstr(L, str, strlen(str));
 254   return p[0];
 255 }
 256
 257
 258 Udata *luaS_newudata (lua_State *L, size_t s, int nuvalue) {
 259   Udata *u;
 260   int i;
 261   GCObject *o;
 262   if (l_unlikely(s > MAX_SIZE - udatamemoffset(nuvalue)))
 263     luaM_toobig(L);
 264   o = luaC_newobj(L, LUA_VUSERDATA, sizeudata(nuvalue, s));
 265   u = gco2u(o);
 266   u->len = s;
 267   u->nuvalue = nuvalue;
 268   u->metatable = NULL;
 269   for (i = 0; i < nuvalue; i++)
 270     setnilvalue(&u->uv[i].uv);
 271   return u;
 272 }
 273