realloc.c

对内存的分配、释放和使用进行检查

/*
 * (c) Copyright 1990 Conor P. Cahill (uunet!virtech!cpcahil).  
 * You may copy, distribute, and use this software as long as this
 * copyright statement is not removed.
 */
#include <stdio.h>
#include "malloc.h"

/*
 * Function:	realloc()
 *
 * Purpose:	to re-allocate a data area.
 *
 * Arguments:	cptr	- pointer to area to reallocate
 *		size	- size to change area to
 *
 * Returns:	pointer to new area (may be same area)
 *
 * Narrative:	verify pointer is within malloc region
 *		obtain mlist pointer from cptr
 *		verify magic number is correct
 *		verify inuse flag is set
 *		verify connection to adjoining segments is correct
 *		save requested size
 *		round-up size to appropriate boundry
 *		IF size is bigger than what is in this segment
 *		    try to join next segment to this segment
 *		IF size is less than what is is this segment
 *		    determine leftover amount of space
 *		ELSE
 *		    allocate new segment of size bites
 *		    IF allocation failed
 *		        return NULL
 *		    copy previous data to new segment
 *		    free previous segment
 *		    return new pointer
 *		split of extra space in this segment (if any)
 *		clear bytes beyound what they had before
 *		return pointer to data 
 */
#ifndef lint
static
char rcs_hdr[] = "$Id: realloc.c,v 1.7 90/05/11 00:13:10 cpcahil Exp $";
#endif

char *
realloc(cptr,size)
	char			* cptr;
	unsigned int		  size;
{
	void			  free();
	char			* func = "realloc";
	int			  i;
	char			* malloc();
	extern int		  malloc_checking;
	extern struct mlist 	* malloc_end;
	extern int		  malloc_errno;
	extern char		* malloc_data_end;
	extern char		* malloc_data_start;
	char			* memcpy();
	char			* new_cptr;
	struct mlist		* ptr;
	int			  r_size;

	/*
	 * IF malloc chain checking is on, go do it.
	 */
	if( malloc_checking )
	{
		(void) malloc_chain_check(1);
	}

	/*
	 * verify that cptr is within the malloc region...
	 */
	if( cptr < malloc_data_start || cptr > malloc_data_end )
	{
		malloc_errno = M_CODE_BAD_PTR;
		malloc_warning(func);
		return (NULL);
	}

	/* 
	 * convert pointer to mlist struct pointer.  To do this we must 
	 * move the pointer backwards the correct number of bytes...
	 */
	
	ptr = (struct mlist *) (cptr - M_SIZE);
	
	if( (ptr->flag&M_MAGIC) != M_MAGIC )
	{
		malloc_errno = M_CODE_BAD_MAGIC;
		malloc_warning(func);
		return(NULL);
	}

	if( ! (ptr->flag & M_INUSE) )
	{
		malloc_errno = M_CODE_NOT_INUSE ;
		malloc_warning(func);
		return(NULL);
	}

 	if( (ptr->prev && (ptr->prev->next != ptr) ) ||
	    (ptr->next && (ptr->next->prev != ptr) ) ||
	    ((ptr->next == NULL) && (ptr->prev == NULL)) )
	{
		malloc_errno = M_CODE_BAD_CONNECT;
		malloc_warning(func);
		return(NULL);
	}

	r_size = ++size;

	M_ROUNDUP(size);

	if( size > ptr->s.size )
	{
		malloc_join(ptr,ptr->next,1,1);
	}

	if( size > ptr->s.size )
	{
		/*
		 * else we can't combine it, so lets allocate a new chunk,
		 * copy the data and free the old chunk...
		 */
		new_cptr = malloc(size);

		if( new_cptr == (char *) 0)
		{
			return(new_cptr);
		}

		if( r_size < ptr->r_size )
		{
			i = r_size;
		}
		else
		{
			i = ptr->r_size;
		}
		(void)memcpy(new_cptr,ptr->data,i);
		free(cptr);
		return(new_cptr);

	} /* else... */

	/*
	 * save amount of real data in new segment (this will be used in the
	 * memset later) and then save requested size of this segment.
	 */

	if( ptr->r_size < r_size )
	{
		i = ptr->r_size;
	}
	else
	{
		i = r_size;
	}

	ptr->r_size = r_size;

	/*
	 * split off extra free space at end of this segment, if possible...
	 */

	malloc_split(ptr);

	malloc_memset( ptr->data+i, M_FILL, ptr->s.size - i);
		
	return(ptr->data);

} /* realloc(... */


/*
 * $Log:	realloc.c,v $
 * Revision 1.7  90/05/11  00:13:10  cpcahil
 * added copyright statment
 * 
 * Revision 1.6  90/02/25  11:01:20  cpcahil
 * added support for malloc chain checking.
 * 
 * Revision 1.5  90/02/24  21:50:31  cpcahil
 * lots of lint fixes
 * 
 * Revision 1.4  90/02/24  17:29:39  cpcahil
 * changed $Header to $Id so full path wouldnt be included as part of rcs 
 * id string
 * 
 * Revision 1.3  90/02/24  17:20:00  cpcahil
 * attempt to get rid of full path in rcs header.
 * 
 * Revision 1.2  90/02/24  15:14:20  cpcahil
 * 1. added function header 
 * 2. changed calls to malloc_warning to conform to new usage
 * 3. added setting of malloc_errno
 *  4. broke up bad pointer determination so that errno's would be more
 *    descriptive
 * 
 * Revision 1.1  90/02/22  23:17:43  cpcahil
 * Initial revision
 * 
 */