gdbmfetch.c

开源的数据库管理系统

/* gdbmfetch.c - Find a key and return the associated data.  */

/*  This file is part of GDBM, the GNU data base manager, by Philip A. Nelson.
    Copyright (C) 1990, 1991, 1993  Free Software Foundation, Inc.

    GDBM 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.

    GDBM 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 GDBM; see the file COPYING.  If not, write to
    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

    You may contact the author by:
       e-mail:  [e-mail]
      us-mail:  Philip A. Nelson
                Computer Science Department
                Western Washington University
                Bellingham, WA 98226
       
*************************************************************************/


/* include system configuration before all else. */
#include "autoconf.h"

#include "gdbmdefs.h"
#include "gdbmerrno.h"

/* Look up a given KEY and return the information associated with that KEY.
   The pointer in the structure that is  returned is a pointer to dynamically
   allocated memory block.  */

datum
gdbm_fetch (dbf, key)
     gdbm_file_info *dbf;
     datum key;
{
  datum  return_val;		/* The return value. */
  int    elem_loc;		/* The location in the bucket. */
  char  *find_data;		/* Returned from find_key. */
  int    hash_val;		/* Returned from find_key. */

  /* Set the default return value. */
  return_val.dptr  = NULL;
  return_val.dsize = 0;

  /* Initialize the gdbm_errno variable. */
  gdbm_errno = GDBM_NO_ERROR;

  /* Find the key and return a pointer to the data. */
  elem_loc = _gdbm_findkey (dbf, key, &find_data, &hash_val);

  /* Copy the data if the key was found.  */
  if (elem_loc >= 0)
    {
      /* This is the item.  Return the associated data. */
      return_val.dsize = dbf->bucket->h_table[elem_loc].data_size;
      if (return_val.dsize == 0)
	return_val.dptr = (char *) malloc (1);
      else
	return_val.dptr = (char *) malloc (return_val.dsize);
      if (return_val.dptr == NULL) _gdbm_fatal (dbf, "malloc error");
      bcopy (find_data, return_val.dptr, return_val.dsize);
    }

  /* Check for an error and return. */
  if (return_val.dptr == NULL) gdbm_errno = GDBM_ITEM_NOT_FOUND;
  return return_val;
}