text: /*
   * fat_write.c
   *
   * R/W (V)FAT 12/16/32 filesystem implementation by Donggeun Kim
   *
   * See file CREDITS for list of people who contributed to this
   * project.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation; either version 2 of
   * the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
   * MA 02111-1307 USA
   */
  
  #include <common.h>
  #include <command.h>
  #include <config.h>
  #include <fat.h>
  #include <asm/byteorder.h>
  #include <part.h>
  #include "fat.c"
  
  static void uppercase(char *str, int len)
  {
  	int i;
  
  	for (i = 0; i < len; i++) {
  		TOUPPER(*str);
  		str++;
  	}
  }
  
  static int total_sector;
  static int disk_write(__u32 startblock, __u32 getsize, __u8 *bufptr)
  {
  	if (cur_dev == NULL)
  		return -1;
  
  	if (startblock + getsize > total_sector) {
  		printf("error: overflow occurs\n");
  		return -1;
  	}
  
  	startblock += part_offset;
  
  	if (cur_dev->block_read) {
  		return cur_dev->block_write(cur_dev->dev, startblock, getsize,
  					   (unsigned long *) bufptr);
  	}
  	return -1;
  }
  
  /*
   * Set short name in directory entry
   */
  static void set_name(dir_entry *dirent, const char *filename)
  {
  	char s_name[VFAT_MAXLEN_BYTES];
  	char *period;
  	int period_location, len, i, ext_num;
  
  	if (filename == NULL)
  		return;
  
  	len = strlen(filename);
  	if (len == 0)
  		return;
  
  	memcpy(s_name, filename, len);
  	uppercase(s_name, len);
  
  	period = strchr(s_name, '.');
  	if (period == NULL) {
  		period_location = len;
  		ext_num = 0;
  	} else {
  		period_location = period - s_name;
  		ext_num = len - period_location - 1;
  	}
  
  	/* Pad spaces when the length of file name is shorter than eight */
  	if (period_location < 8) {
  		memcpy(dirent->name, s_name, period_location);
  		for (i = period_location; i < 8; i++)
  			dirent->name[i] = ' ';
  	} else if (period_location == 8) {
  		memcpy(dirent->name, s_name, period_location);
  	} else {
  		memcpy(dirent->name, s_name, 6);
  		dirent->name[6] = '~';
  		dirent->name[7] = '1';
  	}
  
  	if (ext_num < 3) {
  		memcpy(dirent->ext, s_name + period_location + 1, ext_num);
  		for (i = ext_num; i < 3; i++)
  			dirent->ext[i] = ' ';
  	} else
  		memcpy(dirent->ext, s_name + period_location + 1, 3);
  
  	debug("name : %s\n", dirent->name);
  	debug("ext : %s\n", dirent->ext);
  }
  
  /*
   * Write fat buffer into block device
   */
  static int flush_fat_buffer(fsdata *mydata)
  {
  	int getsize = FATBUFBLOCKS;
  	__u32 fatlength = mydata->fatlength;
  	__u8 *bufptr = mydata->fatbuf;
  	__u32 startblock = mydata->fatbufnum * FATBUFBLOCKS;
  
  	fatlength *= mydata->sect_size;
  	startblock += mydata->fat_sect;
  
  	if (getsize > fatlength)
  		getsize = fatlength;
  
  	/* Write FAT buf */
  	if (disk_write(startblock, getsize, bufptr) < 0) {
  		debug("error: writing FAT blocks\n");
  		return -1;
  	}
  
  	return 0;
  }
  
  /*
   * Get the entry at index 'entry' in a FAT (12/16/32) table.
   * On failure 0x00 is returned.
   * When bufnum is changed, write back the previous fatbuf to the disk.
   */
  static __u32 get_fatent_value(fsdata *mydata, __u32 entry)
  {
  	__u32 bufnum;
  	__u32 off16, offset;
  	__u32 ret = 0x00;
  	__u16 val1, val2;
  
  	switch (mydata->fatsize) {
  	case 32:
  		bufnum = entry / FAT32BUFSIZE;
  		offset = entry - bufnum * FAT32BUFSIZE;
  		break;
  	case 16:
  		bufnum = entry / FAT16BUFSIZE;
  		offset = entry - bufnum * FAT16BUFSIZE;
  		break;
  	case 12:
  		bufnum = entry / FAT12BUFSIZE;
  		offset = entry - bufnum * FAT12BUFSIZE;
  		break;
  
  	default:
  		/* Unsupported FAT size */
  		return ret;
  	}
  
  	debug("FAT%d: entry: 0x%04x = %d, offset: 0x%04x = %d\n",
  	       mydata->fatsize, entry, entry, offset, offset);
  
  	/* Read a new block of FAT entries into the cache. */
  	if (bufnum != mydata->fatbufnum) {
  		int getsize = FATBUFBLOCKS;
  		__u8 *bufptr = mydata->fatbuf;
  		__u32 fatlength = mydata->fatlength;
  		__u32 startblock = bufnum * FATBUFBLOCKS;
  
  		if (getsize > fatlength)
  			getsize = fatlength;
  
  		fatlength *= mydata->sect_size;	/* We want it in bytes now */
  		startblock += mydata->fat_sect;	/* Offset from start of disk */
  
  		/* Write back the fatbuf to the disk */
  		if (mydata->fatbufnum != -1) {
  			if (flush_fat_buffer(mydata) < 0)
  				return -1;
  		}
  
  		if (disk_read(startblock, getsize, bufptr) < 0) {
  			debug("Error reading FAT blocks\n");
  			return ret;
  		}
  		mydata->fatbufnum = bufnum;
  	}
  
  	/* Get the actual entry from the table */
  	switch (mydata->fatsize) {
  	case 32:
  		ret = FAT2CPU32(((__u32 *) mydata->fatbuf)[offset]);
  		break;
  	case 16:
  		ret = FAT2CPU16(((__u16 *) mydata->fatbuf)[offset]);
  		break;
  	case 12:
  		off16 = (offset * 3) / 4;
  
  		switch (offset & 0x3) {
  		case 0:
  			ret = FAT2CPU16(((__u16 *) mydata->fatbuf)[off16]);
  			ret &= 0xfff;
  			break;
  		case 1:
  			val1 = FAT2CPU16(((__u16 *)mydata->fatbuf)[off16]);
  			val1 &= 0xf000;
  			val2 = FAT2CPU16(((__u16 *)mydata->fatbuf)[off16 + 1]);
  			val2 &= 0x00ff;
  			ret = (val2 << 4) | (val1 >> 12);
  			break;
  		case 2:
  			val1 = FAT2CPU16(((__u16 *)mydata->fatbuf)[off16]);
  			val1 &= 0xff00;
  			val2 = FAT2CPU16(((__u16 *)mydata->fatbuf)[off16 + 1]);
  			val2 &= 0x000f;
  			ret = (val2 << 8) | (val1 >> 8);
  			break;
  		case 3:
  			ret = FAT2CPU16(((__u16 *)mydata->fatbuf)[off16]);
  			ret = (ret & 0xfff0) >> 4;
  			break;
  		default:
  			break;
  		}
  		break;
  	}
  	debug("FAT%d: ret: %08x, entry: %08x, offset: %04x\n",
  	       mydata->fatsize, ret, entry, offset);
  
  	return ret;
  }
  
  #ifdef CONFIG_SUPPORT_VFAT
  /*
   * Set the file name information from 'name' into 'slotptr',
   */
  static int str2slot(dir_slot *slotptr, const char *name, int *idx)
  {
  	int j, end_idx = 0;
  
  	for (j = 0; j <= 8; j += 2) {
  		if (name[*idx] == 0x00) {
  			slotptr->name0_4[j] = 0;
  			slotptr->name0_4[j + 1] = 0;
  			end_idx++;
  			goto name0_4;
  		}
  		slotptr->name0_4[j] = name[*idx];
  		(*idx)++;
  		end_idx++;
  	}
  	for (j = 0; j <= 10; j += 2) {
  		if (name[*idx] == 0x00) {
  			slotptr->name5_10[j] = 0;
  			slotptr->name5_10[j + 1] = 0;
  			end_idx++;
  			goto name5_10;
  		}
  		slotptr->name5_10[j] = name[*idx];
  		(*idx)++;
  		end_idx++;
  	}
  	for (j = 0; j <= 2; j += 2) {
  		if (name[*idx] == 0x00) {
  			slotptr->name11_12[j] = 0;
  			slotptr->name11_12[j + 1] = 0;
  			end_idx++;
  			goto name11_12;
  		}
  		slotptr->name11_12[j] = name[*idx];
  		(*idx)++;
  		end_idx++;
  	}
  
  	if (name[*idx] == 0x00)
  		return 1;
  
  	return 0;
  /* Not used characters are filled with 0xff 0xff */
  name0_4:
  	for (; end_idx < 5; end_idx++) {
  		slotptr->name0_4[end_idx * 2] = 0xff;
  		slotptr->name0_4[end_idx * 2 + 1] = 0xff;
  	}
  	end_idx = 5;
  name5_10:
  	end_idx -= 5;
  	for (; end_idx < 6; end_idx++) {
  		slotptr->name5_10[end_idx * 2] = 0xff;
  		slotptr->name5_10[end_idx * 2 + 1] = 0xff;
  	}
  	end_idx = 11;
  name11_12:
  	end_idx -= 11;
  	for (; end_idx < 2; end_idx++) {
  		slotptr->name11_12[end_idx * 2] = 0xff;
  		slotptr->name11_12[end_idx * 2 + 1] = 0xff;
  	}
  
  	return 1;
  }
  
  static int is_next_clust(fsdata *mydata, dir_entry *dentptr);
  static void flush_dir_table(fsdata *mydata, dir_entry **dentptr);
  
  /*
   * Fill dir_slot entries with appropriate name, id, and attr
   * The real directory entry is returned by 'dentptr'
   */
  static void
  fill_dir_slot(fsdata *mydata, dir_entry **dentptr, const char *l_name)
  {
  	dir_slot *slotptr = (dir_slot *)get_vfatname_block;
  	__u8 counter = 0, checksum;
  	int idx = 0, ret;
  	char s_name[16];
  
  	/* Get short file name and checksum value */
  	strncpy(s_name, (*dentptr)->name, 16);
  	checksum = mkcksum(s_name);
  
  	do {
  		memset(slotptr, 0x00, sizeof(dir_slot));
  		ret = str2slot(slotptr, l_name, &idx);
  		slotptr->id = ++counter;
  		slotptr->attr = ATTR_VFAT;
  		slotptr->alias_checksum = checksum;
  		slotptr++;
  	} while (ret == 0);
  
  	slotptr--;
  	slotptr->id |= LAST_LONG_ENTRY_MASK;
  
  	while (counter >= 1) {
  		if (is_next_clust(mydata, *dentptr)) {
  			/* A new cluster is allocated for directory table */
  			flush_dir_table(mydata, dentptr);
  		}
  		memcpy(*dentptr, slotptr, sizeof(dir_slot));
  		(*dentptr)++;
  		slotptr--;
  		counter--;
  	}
  
  	if (is_next_clust(mydata, *dentptr)) {
  		/* A new cluster is allocated for directory table */
  		flush_dir_table(mydata, dentptr);
  	}
  }
  
  static __u32 dir_curclust;
  
  /*
   * Extract the full long filename starting at 'retdent' (which is really
   * a slot) into 'l_name'. If successful also copy the real directory entry
   * into 'retdent'
   * If additional adjacent cluster for directory entries is read into memory,
   * then 'get_vfatname_block' is copied into 'get_dentfromdir_block' and
   * the location of the real directory entry is returned by 'retdent'
   * Return 0 on success, -1 otherwise.
   */
  static int
  get_long_file_name(fsdata *mydata, int curclust, __u8 *cluster,
  	      dir_entry **retdent, char *l_name)
  {
  	dir_entry *realdent;
  	dir_slot *slotptr = (dir_slot *)(*retdent);
  	dir_slot *slotptr2 = NULL;
  	__u8 *buflimit = cluster + mydata->sect_size * ((curclust == 0) ?
  							PREFETCH_BLOCKS :
  							mydata->clust_size);
  	__u8 counter = (slotptr->id & ~LAST_LONG_ENTRY_MASK) & 0xff;
  	int idx = 0, cur_position = 0;
  
  	if (counter > VFAT_MAXSEQ) {
  		debug("Error: VFAT name is too long\n");
  		return -1;
  	}
  
  	while ((__u8 *)slotptr < buflimit) {
  		if (counter == 0)
  			break;
  		if (((slotptr->id & ~LAST_LONG_ENTRY_MASK) & 0xff) != counter)
  			return -1;
  		slotptr++;
  		counter--;
  	}
  
  	if ((__u8 *)slotptr >= buflimit) {
  		if (curclust == 0)
  			return -1;
  		curclust = get_fatent_value(mydata, dir_curclust);
  		if (CHECK_CLUST(curclust, mydata->fatsize)) {
  			debug("curclust: 0x%x\n", curclust);
  			printf("Invalid FAT entry\n");
  			return -1;
  		}
  
  		dir_curclust = curclust;
  
  		if (get_cluster(mydata, curclust, get_vfatname_block,
  				mydata->clust_size * mydata->sect_size) != 0) {
  			debug("Error: reading directory block\n");
  			return -1;
  		}
  
  		slotptr2 = (dir_slot *)get_vfatname_block;
  		while (counter > 0) {
  			if (((slotptr2->id & ~LAST_LONG_ENTRY_MASK)
  			    & 0xff) != counter)
  				return -1;
  			slotptr2++;
  			counter--;
  		}
  
  		/* Save the real directory entry */
  		realdent = (dir_entry *)slotptr2;
  		while ((__u8 *)slotptr2 > get_vfatname_block) {
  			slotptr2--;
  			slot2str(slotptr2, l_name, &idx);
  		}
  	} else {
  		/* Save the real directory entry */
  		realdent = (dir_entry *)slotptr;
  	}
  
  	do {
  		slotptr--;
  		if (slot2str(slotptr, l_name, &idx))
  			break;
  	} while (!(slotptr->id & LAST_LONG_ENTRY_MASK));
  
  	l_name[idx] = '\0';
  	if (*l_name == DELETED_FLAG)
  		*l_name = '\0';
  	else if (*l_name == aRING)
  		*l_name = DELETED_FLAG;
  	downcase(l_name);
  
  	/* Return the real directory entry */
  	*retdent = realdent;
  
  	if (slotptr2) {
  		memcpy(get_dentfromdir_block, get_vfatname_block,
  			mydata->clust_size * mydata->sect_size);
  		cur_position = (__u8 *)realdent - get_vfatname_block;
  		*retdent = (dir_entry *) &get_dentfromdir_block[cur_position];
  	}
  
  	return 0;
  }
  
  #endif
  
  /*
   * Set the entry at index 'entry' in a FAT (16/32) table.
   */
  static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
  {
  	__u32 bufnum, offset;
  
  	switch (mydata->fatsize) {
  	case 32:
  		bufnum = entry / FAT32BUFSIZE;
  		offset = entry - bufnum * FAT32BUFSIZE;
  		break;
  	case 16:
  		bufnum = entry / FAT16BUFSIZE;
  		offset = entry - bufnum * FAT16BUFSIZE;
  		break;
  	default:
  		/* Unsupported FAT size */
  		return -1;
  	}
  
  	/* Read a new block of FAT entries into the cache. */
  	if (bufnum != mydata->fatbufnum) {
  		int getsize = FATBUFBLOCKS;
  		__u8 *bufptr = mydata->fatbuf;
  		__u32 fatlength = mydata->fatlength;
  		__u32 startblock = bufnum * FATBUFBLOCKS;
  
  		fatlength *= mydata->sect_size;
  		startblock += mydata->fat_sect;
  
  		if (getsize > fatlength)
  			getsize = fatlength;
  
  		if (mydata->fatbufnum != -1) {
  			if (flush_fat_buffer(mydata) < 0)
  				return -1;
  		}
  
  		if (disk_read(startblock, getsize, bufptr) < 0) {
  			debug("Error reading FAT blocks\n");
  			return -1;
  		}
  		mydata->fatbufnum = bufnum;
  	}
  
  	/* Set the actual entry */
  	switch (mydata->fatsize) {
  	case 32:
  		((__u32 *) mydata->fatbuf)[offset] = cpu_to_le32(entry_value);
  		break;
  	case 16:
  		((__u16 *) mydata->fatbuf)[offset] = cpu_to_le16(entry_value);
  		break;
  	default:
  		return -1;
  	}
  
  	return 0;
  }
  
  /*
   * Determine the entry value at index 'entry' in a FAT (16/32) table
   */
  static __u32 determine_fatent(fsdata *mydata, __u32 entry)
  {
  	__u32 next_fat, next_entry = entry + 1;
  
  	while (1) {
  		next_fat = get_fatent_value(mydata, next_entry);
  		if (next_fat == 0) {
  			set_fatent_value(mydata, entry, next_entry);
  			break;
  		}
  		next_entry++;
  	}
  	debug("FAT%d: entry: %08x, entry_value: %04x\n",
  	       mydata->fatsize, entry, next_entry);
  
  	return next_entry;
  }
  
  /*
   * Write at most 'size' bytes from 'buffer' into the specified cluster.
   * Return 0 on success, -1 otherwise.
   */
  static int
  set_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer,
  	     unsigned long size)
  {
  	int idx = 0;
  	__u32 startsect;
  
  	if (clustnum > 0)
  		startsect = mydata->data_begin +
  				clustnum * mydata->clust_size;
  	else
  		startsect = mydata->rootdir_sect;
  
  	debug("clustnum: %d, startsect: %d\n", clustnum, startsect);
  
  	if (disk_write(startsect, size / mydata->sect_size, buffer) < 0) {
  		debug("Error writing data\n");
  		return -1;
  	}
  
  	if (size % mydata->sect_size) {
  		__u8 tmpbuf[mydata->sect_size];
  
  		idx = size / mydata->sect_size;
  		buffer += idx * mydata->sect_size;
  		memcpy(tmpbuf, buffer, size % mydata->sect_size);
  
  		if (disk_write(startsect + idx, 1, tmpbuf) < 0) {
  			debug("Error writing data\n");
  			return -1;
  		}
  
  		return 0;
  	}
  
  	return 0;
  }
  
  /*
   * Find the first empty cluster
   */
  static int find_empty_cluster(fsdata *mydata)
  {
  	__u32 fat_val, entry = 3;
  
  	while (1) {
  		fat_val = get_fatent_value(mydata, entry);
  		if (fat_val == 0)
  			break;
  		entry++;
  	}
  
  	return entry;
  }
  
  /*
   * Write directory entries in 'get_dentfromdir_block' to block device
   */
  static void flush_dir_table(fsdata *mydata, dir_entry **dentptr)
  {
  	int dir_newclust = 0;
  
  	if (set_cluster(mydata, dir_curclust,
  		    get_dentfromdir_block,
  		    mydata->clust_size * mydata->sect_size) != 0) {
  		printf("error: wrinting directory entry\n");
  		return;
  	}
  	dir_newclust = find_empty_cluster(mydata);
  	set_fatent_value(mydata, dir_curclust, dir_newclust);
  	if (mydata->fatsize == 32)
  		set_fatent_value(mydata, dir_newclust, 0xffffff8);
  	else if (mydata->fatsize == 16)
  		set_fatent_value(mydata, dir_newclust, 0xfff8);
  
  	dir_curclust = dir_newclust;
  
  	if (flush_fat_buffer(mydata) < 0)
  		return;
  
  	memset(get_dentfromdir_block, 0x00,
  		mydata->clust_size * mydata->sect_size);
  
  	*dentptr = (dir_entry *) get_dentfromdir_block;
  }
  
  /*
   * Set empty cluster from 'entry' to the end of a file
   */
  static int clear_fatent(fsdata *mydata, __u32 entry)
  {
  	__u32 fat_val;
  
  	while (1) {
  		fat_val = get_fatent_value(mydata, entry);
  		if (fat_val != 0)
  			set_fatent_value(mydata, entry, 0);
  		else
  			break;
  
  		if (fat_val == 0xfffffff || fat_val == 0xffff)
  			break;
  
  		entry = fat_val;
  	}
  
  	/* Flush fat buffer */
  	if (flush_fat_buffer(mydata) < 0)
  		return -1;
  
  	return 0;
  }
  
  /*
   * Write at most 'maxsize' bytes from 'buffer' into
   * the file associated with 'dentptr'
   * Return the number of bytes read or -1 on fatal errors.
   */
  static int
  set_contents(fsdata *mydata, dir_entry *dentptr, __u8 *buffer,
  	      unsigned long maxsize)
  {
  	unsigned long filesize = FAT2CPU32(dentptr->size), gotsize = 0;
  	unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
  	__u32 curclust = START(dentptr);
  	__u32 endclust = 0, newclust = 0;
  	unsigned long actsize;
  
  	debug("Filesize: %ld bytes\n", filesize);
  
  	if (maxsize > 0 && filesize > maxsize)
  		filesize = maxsize;
  
  	debug("%ld bytes\n", filesize);
  
  	actsize = bytesperclust;
  	endclust = curclust;
  	do {
  		/* search for consecutive clusters */
  		while (actsize < filesize) {
  			newclust = determine_fatent(mydata, endclust);
  
  			if ((newclust - 1) != endclust)
  				goto getit;
  
  			if (CHECK_CLUST(newclust, mydata->fatsize)) {
  				debug("curclust: 0x%x\n", newclust);
  				debug("Invalid FAT entry\n");
  				return gotsize;
  			}
  			endclust = newclust;
  			actsize += bytesperclust;
  		}
  		/* actsize >= file size */
  		actsize -= bytesperclust;
  		/* set remaining clusters */
  		if (set_cluster(mydata, curclust, buffer, (int)actsize) != 0) {
  			debug("error: writing cluster\n");
  			return -1;
  		}
  
  		/* set remaining bytes */
  		gotsize += (int)actsize;
  		filesize -= actsize;
  		buffer += actsize;
  		actsize = filesize;
  
  		if (set_cluster(mydata, endclust, buffer, (int)actsize) != 0) {
  			debug("error: writing cluster\n");
  			return -1;
  		}
  		gotsize += actsize;
  
  		/* Mark end of file in FAT */
  		if (mydata->fatsize == 16)
  			newclust = 0xffff;
  		else if (mydata->fatsize == 32)
  			newclust = 0xfffffff;
  		set_fatent_value(mydata, endclust, newclust);
  
  		return gotsize;
  getit:
  		if (set_cluster(mydata, curclust, buffer, (int)actsize) != 0) {
  			debug("error: writing cluster\n");
  			return -1;
  		}
  		gotsize += (int)actsize;
  		filesize -= actsize;
  		buffer += actsize;
  
  		if (CHECK_CLUST(curclust, mydata->fatsize)) {
  			debug("curclust: 0x%x\n", curclust);
  			debug("Invalid FAT entry\n");
  			return gotsize;
  		}
  		actsize = bytesperclust;
  		curclust = endclust = newclust;
  	} while (1);
  }
  
  /*
   * Fill dir_entry
   */
  static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
  	const char *filename, __u32 start_cluster, __u32 size, __u8 attr)
  {
  	if (mydata->fatsize == 32)
  		dentptr->starthi =
  			cpu_to_le16((start_cluster & 0xffff0000) >> 16);
  	dentptr->start = cpu_to_le16(start_cluster & 0xffff);
  	dentptr->size = cpu_to_le32(size);
  
  	dentptr->attr = attr;
  
  	set_name(dentptr, filename);
  }
  
  /*
   * Check whether adding a file makes the file system to
   * exceed the size of the block device
   * Return -1 when overflow occurs, otherwise return 0
   */
  static int check_overflow(fsdata *mydata, __u32 clustnum, unsigned long size)
  {
  	__u32 startsect, sect_num;
  
  	if (clustnum > 0) {
  		startsect = mydata->data_begin +
  				clustnum * mydata->clust_size;
  	} else {
  		startsect = mydata->rootdir_sect;
  	}
  
  	sect_num = size / mydata->sect_size;
  	if (size % mydata->sect_size)
  		sect_num++;
  
  	if (startsect + sect_num > total_sector)
  		return -1;
  
  	return 0;
  }
  
  /*
   * Check if adding several entries exceed one cluster boundary
   */
  static int is_next_clust(fsdata *mydata, dir_entry *dentptr)
  {
  	int cur_position;
  
  	cur_position = (__u8 *)dentptr - get_dentfromdir_block;
  
  	if (cur_position >= mydata->clust_size * mydata->sect_size)
  		return 1;
  	else
  		return 0;
  }
  
  static dir_entry *empty_dentptr;
  /*
   * Find a directory entry based on filename or start cluster number
   * If the directory entry is not found,
   * the new position for writing a directory entry will be returned
   */
  static dir_entry *find_directory_entry(fsdata *mydata, int startsect,
  	char *filename, dir_entry *retdent, __u32 start)
  {
  	__u16 prevcksum = 0xffff;
  	__u32 curclust = (startsect - mydata->data_begin) / mydata->clust_size;
  
  	debug("get_dentfromdir: %s\n", filename);
  
  	while (1) {
  		dir_entry *dentptr;
  
  		int i;
  
  		if (get_cluster(mydata, curclust, get_dentfromdir_block,
  			    mydata->clust_size * mydata->sect_size) != 0) {
  			printf("Error: reading directory block\n");
  			return NULL;
  		}
  
  		dentptr = (dir_entry *)get_dentfromdir_block;
  
  		dir_curclust = curclust;
  
  		for (i = 0; i < DIRENTSPERCLUST; i++) {
  			char s_name[14], l_name[VFAT_MAXLEN_BYTES];
  
  			l_name[0] = '\0';
  			if (dentptr->name[0] == DELETED_FLAG) {
  				dentptr++;
  				if (is_next_clust(mydata, dentptr))
  					break;
  				continue;
  			}
  			if ((dentptr->attr & ATTR_VOLUME)) {
  #ifdef CONFIG_SUPPORT_VFAT
  				if ((dentptr->attr & ATTR_VFAT) &&
  				    (dentptr->name[0] & LAST_LONG_ENTRY_MASK)) {
  					prevcksum =
  					((dir_slot *)dentptr)->alias_checksum;
  					get_long_file_name(mydata, curclust,
  						     get_dentfromdir_block,
  						     &dentptr, l_name);
  					debug("vfatname: |%s|\n", l_name);
  				} else
  #endif
  				{
  					/* Volume label or VFAT entry */
  					dentptr++;
  					if (is_next_clust(mydata, dentptr))
  						break;
  					continue;
  				}
  			}
  			if (dentptr->name[0] == 0) {
  				debug("Dentname == NULL - %d\n", i);
  				empty_dentptr = dentptr;
  				return NULL;
  			}
  
  			get_name(dentptr, s_name);
  
  			if (strcmp(filename, s_name)
  			    && strcmp(filename, l_name)) {
  				debug("Mismatch: |%s|%s|\n",
  					s_name, l_name);
  				dentptr++;
  				if (is_next_clust(mydata, dentptr))
  					break;
  				continue;
  			}
  
  			memcpy(retdent, dentptr, sizeof(dir_entry));
  
  			debug("DentName: %s", s_name);
  			debug(", start: 0x%x", START(dentptr));
  			debug(", size:  0x%x %s\n",
  			      FAT2CPU32(dentptr->size),
  			      (dentptr->attr & ATTR_DIR) ?
  			      "(DIR)" : "");
  
  			return dentptr;
  		}
  
  		curclust = get_fatent_value(mydata, dir_curclust);
  		if ((curclust >= 0xffffff8) || (curclust >= 0xfff8)) {
  			empty_dentptr = dentptr;
  			return NULL;
  		}
  		if (CHECK_CLUST(curclust, mydata->fatsize)) {
  			debug("curclust: 0x%x\n", curclust);
  			debug("Invalid FAT entry\n");
  			return NULL;
  		}
  	}
  
  	return NULL;
  }
  
  static int do_fat_write(const char *filename, void *buffer,
  	unsigned long size)
  {
  	dir_entry *dentptr, *retdent;
  	dir_slot *slotptr;
  	__u32 startsect;
  	__u32 start_cluster;
  	boot_sector bs;
  	volume_info volinfo;
  	fsdata datablock;
  	fsdata *mydata = &datablock;
  	int cursect;
  	int root_cluster, ret = -1, name_len;
  	char l_filename[VFAT_MAXLEN_BYTES];
  	int write_size = size;
  
  	dir_curclust = 0;
  
  	if (read_bootsectandvi(&bs, &volinfo, &mydata->fatsize)) {
  		debug("error: reading boot sector\n");
  		return -1;
  	}
  
  	total_sector = bs.total_sect;
  	if (total_sector == 0)
  		total_sector = part_size;
  
  	root_cluster = bs.root_cluster;
  
  	if (mydata->fatsize == 32)
  		mydata->fatlength = bs.fat32_length;
  	else
  		mydata->fatlength = bs.fat_length;
  
  	mydata->fat_sect = bs.reserved;
  
  	cursect = mydata->rootdir_sect
  		= mydata->fat_sect + mydata->fatlength * bs.fats;
  
  	mydata->sect_size = (bs.sector_size[1] << 8) + bs.sector_size[0];
  	mydata->clust_size = bs.cluster_size;
  
  	if (mydata->fatsize == 32) {
  		mydata->data_begin = mydata->rootdir_sect -
  					(mydata->clust_size * 2);
  	} else {
  		int rootdir_size;
  
  		rootdir_size = ((bs.dir_entries[1]  * (int)256 +
  				 bs.dir_entries[0]) *
  				 sizeof(dir_entry)) /
  				 mydata->sect_size;
  		mydata->data_begin = mydata->rootdir_sect +
  					rootdir_size -
  					(mydata->clust_size * 2);
  	}
  
  	mydata->fatbufnum = -1;
  	mydata->fatbuf = malloc(FATBUFSIZE);
  	if (mydata->fatbuf == NULL) {
  		debug("Error: allocating memory\n");
  		return -1;
  	}
  
  	if (disk_read(cursect,
  		(mydata->fatsize == 32) ?
  		(mydata->clust_size) :
  		PREFETCH_BLOCKS, do_fat_read_block) < 0) {
  		debug("Error: reading rootdir block\n");
  		goto exit;
  	}
  	dentptr = (dir_entry *) do_fat_read_block;
  
  	name_len = strlen(filename);
  	if (name_len >= VFAT_MAXLEN_BYTES)
  		name_len = VFAT_MAXLEN_BYTES - 1;
  
  	memcpy(l_filename, filename, name_len);
  	l_filename[name_len] = 0; /* terminate the string */
  	downcase(l_filename);
  
  	startsect = mydata->rootdir_sect;
  	retdent = find_directory_entry(mydata, startsect,
  				l_filename, dentptr, 0);
  	if (retdent) {
  		/* Update file size and start_cluster in a directory entry */
  		retdent->size = cpu_to_le32(size);
  		start_cluster = FAT2CPU16(retdent->start);
  		if (mydata->fatsize == 32)
  			start_cluster |=
  				(FAT2CPU16(retdent->starthi) << 16);
  
  		ret = check_overflow(mydata, start_cluster, size);
  		if (ret) {
  			printf("Error: %ld overflow\n", size);
  			goto exit;
  		}
  
  		ret = clear_fatent(mydata, start_cluster);
  		if (ret) {
  			printf("Error: clearing FAT entries\n");
  			goto exit;
  		}
  
  		ret = set_contents(mydata, retdent, buffer, size);
  		if (ret < 0) {
  			printf("Error: writing contents\n");
  			goto exit;
  		}
  		write_size = ret;
  		debug("attempt to write 0x%x bytes\n", write_size);
  
  		/* Flush fat buffer */
  		ret = flush_fat_buffer(mydata);
  		if (ret) {
  			printf("Error: flush fat buffer\n");
  			goto exit;
  		}
  
  		/* Write directory table to device */
  		ret = set_cluster(mydata, dir_curclust,
  			    get_dentfromdir_block,
  			    mydata->clust_size * mydata->sect_size);
  		if (ret) {
  			printf("Error: writing directory entry\n");
  			goto exit;
  		}
  	} else {
  		slotptr = (dir_slot *)empty_dentptr;
  
  		/* Set short name to set alias checksum field in dir_slot */
  		set_name(empty_dentptr, filename);
  		fill_dir_slot(mydata, &empty_dentptr, filename);
  
  		ret = start_cluster = find_empty_cluster(mydata);
  		if (ret < 0) {
  			printf("Error: finding empty cluster\n");
  			goto exit;
  		}
  
  		ret = check_overflow(mydata, start_cluster, size);
  		if (ret) {
  			printf("Error: %ld overflow\n", size);
  			goto exit;
  		}
  
  		/* Set attribute as archieve for regular file */
  		fill_dentry(mydata, empty_dentptr, filename,
  			start_cluster, size, 0x20);
  
  		ret = set_contents(mydata, empty_dentptr, buffer, size);
  		if (ret < 0) {
  			printf("Error: writing contents\n");
  			goto exit;
  		}
  		write_size = ret;
  		debug("attempt to write 0x%x bytes\n", write_size);
  
  		/* Flush fat buffer */
  		ret = flush_fat_buffer(mydata);
  		if (ret) {
  			printf("Error: flush fat buffer\n");
  			goto exit;
  		}
  
  		/* Write directory table to device */
  		ret = set_cluster(mydata, dir_curclust,
  			    get_dentfromdir_block,
  			    mydata->clust_size * mydata->sect_size);
  		if (ret) {
  			printf("Error: writing directory entry\n");
  			goto exit;
  		}
  	}
  
  exit:
  	free(mydata->fatbuf);
  	return ret < 0 ? ret : write_size;
  }
  
  int file_fat_write(const char *filename, void *buffer, unsigned long maxsize)
  {
  	printf("writing %s\n", filename);
  	return do_fat_write(filename, buffer, maxsize);
  }
  