fat.c

编译后直接运行的ＭＰ３播放器全部Ｃ语言源代码 一个包含FAT文件系统、系统引导 Boot、FLASH Driver等内容的

                        year++;
                    }
                }
                *date = (year << 9) | (month << 5) | day;
            }
        }
    }
    if (tenth)
        *tenth = 0;
#endif /* HAVE_RTC */
}

static int write_long_name(struct fat_file* file,
                           unsigned int firstentry,
                           unsigned int numentries,
                           unsigned char* name,
                           unsigned char* shortname,
                           bool is_directory)
{
    unsigned char buf[SECTOR_SIZE];
    unsigned char* entry;
    unsigned int idx = firstentry % DIR_ENTRIES_PER_SECTOR;
    unsigned int sector = firstentry / DIR_ENTRIES_PER_SECTOR;
    unsigned int i, j=0;
    unsigned char chksum = 0;
    int nameidx=0, namelen = strlen(name);
    int rc;

    LDEBUGF("write_long_name(file:%x, first:%d, num:%d, name:%s)\n",
            file->firstcluster, firstentry, numentries, name);

    rc = fat_seek(file, sector);
    if (rc<0)
        return rc * 10 - 1;

    rc = fat_readwrite(file, 1, buf, false);
    if (rc<1)
        return rc * 10 - 2;

    /* calculate shortname checksum */
    for (i=11; i>0; i--)
        chksum = ((chksum & 1) ? 0x80 : 0) + (chksum >> 1) + shortname[j++];

    /* calc position of last name segment */
    if ( namelen > NAME_BYTES_PER_ENTRY )
        for (nameidx=0;
             nameidx < (namelen - NAME_BYTES_PER_ENTRY);
             nameidx += NAME_BYTES_PER_ENTRY);

    for (i=0; i < numentries; i++) {
        /* new sector? */
        if ( idx >= DIR_ENTRIES_PER_SECTOR ) {
            /* update current sector */
            rc = fat_seek(file, sector);
            if (rc<0)
                return rc * 10 - 3;

            rc = fat_readwrite(file, 1, buf, true);
            if (rc<1)
                return rc * 10 - 4;

            /* read next sector */
            rc = fat_readwrite(file, 1, buf, false);
            if (rc<0) {
                LDEBUGF("Failed writing new sector: %d\n",rc);
                return rc * 10 - 5;
            }
            if (rc==0)
                /* end of dir */
                memset(buf, 0, sizeof buf);

            sector++;
            idx = 0;
        }

        entry = buf + idx * DIR_ENTRY_SIZE;

        /* verify this entry is free */
        if (entry[0] && entry[0] != 0xe5 )
            panicf("Dir entry %d in sector %x is not free! "
                   "%02x %02x %02x %02x",
                   idx, sector,
                   entry[0], entry[1], entry[2], entry[3]);

        memset(entry, 0, DIR_ENTRY_SIZE);
        if ( i+1 < numentries ) {
            /* longname entry */
            int k, l = nameidx;

            entry[FATLONG_ORDER] = numentries-i-1;
            if (i==0) {
                /* mark this as last long entry */
                entry[FATLONG_ORDER] |= 0x40;

                /* pad name with 0xffff  */
                for (k=1; k<12; k++) entry[k] = 0xff;
                for (k=14; k<26; k++) entry[k] = 0xff;
                for (k=28; k<32; k++) entry[k] = 0xff;
            };
            /* set name */
            for (k=0; k<5 && l <= namelen; k++) {
                entry[k*2 + 1] = name[l++];
                entry[k*2 + 2] = 0;
            }
            for (k=0; k<6 && l <= namelen; k++) {
                entry[k*2 + 14] = name[l++];
                entry[k*2 + 15] = 0;
            }
            for (k=0; k<2 && l <= namelen; k++) {
                entry[k*2 + 28] = name[l++];
                entry[k*2 + 29] = 0;
            }

            entry[FATDIR_ATTR] = FAT_ATTR_LONG_NAME;
            entry[FATDIR_FSTCLUSLO] = 0;
            entry[FATLONG_TYPE] = 0;
            entry[FATLONG_CHKSUM] = chksum;
            LDEBUGF("Longname entry %d: %.13s\n", idx, name+nameidx);
        }
        else {
            /* shortname entry */
            unsigned short date=0, time=0, tenth=0;
            LDEBUGF("Shortname entry: %.13s\n", shortname);
            strncpy(entry + FATDIR_NAME, shortname, 11);
            entry[FATDIR_ATTR] = is_directory?FAT_ATTR_DIRECTORY:0;
            entry[FATDIR_NTRES] = 0;

            fat_time(&date, &time, &tenth);
            entry[FATDIR_CRTTIMETENTH] = tenth;
            *(unsigned short*)(entry + FATDIR_CRTTIME) = SWAB16(time);
            *(unsigned short*)(entry + FATDIR_WRTTIME) = SWAB16(time);
            *(unsigned short*)(entry + FATDIR_CRTDATE) = SWAB16(date);
            *(unsigned short*)(entry + FATDIR_WRTDATE) = SWAB16(date);
            *(unsigned short*)(entry + FATDIR_LSTACCDATE) = SWAB16(date);
        }
        idx++;
        nameidx -= NAME_BYTES_PER_ENTRY;
    }

    /* update last sector */
    rc = fat_seek(file, sector);
    if (rc<0)
        return rc * 10 - 6;

    rc = fat_readwrite(file, 1, buf, true);
    if (rc<1)
        return rc * 10 - 7;
    
    return 0;
}

static int add_dir_entry(struct fat_dir* dir,
                         struct fat_file* file,
                         char* name,
                         bool is_directory,
                         bool dotdir)
{
    unsigned char buf[SECTOR_SIZE];
    unsigned char shortname[16];
    int rc;
    unsigned int sector;
    bool done = false;
    bool eof = false;
    bool last = false;
    int entries_needed, entries_found = 0;
    int namelen = strlen(name);
    int firstentry;

    LDEBUGF( "add_dir_entry(%s,%x)\n",
             name, file->firstcluster);

    /* The "." and ".." directory entries must not be long names */
    if(dotdir) {
        int i;
        strncpy(shortname, name, 16);
        for(i = strlen(shortname);i < 12;i++)
            shortname[i] = ' ';
        
        entries_needed = 1;
    } else {
        /* create dos name */
        rc = create_dos_name(name, shortname);
        if (rc < 0)
            return rc * 10 - 0;

        /* one dir entry needed for every 13 bytes of filename,
           plus one entry for the short name */
        entries_needed = namelen / NAME_BYTES_PER_ENTRY + 1;
        if (namelen % NAME_BYTES_PER_ENTRY)
            entries_needed++;
    }

 restart:
    firstentry = 0;

    rc = fat_seek(&dir->file, 0);
    if (rc < 0)
        return rc * 10 - 1;

    for (sector=0; !done; sector++)
    {
        unsigned int i;

        rc = 0;
        if (!eof) {
            rc = fat_readwrite(&dir->file, 1, buf, false);
        }
        if (rc == 0) {
            /* eof: add new sector */
            eof = true;

            memset(buf, 0, sizeof buf);
            LDEBUGF("Adding new sector to dir\n");
            rc = fat_seek(&dir->file, sector);
            if (rc < 0)
                return rc * 10 - 2;

            /* add sectors (we must clear the whole cluster) */
            do {
                rc = fat_readwrite(&dir->file, 1, buf, true);
                if (rc < 1)
                    return rc * 10 - 3;
            } while (dir->file.sectornum < (int)fat_bpb.bpb_secperclus);
        }
        if (rc < 0) {
            DEBUGF( "add_dir_entry() - Couldn't read dir"
                    " (error code %d)\n", rc);
            return rc * 10 - 4;
        }

        /* look for free slots */
        for (i=0; i < DIR_ENTRIES_PER_SECTOR && !done; i++)
        {
            unsigned char firstbyte = buf[i * DIR_ENTRY_SIZE];
            switch (firstbyte) {
            case 0: /* end of dir */
                entries_found = entries_needed;
                LDEBUGF("Found last entry %d\n", 
                        sector * DIR_ENTRIES_PER_SECTOR + i);
                done = true;
                break;

            case 0xe5: /* free entry */
                entries_found++;
                LDEBUGF("Found free entry %d (%d/%d)\n",
                        sector * DIR_ENTRIES_PER_SECTOR + i,
                        entries_found, entries_needed);
                break;

            default:
                entries_found = 0;

                /* check that our intended shortname doesn't already exist */
                if (!strncmp(shortname, buf + i * DIR_ENTRY_SIZE, 12)) {
                    /* filename exists already. make a new one */
                    snprintf(shortname+8, 4, "%03X", (unsigned)rand() & 0xfff);
                    LDEBUGF("Duplicate shortname, changing to %s\n",
                            shortname);

                    /* name has changed, we need to restart search */
                    goto restart;
                }
                break;
            }

            if (!firstentry && (entries_found == entries_needed)) {
                firstentry = sector * DIR_ENTRIES_PER_SECTOR + i;

                /* if we're not extending the dir,
                   we must go back to first free entry */
                if (done)
                    last = true;
                else
                    firstentry -= (entries_needed - 1);
            }
        }
    }

    sector = firstentry / DIR_ENTRIES_PER_SECTOR;
    LDEBUGF("Adding longname to entry %d in sector %d\n",
            firstentry, sector);

    rc = write_long_name(&dir->file, firstentry, 
                         entries_needed, name, shortname, is_directory);
    if (rc < 0)
        return rc * 10 - 5;

    /* remember where the shortname dir entry is located */
    file->direntry = firstentry + entries_needed - 1;
    file->direntries = entries_needed;
    file->dircluster = dir->file.firstcluster;
    LDEBUGF("Added new dir entry %d, using %d slots.\n",
            file->direntry, file->direntries);

    /* advance the end-of-dir marker? */
    if (last)
    {
        unsigned int lastentry = firstentry + entries_needed;

        LDEBUGF("Updating end-of-dir entry %d\n",lastentry);

        if (lastentry % DIR_ENTRIES_PER_SECTOR)
        {
            int idx = (lastentry % DIR_ENTRIES_PER_SECTOR) * DIR_ENTRY_SIZE;

            rc = fat_seek(&dir->file, lastentry / DIR_ENTRIES_PER_SECTOR);
            if (rc < 0)
                return rc * 10 - 6;

            rc = fat_readwrite(&dir->file, 1, buf, false);
            if (rc < 1)
                return rc * 10 - 7;

            /* clear last entry */
            buf[idx] = 0;

            rc = fat_seek(&dir->file, lastentry / DIR_ENTRIES_PER_SECTOR);
            if (rc < 0)
                return rc * 10 - 8;
            
            /* we must clear entire last cluster */
            do {
                rc = fat_readwrite(&dir->file, 1, buf, true);
                if (rc < 1)
                    return rc * 10 - 9;
                memset(buf, 0, sizeof buf);
            } while (dir->file.sectornum < (int)fat_bpb.bpb_secperclus);
        }
        else
        {
            /* add a new sector/cluster for last entry */
            memset(buf, 0, sizeof buf);
            do {
                rc = fat_readwrite(&dir->file, 1, buf, true);
                if (rc < 1)
                    return rc * 10 - 9; /* Same error code as above, can't be
                                           more than -9 */
            } while (dir->file.sectornum < (int)fat_bpb.bpb_secperclus);
        }
    }

    return 0;
}

unsigned char char2dos(unsigned char c)
{
    switch(c)
    {
        case 0xe5: /* Special kanji character */
            c = 0x05;
            break;
        case 0x20:
        case 0x22:
        case 0x2a:
        case 0x2b:
        case 0x2c:
        case 0x2e:
        case 0x3a:
        case 0x3b:
        case 0x3c:
        case 0x3d:
        case 0x3e:
        case 0x3f:
        case 0x5b:
        case 0x5c:
        case 0x5d:
        case 0x7c:
            /* Illegal name */
            c = 0;
            break;
                
        default:
            if(c < 0x20)
            {
                /* Illegal name */
                c = 0;
            }
            break;
    }
    return c;
}

static int create_dos_name(unsigned char *name, unsigned char *newname)
{
    int i,j;

    /* Name part */
    for (i=0, j=0; name[i] && (j < 8); i++)
    {
        unsigned char c = char2dos(name[i]);
        if (c)
            newname[j++] = toupper(c);
    }
    while (j < 8)
        newname[j++] = ' ';

    /* Extension part */
    snprintf(newname+8, 4, "%03X", (unsigned)rand() & 0xfff);