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Member "memcached-1.6.15/vendor/lua/src/lstring.c" (1 Oct 2021, 7499 Bytes) of package /linux/www/memcached-1.6.15.tar.gz:


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    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