ack/util/led/sym.c

#ifndef lint
static char rcsid[] = "$Header$";
#endif

/*
 * Symbol table management.
 */

#include "../../h/out.h"
#include "const.h"
#include "memory.h"

/*
 * Symbol table types. Each hash table entry contains the offset of a symbol
 * struct. `Sy_name' contains the offset the name in the piece of global
 * names. `Sy_next' contains the offset of the next symbol of which the
 * corresponding name has the same hash value.
 */
struct symbol {
	ind_t	sy_name;
	ind_t	sy_next;
};

#define NHASH	256		/* Size of hash table. Should be even. */

static ind_t	hashtable[NHASH];

/*
 * Initialize the symbol table. All indices should be noticeably invalid.
 */
init_symboltable()
{
	register ind_t	*rap;

	for (rap = hashtable; rap < &hashtable[NHASH]; rap++)
		*rap = BADOFF;
}

/*
 * Search for `string' in the symboltable. The hash value of `string' is in
 * `hashval'. The linked list belonging to the entry of hashval
 * in the hash table is followed. If the names match, a pointer to the outname
 * in this element of the list is returned. When a match cannot be found,
 * NIL is returned.
 */ 
struct outname *
searchname(string, hashval)
	char			*string;
	int			hashval;
{
	register char		*rcp;
	register char		*namestring;
	register ind_t		symindex;
	register struct outname	*name;
	register struct symbol	*sym;

	symindex = hashtable[hashval];
	while (symindex != BADOFF) {
		sym = (struct symbol *)address(ALLOSYMB, symindex);
		name = (struct outname *)address(ALLOGLOB, sym->sy_name);
		namestring = address(ALLOGCHR, (ind_t)name->on_foff);
		rcp = string;
		while (*rcp == *namestring++)
			if (*rcp++ == '\0')
				return name;
		symindex = sym->sy_next;
	}
	/* Not found. */
	return (struct outname *)0;
}

/*
 * Enter a new name in the symbol table. We must copy everything to a
 * new entry. `Name' is a private copy, i.e. the pointer to it will not be
 * destroyed by allocation. However, the string of which name->on_foff is the
 * offset can be destroyed, so we save it first.
 */
entername(name, hashval)
	struct outname	*name;
	int		hashval;
{
	ind_t		savindex;
	ind_t		symindex;
	ind_t		namindex;
	struct symbol	*sym;
	struct outname	*newname;
	extern ind_t	savechar();
	extern ind_t	hard_alloc();

	savindex = savechar(ALLOGCHR, (ind_t)name->on_foff);
	symindex = hard_alloc(ALLOSYMB, (long)sizeof(struct symbol));
	namindex = hard_alloc(ALLOGLOB, (long)sizeof(struct outname));
	if (savindex == BADOFF || symindex == BADOFF || namindex == BADOFF)
		fatal("symbol table overflow");
	sym = (struct symbol *)address(ALLOSYMB, symindex);
	sym->sy_name = namindex;
	newname = (struct outname *)address(ALLOGLOB, namindex);
	*newname = *name;
	newname->on_foff = savindex;
	sym->sy_next = hashtable[hashval];
	hashtable[hashval] = symindex;
}

/*
 * Return the index of `name' in the symbol table in the order in which
 * it was entered. We need a REAL index, not a byte offset.
 */
ushort
indexof(name)
	struct outname	*name;
{
	return name - (struct outname *)address(ALLOGLOB, (ind_t)0);
}

/*
 * Assign an integer to the string in p.
 * 0 <= hash(p) < NHASH, so it can - and will - be used
 * as index in a hash table.
 */
int
hash(p)
	register char		*p;
{
	register unsigned int	h = 0;
	register int		c;

	while (c = *p++) {
		h <<= 2;
		h += c;
	}
	return h & (NHASH - 1);
}