filesys.h

MP3 Player Source Code

/** \file filesys.h
 * File system interface, Implemented: FAT16, FAT32.
 *
 * 
 */


#ifndef FAT_H
#define FAT_H

#include "buffer.h"
#include "board.h"

/** Use PSW User Definable Flag to indicate FAT16/32 */
#define IS_FAT_32 UDF

Public extern xdata unsigned long fileSize;



/** Maximum allowable number of fragments in file */
#define MAX_NUMBER_FRAGMENTS 10

/** Fragment Table. */
xdata extern struct fragmentEntry {
  unsigned long start; /**< Starting sector of fragment */
  unsigned long length; /**< Length of fragment in sectors */
} fragment[MAX_NUMBER_FRAGMENTS];

/** 8 first characters of current file name */
xdata extern char currentFileName[12];

/** Start the filing system and initialize all necessary subsystems.
    Init storage and file system. FAT16 and FAT32 are supported */
unsigned char InitFileSystem();

 /** Open a file for reading. 
 * Prepares the Filing System to read a data file from the storage.
 * Files are referred to by their numbers, not file names. This makes the
 * system generic, not necessarily needing a complex file system such as
 * FAT. The way to assign numbers to files is implementation dependent.
 * Returns 0 when ok, error code otherwise.
 * \param fileNumber number of file, starting from beginning of storage,
 * to open. 
 *
 * What this function actually does, is: it starts reading the FAT
 * records from start of the root directory, traversing through
 * subdirectories as it encounters them. When the fileNumber'th valid
 * record is encountered, it sets sectorAddress to point to its
 * first data sector but doesn't load any sector. fileSize is loaded
 * with the size in bytes indicated in the FAT record.
*/
unsigned char OpenFile (unsigned int fileNumber);


/** Read a character from current file.
 * This can be called after calling OpenFile. It is a slow method
 * for reading character based file data.
 * fileSize holds the number of characters still left in file to be read,
 * check for fileSize=0 to detect end-of-file. If FGetChar is called
 * after the end of file is reached, it does nothing and returns 0.
 */
unsigned char FGetChar();

/** Build a fragment table starting from current sector. 
 * Returns number of fragments in song. 
 * This function is used to get fast access to the filesystem when
 * playing so cluster chain needs not be followed when the song
 * is playing, that would be too slow with MMC cards without 
 * extra buffer memory for the file allocation tables.
 * \warning This function is too slow! (several seconds per MP3 file),
 * todo: write specialized routines for FAT16 and FAT32. */

unsigned char BuildFragmentTable(void);

/** Search for next free sector.
 * If freeSector is zero, a new file should be allocated. */    
unsigned char ScanForFreeSector();


/** Next free cluster number */
extern xdata unsigned long freeSector;

extern data unsigned char fatSectorsPerCluster;

void WriteClusterChain();

#endif