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#include "fat_fs.h"
#include "cache.h"
#include "disklab.h"

#include <stdio.h>
#include <string.h>


/* some generic defines */
#define FILENAME_MAX_LG2 6
#define FILENAME_MAX_    ( 1 << FILENAME_MAX_LG2 )
#define NULLFILE         0
#define NULLOFFSET       0
#define retry_count      16
#define LDLINUX_MAGIC    0x3eb202fe

#define MAX_OPEN_LG2     6
#define MAX_OPEN         ( 1 << MAX_OPEN_LG2 )

#define SECTOR_SHIFT     9
#define SECTOR_SIZE      ( 1 << SECTOR_SHIFT )

#define DIRENT_SHIFT     5
#define DIRENT_SIZE      ( 1 << DIRENT_SHIFT )

#define ROOT_DIR_WORD    0x002f

enum fat_type{ FAT12, FAT16, FAT32 };
__u8 FATType = 0;


/* generic information about FAT fs */

__u32 FAT;            /* Location of (first) FAT */
__u32 RootDirArea;    /* Location of root directory area */
__u32 RootDir;        /* Location of root directory proper */
__u32 DataArea;       /* Location of data area */
__u32 TotalSectors;   /* Total number of sectors */
__u32 ClustSize;      /* Bytes/cluster */
__u32 ClustMask;      /* Sector/cluster - 1 */
__u8  CopySuper;      /* Distinguish .bs versus .bss */
__u8  DriveNumber;    /* BIOS drive number */
__u8  ClustShift;     /* Shift count for sectors/cluster */
__u8  ClustByteShift; /* Shift count for bytes/cluster */

/* for SYSLINUX, the block size equal to the sector size */
__u32 blk_size = 1 << SECTOR_SHIFT;

/* used for long name dir entry */
char *NameStart;
int NameLen;


/* file structure. This holds the information for each currently open file */
struct open_file_t {
        __u32 file_sector;    /* sector pointer ( 0 = structure free ) */
        __u32 file_bytesleft; /* number of bytes left */
        __u32 file_left;      /* number of sectors left */
        __u32 pad;            /* padding */
};

struct open_file_t Files[MAX_OPEN];

#define trackbufsize 8192
char trackbuf[trackbufsize];

char MangleBuf[12];


/* the fat bpb data */
struct fat_bpb fat;




/**
 * allocate_file:
 * 
 * Allocate a file structure
 *
 * @return: if successful return the file pointer, or return NULL
 *
 */
struct open_file_t *allocate_file()
{
        struct open_file_t *file;
        int i = 0;
        
        file = Files;

        for (; i < MAX_OPEN; i ++ ) {
                if ( file->file_sector == 0 ) /* found it */
                        return file;
                file ++;
        }

        return NULL; /* not found */
}


/**
 * alloc_fill_dir:
 *
 * Allocate then fill a file structure for a directory starting in
 * sector SECTOR. if successful, return the pointer of filled file
 * structure, or return NULL.
 *
 */
struct open_file_t* alloc_fill_dir(__u32 sector)
{
        struct open_file_t *file;

        file = allocate_file();
        if ( !file )
                return NULL;

        file->file_sector = sector; /* current sector */
        file->file_bytesleft = 0;   /* current offset */
        file->file_left = sector;   /* beginning sector */

        return file;
}


/* Deallocates a file structure */
void close_file(struct open_file_t *file)
{
        if ( file )
                file->file_sector = 0;
}



/* Deallocates a directory structure */
void close_dir(struct fat_dir_entry *dir)
{
        if ( dir )
                *(__u32*)dir = 0;
}





/**
 * getfatsector:
 *
 * check for a particular sector in the FAT cache.
 *
 */
struct cache_struct *getfatsector(__u32 sector)
{
        return get_cache_block(FAT + sector);
}


/**
 * nextcluster: 
 *
 * Advance a cluster pointer in clust_num to the next cluster
 * pointer at in the FAT tables. CF = 0 on return if end of file.
 *
 * @param: clust_num;
 *
 * @return: the next cluster number
 *
 */
__u32 nextcluster(__u32 clust_num)
{
        __u32 next_cluster;
        __u32 fat_sector;
        __u32 offset;
        struct cache_struct *cs;


#if FATType == FAT12
        int lo, hi;
#endif
        
        switch(FATType) {
        case FAT12:
                fat_sector = (clust_num + clust_num / 2) >> SECTOR_SHIFT;
                cs = getfatsector(fat_sector);
                offset = (clust_num * 3 / 2) & ( SECTOR_SIZE -1 );
                if ( offset == 0x1ff ) {
                        /* 
                         * we got the end of the one fat sector, 
                         * but we don't got we have(just one byte, we need two),
                         * so store the low part, then read the next fat
                         * sector, read the high part, then combine it.
                         */
                        lo = *(__u8 *)(cs->data + offset);
                        cs = getfatsector(fat_sector + 1);
                        hi = *(__u8 *)cs->data;
                        next_cluster = (hi << 8) + lo;
                } else 
                        next_cluster = *(__u16 *)(cs->data + offset);
                
                if ( clust_num & 0x0001 )
                        next_cluster >>= 4;         /* cluster number is ODD */
                else
                        next_cluster &= 0x0fff;     /* cluster number is EVEN */
                if ( next_cluster > 0x0ff0 )
                        goto fail;
                break;

        case FAT16:
                fat_sector = clust_num >> (SECTOR_SHIFT - 1);
                offset = clust_num & ( (1 << (SECTOR_SHIFT-1)) -1);
                cs = getfatsector(fat_sector);
                next_cluster = ((__u16 *)cs->data)[offset];
                if ( next_cluster > 0xfff0 )
                        goto fail;
                break;
                
        case FAT32:
                fat_sector = clust_num >> (SECTOR_SHIFT - 2);
                offset = clust_num & ( (1 << (SECTOR_SHIFT-2)) -1);
                cs = getfatsector(fat_sector);
                next_cluster = ((__u32 *)cs->data)[offset] & 0x0fffffff;
                if ( next_cluster > 0x0ffffff0 )
                        goto fail;
                break;
        }

        return next_cluster;

 fail:  /* got an unexcepted cluster number, so return ZERO */
        return 0;
}



/**
 * nextsector:
 * 
 * given a sector  on input, return the next sector of the 
 * same filesystem object, which may be the root directory or a 
 * cluster chain. Returns EOF.
 *
 */
__u32 nextsector(__u32 sector)
{

        __u32 data_sector;
        __u32 cluster;
         
        if ( sector < DataArea ) {
                sector ++;
                /* if we reached the end of root area */
                if ( sector == DataArea ) 
                        sector = 0; /* return 0 */
                return sector;
        }

        
        data_sector = sector - DataArea;
        if ( (data_sector+1) & ClustMask )      /* in a cluster */
                return (++sector);

        /* got a new cluster */
        cluster = nextcluster( (data_sector >> ClustShift) + 2 );
        if ( !cluster  ) 
                return 0;

        /* return the start of the new cluster */
        sector = ( (cluster - 2) << ClustShift ) + DataArea;
        return sector;
 }





/**
 * __getfssec:
 *
 * get multiple sectors from a file
 *
 * This routine makes sure the subransfers do not cross a 64K boundary
 * and will correct the situation if it does, UNLESS *sectos* cross
 * 64K boundaries.
 *
 * @param: buf
 * @param: file structure
 * @param: sectors
 *
 */
void __getfssec(char *buf, struct open_file_t *file, __u32 sectors)
{
        __u32 curr_sector = file->file_sector;
        __u32 frag_start , next_sector;
        __u32 con_sec_cnt;

        do {
                /* get fragment */
                con_sec_cnt = 0;
                frag_start = curr_sector;
                
                do {
                        /* get consective sector  count */
                        con_sec_cnt ++;
                        sectors --;
                        if ( sectors == 0 )
                                break;
                        
                        next_sector = nextsector(curr_sector);
                        if ( !next_sector )
                                break;                        
                }while( next_sector == (++curr_sector) );
               
#if 0           /* Debug message */
                printf("/**************************************************\n");
                printf("You are reading stores at sector --0x%x--0x%x\n", 
                       frag_start, frag_start + con_sec_cnt -1);
                printf("**************************************************/\n");
#endif  
                        
                /* do read */
                getlinsec(buf, frag_start, con_sec_cnt);
                buf += con_sec_cnt << 9;/* adjust buffer pointer */
                        
                if ( !sectors )
                        break;
                //curr_sector --;         /* this is the last sector actually read */
                curr_sector = next_sector;
        }while( sectors );

        /* update the file_sector filed for the next read */
        file->file_sector = nextsector(curr_sector);
        
}



/**
 * getfssec:
 *
 * get multiple sectors from a file 
 *
 *
 * @param: buf
 * @param: file
 * @param: sectors
 * @param: have_more
 *
 * @return: number of bytes read
 *
 */
__u32 getfssec(char *buf, struct open_file_t *file, __u32 sectors, int *have_more)
{
        __u32 bytes_read = sectors << SECTOR_SHIFT;

        if ( sectors > file->file_left )
                sectors = file->file_left;
       
        __getfssec(buf, file, sectors);

        if ( bytes_read >= file->file_bytesleft ) {
                bytes_read = file->file_bytesleft;
                file->file_bytesleft = 0;
                *have_more = 0;
                close_file(file);
                
        } else {
                file->file_bytesleft -= bytes_read;
                *have_more = 1;
        }

        file->file_left -= sectors;
        
        return bytes_read;
}
                
        







/**
 * mangle_dos_name:
 *
 * Mangle a dos filename component pointed to by FILENAME
 * into MangleBuf; ends on encountering any whitespace or 
 * slash.
 *
 * WARNING: saves pointers into the buffer for longname matchs!
 *
 * @param: filename
 * @param: MangleBuf
 *
 */
/**
 * for now, it can't handle this case:
 * xyxzxyxjfdkfjdjf.txt as it will just output the first 11 chars
 * but not care the dot char at the later, so I think we need do 
 * this, but it seems that the SYSLINUX doesn't do it, so I will
 * make it stay as what it was orignal.
 *
 */
void mangle_dos_name(char *MangleBuf, char *filename)
{
       
        char *dst = MangleBuf;
        char *src = filename;
        char c;        
        int i = 0;

        NameStart = filename;
        
        for (; i < 11; i ++)
                MangleBuf[i] = ' ';

        for (i = 0; i < 11; i++) {
                c = *src ++;

                if ( (c <= ' ') || (c == '/') ) 
                        break;
                

                if ( c == '.' ) {
                        dst = &MangleBuf[8];
                        i = 7;
                        continue;
                }

                if (c >= 'a' && c <= 'z')
                        c -= 32;
                if ( (c == 0xe5) && (i == 11) )
                        c = 0x05;
                
                *dst++ = c;
        }
        MangleBuf[12] = '\0';

        while( (*src != '/') && (*src > ' ') )
                src ++;

        NameLen = src - filename;
}


char entry_name[13];


void unicode_to_ascii(char *entry_name, __u16 *unicode_buf)
{
        int i = 0;
        
        for (; i < 13; i++) {
                if ( unicode_buf[i] == 0xffff ) {
                        entry_name[i] = '\0';
                        return;
                }
                entry_name[i] = (char)unicode_buf[i];
        }
}
                
/**
 * long_entry_name:
 *
 * get the long entry name
 *
 */
void long_entry_name(struct fat_long_name_entry *dir)
{
        int id = dir->id & 0x3f;
        __u16 unicode_buf[13];
        
        memcpy(unicode_buf,     dir->name1, 5 * 2);
        memcpy(unicode_buf + 5, dir->name2, 6 * 2);
        memcpy(unicode_buf + 11,dir->name3, 2 * 2);
        
        unicode_to_ascii(entry_name, unicode_buf);

}


__u8 get_checksum(char *dir_name)
{
	int  i;
	__u8 sum=0;
 
	for (i=11; i; i--)
		sum = ((sum & 1) << 7) + (sum >> 1) + *dir_name++;
	return sum;
}

__u32 first_sector(struct fat_dir_entry *dir)
{
        __u32 first_clust, sector;
        
        first_clust = (dir->first_cluster_high << 16) + dir->first_cluster_low;
        sector = ((first_clust - 2) << ClustShift) + DataArea;

        return sector;
}


/* try with the biggest long name */
char long_name[0x40 * 13];

/**
 * search_dos_dir:
 *
 * search a specific directory for a pre-mangled filename in
 * MangleBuf, in the directory starting in sector SECTOR
 *
 * NOTE: This file considers finding a zero-length file an
 * error.  This is so we don't have to deal with that special
 * case elsewhere in the program (most loops have the test
 * at the end).
 *
 * @param: MangleBuf
 * @param: dir_sector, directory sector
 *
 * @out:  file pointer
 * @out:  file length (MAY BE ZERO!)
 * @out:  file attribute
 * @out:  dh, clobbered.
 *
 */
struct open_file_t* search_dos_dir(char *MangleBuf, __u32 dir_sector, \
                                   __u32 *file_len, __u8 *attr)
{
        struct open_file_t*  file;
        struct cache_struct* cs;
        struct fat_dir_entry *dir;
        struct fat_long_name_entry *long_dir;

        __u8  VFATInit, VFATNext, VFATCsum;
        __u8  id;
        __u16 *unicode_buf;
        __u32 slots;
        __u32 entries;
        
        int checksum;
        int have_more;
                
        file = allocate_file();
        if ( !file )
                return NULL;
        
        /*
         * Compute the value of a possible VFAT longname
         * "last" entry (which, of coures, comes first ...)
         */
        slots = (NameLen + 12) / 13;
        slots |= 0x40;

        VFATInit = slots;
        VFATNext = slots;

 
        do {
                cs = get_cache_block(dir_sector);
                dir = (struct fat_dir_entry *)cs->data;
                entries = SECTOR_SIZE / 32;

                /* scan all the entries in a sector */
                do {
                        if ( dir->name[0] == 0 )
                                return NULL;    /* Hit directory high water mark */
                       
                        if ( dir->attr == 0x0f ) {
                                /* it's a long name entry */
                                long_dir = (struct fat_long_name_entry *)dir;
                                id = long_dir->id;
                                if ( id !=VFATNext )
                                        goto not_match;
                        
                                if ( id & 0x40 ) {
                                        /*get the initial checksum value*/
                                        VFATCsum = long_dir->checksum;
                                } else {
                                        if ( long_dir->checksum != VFATCsum )
                                                goto not_match;
                                }
                                
                                id &= 0x3f;
                                VFATNext = --id;
                                
                                /* got the long entry name */
                                long_entry_name(long_dir);
                                memcpy(long_name + id * 13, entry_name, 13);
                                
                                /* 
                                 * if we got the last entry?
                                 * if so, check it, or go on with the next entry
                                 */
                                if ( id == 0 ) {
                                        if ( strcmp(long_name, NameStart) )
                                                goto not_match;
                                }

                                goto next_entry;

                        } else {
                                /* it's a short entry */
                                if ( dir->attr & 0x08 )     /* ingore volume labels */
                                        goto not_match;

                        
                                /* If we have a long name match, then VFATNext must be 0 */
                                if ( !VFATNext )  {  
                                        /*
                                         * we already have a VFAT long name match, however,
                                         * the match is only valid if the checksum matchs.
                                         */
                                        checksum = get_checksum(dir->name);
                                        if ( checksum == VFATCsum )
                                                goto found;        /* got a match on long name */
                               
                                } else { 
                                        if ( strncmp(MangleBuf, dir->name, 11) == 0 )
                                                goto found;                                       
                                }
                        }
           
                not_match:/* find it again */
                        VFATNext = VFATInit;
                
                next_entry:
                        dir ++;
                        
                }while ( --entries );
                
                dir_sector = nextsector(dir_sector);

        }while ( dir_sector ); /* scan another secotr */

 found:
        *file_len = file->file_bytesleft = dir->file_size;
        file->file_sector = first_sector(dir);
        *attr = dir->attr;

        return file;
}


__u32 CurrentDir = 0;


/**
 * searchdir:
 * 
 * open a file
 *
 * @param: filename, the file we wanna open
 * @param: file_len, to return the file length
 *
 * @return: return the file structure on successful, or NULL.
 *
 */
struct open_file_t* searchdir(char *filename)
{
        __u32 dir_sector, prev_dir;
        __u32 file_len;
        __u8  attr;
        char  *p;

        struct open_file_t *file;

        dir_sector = CurrentDir;
        if ( *filename == '/' ) {
                dir_sector = RootDir;
                filename ++;
        }

        while ( *filename ) {
                p = filename;

                /* try to find the end */
                while ( (*p > ' ') && (*p != '/') )
                        p ++;
                
                if (filename == p)
                        return NULL;

                prev_dir = dir_sector;
                
                mangle_dos_name(MangleBuf, filename);
                file = search_dos_dir(MangleBuf, dir_sector, &file_len, &attr);
                if ( !file ) {
                        file_len = 0;
                        return NULL;
                }
                
                if ( *p != '/' )   /* we got a file */                        
                        break;
                
                if ( (attr & 0x10) == 0 ) /* subdirectory */
                        return NULL;
                
                dir_sector = file->file_sector;
                close_file(file);
                
                filename = p + 1; /* search again */                
        }
        
        if ( (attr & 0x18) || (file_len == 0) ) 
                return NULL;
                
        file->file_bytesleft = file_len;
        file->file_left = ( file_len + SECTOR_SIZE -1 ) >> SECTOR_SHIFT;
                        
        return file; 
}




/**
 * readdir:
 *
 * read one file from a directory
 *
 * returns the file's name in the filename string buffer
 *
 * @param: filename
 * @param: file
 *
 */
struct open_file_t * readdir(struct open_file_t* dir_file, char* filename,
                             __u32 *file_len, __u8 *attr)
{
        __u32 sector, sec_off;       
        
        /* make it to be 1 to check if we have met a long name entry before */
        __u8  id = 1;
        __u8  init_id, next_id;
        __u8  entries_left;  
        int i;
        int have_more;
        
        struct cache_struct  *cs;
        struct fat_dir_entry *dir;
        struct fat_long_name_entry *long_dir;
        struct open_file_t *file;

        sector  = dir_file->file_sector;
        sec_off = dir_file->file_bytesleft;
        if ( !sector )
                goto fail;

        entries_left = (SECTOR_SIZE - sec_off) >> 5;
        cs = get_cache_block(sector);
        dir = (struct fat_dir_entry *)(cs->data + sec_off);/* resume last position in sector */
        
        while ( 1 ) {
                if ( dir->name[0] == 0 )
                        goto fail;                

                if  ( dir->attr == 0x0f ) {
                        /* it's a long name */
                        long_dir = (struct fat_long_name_entry *)dir;
                        
                        if ( long_dir->id & 0x40 ) 
                                init_id = id = long_dir->id & 0x3f;
                        else
                                next_id = (long_dir->id & 0x3f) - 1;

                        id --;

                        if ( id != next_id )
                                goto next_entry;
                        
                        long_entry_name(long_dir);
                        memcpy(filename + id * 13, entry_name, 13);

                        
                        /* 
                         * we need go on with the next entry 
                         * and we will fall through to next entry
                         */

                } else {
                        /* it's a short entry */
                        
                        if ( !id ) /* we got a long name match */
                                break;

                        if ( dir->attr & 0x08 ) 
                                goto next_entry;
                        
                        for( i = 0; i < 8; i ++) {
                                if ( dir->name[i] == ' ' )
                                        break;
                                *filename++ = dir->name[i];
                        }
                        
                        *filename++ = '.';
                        
                        for ( i = 8; i < 11; i ++) {
                                if ( dir->name[i] == ' ' )
                                        break;
                                *filename ++ = dir->name[i];
                        }
                        
                        /* check if we have got an extention */
                        if ( ! *(filename - 1) ) 
                                *(filename -2) = '\0';
                        else
                                *filename = '\0';      

                        break;
                }
                
        next_entry:
                dir ++;
                entries_left --;
                
                if ( !entries_left ) {
                        sector = nextsector(sector);
                        if ( !sector )
                                goto fail;
                        cs = (struct cache_struct *)get_cache_block(sector);
                        dir = (struct fat_dir_entry *)cs->data;
                }
        }
        
        /* finally , we get what we want */
        entries_left --;
        if ( !entries_left ) {
                sector = nextsector(sector);
                if ( !sector )
                        goto fail;
        }

        file->file_sector = sector;
        file->file_bytesleft = (SECTOR_SIZE - (entries_left << DIRENT_SHIFT) ) & 0xffff;
                
        *file_len = dir->file_size;
        *attr = dir->attr;

        return file;

 fail:
        close_dir(dir);
        return NULL;
}

 

struct open_file_t* open_file(char *filename)
{
        struct open_file_t *file;
        
        file = searchdir(filename);
        
        /* if we failed, we also will get a NULL value */
        return file;
}

__u32 read_file(struct open_file_t *file, char *buf, int size, int *have_more)
{
        __u32 sectors = ( size + SECTOR_SIZE - 1 ) >> SECTOR_SHIFT;
        
        return getfssec(buf, file, sectors, have_more);
}

void bsr(__u8 *res, int num)
{
        int i = 0;
        
        while (num >>= 1) {
                i ++;
        }
        
        *res = i;
}

/* init. the fs meta data, return the block size */
int init_fs()
{
        int   sectors_per_fat; 
        __u32 clust_num;
        int RootDirSize;

        /* get the fat bpb information */
        getlinsec((char *)&fat, 0, 1);

        TotalSectors = fat.bxSectors ? : fat.bsHugeSectors;
        FAT = fat.bxResSectors;

        sectors_per_fat = fat.bxFATsecs ? : fat.u.fat32.bxFATsecs_32;
        RootDir = RootDirArea = FAT + sectors_per_fat * fat.bxFATs;
        RootDirSize = (fat.bxRootDirEnts+SECTOR_SIZE/32-1) >> (SECTOR_SHIFT-5);
        DataArea = RootDirArea + RootDirSize;

        bsr(&ClustShift, fat.bxSecPerClust);
        ClustByteShift = ClustShift + SECTOR_SHIFT;
        ClustMask = fat.bxSecPerClust - 1;
        ClustSize = fat.bxSecPerClust << SECTOR_SHIFT;

        blk_size = SECTOR_SIZE;

        clust_num = (TotalSectors - DataArea) >> ClustShift;
        if ( clust_num < 4085 )
                FATType = FAT12;
        else if ( clust_num < 65525 )
                FATType = FAT16;
        else 
                FATType = FAT32;

        return blk_size;
}