128 lines
4.7 KiB
C
128 lines
4.7 KiB
C
/****************************************************************************
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* binfmt/symtab_findorderedbyvalue.c
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*
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* Copyright (C) 2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stddef.h>
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#include <debug.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/binfmt/symtab.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: symtab_findorderedbyvalue
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*
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* Description:
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* Find the symbol in the symbol table whose value closest (but not greater
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* than), the provided value. This version assumes that table is ordered
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* with respect to symbol name.
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*
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* Returned Value:
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* A reference to the symbol table entry if an entry with the matching
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* name is found; NULL is returned if the entry is not found.
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*
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****************************************************************************/
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FAR const struct symtab_s *
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symtab_findorderedbyvalue(FAR const struct symtab_s *symtab,
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FAR void *value, int nsyms)
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{
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int low = 0;
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int high = nsyms -1;
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int mid;
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/* Loop until the range has been isolated to a single symbol table
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* entry that may or may not match the search name.
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*/
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DEBUGASSERT(symtab != NULL);
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while (low < high)
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{
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/* Compare the name to the one in the middle. (or just below
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* the middle in the case where one is even and one is odd).
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*/
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mid = (low + high) >> 1;
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if (value < symtab[mid].sym_value)
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{
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high = mid - 1;
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}
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else if (value > symtab[mid].sym_value)
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{
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low = mid + 1;
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}
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else /* if (value == symtab[mid].sym_value) */
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{
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return &symtab[mid];
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}
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}
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/* low == high... One final check. We might not have actually tested
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* the final symtab[] name.
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*
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* Example: Only the last pass through loop, suppose low = 1, high = 2,
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* mid = 1, and symtab[high].sym_name == name. Then we would get here with
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* low = 2, high = 2, but symtab[2].sym_name was never tested.
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*/
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return value == symtab[low].sym_value ? &symtab[low] : NULL;
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}
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