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c56b96a54f
NULL is best for C as discussed - for coreutils - at: https://bugs.gnu.org/66221#53 * bootstrap.conf: Remove dependency on nullptr. * s/nullptr/NULL/. This effectively reverts 93ce19f0d5a1.
123 lines
2.7 KiB
C
123 lines
2.7 KiB
C
/* extendbuf.c -- manage a dynamically-allocated buffer
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Copyright (C) 2004-2026 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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/* Written by James Yougnman <jay@gnu.org>. */
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/* config.h must be included first. */
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#include <config.h>
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/* system headers. */
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#include <assert.h>
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#include <errno.h>
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#include <stdlib.h>
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/* gnulib headers. */
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#include "xalloc.h"
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/* find headers. */
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#include "extendbuf.h"
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/* We initially use a small default size to ensure that this code
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* gets exercised.
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*/
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#ifndef SIZE_DEFAULT
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# define SIZE_DEFAULT 16
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#endif
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static size_t
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decide_size (size_t current, size_t wanted)
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{
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size_t newsize;
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if (0 == current)
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newsize = SIZE_DEFAULT;
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else
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newsize = current;
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while (newsize < wanted)
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{
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if (2 * newsize < newsize)
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return wanted;
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newsize *= 2;
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}
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return newsize;
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}
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void *
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extendbuf (void* existing, size_t wanted, size_t *allocated)
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{
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int saved_errno;
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size_t newsize;
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void *result; /* leave uninitialized to allow static code checkers to identify bugs */
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saved_errno = errno;
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assert (wanted > 0u);
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newsize = decide_size (*allocated, wanted);
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if ( (*allocated) == 0 )
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{
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/* Sanity check: If there is no existing allocation size, there
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* must be no existing allocated buffer.
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*/
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assert (NULL == existing);
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(*allocated) = newsize;
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result = malloc (newsize);
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}
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else
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{
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if (newsize != (*allocated) )
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{
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(*allocated) = newsize;
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result = realloc (existing, newsize);
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if (NULL == result)
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{
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saved_errno = errno;
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}
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}
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else
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{
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result = existing;
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}
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}
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if (result)
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{
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/* malloc () or realloc () may have changed errno, but in the
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success case we want to preserve the previous value.
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*/
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errno = saved_errno;
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}
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return result;
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}
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void *
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xextendbuf (void* existing, size_t wanted, size_t *allocated)
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{
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void *p = extendbuf (existing, wanted, allocated);
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if (NULL == p)
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{
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free (existing);
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xalloc_die ();
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}
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return p;
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}
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