fat.c

Go to the documentation of this file.

/*! \file fat.c \brief FAT16/32 file system driver. */
//*****************************************************************************
//
// File Name    : 'fat.c'
// Title        : FAT16/32 file system driver
// Author       : Pascal Stang
// Date         : 11/07/2000
// Revised      : 12/12/2000
// Version      : 0.3
// Target MCU   : ATmega103 (should work for Atmel AVR Series)
// Editor Tabs  : 4
//
// This code is based in part on work done by Jesper Hansen for his
//      YAMPP MP3 player project.
//
// NOTE: This code is currently below version 1.0, and therefore is considered
// to be lacking in some functionality or documentation, or may not be fully
// tested.  Nonetheless, you can expect most functions to work.
//
// This code is distributed under the GNU Public License
//      which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************


#include <avr/io.h>
#include <avr/pgmspace.h>
#include <string.h>

#include "ata.h"
#include "rprintf.h"
#include "debug.h"

#include "fat.h"
#include "fatconf.h"

// globals
// buffers
unsigned char *SectorBuffer  =      (unsigned char *) FAT_SECTOR_BUFFER_ADDR;
unsigned char *FileNameBuffer =     (unsigned char *) FAT_FILENAME_BUFFER_ADDR;
unsigned char *PathNameBuffer =     (unsigned char *) FAT_PATHNAME_BUFFER_ADDR;

// filesystem constants/metrics
struct partrecord PartInfo;
unsigned char Fat32Enabled;
unsigned long FirstDataSector;
unsigned short BytesPerSector;
unsigned short SectorsPerCluster;
unsigned long FirstFATSector;
unsigned long RootDirStartCluster;

// operating variables
unsigned long CurrentDirStartCluster;   //< current directory starting cluster
struct FileInfoStruct FileInfo;         //< file information for last file accessed
unsigned long FatInCache = 0;


/*************************************************************************/
/*************************************************************************/


unsigned long fatClustToSect(unsigned long clust)
{
    return ((clust-2) * SectorsPerCluster) + FirstDataSector;
}

unsigned int fatClusterSize(void)
{
    // return the number of sectors in a disk cluster
    return SectorsPerCluster;
}

unsigned char fatInit( unsigned char device)
{
    //struct partrecord *pr;
    struct bpb710 *bpb;

    // read partition table
    // TODO.... error checking
    ataReadSectors(DRIVE0, 0, 1, SectorBuffer);
    // map first partition record   
    // save partition information to global PartInfo
    PartInfo = *((struct partrecord *) ((struct partsector *) SectorBuffer)->psPart);
//  PartInfo = *pr;
    
    // Read the Partition BootSector
    // **first sector of partition in PartInfo.prStartLBA
    ataReadSectors( DRIVE0, PartInfo.prStartLBA, 1, SectorBuffer );
    bpb = (struct bpb710 *) ((struct bootsector710 *) SectorBuffer)->bsBPB;

    // setup global disk constants
    FirstDataSector = PartInfo.prStartLBA;
    if(bpb->bpbFATsecs)
    {
        // bpbFATsecs is non-zero and is therefore valid
        FirstDataSector += bpb->bpbResSectors + bpb->bpbFATs * bpb->bpbFATsecs;
    }
    else
    {
        // bpbFATsecs is zero, real value is in bpbBigFATsecs
        FirstDataSector += bpb->bpbResSectors + bpb->bpbFATs * bpb->bpbBigFATsecs;
    }
    SectorsPerCluster   = bpb->bpbSecPerClust;
    BytesPerSector      = bpb->bpbBytesPerSec;
    FirstFATSector      = bpb->bpbResSectors + PartInfo.prStartLBA;

    switch (PartInfo.prPartType)
    {
        case PART_TYPE_DOSFAT16:
        case PART_TYPE_FAT16:
        case PART_TYPE_FAT16LBA:
            // first directory cluster is 2 by default (clusters range 2->big)
            RootDirStartCluster = CLUST_FIRST;
            // push data sector pointer to end of root directory area
            //FirstDataSector += (bpb->bpbRootDirEnts)/DIRENTRIES_PER_SECTOR;
            Fat32Enabled = FALSE;
            break;
        case PART_TYPE_FAT32LBA:
        case PART_TYPE_FAT32:
            // bpbRootClust field exists in FAT32 bpb710, but not in lesser bpb's
            RootDirStartCluster = bpb->bpbRootClust;
            // push data sector pointer to end of root directory area
            // need this? FirstDataSector += (bpb->bpbRootDirEnts)/DIRENTRIES_PER_SECTOR;
            Fat32Enabled = TRUE;
            break;
        default:
            rprintfProgStrM("Found: No Partition!\r\n");
            //return 1;
            break;
    }

    // set current directory to root (\)
    CurrentDirStartCluster = RootDirStartCluster;
    PathNameBuffer[0] = '\\';
    PathNameBuffer[1] = 0;


    // do debug
#ifdef DEBUG_FAT
    switch (PartInfo.prPartType)
    {
        case PART_TYPE_DOSFAT16:
                rprintfProgStrM("Found: DOSFAT 16\r\n");
                break;
        case PART_TYPE_FAT16:
                rprintfProgStrM("Found: FAT16\r\n");
                break;
        case PART_TYPE_FAT16LBA:
                rprintfProgStrM("Found: FAT16 LBA\r\n");
                break;
        case PART_TYPE_FAT32LBA:
                rprintfProgStrM("Found: FAT32 LBA\r\n");
                break;
        case PART_TYPE_FAT32:
                rprintfProgStrM("Found: FAT32\r\n");
                //return 1; 
                break;
        default:
                rprintfProgStrM("Found: No Partition!\r\n");
                //return 1;
                break;
    }

    rprintfProgStrM("First sector    : ");  rprintfu32(PartInfo.prStartLBA);    rprintfCRLF();
    rprintfProgStrM("Size            : ");  rprintfu32(PartInfo.prSize);        rprintfCRLF();
    rprintfProgStrM("bytes/sector    : ");  rprintfu16(bpb->bpbBytesPerSec);    rprintfCRLF();
    rprintfProgStrM("sectors/cluster : ");  rprintfu08(bpb->bpbSecPerClust);    rprintfCRLF();
    rprintfProgStrM("reserved sectors: ");  rprintfu16(bpb->bpbResSectors);     rprintfCRLF();
    rprintfProgStrM("FatSectors      : ");  rprintfu16(bpb->bpbFATsecs);        rprintfCRLF();
    rprintfProgStrM("BigFatSectors   : ");  rprintfu32(bpb->bpbBigFATsecs);     rprintfCRLF();
    rprintfProgStrM("Number of Fats  : ");  rprintfu08(bpb->bpbFATs);           rprintfCRLF();
    rprintfProgStrM("First Fat Sector: ");  rprintfu32(FirstFATSector);         rprintfCRLF();
    rprintfProgStrM("First Data Sect : ");  rprintfu32(FirstDataSector);        rprintfCRLF();
    rprintfProgStrM("RootDirStartClus: ");  rprintfu32(RootDirStartCluster);    rprintfCRLF();
#endif

    return 0;   
}

//////////////////////////////////////////////////////////////

unsigned char fatGetDirEntry(unsigned short entry)
{
    unsigned long sector;
    struct direntry *de = 0;    // avoid compiler warning by initializing
    struct winentry *we;
    unsigned char haveLongNameEntry;
    unsigned char gotEntry;
    unsigned short b;
    int i,index;
    char *fnbPtr;
    unsigned short entrycount = 0;

    // read dir data
    sector = fatClustToSect(CurrentDirStartCluster);

    haveLongNameEntry = 0;
    gotEntry = 0;

    index = 16; // crank it up
    
    //while(entrycount < entry) 
    while(1)
    {
        if(index == 16) // time for next sector ?
        {
            ataReadSectors( DRIVE0, sector++, 1, SectorBuffer);
            de = (struct direntry *) SectorBuffer;
            index = 0;
        }
        
        // check the status of this directory entry slot
        if(de->deName[0] == 0x00)
        {
            // slot is empty and this is the end of directory
            gotEntry = 0;
            break;
        }
        else if(de->deName[0] == 0xE5)
        {
            // this is an empty slot
            // do nothing and move to the next one
        }
        else
        {
            // this is a valid and occupied entry
            // is it a part of a long file/dir name?
            if(de->deAttributes == ATTR_LONG_FILENAME)
            {
                // we have a long name entry
                // cast this directory entry as a "windows" (LFN: LongFileName) entry
                we = (struct winentry *) de;
                
                b = WIN_ENTRY_CHARS*( (we->weCnt-1) & 0x0f);        // index into string
                fnbPtr = &FileNameBuffer[b];
                for (i=0;i<5;i++)   *fnbPtr++ = we->wePart1[i*2];   // copy first part
                for (i=0;i<6;i++)   *fnbPtr++ = we->wePart2[i*2];   // second part
                for (i=0;i<2;i++)   *fnbPtr++ = we->wePart3[i*2];   // and third part
                if (we->weCnt & WIN_LAST) *fnbPtr = 0;              // in case dirnamelength is multiple of 13, add termination
                if ((we->weCnt & 0x0f) == 1) haveLongNameEntry = 1; // flag that we have a complete long name entry set
            }
            else
            {
                // we have a short name entry
                
                // check if this is the short name entry corresponding
                // to the end of a multi-part long name entry
                if(haveLongNameEntry)
                {
                    // a long entry name has been collected
                    if(entrycount == entry)     
                    {
                        // desired entry has been found, break out
                        gotEntry = 1;
                        break;
                    }
                    // otherwise
                    haveLongNameEntry = 0;  // clear long name flag
                    entrycount++;           // increment entry counter      
                }
                else
                {
                    // entry is a short name (8.3 format) without a
                    // corresponding multi-part long name entry
                    fnbPtr = FileNameBuffer;
                    for (i=0;i<8;i++)   *fnbPtr++ = de->deName[i];      // copy name
                    *fnbPtr++ = '.';                                    // insert '.'
                    for (i=0;i<3;i++)   *fnbPtr++ = de->deExtension[i]; // copy extension
                    *fnbPtr = 0;                                        // null-terminate

                    if(entrycount == entry)     
                    {
                        // desired entry has been found, break out
                        gotEntry = 1;
                        break;
                    }
                    // otherwise
                    entrycount++;           // increment entry counter      
                }
            }
        }
        // next directory entry
        de++;
        // next index
        index++;
    }
    
    // we have a file/dir to return
    // store file/dir starting cluster (start of data)
    FileInfo.StartCluster = (unsigned long) ((unsigned long)de->deHighClust << 16) + de->deStartCluster;
    // store file/dir size
    // (note: size field for subdirectory entries is always zero)
    FileInfo.Size = de->deFileSize;
    // store file/dir attributes
    FileInfo.Attr = de->deAttributes;
    // store file/dir creation time
    FileInfo.CreateTime = de->deCTime[0] | de->deCTime[1]<<8;
    // store file/dir creation date
    FileInfo.CreateTime = de->deCDate[0] | de->deCDate[1]<<8;

    return gotEntry;
}

// change directory into 
unsigned char fatChangeDirectory(unsigned short entry)
{
    // get the requested directory entry
    if( fatGetDirEntry(entry) )
    {
        // make sure the entry is a directory
        if(FileInfo.Attr & ATTR_DIRECTORY)
        {
            // change directories into this directory
            // check to see if we are changing back to root directory
            if(FileInfo.StartCluster)
            {
                // standard change directory
                CurrentDirStartCluster = FileInfo.StartCluster;
            }
            else
            {
                // if startCluster pointer is zero,
                // a change to the root directory is intended
                // change directory to root
                CurrentDirStartCluster = RootDirStartCluster;
            }
            // TODO: handle pathname properly for going up a directory
            // set path string
            strcat(PathNameBuffer, FileNameBuffer);
            strcat(PathNameBuffer, "\\");
            // return success
            return TRUE;
        }
        else
        {
            // not a directory, cannot CD into a file!
            return FALSE;
        }
    }
    else
    {
        // not a valid entry, cannot CD!
        return FALSE;
    }
}

void fatPrintDirEntry(void)
{
    // print a formatted dir-style output for most recent file
    // print date
    rprintfNum(10, 2, FALSE, '0', (FileInfo.CreateDate&DD_MONTH_MASK)>>DD_MONTH_SHIFT );    // month
    rprintfChar('/');
    rprintfNum(10, 2, FALSE, '0', (FileInfo.CreateDate&DD_DAY_MASK)>>DD_DAY_SHIFT );        // day
    rprintfChar('/');
    rprintfNum(10, 4, FALSE, '0', (FileInfo.CreateDate&DD_YEAR_MASK)>>DD_YEAR_SHIFT );  // year
    rprintfChar(' ');

    // print time
    rprintfNum(10, 2, FALSE, '0', (FileInfo.CreateTime&DT_HOURS_MASK)>>DT_HOURS_SHIFT );    // month
    rprintfChar(':');
    rprintfNum(10, 2, FALSE, '0', (FileInfo.CreateTime&DT_MINUTES_MASK)>>DT_MINUTES_SHIFT );        // day
    rprintfChar(':');
    rprintfNum(10, 2, FALSE, '0', 2*(FileInfo.CreateTime&DT_2SECONDS_MASK)>>DT_2SECONDS_SHIFT );    // seconds
    rprintfChar(' ');

    // print attributes
    if(FileInfo.Attr & ATTR_VOLUME)     rprintfChar('V'); else rprintfChar('-');
    if(FileInfo.Attr & ATTR_DIRECTORY)  rprintfChar('D'); else rprintfChar('-');
    if(FileInfo.Attr & ATTR_READONLY)   rprintfChar('R'); else rprintfChar('-');
    if(FileInfo.Attr & ATTR_HIDDEN)     rprintfChar('H'); else rprintfChar('-');
    if(FileInfo.Attr & ATTR_SYSTEM)     rprintfChar('S'); else rprintfChar('-');
    if(FileInfo.Attr & ATTR_ARCHIVE)    rprintfChar('A'); else rprintfChar('-');
    rprintfChar(' ');

    // print filesize
    rprintfNum(10, 8, FALSE, ' ', FileInfo.Size);   // filesize
    rprintfChar(' ');

    // print filename
    rprintfStr(FileNameBuffer);
}

void fatDumpDirSlot(unsigned short slot)
{
    unsigned long sector;
    // load correct sector
    sector = fatClustToSect(CurrentDirStartCluster);
    sector += slot/DIRENTRIES_PER_SECTOR;
    // print the entry as a hex table
    debugPrintHexTable(32, SectorBuffer+(slot<<5) );
}

struct FileInfoStruct* fatGetFileInfo(void)
{
    return &FileInfo;
}

// return the size of the last directory entry
unsigned long fatGetFilesize(void)
{
    return FileInfo.Size;
}

// return the long name of the last directory entry
char* fatGetFilename(void)
{   
    return FileNameBuffer;
}

// return the directory of the last directory entry
char* fatGetDirname(void)
{   
    return PathNameBuffer;
}

// load a clusterfull of data
void fatLoadCluster(unsigned long cluster, unsigned char *buffer)
{
    register unsigned char i;
    // read cluster
    //while ( ataReadSectors( DRIVE0, clust2sect(cluster), SectorsPerCluster, buffer) != 0);
    for(i=0; i<SectorsPerCluster; i++)
    {
        ataReadSectors( DRIVE0, fatClustToSect(cluster)+i, 1, buffer+(i<<9) );
        // temporary fix for wierd misaligned cluster problem
        // (only when using FAT16?)
//      ataReadSectors( DRIVE0, fatClustToSect(cluster+8)+i, 1, buffer+(i<<9) );
    }
}


// find next cluster in the FAT chain
unsigned long fatNextCluster(unsigned long cluster)
{
    unsigned long nextCluster;
    unsigned long fatMask;
    unsigned long fatOffset;
    unsigned long sector;
    unsigned int offset;
    
    // get fat offset in bytes
    if(Fat32Enabled)
    {
        // four FAT bytes (32 bits) for every cluster
        fatOffset = cluster << 2;
        // set the FAT bit mask
        fatMask = FAT32_MASK;
    }
    else
    {
        // two FAT bytes (16 bits) for every cluster
        fatOffset = cluster << 1;
        // set the FAT bit mask
        fatMask = FAT16_MASK;
    }
    
    // calculate the FAT sector that we're interested in
    sector = FirstFATSector + (fatOffset / BytesPerSector);
    // calculate offset of the our entry within that FAT sector
    offset = fatOffset % BytesPerSector;

    // if we don't already have this FAT chunk loaded, go get it
    if (sector != FatInCache)
    {
        // read sector of FAT table
        while (ataReadSectors( DRIVE0, sector, 1, (unsigned char*)FAT_CACHE_ADDR) != 0);
        FatInCache = sector;
    }

    // read the nextCluster value
    nextCluster = (*((unsigned long*) &((char*)FAT_CACHE_ADDR)[offset])) & fatMask;

    // check to see if we're at the end of the chain
    if (nextCluster == (CLUST_EOFE & fatMask))
        nextCluster = 0;

#ifdef DEBUG_FAT
    rprintfProgStrM(">");
    rprintfu32(nextCluster);
    rprintfCRLF();
#endif
    
    return nextCluster;
}

---