cpphash.c

gcc库的原代码,对编程有很大帮助.

/* Part of CPP library.  (Macro hash table support.)
   Copyright (C) 1986, 87, 89, 92, 93, 94, 1995 Free Software Foundation, Inc.
   Written by Per Bothner, 1994.
   Based on CCCP program by by Paul Rubin, June 1986
   Adapted to ANSI C, Richard Stallman, Jan 1987

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve
 what you give them.   Help stamp out software-hoarding!  */

#include "cpplib.h"
#include "cpphash.h"

extern char *xmalloc PARAMS ((unsigned));

/* Define a generic NULL if one hasn't already been defined.  */

#ifndef NULL
#define NULL 0
#endif

#ifndef __STDC__
#define const
#define volatile
#endif

/*
 * return hash function on name.  must be compatible with the one
 * computed a step at a time, elsewhere
 */
int
hashf (name, len, hashsize)
     register const U_CHAR *name;
     register int len;
     int hashsize;
{
  register int r = 0;

  while (len--)
    r = HASHSTEP (r, *name++);

  return MAKE_POS (r) % hashsize;
}

/*
 * find the most recent hash node for name name (ending with first
 * non-identifier char) installed by install
 *
 * If LEN is >= 0, it is the length of the name.
 * Otherwise, compute the length by scanning the entire name.
 *
 * If HASH is >= 0, it is the precomputed hash code.
 * Otherwise, compute the hash code.
 */
HASHNODE *
cpp_lookup (pfile, name, len, hash)
     struct parse_file *pfile;
     const U_CHAR *name;
     int len;
     int hash;
{
  register const U_CHAR *bp;
  register HASHNODE *bucket;

  if (len < 0)
    {
      for (bp = name; is_idchar[*bp]; bp++) ;
      len = bp - name;
    }

  if (hash < 0)
    hash = hashf (name, len, HASHSIZE);

  bucket = hashtab[hash];
  while (bucket) {
    if (bucket->length == len && strncmp (bucket->name, name, len) == 0)
      return bucket;
    bucket = bucket->next;
  }
  return (HASHNODE*) 0;
}

/*
 * Delete a hash node.  Some weirdness to free junk from macros.
 * More such weirdness will have to be added if you define more hash
 * types that need it.
 */

/* Note that the DEFINITION of a macro is removed from the hash table
   but its storage is not freed.  This would be a storage leak
   except that it is not reasonable to keep undefining and redefining
   large numbers of macros many times.
   In any case, this is necessary, because a macro can be #undef'd
   in the middle of reading the arguments to a call to it.
   If #undef freed the DEFINITION, that would crash.  */

void
delete_macro (hp)
     HASHNODE *hp;
{

  if (hp->prev != NULL)
    hp->prev->next = hp->next;
  if (hp->next != NULL)
    hp->next->prev = hp->prev;

  /* make sure that the bucket chain header that
     the deleted guy was on points to the right thing afterwards. */
  if (hp == *hp->bucket_hdr)
    *hp->bucket_hdr = hp->next;

  if (hp->type == T_MACRO)
    {
      DEFINITION *d = hp->value.defn;
      struct reflist *ap, *nextap;

      for (ap = d->pattern; ap != NULL; ap = nextap)
	{
	  nextap = ap->next;
	  free (ap);
	}
      if (d->nargs >= 0)
	free (d->args.argnames);
      free (d);
    }

  free (hp);
}
/*
 * install a name in the main hash table, even if it is already there.
 *   name stops with first non alphanumeric, except leading '#'.
 * caller must check against redefinition if that is desired.
 * delete_macro () removes things installed by install () in fifo order.
 * this is important because of the `defined' special symbol used
 * in #if, and also if pushdef/popdef directives are ever implemented.
 *
 * If LEN is >= 0, it is the length of the name.
 * Otherwise, compute the length by scanning the entire name.
 *
 * If HASH is >= 0, it is the precomputed hash code.
 * Otherwise, compute the hash code.
 */
HASHNODE *
install (name, len, type, ivalue, value, hash)
     U_CHAR *name;
     int len;
     enum node_type type;
     int ivalue;
     char *value;
     int hash;
{
  register HASHNODE *hp;
  register int i, bucket;
  register U_CHAR *p, *q;

  if (len < 0) {
    p = name;
    while (is_idchar[*p])
      p++;
    len = p - name;
  }

  if (hash < 0)
    hash = hashf (name, len, HASHSIZE);

  i = sizeof (HASHNODE) + len + 1;
  hp = (HASHNODE *) xmalloc (i);
  bucket = hash;
  hp->bucket_hdr = &hashtab[bucket];
  hp->next = hashtab[bucket];
  hashtab[bucket] = hp;
  hp->prev = NULL;
  if (hp->next != NULL)
    hp->next->prev = hp;
  hp->type = type;
  hp->length = len;
  if (hp->type == T_CONST)
    hp->value.ival = ivalue;
  else
    hp->value.cpval = value;
  hp->name = ((U_CHAR *) hp) + sizeof (HASHNODE);
  p = hp->name;
  q = name;
  for (i = 0; i < len; i++)
    *p++ = *q++;
  hp->name[len] = 0;
  return hp;
}

void
cpp_hash_cleanup (pfile)
     cpp_reader *pfile;
{
  register int i;
  for (i = HASHSIZE; --i >= 0; )
    {
      while (hashtab[i])
	delete_macro (hashtab[i]);
    }
}