Remove redundant initialization of `sub'.

[mLib] / atom.c

/* -*-c-*-
 *
 * $Id: atom.c,v 1.1 2001/01/20 11:50:16 mdw Exp $
 *
 * Atom management
 *
 * (c) 2000 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * mLib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: atom.c,v $
 * Revision 1.1  2001/01/20 11:50:16  mdw
 * Implementation of atom tables (for example, as found in X11).
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <stdio.h>
#include <string.h>

#include "alloc.h"
#include "atom.h"
#include "hash.h"
#include "sym.h"

/*----- Static variables --------------------------------------------------*/

static atom_table atoms;

/*----- Handy macros ------------------------------------------------------*/

#define ATOM_RESOLVE(t) do {						\
  if (t == ATOM_GLOBAL)							\
    t = &atoms;								\
  if (!t->t.t.v)							\
    atom_createtable(t);						\
} while (0)

/*----- Main code ---------------------------------------------------------*/

/* --- @atom_createtable@ --- *
 *
 * Arguments:	@atom_table *t@ = pointer to an atom table
 *
 * Returns:	---
 *
 * Use:		Initializes an atom table.
 */

void atom_createtable(atom_table *t)
{
  sym_create(&t->t);
  t->g = 0;
  t->gseq = 0;
}

/* --- @atom_destroytable@ --- *
 *
 * Arguments:	@atom_table *t@ = pointer to an atom table
 *
 * Returns:	---
 *
 * Use:		Destroys all of the atoms in an atom table.  All of the atoms
 *		(including uninterned atoms) are freed.  Any references to
 *		atoms from the table become invalid, and any association
 *		tables dependent on the atom table are unusable, except that
 *		they may be destroyed safely.
 */

void atom_destroytable(atom_table *t)
{
  atom *a, *aa;

  ATOM_RESOLVE(t);
  for (a = (atom *)t->g; a; a = aa) {
    aa = (atom *)a->b.b.next;
    x_free(t->t.t.a, a);
  }
  sym_destroy(&t->t);
}

/* --- @atom_intern@ --- *
 *
 * Arguments:	@atom_table *t@ = pointer to an atom table
 *		@const char *p@ = pointer to the string to intern
 *
 * Returns:	A pointer to the atom block for the given symbol string.
 *
 * Use:		Interns an atom, returning the atom block.  The string can be
 *		extracted from the atom by means of the @ATOM_NAME@ macro.
 */

atom *atom_intern(atom_table *t, const char *p)
{
  atom *a;
  unsigned f;

  ATOM_RESOLVE(t);
  a = sym_find(&t->t, p, -1, sizeof(atom), &f);
  if (!f)
    a->f = 0;
  return (a);
}

/* --- @atom_gensym@ --- *
 *
 * Arguments:	@atom_table *t@ = pointer to a symbol table
 *
 * Returns:	A pointer to a new atom block, not previously interned.
 *
 * Use:		Creates a new, uninterned atom.  This atom will never be
 *		returned by either @atom_intern@ or any other call to
 *		@atom_gensym@, while the symbol table exists.
 */

atom *atom_gensym(atom_table *t)
{
  atom *a;
  char buf[64];
  size_t sz;

  ATOM_RESOLVE(t);
  sprintf(buf, "*gen-%lu*", t->gseq++);
  sz = strlen(buf) + 1;
  a = x_alloc(t->t.t.a, sizeof(atom) + sz);
  a->b.name = (char *)(a + 1);
  memcpy(a->b.name, buf, sz);
  a->b.len = sz;
  CRC32(a->b.b.hash, 0, buf, sz);
  a->f = ATOMF_GENSYM;
  a->b.b.next = t->g;
  t->g = &a->b.b;
  return (a);
}

/* --- @atom_name@ --- *
 *
 * Arguments:	@atom *a@ = pointer to an atom
 *
 * Returns:	The atom's textual name.
 *
 * Use:		Given an atom, returns the name with which it was interned
 *		(or a made-up name if it was created using @gensym@.
 */

const char *atom_name(const atom *a) { return ATOM_NAME(a); }

/* --- @atom_len@ --- *
 *
 * Arguments:	@atom *a@ = pointer to an atom
 *
 * Returns:	The atom string's length.
 *
 * Use:		Given an atom, return the length of its textual
 *		representation.
 */

size_t atom_len(const atom *a) { return ATOM_LEN(a); }

/* --- @atom_hash@ --- *
 *
 * Arguments:	@atom *a@ = pointer to an atom
 *
 * Returns:	The atom's hash.
 *
 * Use:		Given an atom, returns its hash.
 */

uint32 atom_hash(const atom *a) { return ATOM_HASH(a); }

/* --- @atom_mkiter@ , @atom_next@ --- *
 *
 * Arguments:	@atom_table *t@ = pointer to an atom table
 *		@atom_iter *i@ = pointer to an iterator structure
 *
 * Returns:	Next atom, for @atom_next@; nothing for @atom_mkiter@.
 *
 * Use:		Iterates over atoms (both interned and uninterned).
 */

void atom_mkiter(atom_iter *i, atom_table *t)
{
  ATOM_RESOLVE(t);
  i->i.i.t = &t->t.t;
  i->i.i.p = t->g;
  i->i.i.i = 0;
}

atom *atom_next(atom_iter *i)
{
  atom *a;
  SYM_NEXT(&i->i, a);
  return (a);
}

/*----- That's all, folks -------------------------------------------------*/