filesys.h

/* filesys.h
 *
 * describes FAT structures
 * http://www.c-jump.com/CIS24/Slides/FAT/lecture.html#F01_0020_fat
 * http://www.tavi.co.uk/phobos/fat.html
 */

#ifndef FILESYS_H
#define FILESYS_H

#include <time.h>

#ifndef TRUE
#define TRUE 1
#endif
#ifndef FALSE
#define FALSE 0
#endif

#define MAXBLOCKS     1024
#define BLOCKSIZE     1024
#define FATENTRYCOUNT (BLOCKSIZE / sizeof(fatentry_t))
#define DIRENTRYCOUNT ((BLOCKSIZE - (2*sizeof(int)) ) / sizeof(direntry_t))
#define MAXNAME       256
#define MAXPATHLENGTH 1024

#define UNUSED        -1
#define ENDOFCHAIN     0
#define EOF           -1


typedef unsigned char Byte ;

/* create a type fatentry_t, we set this currently to short (16-bit)
 */
typedef short fatentry_t ;


// a FAT block is a list of 16-bit entries that form a chain of disk addresses

//const int   fatentrycount = (blocksize / sizeof(fatentry_t)) ;

typedef fatentry_t fatblock_t [ FATENTRYCOUNT ] ;


/* create a type direntry_t
 */

typedef struct direntry {
   int         entrylength ;   // records length of this entry (can be used with names of variables length)
   Byte        isdir ;
   Byte        unused ;
   time_t      modtime ;
   int         filelength ;
   fatentry_t  firstblock ;
   char   name [MAXNAME] ;
} direntry_t ;

// a directory block is an array of directory entries

//const int   direntrycount = (blocksize - (2*sizeof(int)) ) / sizeof(direntry_t) ;

typedef struct dirblock {
   int isdir ;
   int nextEntry ;
   direntry_t entrylist [ DIRENTRYCOUNT ] ; // the first two integer are marker and endpos
} dirblock_t ;



// a data block holds the actual data of a filelength, it is an array of 8-bit (byte) elements

typedef Byte datablock_t [ BLOCKSIZE ] ;


// a diskblock can be either a directory block, a FAT block or actual data

typedef union block {
   datablock_t data ;
   dirblock_t  dir  ;
   fatblock_t  fat  ;
} diskblock_t ;

// finally, this is the disk: a list of diskblocks
// the disk is declared as extern, as it is shared in the program
// it has to be defined in the main program filelength

extern diskblock_t virtualDisk [ MAXBLOCKS ] ;


// when a file is opened on this disk, a file handle has to be
// created in the opening program

typedef struct filedescriptor {
   char        mode[3] ;
   fatentry_t  blockno ;           // block no
   int         pos     ;           // byte within a block
   diskblock_t buffer  ;
} MyFILE ;


/* ======================================= D3_D1 FUNCTIONS */
void format() ;

/* ======================================= C3_C1 FUNCTIONS */
MyFILE * myfopen ( const char *, const char * ) ;
void myfclose ( MyFILE * );
void myfputc ( int , MyFILE * );
int myfgetc ( MyFILE * );

/* ======================================= B3_B1 FUNCTIONS */
void mymkdir(char *);
char **mylistdir(char *);

/* ======================================= A5_A1 FUNCTIONS */
void mychdir(char *);
void myremove(char *);
void myrmdir(char *);

/* ======================================= HELPER FUNCTIONS */
void writedisk ( const char * ) ;
void printBlock ( int );
void copyFAT();
void moveToBlock (diskblock_t *, int);
int nextUnusedBlock();
int nextUnusedDir();
int fileLocation(const char *);
void cleanFAT(int);
diskblock_t freeDirBlock();
int fileEntryIndex(const char *);
void printContents(char **);
int isDirEmpty(dirblock_t);

/* ======================================= EXTRA */
void myfvdsys(const char *, const char *);
void myfsysvd(const char *, const char * );
void myfcopy (char *, char* );
void myfmove (char *, char* );

#endif