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/*
* IMFS Directory Access Routines
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include "imfs.h"
#include <string.h>
#include <dirent.h>
/*
* imfs_dir_read
*
* This routine will read the next directory entry based on the directory
* offset. The offset should be equal to -n- time the size of an individual
* dirent structure. If n is not an integer multiple of the sizeof a
* dirent structure, an integer division will be performed to determine
* directory entry that will be returned in the buffer. Count should reflect
* -m- times the sizeof dirent bytes to be placed in the buffer.
* If there are not -m- dirent elements from the current directory position
* to the end of the exisiting file, the remaining entries will be placed in
* the buffer and the returned value will be equal to -m actual- times the
* size of a directory entry.
*/
ssize_t imfs_dir_read(
rtems_libio_t *iop,
void *buffer,
size_t count
)
{
/*
* Read up to element iop->offset in the directory chain of the
* imfs_jnode_t struct for this file descriptor.
*/
rtems_chain_node *the_node;
rtems_chain_control *the_chain;
IMFS_jnode_t *the_jnode;
int bytes_transferred;
int current_entry;
int first_entry;
int last_entry;
struct dirent tmp_dirent;
rtems_filesystem_instance_lock( &iop->pathinfo );
the_jnode = (IMFS_jnode_t *)iop->pathinfo.node_access;
the_chain = &the_jnode->info.directory.Entries;
/* Move to the first of the desired directory entries */
bytes_transferred = 0;
first_entry = iop->offset;
/* protect against using sizes that are not exact multiples of the */
/* -dirent- size. These could result in unexpected results */
last_entry = first_entry
+ (count / sizeof( struct dirent )) * sizeof( struct dirent );
/* The directory was not empty so try to move to the desired entry in chain*/
for (
current_entry = 0,
the_node = rtems_chain_first( the_chain );
current_entry < last_entry
&& !rtems_chain_is_tail( the_chain, the_node );
current_entry += sizeof( struct dirent ),
the_node = rtems_chain_next( the_node )
) {
if( current_entry >= first_entry ) {
/* Move the entry to the return buffer */
tmp_dirent.d_off = current_entry;
tmp_dirent.d_reclen = sizeof( struct dirent );
the_jnode = (IMFS_jnode_t *) the_node;
tmp_dirent.d_ino = the_jnode->st_ino;
tmp_dirent.d_namlen = strlen( the_jnode->name );
strcpy( tmp_dirent.d_name, the_jnode->name );
memcpy(
buffer + bytes_transferred,
(void *)&tmp_dirent,
sizeof( struct dirent )
);
iop->offset += sizeof( struct dirent );
bytes_transferred += sizeof( struct dirent );
}
}
rtems_filesystem_instance_unlock( &iop->pathinfo );
return bytes_transferred;
}
/*
* imfs_dir_lseek
*
* This routine will behave in one of three ways based on the state of
* argument whence. Based on the state of its value the offset argument will
* be interpreted using one of the following methods:
*
* SEEK_SET - offset is the absolute byte offset from the start of the
* logical start of the dirent sequence that represents the
* directory
* SEEK_CUR - offset is used as the relative byte offset from the current
* directory position index held in the iop structure
* SEEK_END - N/A --> This will cause an EINVAL to be returned.
*/
off_t imfs_dir_lseek(
rtems_libio_t *iop,
off_t offset,
int whence
)
{
switch( whence ) {
case SEEK_SET: /* absolute move from the start of the file */
case SEEK_CUR: /* relative move */
iop->offset = (iop->offset/sizeof(struct dirent)) *
sizeof(struct dirent);
break;
case SEEK_END: /* Movement past the end of the directory via lseek */
/* is not a permitted operation */
default:
rtems_set_errno_and_return_minus_one( EINVAL );
break;
}
return 0;
}
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