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** $Id: ltable.c,v 2.32.1.2 2007/12/28 15:32:23 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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** Hence even when the load factor reaches 100%, performance remains good.
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** max size of array part is 2^MAXBITS
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#define MAXBITS (LUAI_BITSINT-2)
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#define MAXASIZE (1 << MAXBITS)
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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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#define dummynode (&dummynode_)
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static const Node dummynode_ = {
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{{NULL}, LUA_TNIL}, /* value */
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{{{NULL}, LUA_TNIL, NULL}} /* key */
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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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if (luai_numeq(n, 0)) /* avoid problems with -0 */
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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, a[0]);
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** returns the `main' position of an element in a table (that is, the index
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** of its hash value)
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static Node *mainposition (const Table *t, const TValue *key) {
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switch (ttype(key)) {
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return hashnum(t, nvalue(key));
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return hashstr(t, rawtsvalue(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 TValue *key) {
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if (ttisnumber(key)) {
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lua_Number n = nvalue(key);
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lua_number2int(k, n);
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if (luai_numeq(cast_num(k), n))
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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 of a traversal is signalled by -1.
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static int findindex (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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Node *n = mainposition(t, key);
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do { /* check whether `key' is somewhere in the chain */
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/* key may be dead already, but it is ok to use it in `next' */
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if (luaO_rawequalObj(key2tval(n), key) ||
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(ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
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gcvalue(gkey(n)) == gcvalue(key))) {
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i = cast_int(n - gnode(t, 0)); /* key index in hash table */
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/* hash elements are numbered after array ones */
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return i + t->sizearray;
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luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
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return 0; /* to avoid warnings */
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int luaH_next (lua_State *L, Table *t, StkId key) {
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int i = findindex(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_num(i+1));
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setobj2s(L, 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(L, key, key2tval(gnode(t, i)));
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setobj2s(L, 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 int computesizes (int nums[], int *narray) {
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int twotoi; /* 2^i */
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int a = 0; /* number of elements smaller than 2^i */
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int na = 0; /* number of elements to go to array part */
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int n = 0; /* optimal size for array part */
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for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
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if (a > twotoi/2) { /* more than half elements present? */
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n = twotoi; /* optimal size (till now) */
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na = a; /* all elements smaller than n will go to array part */
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if (a == *narray) break; /* all elements already counted */
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lua_assert(*narray/2 <= na && na <= *narray);
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static int countint (const TValue *key, int *nums) {
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int k = arrayindex(key);
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if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
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nums[ceillog2(k)]++; /* count as such */
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static int numusearray (const Table *t, int *nums) {
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int ause = 0; /* summation of `nums' */
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int i = 1; /* count to traverse all array keys */
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for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
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int lc = 0; /* counter */
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if (lim > t->sizearray) {
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lim = t->sizearray; /* adjust upper limit */
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break; /* no more elements to count */
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/* count elements in range (2^(lg-1), 2^lg] */
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for (; i <= lim; i++) {
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if (!ttisnil(&t->array[i-1]))
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static int numusehash (const Table *t, int *nums, int *pnasize) {
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int totaluse = 0; /* total number of elements */
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int ause = 0; /* summation of `nums' */
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Node *n = &t->node[i];
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if (!ttisnil(gval(n))) {
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ause += countint(key2tval(n), nums);
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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, TValue);
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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 size) {
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if (size == 0) { /* no elements to hash part? */
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t->node = cast(Node *, dummynode); /* use common `dummynode' */
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lsize = ceillog2(size);
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luaG_runerror(L, "table overflow");
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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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Node *n = gnode(t, i);
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setnilvalue(gkey(n));
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setnilvalue(gval(n));
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t->lsizenode = cast_byte(lsize);
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t->lastfree = gnode(t, size); /* all positions are free */
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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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Node *nold = t->node; /* save old hash ... */
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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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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(L, luaH_setnum(L, t, i+1), &t->array[i]);
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luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
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/* re-insert elements from 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(L, luaH_set(L, t, key2tval(old)), gval(old));
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if (nold != dummynode)
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luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
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void luaH_resizearray (lua_State *L, Table *t, int nasize) {
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int nsize = (t->node == dummynode) ? 0 : sizenode(t);
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resize(L, t, nasize, nsize);
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static void rehash (lua_State *L, Table *t, const TValue *ek) {
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int nums[MAXBITS+1]; /* nums[i] = number of keys between 2^(i-1) and 2^i */
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for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
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nasize = numusearray(t, nums); /* count keys in array part */
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totaluse = nasize; /* all those keys are integer keys */
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totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
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/* count extra key */
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nasize += countint(ek, nums);
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/* compute new size for array part */
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na = computesizes(nums, &nasize);
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/* resize the table to new computed sizes */
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resize(L, t, nasize, totaluse - na);
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** }=============================================================
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Table *luaH_new (lua_State *L, int narray, int nhash) {
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Table *t = luaM_new(L, Table);
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luaC_link(L, obj2gco(t), LUA_TTABLE);
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t->flags = cast_byte(~0);
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/* temporary values (kept only if some malloc fails) */
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t->node = cast(Node *, dummynode);
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setarrayvector(L, t, narray);
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setnodevector(L, t, nhash);
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void luaH_free (lua_State *L, Table *t) {
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if (t->node != dummynode)
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luaM_freearray(L, t->node, sizenode(t), Node);
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luaM_freearray(L, t->array, t->sizearray, TValue);
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static Node *getfreepos (Table *t) {
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while (t->lastfree-- > t->node) {
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if (ttisnil(gkey(t->lastfree)))
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return NULL; /* could not find a free place */
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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 TValue *newkey (lua_State *L, Table *t, const TValue *key) {
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Node *mp = mainposition(t, key);
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if (!ttisnil(gval(mp)) || mp == dummynode) {
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Node *n = getfreepos(t); /* get a free place */
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if (n == NULL) { /* cannot find a free place? */
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rehash(L, t, key); /* grow table */
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return luaH_set(L, t, key); /* re-insert key into grown table */
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lua_assert(n != dummynode);
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othern = mainposition(t, key2tval(mp));
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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 (gnext(othern) != mp) othern = gnext(othern); /* find previous */
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gnext(othern) = 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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memcpy (n, mp, sizeof (*n));
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gnext(mp) = 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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gnext(n) = gnext(mp); /* chain new position */
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gkey(mp)->value = key->value; gkey(mp)->tt = key->tt;
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luaC_barriert(L, t, key);
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lua_assert(ttisnil(gval(mp)));
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** search function for integers
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const TValue *luaH_getnum (Table *t, int key) {
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/* (1 <= key && key <= t->sizearray) */
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if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
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return &t->array[key-1];
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lua_Number nk = cast_num(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)) && luai_numeq(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 TValue *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)) && rawtsvalue(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 TValue *luaH_get (Table *t, const TValue *key) {
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switch (ttype(key)) {
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case LUA_TNIL: return luaO_nilobject;
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case LUA_TSTRING: return luaH_getstr(t, rawtsvalue(key));
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lua_Number n = nvalue(key);
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lua_number2int(k, n);
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if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
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return luaH_getnum(t, k); /* use specialized version */
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/* else go through */
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Node *n = mainposition(t, key);
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do { /* check whether `key' is somewhere in the chain */
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if (luaO_rawequalObj(key2tval(n), key))
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return gval(n); /* that's it */
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return luaO_nilobject;
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TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
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const TValue *p = luaH_get(t, key);
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if (p != luaO_nilobject)
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return cast(TValue *, p);
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if (ttisnil(key)) luaG_runerror(L, "table index is nil");
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else if (ttisnumber(key) && luai_numisnan(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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TValue *luaH_setnum (lua_State *L, Table *t, int key) {
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const TValue *p = luaH_getnum(t, key);
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if (p != luaO_nilobject)
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return cast(TValue *, p);
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setnvalue(&k, cast_num(key));
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return newkey(L, t, &k);
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TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {
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const TValue *p = luaH_getstr(t, key);
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if (p != luaO_nilobject)
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return cast(TValue *, p);
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setsvalue(L, &k, key);
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return newkey(L, t, &k);
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static int unbound_search (Table *t, unsigned int j) {
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unsigned int i = j; /* i is zero or a present index */
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/* find `i' and `j' such that i is present and j is not */
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while (!ttisnil(luaH_getnum(t, j))) {
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if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
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/* table was built with bad purposes: resort to linear search */
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while (!ttisnil(luaH_getnum(t, i))) i++;
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/* now do a binary search between them */
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unsigned int m = (i+j)/2;
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if (ttisnil(luaH_getnum(t, m))) j = m;
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** Try to find a boundary in table `t'. A `boundary' is an integer index
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** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
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int luaH_getn (Table *t) {
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unsigned int j = t->sizearray;
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if (j > 0 && ttisnil(&t->array[j - 1])) {
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/* there is a boundary in the array part: (binary) search for it */
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unsigned int m = (i+j)/2;
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if (ttisnil(&t->array[m - 1])) j = m;
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/* else must find a boundary in hash part */
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else if (t->node == dummynode) /* hash part is empty? */
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return j; /* that is easy... */
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else return unbound_search(t, j);
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#if defined(LUA_DEBUG)
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Node *luaH_mainposition (const Table *t, const TValue *key) {
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return mainposition(t, key);
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int luaH_isdummy (Node *n) { return n == dummynode; }
added
removed
script/lua/ltable.c
