// SPDX-License-Identifier: GPL-2.0+
/*
 * fat_write.c
 *
 * R/W (V)FAT 12/16/32 filesystem implementation by Donggeun Kim
 */

#include <common.h>
#include <command.h>
#include <config.h>
#include <fat.h>
#include <log.h>
#include <malloc.h>
#include <asm/byteorder.h>
#include <part.h>
#include <asm/cache.h>
#include <linux/ctype.h>
#include <div64.h>
#include <linux/math64.h>
#include "fat.c"

static void uppercase(char *str, int len)
{
        int i;

        for (i = 0; i < len; i++) {
                *str = toupper(*str);
                str++;
        }
}

static int total_sector;
static int disk_write(__u32 block, __u32 nr_blocks, void *buf)
{
        ulong ret;

        if (!cur_dev)
                return -1;

        if (cur_part_info.start + block + nr_blocks >
                cur_part_info.start + total_sector) {
                printf("error: overflow occurs\n");
                return -1;
        }

        ret = blk_dwrite(cur_dev, cur_part_info.start + block, nr_blocks, buf);
        if (nr_blocks && ret == 0)
                return -1;

        return ret;
}

/**
 * set_name() - set short name in directory entry
 *
 * @dirent:     directory entry
 * @filename:   long file name
 */
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;

        strncpy(s_name, filename, VFAT_MAXLEN_BYTES - 1);
        s_name[VFAT_MAXLEN_BYTES - 1] = '\0';
        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);
                /*
                 * TODO: Translating two long names with the same first six
                 *       characters to the same short name is utterly wrong.
                 *       Short names must be unique.
                 */
                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_dirty_fat_buffer(fsdata *mydata)
{
        int getsize = FATBUFBLOCKS;
        __u32 fatlength = mydata->fatlength;
        __u8 *bufptr = mydata->fatbuf;
        __u32 startblock = mydata->fatbufnum * FATBUFBLOCKS;

        debug("debug: evicting %d, dirty: %d\n", mydata->fatbufnum,
              (int)mydata->fat_dirty);

        if ((!mydata->fat_dirty) || (mydata->fatbufnum == -1))
                return 0;

        /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */
        if (startblock + getsize > fatlength)
                getsize = fatlength - startblock;

        startblock += mydata->fat_sect;

        /* Write FAT buf */
        if (disk_write(startblock, getsize, bufptr) < 0) {
                debug("error: writing FAT blocks\n");
                return -1;
        }

        if (mydata->fats == 2) {
                /* Update corresponding second FAT blocks */
                startblock += mydata->fatlength;
                if (disk_write(startblock, getsize, bufptr) < 0) {
                        debug("error: writing second FAT blocks\n");
                        return -1;
                }
        }
        mydata->fat_dirty = 0;

        return 0;
}

/*
 * 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 new_dir_table(fat_itr *itr);
static int flush_dir(fat_itr *itr);

/*
 * Fill dir_slot entries with appropriate name, id, and attr
 * 'itr' will point to a next entry
 */
static int
fill_dir_slot(fat_itr *itr, const char *l_name)
{
        __u8 temp_dir_slot_buffer[MAX_LFN_SLOT * sizeof(dir_slot)];
        dir_slot *slotptr = (dir_slot *)temp_dir_slot_buffer;
        __u8 counter = 0, checksum;
        int idx = 0, ret;

        /* Get short file name checksum value */
        checksum = mkcksum(itr->dent->name, itr->dent->ext);

        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) {
                memcpy(itr->dent, slotptr, sizeof(dir_slot));
                slotptr--;
                counter--;

                if (itr->remaining == 0)
                        flush_dir(itr);

                /* allocate a cluster for more entries */
                if (!fat_itr_next(itr) && !itr->dent)
                        if ((itr->is_root && itr->fsdata->fatsize != 32) ||
                            new_dir_table(itr))
                                return -1;
        }

        return 0;
}

/*
 * Set the entry at index 'entry' in a FAT (12/16/32) table.
 */
static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value)
{
        __u32 bufnum, offset, off16;
        __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 -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;

                /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */
                if (startblock + getsize > fatlength)
                        getsize = fatlength - startblock;

                if (flush_dirty_fat_buffer(mydata) < 0)
                        return -1;

                startblock += mydata->fat_sect;

                if (disk_read(startblock, getsize, bufptr) < 0) {
                        debug("Error reading FAT blocks\n");
                        return -1;
                }
                mydata->fatbufnum = bufnum;
        }

        /* Mark as dirty */
        mydata->fat_dirty = 1;

        /* 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;
        case 12:
                off16 = (offset * 3) / 4;

                switch (offset & 0x3) {
                case 0:
                        val1 = cpu_to_le16(entry_value) & 0xfff;
                        ((__u16 *)mydata->fatbuf)[off16] &= ~0xfff;
                        ((__u16 *)mydata->fatbuf)[off16] |= val1;
                        break;
                case 1:
                        val1 = cpu_to_le16(entry_value) & 0xf;
                        val2 = (cpu_to_le16(entry_value) >> 4) & 0xff;

                        ((__u16 *)mydata->fatbuf)[off16] &= ~0xf000;
                        ((__u16 *)mydata->fatbuf)[off16] |= (val1 << 12);

                        ((__u16 *)mydata->fatbuf)[off16 + 1] &= ~0xff;
                        ((__u16 *)mydata->fatbuf)[off16 + 1] |= val2;
                        break;
                case 2:
                        val1 = cpu_to_le16(entry_value) & 0xff;
                        val2 = (cpu_to_le16(entry_value) >> 8) & 0xf;

                        ((__u16 *)mydata->fatbuf)[off16] &= ~0xff00;
                        ((__u16 *)mydata->fatbuf)[off16] |= (val1 << 8);

                        ((__u16 *)mydata->fatbuf)[off16 + 1] &= ~0xf;
                        ((__u16 *)mydata->fatbuf)[off16 + 1] |= val2;
                        break;
                case 3:
                        val1 = cpu_to_le16(entry_value) & 0xfff;
                        ((__u16 *)mydata->fatbuf)[off16] &= ~0xfff0;
                        ((__u16 *)mydata->fatbuf)[off16] |= (val1 << 4);
                        break;
                default:
                        break;
                }

                break;
        default:
                return -1;
        }

        return 0;
}

/*
 * Determine the next free cluster after 'entry' in a FAT (12/16/32) table
 * and link it to 'entry'. EOC marker is not set on returned entry.
 */
static __u32 determine_fatent(fsdata *mydata, __u32 entry)
{
        __u32 next_fat, next_entry = entry + 1;

        while (1) {
                next_fat = get_fatent(mydata, next_entry);
                if (next_fat == 0) {
                        /* found free entry, link to entry */
                        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;
}

/**
 * set_sectors() - write data to sectors
 *
 * Write 'size' bytes from 'buffer' into the specified sector.
 *
 * @mydata:     data to be written
 * @startsect:  sector to be written to
 * @buffer:     data to be written
 * @size:       bytes to be written (but not more than the size of a cluster)
 * Return:      0 on success, -1 otherwise
 */
static int
set_sectors(fsdata *mydata, u32 startsect, u8 *buffer, u32 size)
{
        u32 nsects = 0;
        int ret;

        debug("startsect: %d\n", startsect);

        if ((unsigned long)buffer & (ARCH_DMA_MINALIGN - 1)) {
                ALLOC_CACHE_ALIGN_BUFFER(__u8, tmpbuf, mydata->sect_size);

                debug("FAT: Misaligned buffer address (%p)\n", buffer);

                while (size >= mydata->sect_size) {
                        memcpy(tmpbuf, buffer, mydata->sect_size);
                        ret = disk_write(startsect++, 1, tmpbuf);
                        if (ret != 1) {
                                debug("Error writing data (got %d)\n", ret);
                                return -1;
                        }

                        buffer += mydata->sect_size;
                        size -= mydata->sect_size;
                }
        } else if (size >= mydata->sect_size) {
                nsects = size / mydata->sect_size;
                ret = disk_write(startsect, nsects, buffer);
                if (ret != nsects) {
                        debug("Error writing data (got %d)\n", ret);
                        return -1;
                }

                startsect += nsects;
                buffer += nsects * mydata->sect_size;
                size -= nsects * mydata->sect_size;
        }

        if (size) {
                ALLOC_CACHE_ALIGN_BUFFER(__u8, tmpbuf, mydata->sect_size);
                /* Do not leak content of stack */
                memset(tmpbuf, 0, mydata->sect_size);
                memcpy(tmpbuf, buffer, size);
                ret = disk_write(startsect, 1, tmpbuf);
                if (ret != 1) {
                        debug("Error writing data (got %d)\n", ret);
                        return -1;
                }
        }

        return 0;
}

/**
 * set_cluster() - write data to cluster
 *
 * Write 'size' bytes from 'buffer' into the specified cluster.
 *
 * @mydata:     data to be written
 * @clustnum:   cluster to be written to
 * @buffer:     data to be written
 * @size:       bytes to be written (but not more than the size of a cluster)
 * Return:      0 on success, -1 otherwise
 */
static int
set_cluster(fsdata *mydata, u32 clustnum, u8 *buffer, u32 size)
{
        return set_sectors(mydata, clust_to_sect(mydata, clustnum),
                           buffer, size);
}

static int
flush_dir(fat_itr *itr)
{
        fsdata *mydata = itr->fsdata;
        u32 startsect, sect_offset, nsects;

        if (!itr->is_root || mydata->fatsize == 32)
                return set_cluster(mydata, itr->clust, itr->block,
                                   mydata->clust_size * mydata->sect_size);

        sect_offset = itr->clust * mydata->clust_size;
        startsect = mydata->rootdir_sect + sect_offset;
        /* do not write past the end of rootdir */
        nsects = min_t(u32, mydata->clust_size,
                       mydata->rootdir_size - sect_offset);

        return set_sectors(mydata, startsect, itr->block,
                           nsects * mydata->sect_size);
}

/*
 * Read and modify data on existing and consecutive cluster blocks
 */
static int
get_set_cluster(fsdata *mydata, __u32 clustnum, loff_t pos, __u8 *buffer,
                loff_t size, loff_t *gotsize)
{
        static u8 *tmpbuf_cluster;
        unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
        __u32 startsect;
        loff_t wsize;
        int clustcount, i, ret;

        *gotsize = 0;
        if (!size)
                return 0;

        if (!tmpbuf_cluster) {
                tmpbuf_cluster = memalign(ARCH_DMA_MINALIGN, MAX_CLUSTSIZE);
                if (!tmpbuf_cluster)
                        return -1;
        }

        assert(pos < bytesperclust);
        startsect = clust_to_sect(mydata, clustnum);

        debug("clustnum: %d, startsect: %d, pos: %lld\n",
              clustnum, startsect, pos);

        /* partial write at beginning */
        if (pos) {
                wsize = min(bytesperclust - pos, size);
                ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
                if (ret != mydata->clust_size) {
                        debug("Error reading data (got %d)\n", ret);
                        return -1;
                }

                memcpy(tmpbuf_cluster + pos, buffer, wsize);
                ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
                if (ret != mydata->clust_size) {
                        debug("Error writing data (got %d)\n", ret);
                        return -1;
                }

                size -= wsize;
                buffer += wsize;
                *gotsize += wsize;

                startsect += mydata->clust_size;

                if (!size)
                        return 0;
        }

        /* full-cluster write */
        if (size >= bytesperclust) {
                clustcount = lldiv(size, bytesperclust);

                if (!((unsigned long)buffer & (ARCH_DMA_MINALIGN - 1))) {
                        wsize = clustcount * bytesperclust;
                        ret = disk_write(startsect,
                                         clustcount * mydata->clust_size,
                                         buffer);
                        if (ret != clustcount * mydata->clust_size) {
                                debug("Error writing data (got %d)\n", ret);
                                return -1;
                        }

                        size -= wsize;
                        buffer += wsize;
                        *gotsize += wsize;

                        startsect += clustcount * mydata->clust_size;
                } else {
                        for (i = 0; i < clustcount; i++) {
                                memcpy(tmpbuf_cluster, buffer, bytesperclust);
                                ret = disk_write(startsect,
                                                 mydata->clust_size,
                                                 tmpbuf_cluster);
                                if (ret != mydata->clust_size) {
                                        debug("Error writing data (got %d)\n",
                                              ret);
                                        return -1;
                                }

                                size -= bytesperclust;
                                buffer += bytesperclust;
                                *gotsize += bytesperclust;

                                startsect += mydata->clust_size;
                        }
                }
        }

        /* partial write at end */
        if (size) {
                wsize = size;
                ret = disk_read(startsect, mydata->clust_size, tmpbuf_cluster);
                if (ret != mydata->clust_size) {
                        debug("Error reading data (got %d)\n", ret);
                        return -1;
                }
                memcpy(tmpbuf_cluster, buffer, wsize);
                ret = disk_write(startsect, mydata->clust_size, tmpbuf_cluster);
                if (ret != mydata->clust_size) {
                        debug("Error writing data (got %d)\n", ret);
                        return -1;
                }

                size -= wsize;
                buffer += wsize;
                *gotsize += wsize;
        }

        assert(!size);

        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(mydata, entry);
                if (fat_val == 0)
                        break;
                entry++;
        }

        return entry;
}

/*
 * Allocate a cluster for additional directory entries
 */
static int new_dir_table(fat_itr *itr)
{
        fsdata *mydata = itr->fsdata;
        int dir_newclust = 0;
        unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;

        dir_newclust = find_empty_cluster(mydata);
        set_fatent_value(mydata, itr->clust, 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);
        else if (mydata->fatsize == 12)
                set_fatent_value(mydata, dir_newclust, 0xff8);

        itr->clust = dir_newclust;
        itr->next_clust = dir_newclust;

        if (flush_dirty_fat_buffer(mydata) < 0)
                return -1;

        memset(itr->block, 0x00, bytesperclust);

        itr->dent = (dir_entry *)itr->block;
        itr->last_cluster = 1;
        itr->remaining = bytesperclust / sizeof(dir_entry) - 1;

        return 0;
}

/*
 * Set empty cluster from 'entry' to the end of a file
 */
static int clear_fatent(fsdata *mydata, __u32 entry)
{
        __u32 fat_val;

        while (!CHECK_CLUST(entry, mydata->fatsize)) {
                fat_val = get_fatent(mydata, entry);
                if (fat_val != 0)
                        set_fatent_value(mydata, entry, 0);
                else
                        break;

                entry = fat_val;
        }

        /* Flush fat buffer */
        if (flush_dirty_fat_buffer(mydata) < 0)
                return -1;

        return 0;
}

/*
 * Set start cluster in directory entry
 */
static void set_start_cluster(const fsdata *mydata, dir_entry *dentptr,
                              __u32 start_cluster)
{
        if (mydata->fatsize == 32)
                dentptr->starthi =
                        cpu_to_le16((start_cluster & 0xffff0000) >> 16);
        dentptr->start = cpu_to_le16(start_cluster & 0xffff);
}

/*
 * 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, loff_t size)
{
        __u32 startsect, sect_num, offset;

        if (clustnum > 0)
                startsect = clust_to_sect(mydata, clustnum);
        else
                startsect = mydata->rootdir_sect;

        sect_num = div_u64_rem(size, mydata->sect_size, &offset);

        if (offset != 0)
                sect_num++;

        if (startsect + sect_num > total_sector)
                return -1;
        return 0;
}

/*
 * Write at most 'maxsize' bytes from 'buffer' into
 * the file associated with 'dentptr'
 * Update the number of bytes written in *gotsize and return 0
 * or return -1 on fatal errors.
 */
static int
set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
             loff_t maxsize, loff_t *gotsize)
{
        unsigned int bytesperclust = mydata->clust_size * mydata->sect_size;
        __u32 curclust = START(dentptr);
        __u32 endclust = 0, newclust = 0;
        u64 cur_pos, filesize;
        loff_t offset, actsize, wsize;

        *gotsize = 0;
        filesize = pos + maxsize;

        debug("%llu bytes\n", filesize);

        if (!filesize) {
                if (!curclust)
                        return 0;
                if (!CHECK_CLUST(curclust, mydata->fatsize) ||
                    IS_LAST_CLUST(curclust, mydata->fatsize)) {
                        clear_fatent(mydata, curclust);
                        set_start_cluster(mydata, dentptr, 0);
                        return 0;
                }
                debug("curclust: 0x%x\n", curclust);
                debug("Invalid FAT entry\n");
                return -1;
        }

        if (!curclust) {
                assert(pos == 0);
                goto set_clusters;
        }

        /* go to cluster at pos */
        cur_pos = bytesperclust;
        while (1) {
                if (pos <= cur_pos)
                        break;
                if (IS_LAST_CLUST(curclust, mydata->fatsize))
                        break;

                newclust = get_fatent(mydata, curclust);
                if (!IS_LAST_CLUST(newclust, mydata->fatsize) &&
                    CHECK_CLUST(newclust, mydata->fatsize)) {
                        debug("curclust: 0x%x\n", curclust);
                        debug("Invalid FAT entry\n");
                        return -1;
                }

                cur_pos += bytesperclust;
                curclust = newclust;
        }
        if (IS_LAST_CLUST(curclust, mydata->fatsize)) {
                assert(pos == cur_pos);
                goto set_clusters;
        }

        assert(pos < cur_pos);
        cur_pos -= bytesperclust;

        /* overwrite */
        assert(IS_LAST_CLUST(curclust, mydata->fatsize) ||
               !CHECK_CLUST(curclust, mydata->fatsize));

        while (1) {
                /* search for allocated consecutive clusters */
                actsize = bytesperclust;
                endclust = curclust;
                while (1) {
                        if (filesize <= (cur_pos + actsize))
                                break;

                        newclust = get_fatent(mydata, endclust);

                        if (newclust != endclust + 1)
                                break;
                        if (IS_LAST_CLUST(newclust, mydata->fatsize))
                                break;
                        if (CHECK_CLUST(newclust, mydata->fatsize)) {
                                debug("curclust: 0x%x\n", curclust);
                                debug("Invalid FAT entry\n");
                                return -1;
                        }

                        actsize += bytesperclust;
                        endclust = newclust;
                }

                /* overwrite to <curclust..endclust> */
                if (pos < cur_pos)
                        offset = 0;
                else
                        offset = pos - cur_pos;
                wsize = min_t(unsigned long long, actsize, filesize - cur_pos);
                wsize -= offset;

                if (get_set_cluster(mydata, curclust, offset,
                                    buffer, wsize, &actsize)) {
                        printf("Error get-and-setting cluster\n");
                        return -1;
                }
                buffer += wsize;
                *gotsize += wsize;
                cur_pos += offset + wsize;

                if (filesize <= cur_pos)
                        break;

                if (IS_LAST_CLUST(newclust, mydata->fatsize))
                        /* no more clusters */
                        break;

                curclust = newclust;
        }

        if (filesize <= cur_pos) {
                /* no more write */
                newclust = get_fatent(mydata, endclust);
                if (!IS_LAST_CLUST(newclust, mydata->fatsize)) {
                        /* truncate the rest */
                        clear_fatent(mydata, newclust);

                        /* Mark end of file in FAT */
                        if (mydata->fatsize == 12)
                                newclust = 0xfff;
                        else if (mydata->fatsize == 16)
                                newclust = 0xffff;
                        else if (mydata->fatsize == 32)
                                newclust = 0xfffffff;
                        set_fatent_value(mydata, endclust, newclust);
                }

                return 0;
        }

        curclust = endclust;
        filesize -= cur_pos;
        assert(!do_div(cur_pos, bytesperclust));

set_clusters:
        /* allocate and write */
        assert(!pos);

        /* Assure that curclust is valid */
        if (!curclust) {
                curclust = find_empty_cluster(mydata);
                set_start_cluster(mydata, dentptr, curclust);
        } else {
                newclust = get_fatent(mydata, curclust);

                if (IS_LAST_CLUST(newclust, mydata->fatsize)) {
                        newclust = determine_fatent(mydata, curclust);
                        set_fatent_value(mydata, curclust, newclust);
                        curclust = newclust;
                } else {
                        debug("error: something wrong\n");
                        return -1;
                }
        }

        /* TODO: already partially written */
        if (check_overflow(mydata, curclust, filesize)) {
                printf("Error: no space left: %llu\n", filesize);
                return -1;
        }

        actsize = bytesperclust;
        endclust = curclust;
        do {
                /* search for consecutive clusters */
                while (actsize < filesize) {
                        newclust = determine_fatent(mydata, endclust);

                        if ((newclust - 1) != endclust)
                                /* write to <curclust..endclust> */
                                goto getit;

                        if (CHECK_CLUST(newclust, mydata->fatsize)) {
                                debug("newclust: 0x%x\n", newclust);
                                debug("Invalid FAT entry\n");
                                return 0;
                        }
                        endclust = newclust;
                        actsize += bytesperclust;
                }

                /* set remaining bytes */
                actsize = filesize;
                if (set_cluster(mydata, curclust, buffer, (u32)actsize) != 0) {
                        debug("error: writing cluster\n");
                        return -1;
                }
                *gotsize += actsize;

                /* Mark end of file in FAT */
                if (mydata->fatsize == 12)
                        newclust = 0xfff;
                else if (mydata->fatsize == 16)
                        newclust = 0xffff;
                else if (mydata->fatsize == 32)
                        newclust = 0xfffffff;
                set_fatent_value(mydata, endclust, newclust);

                return 0;
getit:
                if (set_cluster(mydata, curclust, buffer, (u32)actsize) != 0) {
                        debug("error: writing cluster\n");
                        return -1;
                }
                *gotsize += actsize;
                filesize -= actsize;
                buffer += actsize;

                if (CHECK_CLUST(newclust, mydata->fatsize)) {
                        debug("newclust: 0x%x\n", newclust);
                        debug("Invalid FAT entry\n");
                        return 0;
                }
                actsize = bytesperclust;
                curclust = endclust = newclust;
        } while (1);

        return 0;
}

/*
 * Fill dir_entry
 */
static void fill_dentry(fsdata *mydata, dir_entry *dentptr,
        const char *filename, __u32 start_cluster, __u32 size, __u8 attr)
{
        set_start_cluster(mydata, dentptr, start_cluster);
        dentptr->size = cpu_to_le32(size);

        dentptr->attr = attr;

        set_name(dentptr, filename);
}

/*
 * 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(fat_itr *itr, char *filename)
{
        int match = 0;

        while (fat_itr_next(itr)) {
                /* check both long and short name: */
                if (!strcasecmp(filename, itr->name))
                        match = 1;
                else if (itr->name != itr->s_name &&
                         !strcasecmp(filename, itr->s_name))
                        match = 1;

                if (!match)
                        continue;

                if (itr->dent->name[0] == '\0')
                        return NULL;
                else

                        return itr->dent;
        }

        /* allocate a cluster for more entries */
        if (!itr->dent &&
            (!itr->is_root || itr->fsdata->fatsize == 32) &&
            new_dir_table(itr))
                /* indicate that allocating dent failed */
                itr->dent = NULL;

        return NULL;
}

static int split_filename(char *filename, char **dirname, char **basename)
{
        char *p, *last_slash, *last_slash_cont;

again:
        p = filename;
        last_slash = NULL;
        last_slash_cont = NULL;
        while (*p) {
                if (ISDIRDELIM(*p)) {
                        last_slash = p;
                        last_slash_cont = p;
                        /* continuous slashes */
                        while (ISDIRDELIM(*p))
                                last_slash_cont = p++;
                        if (!*p)
                                break;
                }
                p++;
        }

        if (last_slash) {
                if (last_slash_cont == (filename + strlen(filename) - 1)) {
                        /* remove trailing slashes */
                        *last_slash = '\0';
                        goto again;
                }

                if (last_slash == filename) {
                        /* avoid ""(null) directory */
                        *dirname = "/";
                } else {
                        *last_slash = '\0';
                        *dirname = filename;
                }

                *last_slash_cont = '\0';
                *basename = last_slash_cont + 1;
        } else {
                *dirname = "/"; /* root by default */
                *basename = filename;
        }

        return 0;
}

/**
 * normalize_longname() - check long file name and convert to lower case
 *
 * We assume here that the FAT file system is using an 8bit code page.
 * Linux typically uses CP437, EDK2 assumes CP1250.
 *
 * @l_filename: preallocated buffer receiving the normalized name
 * @filename:   filename to normalize
 * Return:      0 on success, -1 on failure
 */
static int normalize_longname(char *l_filename, const char *filename)
{
        const char *p, illegal[] = "<>:\"/\\|?*";

        if (strlen(filename) >= VFAT_MAXLEN_BYTES)
                return -1;

        for (p = filename; *p; ++p) {
                if ((unsigned char)*p < 0x20)
                        return -1;
                if (strchr(illegal, *p))
                        return -1;
        }

        strcpy(l_filename, filename);
        downcase(l_filename, VFAT_MAXLEN_BYTES);

        return 0;
}

int file_fat_write_at(const char *filename, loff_t pos, void *buffer,
                      loff_t size, loff_t *actwrite)
{
        dir_entry *retdent;
        fsdata datablock = { .fatbuf = NULL, };
        fsdata *mydata = &datablock;
        fat_itr *itr = NULL;
        int ret = -1;
        char *filename_copy, *parent, *basename;
        char l_filename[VFAT_MAXLEN_BYTES];

        debug("writing %s\n", filename);

        filename_copy = strdup(filename);
        if (!filename_copy)
                return -ENOMEM;

        split_filename(filename_copy, &parent, &basename);
        if (!strlen(basename)) {
                ret = -EINVAL;
                goto exit;
        }

        filename = basename;
        if (normalize_longname(l_filename, filename)) {
                printf("FAT: illegal filename (%s)\n", filename);
                ret = -EINVAL;
                goto exit;
        }

        itr = malloc_cache_aligned(sizeof(fat_itr));
        if (!itr) {
                ret = -ENOMEM;
                goto exit;
        }

        ret = fat_itr_root(itr, &datablock);
        if (ret)
                goto exit;

        total_sector = datablock.total_sect;

        ret = fat_itr_resolve(itr, parent, TYPE_DIR);
        if (ret) {
                printf("%s: doesn't exist (%d)\n", parent, ret);
                goto exit;
        }

        retdent = find_directory_entry(itr, l_filename);

        if (retdent) {
                if (fat_itr_isdir(itr)) {
                        ret = -EISDIR;
                        goto exit;
                }

                /* A file exists */
                if (pos == -1)
                        /* Append to the end */
                        pos = FAT2CPU32(retdent->size);
                if (pos > retdent->size) {
                        /* No hole allowed */
                        ret = -EINVAL;
                        goto exit;
                }

                /* Update file size in a directory entry */
                retdent->size = cpu_to_le32(pos + size);
        } else {
                /* Create a new file */

                if (itr->is_root) {
                        /* root dir cannot have "." or ".." */
                        if (!strcmp(l_filename, ".") ||
                            !strcmp(l_filename, "..")) {
                                ret = -EINVAL;
                                goto exit;
                        }
                }

                if (!itr->dent) {
                        printf("Error: allocating new dir entry\n");
                        ret = -EIO;
                        goto exit;
                }

                if (pos) {
                        /* No hole allowed */
                        ret = -EINVAL;
                        goto exit;
                }

                memset(itr->dent, 0, sizeof(*itr->dent));

                /* Calculate checksum for short name */
                set_name(itr->dent, filename);

                /* Set long name entries */
                if (fill_dir_slot(itr, filename)) {
                        ret = -EIO;
                        goto exit;
                }

                /* Set short name entry */
                fill_dentry(itr->fsdata, itr->dent, filename, 0, size,
                            ATTR_ARCH);

                retdent = itr->dent;
        }

        ret = set_contents(mydata, retdent, pos, buffer, size, actwrite);
        if (ret < 0) {
                printf("Error: writing contents\n");
                ret = -EIO;
                goto exit;
        }
        debug("attempt to write 0x%llx bytes\n", *actwrite);

        /* Flush fat buffer */
        ret = flush_dirty_fat_buffer(mydata);
        if (ret) {
                printf("Error: flush fat buffer\n");
                ret = -EIO;
                goto exit;
        }

        /* Write directory table to device */
        ret = flush_dir(itr);
        if (ret) {
                printf("Error: writing directory entry\n");
                ret = -EIO;
        }

exit:
        free(filename_copy);
        free(mydata->fatbuf);
        free(itr);
        return ret;
}

int file_fat_write(const char *filename, void *buffer, loff_t offset,
                   loff_t maxsize, loff_t *actwrite)
{
        return file_fat_write_at(filename, offset, buffer, maxsize, actwrite);
}

static int fat_dir_entries(fat_itr *itr)
{
        fat_itr *dirs;
        fsdata fsdata = { .fatbuf = NULL, }, *mydata = &fsdata;
                                                /* for FATBUFSIZE */
        int count;

        dirs = malloc_cache_aligned(sizeof(fat_itr));
        if (!dirs) {
                debug("Error: allocating memory\n");
                count = -ENOMEM;
                goto exit;
        }

        /* duplicate fsdata */
        fat_itr_child(dirs, itr);
        fsdata = *dirs->fsdata;

        /* allocate local fat buffer */
        fsdata.fatbuf = malloc_cache_aligned(FATBUFSIZE);
        if (!fsdata.fatbuf) {
                debug("Error: allocating memory\n");
                count = -ENOMEM;
                goto exit;
        }
        fsdata.fatbufnum = -1;
        dirs->fsdata = &fsdata;

        for (count = 0; fat_itr_next(dirs); count++)
                ;

exit:
        free(fsdata.fatbuf);
        free(dirs);
        return count;
}

static int delete_dentry(fat_itr *itr)
{
        fsdata *mydata = itr->fsdata;
        dir_entry *dentptr = itr->dent;

        /* free cluster blocks */
        clear_fatent(mydata, START(dentptr));
        if (flush_dirty_fat_buffer(mydata) < 0) {
                printf("Error: flush fat buffer\n");
                return -EIO;
        }

        /*
         * update a directory entry
         * TODO:
         *  - long file name support
         *  - find and mark the "new" first invalid entry as name[0]=0x00
         */
        memset(dentptr, 0, sizeof(*dentptr));
        dentptr->name[0] = 0xe5;

        if (flush_dir(itr)) {
                printf("error: writing directory entry\n");
                return -EIO;
        }

        return 0;
}

int fat_unlink(const char *filename)
{
        fsdata fsdata = { .fatbuf = NULL, };
        fat_itr *itr = NULL;
        int n_entries, ret;
        char *filename_copy, *dirname, *basename;

        filename_copy = strdup(filename);
        if (!filename_copy) {
                printf("Error: allocating memory\n");
                ret = -ENOMEM;
                goto exit;
        }
        split_filename(filename_copy, &dirname, &basename);

        if (!strcmp(dirname, "/") && !strcmp(basename, "")) {
                printf("Error: cannot remove root\n");
                ret = -EINVAL;
                goto exit;
        }

        itr = malloc_cache_aligned(sizeof(fat_itr));
        if (!itr) {
                printf("Error: allocating memory\n");
                ret = -ENOMEM;
                goto exit;
        }

        ret = fat_itr_root(itr, &fsdata);
        if (ret)
                goto exit;

        total_sector = fsdata.total_sect;

        ret = fat_itr_resolve(itr, dirname, TYPE_DIR);
        if (ret) {
                printf("%s: doesn't exist (%d)\n", dirname, ret);
                ret = -ENOENT;
                goto exit;
        }

        if (!find_directory_entry(itr, basename)) {
                printf("%s: doesn't exist\n", basename);
                ret = -ENOENT;
                goto exit;
        }

        if (fat_itr_isdir(itr)) {
                n_entries = fat_dir_entries(itr);
                if (n_entries < 0) {
                        ret = n_entries;
                        goto exit;
                }
                if (n_entries > 2) {
                        printf("Error: directory is not empty: %d\n",
                               n_entries);
                        ret = -EINVAL;
                        goto exit;
                }
        }

        ret = delete_dentry(itr);

exit:
        free(fsdata.fatbuf);
        free(itr);
        free(filename_copy);

        return ret;
}

int fat_mkdir(const char *new_dirname)
{
        dir_entry *retdent;
        fsdata datablock = { .fatbuf = NULL, };
        fsdata *mydata = &datablock;
        fat_itr *itr = NULL;
        char *dirname_copy, *parent, *dirname;
        char l_dirname[VFAT_MAXLEN_BYTES];
        int ret = -1;
        loff_t actwrite;
        unsigned int bytesperclust;
        dir_entry *dotdent = NULL;

        dirname_copy = strdup(new_dirname);
        if (!dirname_copy)
                goto exit;

        split_filename(dirname_copy, &parent, &dirname);
        if (!strlen(dirname)) {
                ret = -EINVAL;
                goto exit;
        }

        if (normalize_longname(l_dirname, dirname)) {
                printf("FAT: illegal filename (%s)\n", dirname);
                ret = -EINVAL;
                goto exit;
        }

        itr = malloc_cache_aligned(sizeof(fat_itr));
        if (!itr) {
                ret = -ENOMEM;
                goto exit;
        }

        ret = fat_itr_root(itr, &datablock);
        if (ret)
                goto exit;

        total_sector = datablock.total_sect;

        ret = fat_itr_resolve(itr, parent, TYPE_DIR);
        if (ret) {
                printf("%s: doesn't exist (%d)\n", parent, ret);
                goto exit;
        }

        retdent = find_directory_entry(itr, l_dirname);

        if (retdent) {
                printf("%s: already exists\n", l_dirname);
                ret = -EEXIST;
                goto exit;
        } else {
                if (itr->is_root) {
                        /* root dir cannot have "." or ".." */
                        if (!strcmp(l_dirname, ".") ||
                            !strcmp(l_dirname, "..")) {
                                ret = -EINVAL;
                                goto exit;
                        }
                }

                if (!itr->dent) {
                        printf("Error: allocating new dir entry\n");
                        ret = -EIO;
                        goto exit;
                }

                memset(itr->dent, 0, sizeof(*itr->dent));

                /* Set short name to set alias checksum field in dir_slot */
                set_name(itr->dent, dirname);
                fill_dir_slot(itr, dirname);

                /* Set attribute as archive for regular file */
                fill_dentry(itr->fsdata, itr->dent, dirname, 0, 0,
                            ATTR_DIR | ATTR_ARCH);

                retdent = itr->dent;
        }

        /* Default entries */
        bytesperclust = mydata->clust_size * mydata->sect_size;
        dotdent = malloc_cache_aligned(bytesperclust);
        if (!dotdent) {
                ret = -ENOMEM;
                goto exit;
        }
        memset(dotdent, 0, bytesperclust);

        memcpy(dotdent[0].name, ".       ", 8);
        memcpy(dotdent[0].ext, "   ", 3);
        dotdent[0].attr = ATTR_DIR | ATTR_ARCH;

        memcpy(dotdent[1].name, "..      ", 8);
        memcpy(dotdent[1].ext, "   ", 3);
        dotdent[1].attr = ATTR_DIR | ATTR_ARCH;
        set_start_cluster(mydata, &dotdent[1], itr->start_clust);

        ret = set_contents(mydata, retdent, 0, (__u8 *)dotdent,
                           bytesperclust, &actwrite);
        if (ret < 0) {
                printf("Error: writing contents\n");
                goto exit;
        }
        /* Write twice for "." */
        set_start_cluster(mydata, &dotdent[0], START(retdent));
        ret = set_contents(mydata, retdent, 0, (__u8 *)dotdent,
                           bytesperclust, &actwrite);
        if (ret < 0) {
                printf("Error: writing contents\n");
                goto exit;
        }

        /* Flush fat buffer */
        ret = flush_dirty_fat_buffer(mydata);
        if (ret) {
                printf("Error: flush fat buffer\n");
                goto exit;
        }

        /* Write directory table to device */
        ret = flush_dir(itr);
        if (ret)
                printf("Error: writing directory entry\n");

exit:
        free(dirname_copy);
        free(mydata->fatbuf);
        free(itr);
        free(dotdent);
        return ret;
}