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/* $Id: symbol.c,v 1.1 2004-05-03 05:17:48 behdad Exp $
*
* Symbol table maintenance. Implements an abstract data type called
* the symbol table.
*/
#include "c2man.h"
#include "symbol.h"
/* Create a symbol table.
* Return a pointer to the symbol table or NULL if an error occurs.
*/
SymbolTable *
create_symbol_table ()
{
SymbolTable *symtab;
int i;
symtab = (SymbolTable *)safe_malloc(sizeof(SymbolTable));
for (i = 0; i < SYM_MAX_HASH; ++i)
symtab->bucket[i] = NULL;
return symtab;
}
/* Free the memory allocated to the symbol table.
*/
void
destroy_symbol_table (symtab)
SymbolTable *symtab;
{
int i;
Symbol *sym, *next;
for (i = 0; i < SYM_MAX_HASH; ++i) {
sym = symtab->bucket[i];
while (sym != NULL) {
next = sym->next;
free(sym->name);
free(sym);
sym = next;
}
}
free(symtab);
}
/* This is a simple hash function mapping a symbol name to a hash bucket. */
static unsigned int
hash (name)
char *name;
{
char *s;
unsigned int h;
h = 0;
s = name;
while (*s != '\0')
h = (h << 1) ^ *s++;
return h % SYM_MAX_HASH;
}
/* Search the list of symbols <list> for the symbol <name>.
* Return a pointer to the symbol or NULL if not found.
*/
static Symbol *
search_symbol_list (list, name)
Symbol *list;
char *name;
{
Symbol *sym;
for (sym = list; sym != NULL; sym = sym->next) {
if (strcmp(sym->name, name) == 0)
return sym;
}
return NULL;
}
/* Look for symbol <name> in symbol table <symtab>.
* Return a pointer to the symbol or NULL if not found.
*/
Symbol *
find_symbol (symtab, name)
SymbolTable *symtab;
char *name;
{
return search_symbol_list(symtab->bucket[hash(name)], name);
}
/* If the symbol <name> does not already exist in symbol table <symtab>,
* then add the symbol to the symbol table.
* Return a pointer to the symbol or NULL on an error.
*/
Symbol *
new_symbol (symtab, name, flags)
SymbolTable *symtab; /* symbol table */
char *name; /* symbol name */
int flags; /* symbol attributes */
{
Symbol *sym;
int i;
if ((sym = find_symbol(symtab, name)) == NULL) {
sym = (Symbol *)safe_malloc(sizeof(Symbol));
sym->name = strduplicate(name);
sym->flags = flags;
sym->valtype = SYMVAL_NONE;
i = hash(name);
sym->next = symtab->bucket[i];
symtab->bucket[i] = sym;
}
return sym;
}
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