FAT file functions
[FAT support]

Collaboration diagram for FAT file functions:

Data Structures
struct	fat_dir_entry_struct
Defines
#define	FAT_ATTRIB_READONLY   (1 << 0)
#define	FAT_ATTRIB_HIDDEN   (1 << 1)
#define	FAT_ATTRIB_SYSTEM   (1 << 2)
#define	FAT_ATTRIB_VOLUME   (1 << 3)
#define	FAT_ATTRIB_DIR   (1 << 4)
#define	FAT_ATTRIB_ARCHIVE   (1 << 5)
#define	FAT_SEEK_SET   0
#define	FAT_SEEK_CUR   1
#define	FAT_SEEK_END   2
Functions
uint8_t	fat_get_dir_entry_of_path (struct fat_fs_struct *fs, const char *path, struct fat_dir_entry_struct *dir_entry)
struct fat_file_struct *	fat_open_file (struct fat_fs_struct *fs, const struct fat_dir_entry_struct *dir_entry)
void	fat_close_file (struct fat_file_struct *fd)
intptr_t	fat_read_file (struct fat_file_struct *fd, uint8_t *buffer, uintptr_t buffer_len)
intptr_t	fat_write_file (struct fat_file_struct *fd, const uint8_t *buffer, uintptr_t buffer_len)
uint8_t	fat_seek_file (struct fat_file_struct *fd, int32_t *offset, uint8_t whence)
uint8_t	fat_resize_file (struct fat_file_struct *fd, uint32_t size)
uint8_t	fat_create_file (struct fat_dir_struct *parent, const char *file, struct fat_dir_entry_struct *dir_entry)
uint8_t	fat_delete_file (struct fat_fs_struct *fs, struct fat_dir_entry_struct *dir_entry)

---

Detailed Description

Functions for managing files.

---

Define Documentation

#define FAT_ATTRIB_ARCHIVE   (1 << 5)

The file has to be archived.

Definition at line 50 of file fat.h.

#define FAT_ATTRIB_DIR   (1 << 4)

The file is a directory.

Definition at line 48 of file fat.h.

Referenced by fat_create_dir(), fat_get_dir_entry_of_path(), fat_open_dir(), fat_open_file(), WaspSD::getAttributes(), WaspSD::isDir(), WaspSD::isFile(), and WaspSD::ls().

#define FAT_ATTRIB_HIDDEN   (1 << 1)

The file is hidden.

Definition at line 42 of file fat.h.

#define FAT_ATTRIB_READONLY   (1 << 0)

The file is read-only.

Definition at line 40 of file fat.h.

Referenced by WaspSD::getAttributes(), and WaspSD::ls().

#define FAT_ATTRIB_SYSTEM   (1 << 2)

The file is a system file.

Definition at line 44 of file fat.h.

#define FAT_ATTRIB_VOLUME   (1 << 3)

The file is empty and has the volume label as its name.

Definition at line 46 of file fat.h.

#define FAT_SEEK_CUR   1

The given offset is relative to the current read/write position.

Definition at line 55 of file fat.h.

Referenced by fat_seek_file().

#define FAT_SEEK_END   2

The given offset is relative to the end of the file.

Definition at line 57 of file fat.h.

Referenced by fat_seek_file().

#define FAT_SEEK_SET   0

The given offset is relative to the beginning of the file.

Definition at line 53 of file fat.h.

Referenced by WaspSD::cat(), WaspSD::catBin(), fat_seek_file(), and WaspSD::writeSD().

---

Function Documentation

void fat_close_file

(

struct fat_file_struct *

fd

)

Closes a file.

Parameters:

[in]

fd

The file handle of the file to close.

See also:

fat_open_file

Definition at line 964 of file fat.c.

References fat_file_struct::dir_entry, fat_write_dir_entry(), and fat_file_struct::fs.

Referenced by WaspSD::cat(), WaspSD::catBin(), WaspSD::catln(), WaspSD::closeFile(), WaspSD::indexOf(), WaspSD::numln(), and WaspSD::writeSD().

{
    if(fd)
    {
#if FAT_DELAY_DIRENTRY_UPDATE
        /* write directory entry */
        fat_write_dir_entry(fd->fs, &fd->dir_entry);
#endif

#if USE_DYNAMIC_MEMORY
        free(fd);
#else
        fd->fs = 0;
#endif
    }
}

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uint8_t fat_create_file	(	struct fat_dir_struct *	parent,
		const char *	file,
		struct fat_dir_entry_struct *	dir_entry
	)

Creates a file.

Creates a file and obtains the directory entry of the new file. If the file to create already exists, the directory entry of the existing file will be returned within the dir_entry parameter.

Note:

The file name is not checked for invalid characters.

The generation of the short 8.3 file name is quite simple. The first eight characters are used for the filename. The extension, if any, is made up of the first three characters following the last dot within the long filename. If the filename (without the extension) is longer than eight characters, the lower byte of the cluster number replaces the last two characters to avoid name clashes. In any other case, it is your responsibility to avoid name clashes.

Parameters:

[in]	parent	The handle of the directory in which to create the file.
[in]	file	The name of the file to create.
[out]	dir_entry	The directory entry to fill for the new file.

Returns:

0 on failure, 1 on success.

See also:

fat_delete_file

Definition at line 2055 of file fat.c.

References fat_dir_entry_struct::entry_offset, fat_find_offset_for_dir_entry(), fat_read_dir(), fat_reset_dir(), fat_write_dir_entry(), fat_dir_struct::fs, and fat_dir_entry_struct::long_name.

Referenced by WaspSD::create().

{
    if(!parent || !file || !file[0] || !dir_entry)
        return 0;

    /* check if the file already exists */
    while(1)
    {
        if(!fat_read_dir(parent, dir_entry))
            break;

        if(strcmp(file, dir_entry->long_name) == 0)
        {
            fat_reset_dir(parent);
            return 0;
        }
    }

    struct fat_fs_struct* fs = parent->fs;

    /* prepare directory entry with values already known */
    memset(dir_entry, 0, sizeof(*dir_entry));
    strncpy(dir_entry->long_name, file, sizeof(dir_entry->long_name) - 1);

    /* find place where to store directory entry */
    if(!(dir_entry->entry_offset = fat_find_offset_for_dir_entry(fs, parent, dir_entry)))
        return 0;
    
    /* write directory entry to disk */
    if(!fat_write_dir_entry(fs, dir_entry))
        return 0;
    
    return 1;
}

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uint8_t fat_delete_file	(	struct fat_fs_struct *	fs,
		struct fat_dir_entry_struct *	dir_entry
	)

Deletes a file or directory.

If a directory is deleted without first deleting its subdirectories and files, disk space occupied by these files will get wasted as there is no chance to release it and mark it as free.

Parameters:

[in]	fs	The filesystem on which to operate.
[in]	dir_entry	The directory entry of the file to delete.

Returns:

0 on failure, 1 on success.

See also:

fat_create_file

Definition at line 2106 of file fat.c.

References fat_dir_entry_struct::cluster, partition_struct::device_read, partition_struct::device_write, fat_dir_entry_struct::entry_offset, FAT_DIRENTRY_DELETED, fat_free_clusters(), and fat_fs_struct::partition.

Referenced by WaspSD::delDir(), and WaspSD::delFile().

{
    if(!fs || !dir_entry)
        return 0;

    /* get offset of the file's directory entry */
    offset_t dir_entry_offset = dir_entry->entry_offset;
    if(!dir_entry_offset)
        return 0;

#if FAT_LFN_SUPPORT
    uint8_t buffer[12];
    while(1)
    {
        /* read directory entry */
        if(!fs->partition->device_read(dir_entry_offset, buffer, sizeof(buffer)))
            return 0;
        
        /* mark the directory entry as deleted */
        buffer[0] = FAT_DIRENTRY_DELETED;
        
        /* write back entry */
        if(!fs->partition->device_write(dir_entry_offset, buffer, sizeof(buffer)))
            return 0;

        /* check if we deleted the whole entry */
        if(buffer[11] != 0x0f)
            break;

        dir_entry_offset += 32;
    }
#else
    /* mark the directory entry as deleted */
    uint8_t first_char = FAT_DIRENTRY_DELETED;
    if(!fs->partition->device_write(dir_entry_offset, &first_char, 1))
        return 0;
#endif

    /* We deleted the directory entry. The next thing to do is
     * marking all occupied clusters as free.
     */
    return (dir_entry->cluster == 0 || fat_free_clusters(fs, dir_entry->cluster));
}

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uint8_t fat_get_dir_entry_of_path	(	struct fat_fs_struct *	fs,
		const char *	path,
		struct fat_dir_entry_struct *	dir_entry
	)

Retrieves the directory entry of a path.

The given path may both describe a file or a directory.

Parameters:

[in]	fs	The FAT filesystem on which to search.
[in]	path	The path of which to read the directory entry.
[out]	dir_entry	The directory entry to fill.

Returns:

0 on failure, 1 on success.

See also:

fat_read_dir

Definition at line 850 of file fat.c.

References fat_dir_entry_struct::attributes, FAT_ATTRIB_DIR, fat_close_dir(), fat_open_dir(), fat_read_dir(), and fat_dir_entry_struct::long_name.

Referenced by WaspSD::init().

{
    if(!fs || !path || path[0] == '\0' || !dir_entry)
        return 0;

    if(path[0] == '/')
        ++path;

    /* begin with the root directory */
    memset(dir_entry, 0, sizeof(*dir_entry));
    dir_entry->attributes = FAT_ATTRIB_DIR;

    while(1)
    {
        if(path[0] == '\0')
            return 1;

        struct fat_dir_struct* dd = fat_open_dir(fs, dir_entry);
        if(!dd)
            break;

        /* extract the next hierarchy we will search for */
        const char* sub_path = strchr(path, '/');
        uint8_t length_to_sep;
        if(sub_path)
        {
            length_to_sep = sub_path - path;
            ++sub_path;
        }
        else
        {
            length_to_sep = strlen(path);
            sub_path = path + length_to_sep;
        }
        
        /* read directory entries */
        while(fat_read_dir(dd, dir_entry))
        {
            /* check if we have found the next hierarchy */
            if((strlen(dir_entry->long_name) != length_to_sep ||
                strncmp(path, dir_entry->long_name, length_to_sep) != 0))
                continue;

            fat_close_dir(dd);
            dd = 0;

            if(path[length_to_sep] == '\0')
                /* we iterated through the whole path and have found the file */
                return 1;

            if(dir_entry->attributes & FAT_ATTRIB_DIR)
            {
                /* we found a parent directory of the file we are searching for */
                path = sub_path;
                break;
            }

            /* a parent of the file exists, but not the file itself */
            return 0;
        }

        fat_close_dir(dd);
    }
    
    return 0;
}

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struct fat_file_struct* fat_open_file	(	struct fat_fs_struct *	fs,
		const struct fat_dir_entry_struct *	dir_entry
	)			[read]

Opens a file on a FAT filesystem.

Parameters:

[in]	fs	The filesystem on which the file to open lies.
[in]	dir_entry	The directory entry of the file to open.

Returns:

The file handle, or 0 on failure.

See also:

fat_close_file

Definition at line 926 of file fat.c.

References fat_dir_entry_struct::attributes, fat_dir_entry_struct::cluster, fat_file_struct::dir_entry, FAT_ATTRIB_DIR, FAT_FILE_COUNT, fat_file_handles, fat_file_struct::fs, fat_file_struct::pos, and fat_file_struct::pos_cluster.

Referenced by WaspSD::openFile().

{
    if(!fs || !dir_entry || (dir_entry->attributes & FAT_ATTRIB_DIR))
        return 0;

#if USE_DYNAMIC_MEMORY
    struct fat_file_struct* fd = malloc(sizeof(*fd));
    if(!fd)
        return 0;
#else
    struct fat_file_struct* fd = fat_file_handles;
    uint8_t i;
    for(i = 0; i < FAT_FILE_COUNT; ++i)
    {
        if(!fd->fs)
            break;

        ++fd;
    }
    if(i >= FAT_FILE_COUNT)
        return 0;
#endif
    
    memcpy(&fd->dir_entry, dir_entry, sizeof(*dir_entry));
    fd->fs = fs;
    fd->pos = 0;
    fd->pos_cluster = dir_entry->cluster;

    return fd;
}

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intptr_t fat_read_file	(	struct fat_file_struct *	fd,
		uint8_t *	buffer,
		uintptr_t	buffer_len
	)

Reads data from a file.

The data requested is read from the current file location.

Parameters:

[in]	fd	The file handle of the file from which to read.
[out]	buffer	The buffer into which to write.
[in]	buffer_len	The amount of data to read.

Returns:

The number of bytes read, 0 on end of file, or -1 on failure.

See also:

fat_write_file

Definition at line 993 of file fat.c.

References fat_dir_entry_struct::cluster, fat_header_struct::cluster_size, partition_struct::device_read, fat_file_struct::dir_entry, fat_cluster_offset(), fat_get_next_cluster(), fat_dir_entry_struct::file_size, fat_file_struct::fs, fat_fs_struct::header, fat_fs_struct::partition, fat_file_struct::pos, and fat_file_struct::pos_cluster.

Referenced by WaspSD::cat(), WaspSD::catBin(), WaspSD::catln(), WaspSD::indexOf(), and WaspSD::numln().

{
    /* check arguments */
    if(!fd || !buffer || buffer_len < 1)
        return -1;

    /* determine number of bytes to read */
    if(fd->pos + buffer_len > fd->dir_entry.file_size)
        buffer_len = fd->dir_entry.file_size - fd->pos;
    if(buffer_len == 0)
        return 0;
    
    uint16_t cluster_size = fd->fs->header.cluster_size;
    cluster_t cluster_num = fd->pos_cluster;
    uintptr_t buffer_left = buffer_len;
    uint16_t first_cluster_offset = (uint16_t) (fd->pos & (cluster_size - 1));

    /* find cluster in which to start reading */
    if(!cluster_num)
    {
        cluster_num = fd->dir_entry.cluster;
        
        if(!cluster_num)
        {
            if(!fd->pos)
                return 0;
            else
                return -1;
        }

        if(fd->pos)
        {
            uint32_t pos = fd->pos;
            while(pos >= cluster_size)
            {
                pos -= cluster_size;
                cluster_num = fat_get_next_cluster(fd->fs, cluster_num);
                if(!cluster_num)
                    return -1;
            }
        }
    }
    
    /* read data */
    do
    {
        /* calculate data size to copy from cluster */
        offset_t cluster_offset = fat_cluster_offset(fd->fs, cluster_num) + first_cluster_offset;
        uint16_t copy_length = cluster_size - first_cluster_offset;
        if(copy_length > buffer_left)
            copy_length = buffer_left;

        /* read data */
        if(!fd->fs->partition->device_read(cluster_offset, buffer, copy_length))
            return buffer_len - buffer_left;

        /* calculate new file position */
        buffer += copy_length;
        buffer_left -= copy_length;
        fd->pos += copy_length;

        if(first_cluster_offset + copy_length >= cluster_size)
        {
            /* we are on a cluster boundary, so get the next cluster */
            if((cluster_num = fat_get_next_cluster(fd->fs, cluster_num)))
            {
                first_cluster_offset = 0;
            }
            else
            {
                fd->pos_cluster = 0;
                return buffer_len - buffer_left;
            }
        }

        fd->pos_cluster = cluster_num;

    } while(buffer_left > 0); /* check if we are done */

    return buffer_len;
}

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uint8_t fat_resize_file	(	struct fat_file_struct *	fd,
		uint32_t	size
	)

Resizes a file to have a specific size.

Enlarges or shrinks the file pointed to by the file descriptor to have exactly the specified size.

If the file is truncated, all bytes having an equal or larger offset than the given size are lost. If the file is expanded, the additional bytes are allocated.

Note:

Please be aware that this function just allocates or deallocates disk space, it does not explicitely clear it. To avoid data leakage, this must be done manually.

Parameters:

[in]	fd	The file decriptor of the file which to resize.
[in]	size	The new size of the file.

Returns:

0 on failure, 1 on success.

Definition at line 1288 of file fat.c.

References fat_dir_entry_struct::cluster, fat_header_struct::cluster_size, fat_file_struct::dir_entry, fat_append_clusters(), fat_free_clusters(), fat_get_next_cluster(), fat_terminate_clusters(), fat_write_dir_entry(), fat_dir_entry_struct::file_size, fat_file_struct::fs, fat_fs_struct::header, fat_file_struct::pos, and fat_file_struct::pos_cluster.

Referenced by fat_seek_file().

{
    if(!fd)
        return 0;

    cluster_t cluster_num = fd->dir_entry.cluster;
    uint16_t cluster_size = fd->fs->header.cluster_size;
    uint32_t size_new = size;

    do
    {
        if(cluster_num == 0 && size_new == 0)
            /* the file stays empty */
            break;

        /* seek to the next cluster as long as we need the space */
        while(size_new > cluster_size)
        {
            /* get next cluster of file */
            cluster_t cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
            if(cluster_num_next)
            {
                cluster_num = cluster_num_next;
                size_new -= cluster_size;
            }
            else
            {
                break;
            }
        }

        if(size_new > cluster_size || cluster_num == 0)
        {
            /* Allocate new cluster chain and append
             * it to the existing one, if available.
             */
            cluster_t cluster_count = (size_new + cluster_size - 1) / cluster_size;
            cluster_t cluster_new_chain = fat_append_clusters(fd->fs, cluster_num, cluster_count);
            if(!cluster_new_chain)
                return 0;

            if(!cluster_num)
            {
                cluster_num = cluster_new_chain;
                fd->dir_entry.cluster = cluster_num;
            }
        }

        /* write new directory entry */
        fd->dir_entry.file_size = size;
        if(size == 0)
            fd->dir_entry.cluster = 0;
        if(!fat_write_dir_entry(fd->fs, &fd->dir_entry))
            return 0;

        if(size == 0)
        {
            /* free all clusters of file */
            fat_free_clusters(fd->fs, cluster_num);
        }
        else if(size_new <= cluster_size)
        {
            /* free all clusters no longer needed */
            fat_terminate_clusters(fd->fs, cluster_num);
        }

    } while(0);

    /* correct file position */
    if(size < fd->pos)
    {
        fd->pos = size;
        fd->pos_cluster = 0;
    }

    return 1;
}

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uint8_t fat_seek_file	(	struct fat_file_struct *	fd,
		int32_t *	offset,
		uint8_t	whence
	)

Repositions the read/write file offset.

Changes the file offset where the next call to fat_read_file() or fat_write_file() starts reading/writing.

If the new offset is beyond the end of the file, fat_resize_file() is implicitly called, i.e. the file is expanded.

The new offset can be given in different ways determined by the whence parameter:

• FAT_SEEK_SET: *offset is relative to the beginning of the file.
• FAT_SEEK_CUR: *offset is relative to the current file position.
• FAT_SEEK_END: *offset is relative to the end of the file.

The resulting absolute offset is written to the location the offset parameter points to.

Parameters:

[in]	fd	The file decriptor of the file on which to seek.
[in,out]	offset	A pointer to the new offset, as affected by the whence parameter. The function writes the new absolute offset to this location before it returns.
[in]	whence	Affects the way offset is interpreted, see above.

Returns:

0 on failure, 1 on success.

Definition at line 1233 of file fat.c.

References fat_file_struct::dir_entry, fat_resize_file(), FAT_SEEK_CUR, FAT_SEEK_END, FAT_SEEK_SET, FAT_WRITE_SUPPORT, fat_dir_entry_struct::file_size, fat_file_struct::pos, and fat_file_struct::pos_cluster.

Referenced by WaspSD::cat(), WaspSD::catBin(), and WaspSD::writeSD().

{
    if(!fd || !offset)
        return 0;

    uint32_t new_pos = fd->pos;
    switch(whence)
    {
        case FAT_SEEK_SET:
            new_pos = *offset;
            break;
        case FAT_SEEK_CUR:
            new_pos += *offset;
            break;
        case FAT_SEEK_END:
            new_pos = fd->dir_entry.file_size + *offset;
            break;
        default:
            return 0;
    }

    if(new_pos > fd->dir_entry.file_size
#if FAT_WRITE_SUPPORT
       && !fat_resize_file(fd, new_pos)
#endif
       )
        return 0;

    fd->pos = new_pos;
    fd->pos_cluster = 0;

    *offset = (int32_t) new_pos;
    return 1;
}

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intptr_t fat_write_file	(	struct fat_file_struct *	fd,
		const uint8_t *	buffer,
		uintptr_t	buffer_len
	)

Writes data to a file.

The data is written to the current file location.

Parameters:

[in]	fd	The file handle of the file to which to write.
[in]	buffer	The buffer from which to read the data to be written.
[in]	buffer_len	The amount of data to write.

Returns:

The number of bytes written, 0 on disk full, or -1 on failure.

See also:

fat_read_file

Definition at line 1088 of file fat.c.

References fat_dir_entry_struct::cluster, fat_header_struct::cluster_size, partition_struct::device_write, fat_file_struct::dir_entry, fat_append_clusters(), fat_cluster_offset(), fat_get_next_cluster(), fat_write_dir_entry(), fat_dir_entry_struct::file_size, fat_file_struct::fs, fat_fs_struct::header, fat_fs_struct::partition, fat_file_struct::pos, and fat_file_struct::pos_cluster.

Referenced by WaspSD::writeSD().

{
    /* check arguments */
    if(!fd || !buffer || buffer_len < 1)
        return -1;
    if(fd->pos > fd->dir_entry.file_size)
        return -1;

    uint16_t cluster_size = fd->fs->header.cluster_size;
    cluster_t cluster_num = fd->pos_cluster;
    uintptr_t buffer_left = buffer_len;
    uint16_t first_cluster_offset = (uint16_t) (fd->pos & (cluster_size - 1));

    /* find cluster in which to start writing */
    if(!cluster_num)
    {
        cluster_num = fd->dir_entry.cluster;
        
        if(!cluster_num)
        {
            if(!fd->pos)
            {
                /* empty file */
                fd->dir_entry.cluster = cluster_num = fat_append_clusters(fd->fs, 0, 1);
                if(!cluster_num)
                    return -1;
            }
            else
            {
                return -1;
            }
        }

        if(fd->pos)
        {
            uint32_t pos = fd->pos;
            cluster_t cluster_num_next;
            while(pos >= cluster_size)
            {
                pos -= cluster_size;
                cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
                if(!cluster_num_next && pos == 0)
                    /* the file exactly ends on a cluster boundary, and we append to it */
                    cluster_num_next = fat_append_clusters(fd->fs, cluster_num, 1);
                if(!cluster_num_next)
                    return -1;

                cluster_num = cluster_num_next;
            }
        }
    }
    
    /* write data */
    do
    {
        /* calculate data size to write to cluster */
        offset_t cluster_offset = fat_cluster_offset(fd->fs, cluster_num) + first_cluster_offset;
        uint16_t write_length = cluster_size - first_cluster_offset;
        if(write_length > buffer_left)
            write_length = buffer_left;

        /* write data which fits into the current cluster */
        if(!fd->fs->partition->device_write(cluster_offset, buffer, write_length))
            break;

        /* calculate new file position */
        buffer += write_length;
        buffer_left -= write_length;
        fd->pos += write_length;

        if(first_cluster_offset + write_length >= cluster_size)
        {
            /* we are on a cluster boundary, so get the next cluster */
            cluster_t cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
            if(!cluster_num_next && buffer_left > 0)
                /* we reached the last cluster, append a new one */
                cluster_num_next = fat_append_clusters(fd->fs, cluster_num, 1);
            if(!cluster_num_next)
            {
                fd->pos_cluster = 0;
                break;
            }

            cluster_num = cluster_num_next;
            first_cluster_offset = 0;
        }

        fd->pos_cluster = cluster_num;

    } while(buffer_left > 0); /* check if we are done */

    /* update directory entry */
    if(fd->pos > fd->dir_entry.file_size)
    {
#if !FAT_DELAY_DIRENTRY_UPDATE
        uint32_t size_old = fd->dir_entry.file_size;
#endif

        /* update file size */
        fd->dir_entry.file_size = fd->pos;

#if !FAT_DELAY_DIRENTRY_UPDATE
        /* write directory entry */
        if(!fat_write_dir_entry(fd->fs, &fd->dir_entry))
        {
            /* We do not return an error here since we actually wrote
             * some data to disk. So we calculate the amount of data
             * we wrote to disk and which lies within the old file size.
             */
            buffer_left = fd->pos - size_old;
            fd->pos = size_old;
        }
#endif
    }

    return buffer_len - buffer_left;
}

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