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** $Id: ltable.c,v 1.132 2003/04/03 13:35:34 roberto Exp $
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** See Copyright Notice in lua.h
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** Implementation of tables (aka arrays, objects, or hash tables).
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** Tables keep its elements in two parts: an array part and a hash part.
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** Non-negative integer keys are all candidates to be kept in the array
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** part. The actual size of the array is the largest `n' such that at
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** least half the slots between 0 and n are in use.
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** Hash uses a mix of chained scatter table with Brent's variation.
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** A main invariant of these tables is that, if an element is not
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** in its main position (i.e. the `original' position that its hash gives
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** to it), then the colliding element is in its own main position.
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** In other words, there are collisions only when two elements have the
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** same main position (i.e. the same hash values for that table size).
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** Because of that, the load factor of these tables can be 100% without
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** performance penalties.
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** max size of array part is 2^MAXBITS
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#define MAXBITS (BITS_INT-2)
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/* check whether `x' < 2^MAXBITS */
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#define toobig(x) ((((x)-1) >> MAXBITS) != 0)
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/* function to convert a lua_Number to int (with any rounding method) */
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#ifndef lua_number2int
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#define lua_number2int(i,n) ((i)=(int)(n))
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#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
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#define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
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#define hashboolean(t,p) hashpow2(t, p)
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** for some types, it is better to avoid modulus by power of 2, as
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** they tend to have many 2 factors.
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#define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
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#define hashpointer(t,p) hashmod(t, IntPoint(p))
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** number of ints inside a lua_Number
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#define numints cast(int, sizeof(lua_Number)/sizeof(int))
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** hash for lua_Numbers
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static Node *hashnum (const Table *t, lua_Number n) {
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unsigned int a[numints];
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n += 1; /* normalize number (avoid -0) */
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lua_assert(sizeof(a) <= sizeof(n));
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memcpy(a, &n, sizeof(a));
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for (i = 1; i < numints; i++) a[0] += a[i];
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return hashmod(t, cast(lu_hash, a[0]));
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** returns the `main' position of an element in a table (that is, the index
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Node *luaH_mainposition (const Table *t, const TObject *key) {
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switch (ttype(key)) {
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return hashnum(t, nvalue(key));
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return hashstr(t, tsvalue(key));
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return hashboolean(t, bvalue(key));
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case LUA_TLIGHTUSERDATA:
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return hashpointer(t, pvalue(key));
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return hashpointer(t, gcvalue(key));
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** returns the index for `key' if `key' is an appropriate key to live in
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** the array part of the table, -1 otherwise.
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static int arrayindex (const TObject *key) {
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if (ttisnumber(key)) {
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lua_number2int(k, (nvalue(key)));
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if (cast(lua_Number, k) == nvalue(key) && k >= 1 && !toobig(k))
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return -1; /* `key' did not match some condition */
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** returns the index of a `key' for table traversals. First goes all
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** elements in the array part, then elements in the hash part. The
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** beginning and end of a traversal are signalled by -1.
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static int luaH_index (lua_State *L, Table *t, StkId key) {
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if (ttisnil(key)) return -1; /* first iteration */
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if (0 <= i && i <= t->sizearray) { /* is `key' inside array part? */
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return i-1; /* yes; that's the index (corrected to C) */
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const TObject *v = luaH_get(t, key);
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if (v == &luaO_nilobject)
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luaG_runerror(L, "invalid key for `next'");
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i = cast(int, (cast(const lu_byte *, v) -
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cast(const lu_byte *, gval(gnode(t, 0)))) / sizeof(Node));
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return i + t->sizearray; /* hash elements are numbered after array ones */
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int luaH_next (lua_State *L, Table *t, StkId key) {
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int i = luaH_index(L, t, key); /* find original element */
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for (i++; i < t->sizearray; i++) { /* try first array part */
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if (!ttisnil(&t->array[i])) { /* a non-nil value? */
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setnvalue(key, cast(lua_Number, i+1));
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setobj2s(key+1, &t->array[i]);
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for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
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if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
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setobj2s(key, gkey(gnode(t, i)));
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setobj2s(key+1, gval(gnode(t, i)));
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return 0; /* no more elements */
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** {=============================================================
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** ==============================================================
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static void computesizes (int nums[], int ntotal, int *narray, int *nhash) {
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int a = nums[0]; /* number of elements smaller than 2^i */
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int na = a; /* number of elements to go to array part */
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int n = (na == 0) ? -1 : 0; /* (log of) optimal size for array part */
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for (i = 1; a < *narray && *narray >= twoto(i-1); i++) {
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if (a >= twoto(i-1)) { /* more than half elements in use? */
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lua_assert(na <= *narray && *narray <= ntotal);
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*nhash = ntotal - na;
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*narray = (n == -1) ? 0 : twoto(n);
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lua_assert(na <= *narray && na >= *narray/2);
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static void numuse (const Table *t, int *narray, int *nhash) {
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/* count elements in array part */
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for (i=0, lg=0; lg<=MAXBITS; lg++) { /* for each slice [2^(lg-1) to 2^lg) */
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int ttlg = twoto(lg); /* 2^lg */
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if (ttlg > t->sizearray) {
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if (i >= ttlg) break;
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for (; i<ttlg; i++) {
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if (!ttisnil(&t->array[i])) {
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for (; lg<=MAXBITS; lg++) nums[lg] = 0; /* reset other counts */
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*narray = totaluse; /* all previous uses were in array part */
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/* count elements in hash part */
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Node *n = &t->node[i];
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if (!ttisnil(gval(n))) {
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int k = arrayindex(gkey(n));
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if (k >= 0) { /* is `key' an appropriate array index? */
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nums[luaO_log2(k-1)+1]++; /* count as such */
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computesizes(nums, totaluse, narray, nhash);
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static void setarrayvector (lua_State *L, Table *t, int size) {
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luaM_reallocvector(L, t->array, t->sizearray, size, TObject);
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for (i=t->sizearray; i<size; i++)
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setnilvalue(&t->array[i]);
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static void setnodevector (lua_State *L, Table *t, int lsize) {
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int size = twoto(lsize);
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luaG_runerror(L, "table overflow");
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if (lsize == 0) { /* no elements to hash part? */
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t->node = G(L)->dummynode; /* use common `dummynode' */
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lua_assert(ttisnil(gkey(t->node))); /* assert invariants: */
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lua_assert(ttisnil(gval(t->node)));
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lua_assert(t->node->next == NULL); /* (`dummynode' must be empty) */
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t->node = luaM_newvector(L, size, Node);
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for (i=0; i<size; i++) {
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t->node[i].next = NULL;
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setnilvalue(gkey(gnode(t, i)));
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setnilvalue(gval(gnode(t, i)));
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t->lsizenode = cast(lu_byte, lsize);
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t->firstfree = gnode(t, size-1); /* first free position to be used */
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static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
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int oldasize = t->sizearray;
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int oldhsize = t->lsizenode;
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nold = t->node; /* save old hash ... */
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else { /* old hash is `dummynode' */
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lua_assert(t->node == G(L)->dummynode);
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temp[0] = t->node[0]; /* copy it to `temp' */
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setnilvalue(gkey(G(L)->dummynode)); /* restate invariant */
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setnilvalue(gval(G(L)->dummynode));
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lua_assert(G(L)->dummynode->next == NULL);
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if (nasize > oldasize) /* array part must grow? */
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setarrayvector(L, t, nasize);
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/* create new hash part with appropriate size */
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setnodevector(L, t, nhsize);
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/* re-insert elements */
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if (nasize < oldasize) { /* array part must shrink? */
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t->sizearray = nasize;
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/* re-insert elements from vanishing slice */
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for (i=nasize; i<oldasize; i++) {
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if (!ttisnil(&t->array[i]))
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setobjt2t(luaH_setnum(L, t, i+1), &t->array[i]);
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luaM_reallocvector(L, t->array, oldasize, nasize, TObject);
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/* re-insert elements in hash part */
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for (i = twoto(oldhsize) - 1; i >= 0; i--) {
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if (!ttisnil(gval(old)))
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setobjt2t(luaH_set(L, t, gkey(old)), gval(old));
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luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
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static void rehash (lua_State *L, Table *t) {
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numuse(t, &nasize, &nhsize); /* compute new sizes for array and hash parts */
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resize(L, t, nasize, luaO_log2(nhsize)+1);
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** }=============================================================
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Table *luaH_new (lua_State *L, int narray, int lnhash) {
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Table *t = luaM_new(L, Table);
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luaC_link(L, valtogco(t), LUA_TTABLE);
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t->metatable = hvalue(defaultmeta(L));
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t->flags = cast(lu_byte, ~0);
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/* temporary values (kept only if some malloc fails) */
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setarrayvector(L, t, narray);
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setnodevector(L, t, lnhash);
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void luaH_free (lua_State *L, Table *t) {
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luaM_freearray(L, t->node, sizenode(t), Node);
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luaM_freearray(L, t->array, t->sizearray, TObject);
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** try to remove an element from a hash table; cannot move any element
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** (because gc can call `remove' during a table traversal)
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void luaH_remove (Table *t, Node *e) {
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Node *mp = luaH_mainposition(t, gkey(e));
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if (e != mp) { /* element not in its main position? */
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while (mp->next != e) mp = mp->next; /* find previous */
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mp->next = e->next; /* remove `e' from its list */
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if (e->next != NULL) ??
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lua_assert(ttisnil(gval(node)));
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setnilvalue(gkey(e)); /* clear node `e' */
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** inserts a new key into a hash table; first, check whether key's main
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** position is free. If not, check whether colliding node is in its main
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** position or not: if it is not, move colliding node to an empty place and
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** put new key in its main position; otherwise (colliding node is in its main
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** position), new key goes to an empty position.
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static TObject *newkey (lua_State *L, Table *t, const TObject *key) {
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Node *mp = luaH_mainposition(t, key);
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if (!ttisnil(gval(mp))) { /* main position is not free? */
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Node *othern = luaH_mainposition(t, gkey(mp)); /* `mp' of colliding node */
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Node *n = t->firstfree; /* get a free place */
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if (othern != mp) { /* is colliding node out of its main position? */
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/* yes; move colliding node into free position */
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while (othern->next != mp) othern = othern->next; /* find previous */
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othern->next = n; /* redo the chain with `n' in place of `mp' */
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*n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
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mp->next = NULL; /* now `mp' is free */
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setnilvalue(gval(mp));
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else { /* colliding node is in its own main position */
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/* new node will go into free position */
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n->next = mp->next; /* chain new position */
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setobj2t(gkey(mp), key); /* write barrier */
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lua_assert(ttisnil(gval(mp)));
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for (;;) { /* correct `firstfree' */
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if (ttisnil(gkey(t->firstfree)))
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return gval(mp); /* OK; table still has a free place */
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else if (t->firstfree == t->node) break; /* cannot decrement from here */
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else (t->firstfree)--;
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/* no more free places; must create one */
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setbvalue(gval(mp), 0); /* avoid new key being removed */
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rehash(L, t); /* grow table */
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val = cast(TObject *, luaH_get(t, key)); /* get new position */
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lua_assert(ttisboolean(val));
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** generic search function
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static const TObject *luaH_getany (Table *t, const TObject *key) {
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if (ttisnil(key)) return &luaO_nilobject;
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Node *n = luaH_mainposition(t, key);
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do { /* check whether `key' is somewhere in the chain */
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if (luaO_rawequalObj(gkey(n), key)) return gval(n); /* that's it */
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return &luaO_nilobject;
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** search function for integers
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const TObject *luaH_getnum (Table *t, int key) {
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if (1 <= key && key <= t->sizearray)
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return &t->array[key-1];
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lua_Number nk = cast(lua_Number, key);
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Node *n = hashnum(t, nk);
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do { /* check whether `key' is somewhere in the chain */
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if (ttisnumber(gkey(n)) && nvalue(gkey(n)) == nk)
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return gval(n); /* that's it */
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return &luaO_nilobject;
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** search function for strings
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const TObject *luaH_getstr (Table *t, TString *key) {
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Node *n = hashstr(t, key);
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do { /* check whether `key' is somewhere in the chain */
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if (ttisstring(gkey(n)) && tsvalue(gkey(n)) == key)
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return gval(n); /* that's it */
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return &luaO_nilobject;
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** main search function
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const TObject *luaH_get (Table *t, const TObject *key) {
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switch (ttype(key)) {
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case LUA_TSTRING: return luaH_getstr(t, tsvalue(key));
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lua_number2int(k, (nvalue(key)));
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if (cast(lua_Number, k) == nvalue(key)) /* is an integer index? */
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return luaH_getnum(t, k); /* use specialized version */
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/* else go through */
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default: return luaH_getany(t, key);
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TObject *luaH_set (lua_State *L, Table *t, const TObject *key) {
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const TObject *p = luaH_get(t, key);
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if (p != &luaO_nilobject)
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return cast(TObject *, p);
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if (ttisnil(key)) luaG_runerror(L, "table index is nil");
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else if (ttisnumber(key) && nvalue(key) != nvalue(key))
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luaG_runerror(L, "table index is NaN");
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return newkey(L, t, key);
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TObject *luaH_setnum (lua_State *L, Table *t, int key) {
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const TObject *p = luaH_getnum(t, key);
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if (p != &luaO_nilobject)
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return cast(TObject *, p);
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setnvalue(&k, cast(lua_Number, key));
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return newkey(L, t, &k);
added
removed
bam/src/lua/src/ltable.c
