ceph/src/civetweb/src/third_party/lua-5.3.1/src/lstring.c

   1 /*
   2 ** $Id: lstring.c,v 2.49 2015/06/01 16:34:37 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 memory"
  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 int luaS_eqlngstr (TString *a, TString *b) {
  41   size_t len = a->u.lnglen;
  42   lua_assert(a->tt == LUA_TLNGSTR && b->tt == LUA_TLNGSTR);
  43   return (a == b) ||  /* same instance or... */
  44     ((len == b->u.lnglen) &&  /* equal length and ... */
  45      (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
  46 }
  47
  48
  49 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
  50   unsigned int h = seed ^ cast(unsigned int, l);
  51   size_t l1;
  52   size_t step = (l >> LUAI_HASHLIMIT) + 1;
  53   for (l1 = l; l1 >= step; l1 -= step)
  54     h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1]));
  55   return h;
  56 }
  57
  58
  59 /*
  60 ** resizes the string table
  61 */
  62 void luaS_resize (lua_State *L, int newsize) {
  63   int i;
  64   stringtable *tb = &G(L)->strt;
  65   if (newsize > tb->size) {  /* grow table if needed */
  66     luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
  67     for (i = tb->size; i < newsize; i++)
  68       tb->hash[i] = NULL;
  69   }
  70   for (i = 0; i < tb->size; i++) {  /* rehash */
  71     TString *p = tb->hash[i];
  72     tb->hash[i] = NULL;
  73     while (p) {  /* for each node in the list */
  74       TString *hnext = p->u.hnext;  /* save next */
  75       unsigned int h = lmod(p->hash, newsize);  /* new position */
  76       p->u.hnext = tb->hash[h];  /* chain it */
  77       tb->hash[h] = p;
  78       p = hnext;
  79     }
  80   }
  81   if (newsize < tb->size) {  /* shrink table if needed */
  82     /* vanishing slice should be empty */
  83     lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
  84     luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
  85   }
  86   tb->size = newsize;
  87 }
  88
  89
  90 /*
  91 ** Clear API string cache. (Entries cannot be empty, so fill them with
  92 ** a non-collectable string.)
  93 */
  94 void luaS_clearcache (global_State *g) {
  95   int i;
  96   for (i = 0; i < STRCACHE_SIZE; i++) {
  97     if (iswhite(g->strcache[i][0]))  /* will entry be collected? */
  98       g->strcache[i][0] = g->memerrmsg;  /* replace it with something fixed */
  99   }
 100 }
 101
 102
 103 /*
 104 ** Initialize the string table and the string cache
 105 */
 106 void luaS_init (lua_State *L) {
 107   global_State *g = G(L);
 108   int i;
 109   luaS_resize(L, MINSTRTABSIZE);  /* initial size of string table */
 110   /* pre-create memory-error message */
 111   g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
 112   luaC_fix(L, obj2gco(g->memerrmsg));  /* it should never be collected */
 113   for (i = 0; i < STRCACHE_SIZE; i++)  /* fill cache with valid strings */
 114     g->strcache[i][0] = g->memerrmsg;
 115 }
 116
 117
 118
 119 /*
 120 ** creates a new string object
 121 */
 122 static TString *createstrobj (lua_State *L, const char *str, size_t l,
 123                               int tag, unsigned int h) {
 124   TString *ts;
 125   GCObject *o;
 126   size_t totalsize;  /* total size of TString object */
 127   totalsize = sizelstring(l);
 128   o = luaC_newobj(L, tag, totalsize);
 129   ts = gco2ts(o);
 130   ts->hash = h;
 131   ts->extra = 0;
 132   memcpy(getaddrstr(ts), str, l * sizeof(char));
 133   getaddrstr(ts)[l] = '\0';  /* ending 0 */
 134   return ts;
 135 }
 136
 137
 138 void luaS_remove (lua_State *L, TString *ts) {
 139   stringtable *tb = &G(L)->strt;
 140   TString **p = &tb->hash[lmod(ts->hash, tb->size)];
 141   while (*p != ts)  /* find previous element */
 142     p = &(*p)->u.hnext;
 143   *p = (*p)->u.hnext;  /* remove element from its list */
 144   tb->nuse--;
 145 }
 146
 147
 148 /*
 149 ** checks whether short string exists and reuses it or creates a new one
 150 */
 151 static TString *internshrstr (lua_State *L, const char *str, size_t l) {
 152   TString *ts;
 153   global_State *g = G(L);
 154   unsigned int h = luaS_hash(str, l, g->seed);
 155   TString **list = &g->strt.hash[lmod(h, g->strt.size)];
 156   for (ts = *list; ts != NULL; ts = ts->u.hnext) {
 157     if (l == ts->shrlen &&
 158         (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
 159       /* found! */
 160       if (isdead(g, ts))  /* dead (but not collected yet)? */
 161         changewhite(ts);  /* resurrect it */
 162       return ts;
 163     }
 164   }
 165   if (g->strt.nuse >= g->strt.size && g->strt.size <= MAX_INT/2) {
 166     luaS_resize(L, g->strt.size * 2);
 167     list = &g->strt.hash[lmod(h, g->strt.size)];  /* recompute with new size */
 168   }
 169   ts = createstrobj(L, str, l, LUA_TSHRSTR, h);
 170   ts->shrlen = cast_byte(l);
 171   ts->u.hnext = *list;
 172   *list = ts;
 173   g->strt.nuse++;
 174   return ts;
 175 }
 176
 177
 178 /*
 179 ** new string (with explicit length)
 180 */
 181 TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
 182   if (l <= LUAI_MAXSHORTLEN)  /* short string? */
 183     return internshrstr(L, str, l);
 184   else {
 185     TString *ts;
 186     if (l + 1 > (MAX_SIZE - sizeof(TString))/sizeof(char))
 187       luaM_toobig(L);
 188     ts = createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed);
 189     ts->u.lnglen = l;
 190     return ts;
 191   }
 192 }
 193
 194
 195 /*
 196 ** Create or reuse a zero-terminated string, first checking in the
 197 ** cache (using the string address as a key). The cache can contain
 198 ** only zero-terminated strings, so it is safe to use 'strcmp' to
 199 ** check hits.
 200 */
 201 TString *luaS_new (lua_State *L, const char *str) {
 202   unsigned int i = point2uint(str) % STRCACHE_SIZE;  /* hash */
 203   TString **p = G(L)->strcache[i];
 204   if (strcmp(str, getstr(p[0])) == 0)  /* hit? */
 205     return p[0];  /* that it is */
 206   else {  /* normal route */
 207     TString *s = luaS_newlstr(L, str, strlen(str));
 208     p[0] = s;
 209     return s;
 210   }
 211 }
 212
 213
 214 Udata *luaS_newudata (lua_State *L, size_t s) {
 215   Udata *u;
 216   GCObject *o;
 217   if (s > MAX_SIZE - sizeof(Udata))
 218     luaM_toobig(L);
 219   o = luaC_newobj(L, LUA_TUSERDATA, sizeludata(s));
 220   u = gco2u(o);
 221   u->len = s;
 222   u->metatable = NULL;
 223   setuservalue(L, u, luaO_nilobject);
 224   return u;
 225 }
 226