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/*
** tree.c
** TecCGraf - PUC-Rio
*/
char *rcs_tree="$Id: tree.c,v 1.15 1996/01/26 18:03:19 roberto Exp $";
#include <string.h>
#include "mem.h"
#include "lua.h"
#include "tree.h"
#include "hash.h"
#include "table.h"
#define lua_streq(a,b) (a[0] == b[0] && strcmp(a,b) == 0)
#define NUM_HASHS 64
typedef struct {
int size;
int nuse; /* number of elements (including EMPTYs) */
TaggedString **hash;
} stringtable;
static stringtable string_root[NUM_HASHS];
static TaggedString EMPTY = {NOT_USED, NOT_USED, 0, 0, {0}};
static unsigned long hash (char *str)
{
unsigned long h = 0;
while (*str)
h = ((h<<5)-h)^(unsigned char)*(str++);
return h;
}
static void grow (stringtable *tb)
{
int newsize = luaI_redimension(tb->size);
TaggedString **newhash = newvector(newsize, TaggedString *);
int i;
for (i=0; i<newsize; i++)
newhash[i] = NULL;
if (tb->size > 0)
{ /* rehash */
tb->nuse = 0;
for (i=0; i<tb->size; i++)
if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY)
{
int h = tb->hash[i]->hash%newsize;
while (newhash[h])
h = (h+1)%newsize;
newhash[h] = tb->hash[i];
tb->nuse++;
}
luaI_free(tb->hash);
}
tb->size = newsize;
tb->hash = newhash;
}
static TaggedString *insert (char *str, stringtable *tb)
{
TaggedString *ts;
unsigned long h = hash(str);
int i;
int j = -1;
if ((Long)tb->nuse*3 >= (Long)tb->size*2)
grow(tb);
i = h%tb->size;
while (tb->hash[i])
{
if (tb->hash[i] == &EMPTY)
j = i;
else if (lua_streq(str, tb->hash[i]->str))
return tb->hash[i];
i = (i+1)%tb->size;
}
/* not found */
if (j != -1) /* is there an EMPTY space? */
i = j;
else
tb->nuse++;
ts = tb->hash[i] = (TaggedString *)luaI_malloc(sizeof(TaggedString)+strlen(str));
strcpy(ts->str, str);
ts->marked = 0;
ts->hash = h;
ts->varindex = ts->constindex = NOT_USED;
return ts;
}
TaggedString *lua_createstring (char *str)
{
return insert(str, &string_root[(unsigned)str[0]%NUM_HASHS]);
}
TaggedString *luaI_createfixedstring (char *str)
{
TaggedString *ts = lua_createstring(str);
ts->marked = 2; /* to avoid GC */
return ts;
}
/*
** Garbage collection function.
** This function traverse the string list freeing unindexed strings
*/
Long lua_strcollector (void)
{
Long counter = 0;
int i;
for (i=0; i<NUM_HASHS; i++)
{
stringtable *tb = &string_root[i];
int j;
for (j=0; j<tb->size; j++)
{
TaggedString *t = tb->hash[j];
if (t != NULL && t != &EMPTY && t->marked != 2)
{
if (t->marked)
t->marked = 0;
else
{
luaI_free(t);
tb->hash[j] = &EMPTY;
counter++;
}
}
}
}
return counter;
}
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