lfscheck.c

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/* lfscheck.c - lfscheck */

#include <xinu.h>
#include <ramdisk.h>

/*------------------------------------------------------------------------
 * lfscheck  -  Check a directory to verify it contains a Xinu file system
 *------------------------------------------------------------------------
 */
status  lfscheck (
      struct lfdir  *dirptr     /* Ptr to an in-core directory  */
    )
{
    uint32  reverse;        /* LFS_ID in reverse byte order */

    /* Verify the File System ID, all 0's and all 1's fields */

    if ( (dirptr->lfd_fsysid != LFS_ID)       ||
         (dirptr->lfd_allzeros != 0x00000000) ||
         (dirptr->lfd_allones  != 0xffffffff) ) {
        return SYSERR;
    }

    /* Check the reverse-order File System ID field */

    reverse = ((LFS_ID>>24) & 0x000000ff) | 
          ((LFS_ID>> 8) & 0x0000ff00) |
          ((LFS_ID<< 8) & 0x00ff0000) |
          ((LFS_ID<<24) & 0xff000000) ;

    if (dirptr->lfd_revid != reverse) {
        return SYSERR;
    }

    /* Extra sanity check - verify file count is positive */
    if (dirptr->lfd_nfiles < 0){
        return SYSERR;
    }
    return OK;
}