FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/lua/lstring.c

     /*
     ** $Id: lstring.c,v 2.26.1.1 2013/04/12 18:48:47 roberto Exp $
     ** String table (keeps all strings handled by Lua)
     ** See Copyright Notice in lua.h
     */
     
     
     #define lstring_c
     #define LUA_CORE
    
    #include <sys/lua/lua.h>
    
    #include "lmem.h"
    #include "lobject.h"
    #include "lstate.h"
    #include "lstring.h"
    
    
    /*
    ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to
    ** compute its hash
    */
    #if !defined(LUAI_HASHLIMIT)
    #define LUAI_HASHLIMIT          5
    #endif
    
    
    /*
    ** equality for long strings
    */
    int luaS_eqlngstr (TString *a, TString *b) {
      size_t len = a->tsv.len;
      lua_assert(a->tsv.tt == LUA_TLNGSTR && b->tsv.tt == LUA_TLNGSTR);
      return (a == b) ||  /* same instance or... */
        ((len == b->tsv.len) &&  /* equal length and ... */
         (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
    }
    
    
    /*
    ** equality for strings
    */
    int luaS_eqstr (TString *a, TString *b) {
      return (a->tsv.tt == b->tsv.tt) &&
             (a->tsv.tt == LUA_TSHRSTR ? eqshrstr(a, b) : luaS_eqlngstr(a, b));
    }
    
    
    unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
      unsigned int h = seed ^ cast(unsigned int, l);
      size_t l1;
      size_t step = (l >> LUAI_HASHLIMIT) + 1;
      for (l1 = l; l1 >= step; l1 -= step)
        h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1]));
      return h;
    }
    
    
    /*
    ** resizes the string table
    */
    void luaS_resize (lua_State *L, int newsize) {
      int i;
      stringtable *tb = &G(L)->strt;
      /* cannot resize while GC is traversing strings */
      luaC_runtilstate(L, ~bitmask(GCSsweepstring));
      if (newsize > tb->size) {
        luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
        for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL;
      }
      /* rehash */
      for (i=0; i<tb->size; i++) {
        GCObject *p = tb->hash[i];
        tb->hash[i] = NULL;
        while (p) {  /* for each node in the list */
          GCObject *next = gch(p)->next;  /* save next */
          unsigned int h = lmod(gco2ts(p)->hash, newsize);  /* new position */
          gch(p)->next = tb->hash[h];  /* chain it */
          tb->hash[h] = p;
          resetoldbit(p);  /* see MOVE OLD rule */
          p = next;
        }
      }
      if (newsize < tb->size) {
        /* shrinking slice must be empty */
        lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
        luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
      }
      tb->size = newsize;
    }
    
    
    /*
    ** creates a new string object
    */
    static TString *createstrobj (lua_State *L, const char *str, size_t l,
                                  int tag, unsigned int h, GCObject **list) {
      TString *ts;
      char *sbuf;
     size_t totalsize;  /* total size of TString object */
     totalsize = sizeof(TString) + ((l + 1) * sizeof(char));
     ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts;
     ts->tsv.len = l;
     ts->tsv.hash = h;
     ts->tsv.extra = 0;
     sbuf = (char *)(TString *)(ts + 1);
     memcpy(sbuf, str, l*sizeof(char));
     sbuf[l] = '\0';  /* ending 0 */
     return ts;
   }
   
   
   /*
   ** creates a new short string, inserting it into string table
   */
   static TString *newshrstr (lua_State *L, const char *str, size_t l,
                                          unsigned int h) {
     GCObject **list;  /* (pointer to) list where it will be inserted */
     stringtable *tb = &G(L)->strt;
     TString *s;
     if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
       luaS_resize(L, tb->size*2);  /* too crowded */
     list = &tb->hash[lmod(h, tb->size)];
     s = createstrobj(L, str, l, LUA_TSHRSTR, h, list);
     tb->nuse++;
     return s;
   }
   
   
   /*
   ** checks whether short string exists and reuses it or creates a new one
   */
   static TString *internshrstr (lua_State *L, const char *str, size_t l) {
     GCObject *o;
     global_State *g = G(L);
     unsigned int h = luaS_hash(str, l, g->seed);
     for (o = g->strt.hash[lmod(h, g->strt.size)];
          o != NULL;
          o = gch(o)->next) {
       TString *ts = rawgco2ts(o);
       if (h == ts->tsv.hash &&
           l == ts->tsv.len &&
           (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
         if (isdead(G(L), o))  /* string is dead (but was not collected yet)? */
           changewhite(o);  /* resurrect it */
         return ts;
       }
     }
     return newshrstr(L, str, l, h);  /* not found; create a new string */
   }
   
   
   /*
   ** new string (with explicit length)
   */
   TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
     if (l <= LUAI_MAXSHORTLEN)  /* short string? */
       return internshrstr(L, str, l);
     else {
       if (l + 1 > (MAX_SIZET - sizeof(TString))/sizeof(char))
         luaM_toobig(L);
       return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL);
     }
   }
   
   
   /*
   ** new zero-terminated string
   */
   TString *luaS_new (lua_State *L, const char *str) {
     return luaS_newlstr(L, str, strlen(str));
   }
   
   
   Udata *luaS_newudata (lua_State *L, size_t s, Table *e) {
     Udata *u;
     if (s > MAX_SIZET - sizeof(Udata))
       luaM_toobig(L);
     u = &luaC_newobj(L, LUA_TUSERDATA, sizeof(Udata) + s, NULL, 0)->u;
     u->uv.len = s;
     u->uv.metatable = NULL;
     u->uv.env = e;
     return u;
   }

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