mirror of https://github.com/lua/lua
257 lines
7.4 KiB
C
257 lines
7.4 KiB
C
/*
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** $Id: ltable.c,v 1.28 1999/10/26 10:53:40 roberto Exp roberto $
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** Lua tables (hash)
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** See Copyright Notice in lua.h
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*/
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/*
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** Implementation of tables (aka arrays, objects, or hash tables);
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** 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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*/
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#include "lauxlib.h"
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#include "lmem.h"
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#include "lobject.h"
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#include "lstate.h"
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#include "ltable.h"
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#include "lua.h"
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#define gcsize(n) numblocks(n*2, sizeof(Hash))
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#define TagDefault LUA_T_ARRAY;
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/*
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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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*/
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Node *luaH_mainposition (const Hash *t, const TObject *key) {
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unsigned long h;
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switch (ttype(key)) {
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case LUA_T_NUMBER:
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h = (unsigned long)(long)nvalue(key);
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break;
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case LUA_T_STRING: case LUA_T_USERDATA:
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h = tsvalue(key)->hash;
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break;
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case LUA_T_ARRAY:
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h = IntPoint(avalue(key));
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break;
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case LUA_T_PROTO:
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h = IntPoint(tfvalue(key));
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break;
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case LUA_T_CPROTO:
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h = IntPoint(fvalue(key));
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break;
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case LUA_T_CLOSURE:
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h = IntPoint(clvalue(key));
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break;
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default:
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lua_error("unexpected type to index table");
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h = 0; /* to avoid warnings */
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}
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return &t->node[h%(unsigned int)t->size];
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}
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const TObject *luaH_get (const Hash *t, const TObject *key) {
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Node *n = luaH_mainposition(t, key);
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do {
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if (luaO_equalObj(key, &n->key))
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return &n->val;
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n = n->next;
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} while (n);
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return &luaO_nilobject;
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}
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int luaH_pos (const Hash *t, const TObject *key) {
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const TObject *v = luaH_get(t, key);
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return (v == &luaO_nilobject) ? -1 : /* key not found */
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((const char *)v - (const char *)(&t->node[0].val))/sizeof(Node);
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}
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static Node *hashnodecreate (int nhash) {
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Node *v = luaM_newvector(nhash, Node);
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int i;
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for (i=0; i<nhash; i++) {
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ttype(&v[i].key) = ttype(&v[i].val) = LUA_T_NIL;
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v[i].next = NULL;
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}
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return v;
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}
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static void setnodevector (Hash *t, int size) {
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t->node = hashnodecreate(size);
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t->size = size;
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t->firstfree = &t->node[size-1]; /* first free position to be used */
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L->nblocks += gcsize(size);
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}
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Hash *luaH_new (int size) {
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Hash *t = luaM_new(Hash);
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setnodevector(t, luaO_redimension(size+1));
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t->htag = TagDefault;
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t->next = L->roottable;
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L->roottable = t;
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t->marked = 0;
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return t;
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}
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void luaH_free (Hash *t) {
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L->nblocks -= gcsize(t->size);
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luaM_free(t->node);
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luaM_free(t);
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}
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static int newsize (const Hash *t) {
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Node *v = t->node;
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int size = t->size;
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int realuse = 0;
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int i;
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for (i=0; i<size; i++) {
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if (ttype(&v[i].val) != LUA_T_NIL)
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realuse++;
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}
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return luaO_redimension(realuse*2);
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}
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/*
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** the rehash is done in two stages: first, we insert only the elements whose
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** main position is free, to avoid needless collisions. In the second stage,
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** we insert the other elements.
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*/
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static void rehash (Hash *t) {
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int oldsize = t->size;
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Node *nold = t->node;
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int i;
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L->nblocks -= gcsize(oldsize);
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setnodevector(t, newsize(t)); /* create new array of nodes */
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/* first loop; set only elements that can go in their main positions */
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for (i=0; i<oldsize; i++) {
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Node *old = nold+i;
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if (ttype(&old->val) == LUA_T_NIL)
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old->next = NULL; /* `remove' it for next loop */
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else {
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Node *mp = luaH_mainposition(t, &old->key); /* new main position */
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if (ttype(&mp->key) == LUA_T_NIL) { /* is it empty? */
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mp->key = old->key; /* put element there */
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mp->val = old->val;
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old->next = NULL; /* `remove' it for next loop */
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}
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else /* it will be copied in next loop */
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old->next = mp; /* to be used in next loop */
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}
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}
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/* update `firstfree' */
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while (ttype(&t->firstfree->key) != LUA_T_NIL) t->firstfree--;
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/* second loop; update elements with colision */
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for (i=0; i<oldsize; i++) {
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Node *old = nold+i;
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if (old->next) { /* wasn't already `removed'? */
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Node *mp = old->next; /* main position */
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Node *e = t->firstfree; /* actual position */
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e->key = old->key; /* put element in the free position */
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e->val = old->val;
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e->next = mp->next; /* chain actual position in main position's list */
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mp->next = e;
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do { /* update `firstfree' */
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t->firstfree--;
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} while (ttype(&t->firstfree->key) != LUA_T_NIL);
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}
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}
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luaM_free(nold); /* free old array */
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}
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/*
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** sets a pair key-value in a hash table; first, check whether key is
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** already present; if not, check whether key's main position is free;
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** if not, check whether colliding node is in its main position or not;
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** if it is not, move colliding node to an empty place and put new pair
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** in its main position; otherwise (colliding node is in its main position),
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** new pair goes to an empty position.
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** Tricky point: the only place where an old element is moved is when
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** we move the colliding node to an empty place; nevertheless, its old
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** value is still in that position until we set the value for the new
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** pair; therefore, even when `val' points to an element of this table
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** (this happens when we use `luaH_move'), there is no problem.
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*/
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void luaH_set (Hash *t, const TObject *key, const TObject *val) {
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Node *mp = luaH_mainposition(t, key);
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Node *n = mp;
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do { /* check whether `key' is somewhere in the chain */
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if (luaO_equalObj(key, &n->key)) {
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n->val = *val; /* update value */
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return; /* that's all */
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}
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else n = n->next;
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} while (n);
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/* `key' not found; must insert it */
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if (ttype(&mp->key) != LUA_T_NIL) { /* main position is not free? */
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Node *othern; /* main position of colliding node */
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n = t->firstfree; /* get a free place */
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/* is colliding node out of its main position? (can only happens if
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its position if after "firstfree") */
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if (mp > n && (othern=luaH_mainposition(t, &mp->key)) != mp) {
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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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}
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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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mp->next = n;
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mp = n;
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}
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}
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mp->key = *key;
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mp->val = *val;
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for (;;) { /* check free places */
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if (ttype(&(t->firstfree)->key) == LUA_T_NIL)
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return; /* 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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}
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rehash(t); /* no more free places */
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}
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void luaH_setint (Hash *t, int key, const TObject *val) {
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TObject index;
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ttype(&index) = LUA_T_NUMBER;
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nvalue(&index) = key;
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luaH_set(t, &index, val);
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}
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const TObject *luaH_getint (const Hash *t, int key) {
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TObject index;
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ttype(&index) = LUA_T_NUMBER;
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nvalue(&index) = key;
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return luaH_get(t, &index);
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}
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