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

     /*
     ** $Id: ltable.c,v 2.72.1.1 2013/04/12 18:48:47 roberto Exp $
     ** Lua tables (hash)
     ** See Copyright Notice in lua.h
     */
     
     
     /*
     ** Implementation of tables (aka arrays, objects, or hash tables).
    ** Tables keep its elements in two parts: an array part and a hash part.
    ** Non-negative integer keys are all candidates to be kept in the array
    ** part. The actual size of the array is the largest `n' such that at
    ** least half the slots between 0 and n are in use.
    ** Hash uses a mix of chained scatter table with Brent's variation.
    ** A main invariant of these tables is that, if an element is not
    ** in its main position (i.e. the `original' position that its hash gives
    ** to it), then the colliding element is in its own main position.
    ** Hence even when the load factor reaches 100%, performance remains good.
    */
    
    
    #define ltable_c
    #define LUA_CORE
    
    #include <sys/lua/lua.h>
    
    #include "ldebug.h"
    #include "ldo.h"
    #include "lgc.h"
    #include "lmem.h"
    #include "lobject.h"
    #include "lstate.h"
    #include "lstring.h"
    #include "ltable.h"
    #include "lvm.h"
    
    
    /*
    ** max size of array part is 2^MAXBITS
    */
    #if LUAI_BITSINT >= 32
    #define MAXBITS         30
    #else
    #define MAXBITS         (LUAI_BITSINT-2)
    #endif
    
    #define MAXASIZE        (1 << MAXBITS)
    
    
    #define hashpow2(t,n)           (gnode(t, lmod((n), sizenode(t))))
    
    #define hashstr(t,str)          hashpow2(t, (str)->tsv.hash)
    #define hashboolean(t,p)        hashpow2(t, p)
    
    
    /*
    ** for some types, it is better to avoid modulus by power of 2, as
    ** they tend to have many 2 factors.
    */
    #define hashmod(t,n)    (gnode(t, ((n) % ((sizenode(t)-1)|1))))
    
    
    #define hashpointer(t,p)        hashmod(t, IntPoint(p))
    
    
    #define dummynode               (&dummynode_)
    
    #define isdummy(n)              ((n) == dummynode)
    
    static const Node dummynode_ = {
      {NILCONSTANT},  /* value */
      {{NILCONSTANT, NULL}}  /* key */
    };
    
    
    /*
    ** hash for lua_Numbers
    */
    static Node *hashnum (const Table *t, lua_Number n) {
      int i;
      luai_hashnum(i, n);
      if (i < 0) {
        if (cast(unsigned int, i) == 0u - i)  /* use unsigned to avoid overflows */
          i = 0;  /* handle INT_MIN */
        i = -i;  /* must be a positive value */
      }
      return hashmod(t, i);
    }
    
    
    
    /*
    ** returns the `main' position of an element in a table (that is, the index
    ** of its hash value)
    */
    static Node *mainposition (const Table *t, const TValue *key) {
      switch (ttype(key)) {
        case LUA_TNUMBER:
          return hashnum(t, nvalue(key));
       case LUA_TLNGSTR: {
         TString *s = rawtsvalue(key);
         if (s->tsv.extra == 0) {  /* no hash? */
           s->tsv.hash = luaS_hash(getstr(s), s->tsv.len, s->tsv.hash);
           s->tsv.extra = 1;  /* now it has its hash */
         }
         return hashstr(t, rawtsvalue(key));
       }
       case LUA_TSHRSTR:
         return hashstr(t, rawtsvalue(key));
       case LUA_TBOOLEAN:
         return hashboolean(t, bvalue(key));
       case LUA_TLIGHTUSERDATA:
         return hashpointer(t, pvalue(key));
       case LUA_TLCF:
         return hashpointer(t, fvalue(key));
       default:
         return hashpointer(t, gcvalue(key));
     }
   }
   
   
   /*
   ** returns the index for `key' if `key' is an appropriate key to live in
   ** the array part of the table, -1 otherwise.
   */
   static int arrayindex (const TValue *key) {
     if (ttisnumber(key)) {
       lua_Number n = nvalue(key);
       int k;
       lua_number2int(k, n);
       if (luai_numeq(cast_num(k), n))
         return k;
     }
     return -1;  /* `key' did not match some condition */
   }
   
   
   /*
   ** returns the index of a `key' for table traversals. First goes all
   ** elements in the array part, then elements in the hash part. The
   ** beginning of a traversal is signaled by -1.
   */
   static int findindex (lua_State *L, Table *t, StkId key) {
     int i;
     if (ttisnil(key)) return -1;  /* first iteration */
     i = arrayindex(key);
     if (0 < i && i <= t->sizearray)  /* is `key' inside array part? */
       return i-1;  /* yes; that's the index (corrected to C) */
     else {
       Node *n = mainposition(t, key);
       for (;;) {  /* check whether `key' is somewhere in the chain */
         /* key may be dead already, but it is ok to use it in `next' */
         if (luaV_rawequalobj(gkey(n), key) ||
               (ttisdeadkey(gkey(n)) && iscollectable(key) &&
                deadvalue(gkey(n)) == gcvalue(key))) {
           i = cast_int(n - gnode(t, 0));  /* key index in hash table */
           /* hash elements are numbered after array ones */
           return i + t->sizearray;
         }
         else n = gnext(n);
         if (n == NULL)
           luaG_runerror(L, "invalid key to " LUA_QL("next"));  /* key not found */
       }
     }
   }
   
   
   int luaH_next (lua_State *L, Table *t, StkId key) {
     int i = findindex(L, t, key);  /* find original element */
     for (i++; i < t->sizearray; i++) {  /* try first array part */
       if (!ttisnil(&t->array[i])) {  /* a non-nil value? */
         setnvalue(key, cast_num(i+1));
         setobj2s(L, key+1, &t->array[i]);
         return 1;
       }
     }
     for (i -= t->sizearray; i < sizenode(t); i++) {  /* then hash part */
       if (!ttisnil(gval(gnode(t, i)))) {  /* a non-nil value? */
         setobj2s(L, key, gkey(gnode(t, i)));
         setobj2s(L, key+1, gval(gnode(t, i)));
         return 1;
       }
     }
     return 0;  /* no more elements */
   }
   
   
   /*
   ** {=============================================================
   ** Rehash
   ** ==============================================================
   */
   
   
   static int computesizes (int nums[], int *narray) {
     int i;
     int twotoi;  /* 2^i */
     int a = 0;  /* number of elements smaller than 2^i */
     int na = 0;  /* number of elements to go to array part */
     int n = 0;  /* optimal size for array part */
     for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
       if (nums[i] > 0) {
         a += nums[i];
         if (a > twotoi/2) {  /* more than half elements present? */
           n = twotoi;  /* optimal size (till now) */
           na = a;  /* all elements smaller than n will go to array part */
         }
       }
       if (a == *narray) break;  /* all elements already counted */
     }
     *narray = n;
     lua_assert(*narray/2 <= na && na <= *narray);
     return na;
   }
   
   
   static int countint (const TValue *key, int *nums) {
     int k = arrayindex(key);
     if (0 < k && k <= MAXASIZE) {  /* is `key' an appropriate array index? */
       nums[luaO_ceillog2(k)]++;  /* count as such */
       return 1;
     }
     else
       return 0;
   }
   
   
   static int numusearray (const Table *t, int *nums) {
     int lg;
     int ttlg;  /* 2^lg */
     int ause = 0;  /* summation of `nums' */
     int i = 1;  /* count to traverse all array keys */
     for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) {  /* for each slice */
       int lc = 0;  /* counter */
       int lim = ttlg;
       if (lim > t->sizearray) {
         lim = t->sizearray;  /* adjust upper limit */
         if (i > lim)
           break;  /* no more elements to count */
       }
       /* count elements in range (2^(lg-1), 2^lg] */
       for (; i <= lim; i++) {
         if (!ttisnil(&t->array[i-1]))
           lc++;
       }
       nums[lg] += lc;
       ause += lc;
     }
     return ause;
   }
   
   
   static int numusehash (const Table *t, int *nums, int *pnasize) {
     int totaluse = 0;  /* total number of elements */
     int ause = 0;  /* summation of `nums' */
     int i = sizenode(t);
     while (i--) {
       Node *n = &t->node[i];
       if (!ttisnil(gval(n))) {
         ause += countint(gkey(n), nums);
         totaluse++;
       }
     }
     *pnasize += ause;
     return totaluse;
   }
   
   
   static void setarrayvector (lua_State *L, Table *t, int size) {
     int i;
     luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
     for (i=t->sizearray; i<size; i++)
        setnilvalue(&t->array[i]);
     t->sizearray = size;
   }
   
   
   static void setnodevector (lua_State *L, Table *t, int size) {
     int lsize;
     if (size == 0) {  /* no elements to hash part? */
       t->node = cast(Node *, dummynode);  /* use common `dummynode' */
       lsize = 0;
     }
     else {
       int i;
       lsize = luaO_ceillog2(size);
       if (lsize > MAXBITS)
         luaG_runerror(L, "table overflow");
       size = twoto(lsize);
       t->node = luaM_newvector(L, size, Node);
       for (i=0; i<size; i++) {
         Node *n = gnode(t, i);
         gnext(n) = NULL;
         setnilvalue(gkey(n));
         setnilvalue(gval(n));
       }
     }
     t->lsizenode = cast_byte(lsize);
     t->lastfree = gnode(t, size);  /* all positions are free */
   }
   
   
   void luaH_resize (lua_State *L, Table *t, int nasize, int nhsize) {
     int i;
     int oldasize = t->sizearray;
     int oldhsize = t->lsizenode;
     Node *nold = t->node;  /* save old hash ... */
     if (nasize > oldasize)  /* array part must grow? */
       setarrayvector(L, t, nasize);
     /* create new hash part with appropriate size */
     setnodevector(L, t, nhsize);
     if (nasize < oldasize) {  /* array part must shrink? */
       t->sizearray = nasize;
       /* re-insert elements from vanishing slice */
       for (i=nasize; i<oldasize; i++) {
         if (!ttisnil(&t->array[i]))
           luaH_setint(L, t, i + 1, &t->array[i]);
       }
       /* shrink array */
       luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
     }
     /* re-insert elements from hash part */
     for (i = twoto(oldhsize) - 1; i >= 0; i--) {
       Node *old = nold+i;
       if (!ttisnil(gval(old))) {
         /* doesn't need barrier/invalidate cache, as entry was
            already present in the table */
         setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
       }
     }
     if (!isdummy(nold))
       luaM_freearray(L, nold, cast(size_t, twoto(oldhsize))); /* free old array */
   }
   
   
   void luaH_resizearray (lua_State *L, Table *t, int nasize) {
     int nsize = isdummy(t->node) ? 0 : sizenode(t);
     luaH_resize(L, t, nasize, nsize);
   }
   
   
   static void rehash (lua_State *L, Table *t, const TValue *ek) {
     int nasize, na;
     int nums[MAXBITS+1];  /* nums[i] = number of keys with 2^(i-1) < k <= 2^i */
     int i;
     int totaluse;
     for (i=0; i<=MAXBITS; i++) nums[i] = 0;  /* reset counts */
     nasize = numusearray(t, nums);  /* count keys in array part */
     totaluse = nasize;  /* all those keys are integer keys */
     totaluse += numusehash(t, nums, &nasize);  /* count keys in hash part */
     /* count extra key */
     nasize += countint(ek, nums);
     totaluse++;
     /* compute new size for array part */
     na = computesizes(nums, &nasize);
     /* resize the table to new computed sizes */
     luaH_resize(L, t, nasize, totaluse - na);
   }
   
   
   
   /*
   ** }=============================================================
   */
   
   
   Table *luaH_new (lua_State *L) {
     Table *t = &luaC_newobj(L, LUA_TTABLE, sizeof(Table), NULL, 0)->h;
     t->metatable = NULL;
     t->flags = cast_byte(~0);
     t->array = NULL;
     t->sizearray = 0;
     setnodevector(L, t, 0);
     return t;
   }
   
   
   void luaH_free (lua_State *L, Table *t) {
     if (!isdummy(t->node))
       luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
     luaM_freearray(L, t->array, t->sizearray);
     luaM_free(L, t);
   }
   
   
   static Node *getfreepos (Table *t) {
     while (t->lastfree > t->node) {
       t->lastfree--;
       if (ttisnil(gkey(t->lastfree)))
         return t->lastfree;
     }
     return NULL;  /* could not find a free place */
   }
   
   
   
   /*
   ** inserts a new key into a hash table; first, check whether key's main
   ** position is free. If not, check whether colliding node is in its main
   ** position or not: if it is not, move colliding node to an empty place and
   ** put new key in its main position; otherwise (colliding node is in its main
   ** position), new key goes to an empty position.
   */
   TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
     Node *mp;
     if (ttisnil(key)) luaG_runerror(L, "table index is nil");
   #if defined LUA_HAS_FLOAT_NUMBERS
     else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
       luaG_runerror(L, "table index is NaN");
   #endif
     mp = mainposition(t, key);
     if (!ttisnil(gval(mp)) || isdummy(mp)) {  /* main position is taken? */
       Node *othern;
       Node *n = getfreepos(t);  /* get a free place */
       if (n == NULL) {  /* cannot find a free place? */
         rehash(L, t, key);  /* grow table */
         /* whatever called 'newkey' take care of TM cache and GC barrier */
         return luaH_set(L, t, key);  /* insert key into grown table */
       }
       lua_assert(!isdummy(n));
       othern = mainposition(t, gkey(mp));
       if (othern != mp) {  /* is colliding node out of its main position? */
         /* yes; move colliding node into free position */
         while (gnext(othern) != mp) othern = gnext(othern);  /* find previous */
         gnext(othern) = n;  /* redo the chain with `n' in place of `mp' */
         *n = *mp;  /* copy colliding node into free pos. (mp->next also goes) */
         gnext(mp) = NULL;  /* now `mp' is free */
         setnilvalue(gval(mp));
       }
       else {  /* colliding node is in its own main position */
         /* new node will go into free position */
         gnext(n) = gnext(mp);  /* chain new position */
         gnext(mp) = n;
         mp = n;
       }
     }
     setobj2t(L, gkey(mp), key);
     luaC_barrierback(L, obj2gco(t), key);
     lua_assert(ttisnil(gval(mp)));
     return gval(mp);
   }
   
   
   /*
   ** search function for integers
   */
   const TValue *luaH_getint (Table *t, int key) {
     /* (1 <= key && key <= t->sizearray) */
     if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
       return &t->array[key-1];
     else {
       lua_Number nk = cast_num(key);
       Node *n = hashnum(t, nk);
       do {  /* check whether `key' is somewhere in the chain */
         if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
           return gval(n);  /* that's it */
         else n = gnext(n);
       } while (n);
       return luaO_nilobject;
     }
   }
   
   
   /*
   ** search function for short strings
   */
   const TValue *luaH_getstr (Table *t, TString *key) {
     Node *n = hashstr(t, key);
     lua_assert(key->tsv.tt == LUA_TSHRSTR);
     do {  /* check whether `key' is somewhere in the chain */
       if (ttisshrstring(gkey(n)) && eqshrstr(rawtsvalue(gkey(n)), key))
         return gval(n);  /* that's it */
       else n = gnext(n);
     } while (n);
     return luaO_nilobject;
   }
   
   
   /*
   ** main search function
   */
   const TValue *luaH_get (Table *t, const TValue *key) {
     switch (ttype(key)) {
       case LUA_TSHRSTR: return luaH_getstr(t, rawtsvalue(key));
       case LUA_TNIL: return luaO_nilobject;
       case LUA_TNUMBER: {
         int k;
         lua_Number n = nvalue(key);
         lua_number2int(k, n);
         if (luai_numeq(cast_num(k), n)) /* index is int? */
           return luaH_getint(t, k);  /* use specialized version */
         /* else go through */
       }
         zfs_fallthrough;
       default: {
         Node *n = mainposition(t, key);
         do {  /* check whether `key' is somewhere in the chain */
           if (luaV_rawequalobj(gkey(n), key))
             return gval(n);  /* that's it */
           else n = gnext(n);
         } while (n);
         return luaO_nilobject;
       }
     }
   }
   
   
   /*
   ** beware: when using this function you probably need to check a GC
   ** barrier and invalidate the TM cache.
   */
   TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
     const TValue *p = luaH_get(t, key);
     if (p != luaO_nilobject)
       return cast(TValue *, p);
     else return luaH_newkey(L, t, key);
   }
   
   
   void luaH_setint (lua_State *L, Table *t, int key, TValue *value) {
     const TValue *p = luaH_getint(t, key);
     TValue *cell;
     if (p != luaO_nilobject)
       cell = cast(TValue *, p);
     else {
       TValue k;
       setnvalue(&k, cast_num(key));
       cell = luaH_newkey(L, t, &k);
     }
     setobj2t(L, cell, value);
   }
   
   
   static int unbound_search (Table *t, unsigned int j) {
     unsigned int i = j;  /* i is zero or a present index */
     j++;
     /* find `i' and `j' such that i is present and j is not */
     while (!ttisnil(luaH_getint(t, j))) {
       i = j;
       j *= 2;
       if (j > cast(unsigned int, MAX_INT)) {  /* overflow? */
         /* table was built with bad purposes: resort to linear search */
         i = 1;
         while (!ttisnil(luaH_getint(t, i))) i++;
         return i - 1;
       }
     }
     /* now do a binary search between them */
     while (j - i > 1) {
       unsigned int m = (i+j)/2;
       if (ttisnil(luaH_getint(t, m))) j = m;
       else i = m;
     }
     return i;
   }
   
   
   /*
   ** Try to find a boundary in table `t'. A `boundary' is an integer index
   ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
   */
   int luaH_getn (Table *t) {
     unsigned int j = t->sizearray;
     if (j > 0 && ttisnil(&t->array[j - 1])) {
       /* there is a boundary in the array part: (binary) search for it */
       unsigned int i = 0;
       while (j - i > 1) {
         unsigned int m = (i+j)/2;
         if (ttisnil(&t->array[m - 1])) j = m;
         else i = m;
       }
       return i;
     }
     /* else must find a boundary in hash part */
     else if (isdummy(t->node))  /* hash part is empty? */
       return j;  /* that is easy... */
     else return unbound_search(t, j);
   }
   
   
   
   #if defined(LUA_DEBUG)
   
   Node *luaH_mainposition (const Table *t, const TValue *key) {
     return mainposition(t, key);
   }
   
   int luaH_isdummy (Node *n) { return isdummy(n); }
   
   #endif

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