/*------------------------------------------------------------------------
* lflControl - Provide control functions for a local file pseudo-device
*------------------------------------------------------------------------
*/
devcall lflControl (
struct dentry *devptr, /* entry in device switch table */
int32 func, /* a control function */
int32 arg1, /* argument #1 */
int32 arg2 /* argument #2 */
)
{
struct lflcblk *lfptr; /* ptr to open file table entry */
int32 retval; /* return value from func. call */
/* Obtain exclusive use of the file */
lfptr = &lfltab[devptr->dvminor];
wait(lfptr->lfmutex);
/* If file is not open, return an error */
if (lfptr->lfstate != LF_USED) {
signal(lfptr->lfmutex);
return SYSERR;
}
switch (func) {
/* Truncate a file */
case LF_CTL_TRUNC:
wait(Lf_data.lf_mutex);
retval = lftruncate(lfptr);
signal(Lf_data.lf_mutex);
signal(lfptr->lfmutex);
return retval;
default:
kprintf("lfControl: function %d not valid\n\r", func);
signal(lfptr->lfmutex);
return SYSERR;
}
}
/*------------------------------------------------------------------------
* lfstruncate - truncate a file by freeing its index and data blocks
* (assumes directory mutex held)
*------------------------------------------------------------------------
*/
status lfstruncate (
char *name /* file name to truncate */
)
{
char *nam, *cmp; /* ptrs used during comparison */
int32 i; /* general loop index */
struct lflcblk *lfptr; /* ptr to open file table entry */
struct lfdir *dirptr; /* ptr to in-memory directory */
bool8 found; /* was the name found? */
int32 retval; /* value returned from function */
struct ldentry *ldptr; /* ptr to an entry in directory */
ibid32 ifree; /* start of index blk free list */
ibid32 firstib; /* first index blk of the file */
ibid32 nextib; /* walks down list of the */
/* file's index blocks */
dbid32 nextdb; /* next data block to free */
struct lfiblk iblock; /* buffer for one index block */
/* Check length of name file (leaving space for NULLCH */
nam = name;
for (i=0; i< LF_NAME_LEN; i++) {
if (*nam++ == NULLCH) {
break;
}
}
if (i >= LF_NAME_LEN) { /* name is too long */
//kprintf("Name is too long\r\n");
return SYSERR;
}
/* Check if named file is open */
for (i=0; i<Nlfl; i++) { /* search file pseudo-devices */
lfptr = &lfltab[i];
if (lfptr->lfstate == LF_USED) {
/* Compare requested name to name of open file */
nam = name;
cmp = lfptr->lfname;
while(*nam != NULLCH) {
if (*nam != *cmp) {
break;
}
nam++;
cmp++;
}
/* if named file is open, call lftruncate directly */
if ( (*nam==NULLCH) && (*cmp == NULLCH) ) {
//kprintf("file to truncate is open\r\n");
wait(lfptr->lfmutex);
retval = lftruncate(lfptr);
signal(lfptr->lfmutex);
//kprintf("truncated the open file\r\n");
return retval;
}
}
}
/* Named file is not open */
/* Obtain copy of directory if not already present in memory */
dirptr = &Lf_data.lf_dir;
if (! Lf_data.lf_dirpresent) {
retval = read(Lf_data.lf_dskdev,(char *)dirptr,LF_AREA_DIR);
if (retval == SYSERR ) {
//kprintf("Cannot not read directory into memory\r\n");
return SYSERR;
}
Lf_data.lf_dirpresent = TRUE;
}
/* Search directory to see if file exists */
found = FALSE;
for (i=0; i<dirptr->lfd_nfiles; i++) {
ldptr = &dirptr->lfd_files[i];
nam = name;
cmp = ldptr->ld_name;
while(*nam != NULLCH) {
if (*nam != *cmp) {
break;
}
nam++;
cmp++;
}
if ( (*nam==NULLCH) && (*cmp==NULLCH) ) { /* name found */
found = TRUE;
break;
}
}
/* if file does not exist, return SYSERR */
if (! found) {
signal(Lf_data.lf_mutex);
//kprintf("Named file to truncate does not exist\r\n");
return SYSERR;
}
/* if file is in directory, free its index and data blocks */
else {
if (ldptr->ld_size == 0) { /* file is already empty */
return OK;
}
/* Obtain ID of first index block on free list */
ifree = Lf_data.lf_dir.lfd_ifree;
/* Record file's first i-block and clear directory entry */
firstib = ldptr->ld_ilist;
ldptr->ld_ilist = LF_INULL;
ldptr->ld_size = 0;
Lf_data.lf_dirdirty = TRUE;
/* Walk along index block list, disposing of each data block*/
/* and clearing the corresponding pointer. A note on loop */
/* termination: last pointer is set to ifree below. */
for (nextib=firstib; nextib!=ifree; nextib=iblock.ib_next) {
/* Obtain a copy of current index block from disk */
lfibget(Lf_data.lf_dskdev, nextib, &iblock);
/* Free each data block in the index block */
for (i=0; i<LF_IBLEN; i++) { /* for each d-block */
/* Free the data block */
nextdb = iblock.ib_dba[i];
if (nextdb != LF_DNULL) {
lfdbfree(Lf_data.lf_dskdev, nextdb);
}
/* Clear entry in i-block for this d-block */
iblock.ib_dba[i] = LF_DNULL;
}
/* Clear offset (just to make debugging easier) */
iblock.ib_offset = 0;
/* For the last index block on the list, make it point */
/* to the current free list */
if (iblock.ib_next == LF_INULL) {
iblock.ib_next = ifree;
}
/* Write cleared i-block back to disk */
lfibput(Lf_data.lf_dskdev, nextib, &iblock);
}
/* Last index block on the file list now points to first node */
/* on the current free list. Once we make the free list */
/* point to the first index block on the file list, the */
/* entire set of index blocks will be on the free list */
Lf_data.lf_dir.lfd_ifree = firstib;
/* Indicate that directory has changed and return */
Lf_data.lf_dirdirty = TRUE;
return OK;
}
}
