📄 fat.c
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/*C**************************************************************************
* NAME: fat.c
*----------------------------------------------------------------------------
* Copyright (c) 2003 Atmel.
*----------------------------------------------------------------------------
* RELEASE: snd1c-refd-nf-4_0_3
* REVISION: 1.41
*----------------------------------------------------------------------------
* PURPOSE:
* FAT16/FAT12 file-system basics functions
*
* NOTES:
* Supports only the first partition
* Supports only 512 bytes sector size
* Supports only file fragmentation < MAX_FILE_FRAGMENT_NUMBER
* Supports only one file openned at a time
*
* Global Variables:
* - gl_buffer: array of bytes in pdata space
*****************************************************************************/
/*_____ I N C L U D E S ____________________________________________________*/
#include "config.h" /* system configuration */
#include "..\mem\hard.h" /* low level function definition */
#include "file.h" /* file function definition */
#include "fat.h" /* fat file-system definition */
/*_____ M A C R O S ________________________________________________________*/
/*_____ D E F I N I T I O N ________________________________________________*/
extern bit reserved_disk_space;
extern pdata Byte gl_buffer[];
extern xdata Byte fat_buf_sector[]; /* 512 bytes buffer */
extern char pdata *lfn_name; /* long filename limited to MAX_FILENAME_LEN chars */
/* disk management */
extern data Uint32 fat_ptr_fats; /* address of the first byte of FAT */
extern data Uint32 fat_ptr_rdir; /* address of the first byte of root dir */
extern data Uint32 fat_ptr_data; /* address of the first byte of data */
extern data Byte fat_cluster_size; /* cluster size (sector count) */
extern idata Byte fat_cluster_mask; /* mask for end of cluster test */
extern bdata bit dir_is_root; /* TRUE: point the root directory */
extern bdata bit fat_is_fat16; /* TRUE: FAT16 - FALSE: FAT12 */
extern bdata bit fat_open_mode; /* READ or WRITE */
extern bdata bit fat_2_is_present; /* TRUE: 2 FATs - FALSE: 1 FAT */
extern bdata bit flag_end_disk_file;
extern xdata Uint32 fat_count_of_clusters;/* number of cluster - 2 */
extern xdata Uint16 fat_root_entry; /* position in root dir */
extern xdata Union32 fat_file_size;
extern xdata Uint16 fat_fat_size; /* FAT size in sector count */
/* directory management */
extern idata Uint32 fat_dir_current_sect; /* sector of selected entry in dir list */
extern xdata Uint16 fat_dir_list_index; /* index of current entry in dir list */
extern xdata Uint16 fat_dir_list_last; /* index of last entry in dir list */
extern idata Uint16 fat_dclust_byte_count;/* byte counter in directory sector */
extern idata Uint16 fat_dchain_index; /* the number of the fragment of the dir, in fact
the index of the table in the cluster chain */
extern idata Byte fat_dchain_nb_clust; /* the offset of the cluster from the first cluster
of the dir fragment */
extern xdata Uint32 fat_dir_start_sect; /* start sector of dir list */
extern xdata Uint16 fat_dir_current_offs; /* entry offset from fat_dir_current_sect */
extern xdata Byte fat_last_dclust_index;/* index of the last cluster in directory chain */
extern xdata fat_st_cache fat_cache; /* The cache structure, see the .h for more info */
extern xdata fat_st_clust_chain dclusters[MAX_DIR_FRAGMENT_NUMBER];
/* cluster chain for the current directory */
extern xdata char ext[3]; /* file extension (limited to 3 characters) */
#define fat_dir_entry_list fat_buf_sector /* manual variable overlay */
/* file management */
extern data Uint16 fat_fclust_byte_count;/* byte counter in file cluster */
extern idata Byte fat_last_clust_index; /* index of the last cluster in file chain */
extern idata Byte fat_fchain_index; /* the number of the fragment of the file, in fact
the index of the table in the cluster chain */
extern idata Uint16 fat_fchain_nb_clust; /* the offset of the cluster from the first cluster
of the file fragment */
extern xdata fat_st_clust_chain fclusters[MAX_FILE_FRAGMENT_NUMBER];
/* cluster chain for the current file */
/* Mode repeat A/B variables */
extern xdata Byte fat_fchain_index_save;
extern xdata Byte fat_fchain_nb_clust_save;
extern xdata Uint16 fat_fclust_byte_count_save;
static xdata fat_st_free_space free_space;
/*_____ D E C L A R A T I O N ______________________________________________*/
static void fat_get_dir_entry (fat_st_dir_entry xdata *);
static void fat_get_dir_file_list (Byte);
static bit fat_get_clusters (fat_st_clust_chain xdata *, Byte);
static bit fat_set_clusters (void);
static bit fat_dopen (void);
static bit fat_dseek (Int16);
static Byte fat_dgetc (void);
code Byte PBR_record_part1[] =
{
0xEB, 0x3C, 0x90, /* JMP instruction to boot code */
'O', 'E', 'M', ' ', 'N', 'A', 'M', 'E', /* OEM name */
SECTOR_SIZE, SECTOR_SIZE >> 8, /* number of bytes per sector */
0x00, /* number of sector per cluster */
NB_RESERVED, NB_RESERVED >> 8, /* number of reserved sector */
NB_FATS, /* number of FAT */
NB_ROOT_ENTRY, NB_ROOT_ENTRY >> 8, /* number of root directory entries */
0x00, 0x00, /* total sectors if less than 65535 */
HARD_DISK, /* media byte */
};
code Byte PBR_record_part2[] =
{
FAT_DRIVE_NUMBER, /* Drive number */
0x00, /* not used */
FAT_EXT_SIGN, /* extended boot signature */
0x00, 0x00, 0x00, 0x00, /* volume ID */
'N', 'O', ' ', 'N', 'A', 'M', 'E', ' ', ' ', ' ', ' ', /* volume label */
'F', 'A', 'T', '1', 0x00, ' ', ' ', ' ', /* File system type in ASCII */
};
/*F**************************************************************************
* NAME: fat_load_sector
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
*----------------------------------------------------------------------------
* PURPOSE:
* This function load a sector in fat_buf_sector
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
*----------------------------------------------------------------------------
* REQUIREMENTS:
*
*****************************************************************************/
bit fat_load_sector(Uint32 sector)
{
Uint16 i;
if (Hard_read_open(sector) == OK)
{
for (i = 0; i < (SECTOR_SIZE); i++)
{
fat_buf_sector[i++] = Hard_read_byte();
fat_buf_sector[i++] = Hard_read_byte();
fat_buf_sector[i++] = Hard_read_byte();
fat_buf_sector[i] = Hard_read_byte();
}
Hard_read_close();
return OK;
}
else
{
return KO;
}
}
/*F**************************************************************************
* NAME: fat_install
*----------------------------------------------------------------------------
* PARAMS:
*
* return:
* - OK: intallation succeeded
* - KO: - partition 1 signature not recognized
* - FAT type is not FAT12/FAT16
* - sector size is not 512 bytes
* - MBR or PBR signatures are not correct
* - low level read open failure
*----------------------------------------------------------------------------
* PURPOSE:
* Install the fat system, read mbr, bootrecords...
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
* if MBR not found, try to mount unpartitionned FAT
* sector size is fixed to 512 bytes to simplify low level drivers
* fat_ptr_fats = partition offset + nb_reserved_sector
* fat_ptr_rdir = fat_ptr_fat + fat_size * nb_fat
* fat_ptr_data = fat_ptr_rdir + nb_root_entries * 32 / 512
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
bit fat_install (void)
{
Uint32 fat_nb_sector;
/* MBR/PBR determination */
fat_ptr_fats = 1;
if (fat_load_sector(MBR_ADDRESS) == OK)
{
if ((fat_buf_sector[0] == 0xEB) && /* PBR Byte 0 */
(fat_buf_sector[2] == 0x90) && /* PBR Byte 2 */
((fat_buf_sector[21] & 0xF0) == 0xF0)) /* PBR Byte 21 : Media byte */
{
if ((fat_buf_sector[510] != LOW(BR_SIGNATURE)) && /* check PBR signature */
(fat_buf_sector[511] != HIGH(BR_SIGNATURE)))
{
return KO;
}
else
{
fat_ptr_fats = 0x00000000; /* first sector is PBR */
}
}
else
{ /* first sector is MBR */
if ((fat_buf_sector[446] != PARTITION_ACTIVE) &&
(fat_buf_sector[446] != 0x00))
{
return KO; /* not a MBR */
}
else
{
/* read partition offset (in sectors) at offset 8 */
((Byte*)&fat_ptr_fats)[3] = fat_buf_sector[454];
((Byte*)&fat_ptr_fats)[2] = fat_buf_sector[455];
((Byte*)&fat_ptr_fats)[1] = fat_buf_sector[456];
((Byte*)&fat_ptr_fats)[0] = fat_buf_sector[457];
if ((fat_buf_sector[510] != LOW(BR_SIGNATURE)) && /* check PBR signature */
(fat_buf_sector[511] != HIGH(BR_SIGNATURE)))
{
return KO;
}
}
}
}
else
{
return KO;
}
/* read and check usefull PBR info */
if (fat_load_sector(fat_ptr_fats) == OK)
{
if ((fat_buf_sector[11] != LOW(SECTOR_SIZE)) || /* read sector size (in bytes) */
(fat_buf_sector[12] != HIGH(SECTOR_SIZE)))
{
return KO;
}
/* read cluster size (in sector) */
fat_cluster_size = fat_buf_sector[13];
fat_cluster_mask = HIGH((Uint16)fat_cluster_size * SECTOR_SIZE) - 1;
/* compute FATs sector address: add reserved sector number */
fat_ptr_fats += fat_buf_sector[14];
fat_ptr_fats += (Uint16)fat_buf_sector[15] << 8;
/* read number of FATs */
if (fat_buf_sector[16] == 2)
fat_2_is_present = TRUE;
else
fat_2_is_present = FALSE;
/* read number of dir entries and compute rdir offset */
((Byte*)&fat_ptr_data)[3] = fat_buf_sector[17];
((Byte*)&fat_ptr_data)[2] = fat_buf_sector[18];
((Byte*)&fat_ptr_data)[1] = 0;
((Byte*)&fat_ptr_data)[0] = 0;
fat_ptr_data = (fat_ptr_data * DIR_SIZE) / SECTOR_SIZE;
/* read number of sector in partition (<32Mb) */
((Byte*)&fat_nb_sector)[3] = fat_buf_sector[19];
((Byte*)&fat_nb_sector)[2] = fat_buf_sector[20];
((Byte*)&fat_nb_sector)[1] = 0x00;
((Byte*)&fat_nb_sector)[0] = 0x00;
/* compute root directory sector address */
((Byte*)&fat_fat_size)[1] = fat_buf_sector[22];
((Byte*)&fat_fat_size)[0] = fat_buf_sector[23];
fat_ptr_rdir = fat_buf_sector[16] * fat_fat_size;
fat_ptr_rdir += fat_ptr_fats;
/* read number of sector in partition (>32Mb) */
if (!fat_nb_sector)
{
((Byte*)&fat_nb_sector)[3] = fat_buf_sector[32];
((Byte*)&fat_nb_sector)[2] = fat_buf_sector[33];
((Byte*)&fat_nb_sector)[1] = fat_buf_sector[34];
((Byte*)&fat_nb_sector)[0] = fat_buf_sector[35];
}
fat_count_of_clusters = (fat_nb_sector - (1 + (fat_buf_sector[16] * fat_fat_size) + fat_ptr_data))
/ fat_cluster_size;
if (fat_count_of_clusters <= MAX_CLUSTERS12)
fat_is_fat16 = FALSE;
else
if (fat_count_of_clusters <= MAX_CLUSTERS16)
fat_is_fat16 = TRUE;
/* else is FAT32 not supported */
/* compute data sector address */
fat_ptr_data += fat_ptr_rdir;
/* check partition signature */
if ((fat_buf_sector[510] != LOW(BR_SIGNATURE)) &&
(fat_buf_sector[511] != HIGH(BR_SIGNATURE)))
{
return KO;
}
return OK;
}
else
{ /* low level error */
return KO;
}
}
/*F**************************************************************************
* NAME: fat_get_dir_entry
*----------------------------------------------------------------------------
* PARAMS:
* entry: directory entry structure
*
* return:
*----------------------------------------------------------------------------
* PURPOSE:
* Get from directory all information about a directory or file entry
*----------------------------------------------------------------------------
* EXAMPLE:
*----------------------------------------------------------------------------
* NOTE:
* This function reads directly datas from sectors
* It automaticaly computes difference between LFN and normal entries
*----------------------------------------------------------------------------
* REQUIREMENTS:
*****************************************************************************/
void fat_get_dir_entry (fat_st_dir_entry xdata *entry)
{
bit exit_flag = FALSE;
bit lfn_entry_found = FALSE;
Byte i;
/* clear the name buffer */
for (i = MAX_FILENAME_LEN; i != 0; lfn_name[--i] = '\0');
while (!exit_flag)
/* loop while the entry is not a normal one. */
{
/* read the directory entry */
if (dir_is_root == TRUE)
{ /* root dir is linear -> Hard_read_byte() */
for (i = 0; i < DIR_SIZE; i++)
gl_buffer[i] = Hard_read_byte();
}
else
{ /* subdir can be fragmented -> dgetc() */
for (i = 0; i < DIR_SIZE; i++)
gl_buffer[i] = fat_dgetc();
}
/*computes gathered data
/* check if we have a LFN entry */
if (gl_buffer[11] != ATTR_LFN_ENTRY)
{
if (!lfn_entry_found)
{
/* true DOS 8.3 entry format */
for (i = 0; i < 8; i++)
{
lfn_name[i] = gl_buffer[i];
if (lfn_name[i] == ' ')
{ /* space is end of name */
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