px4-firmware/nuttx/binfmt/symtab_findbyvalue.c

/****************************************************************************
 * binfmt/symtab_findbyvalue.c
 *
 *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stddef.h>
#include <debug.h>
#include <assert.h>
#include <errno.h>

#include <nuttx/binfmt/symtab.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/***********************************************************************
 * Public Functions
 ***********************************************************************/

/****************************************************************************
 * Name: symtab_findbyvalue
 *
 * Description:
 *   Find the symbol in the symbol table whose value closest (but not greater
 *   than), the provided value. This version assumes that table is not ordered
 *   with respect to symbol name and, hence, access time will be linear with
 *   respect to nsyms.
 *
 * Returned Value:
 *   A reference to the symbol table entry if an entry with the matching
 *   name is found; NULL is returned if the entry is not found.
 *
 ****************************************************************************/

FAR const struct symtab_s *
symtab_findbyvalue(FAR const struct symtab_s *symtab,
                   FAR void *value, int nsyms)
{
  FAR const struct symtab_s *retval = NULL;

  DEBUGASSERT(symtab != NULL);
  for (; nsyms > 0; symtab++, nsyms--)
    {
      /* Look for symbols of lesser or equal value (probably address) to value */

      if (symtab->sym_value <= value)
        {
          /* Found one.  Is it the largest we have found so far? */

          if (!retval || symtab->sym_value > retval->sym_value)
            {
              /* Yes, then it is the new candidate for the symbol whose value
               * just below 'value'
               */

              retval = symtab;

              /* If it is exactly equal to the search 'value', then we might as
               * well terminate early because we can't do any better than that.
               */

              if (retval->sym_value == value)
                {
                  break;
                }
            }
        }
    }

  return retval;
}