MaxOS::filesystem::format::Fat32File Class Reference

Handles the file operations on the FAT32 filesystem. More...

#include <fat32.h>

Inheritance diagram for MaxOS::filesystem::format::Fat32File:

Public Member Functions
	Fat32File (Fat32Volume *volume, Fat32Directory *parent, dir_entry_t *info, const string &name)
	Construct a new Fat32 File object.
void	write (common::buffer_t *data, size_t amount) final
	write data to the file (at the current seek position, updated to be += amount)
void	read (common::buffer_t *data, size_t amount) final
	read data from the file (at the current seek position, updated to be += amount)
void	flush () final
	Flush the file to the disk.
uint32_t	first_cluster () const
	Get the first cluster of the directory.
Public Member Functions inherited from MaxOS::filesystem::File
void	seek (SeekType seek_type, size_t offset)
	Seek to a position in the file.
uint32_t	position () const
	Get where the file is currently at (amount read/write/seeked)
size_t	size () const
	Get the size of the file.
string	name ()
	Get the name of the file.

Additional Inherited Members
Protected Attributes inherited from MaxOS::filesystem::File
uint32_t	m_offset = 0
	The current offset in the file.
string	m_name
	The name of the file.
size_t	m_size = 0
	The size of the file.

Detailed Description

Handles the file operations on the FAT32 filesystem.

Definition at line 207 of file fat32.h.

Constructor & Destructor Documentation

Fat32File()

Fat32File::Fat32File	(	Fat32Volume *	volume,
		Fat32Directory *	parent,
		dir_entry_t *	info,
		const string &	name
	)

Construct a new Fat32 File object.

Parameters

volume	The helper volume object
parent	The directory that contains this file
info	The directory entry information that describes this file
name	The name of the file

Definition at line 239 of file fat32.cpp.

        : m_volume(volume),
        m_parent_directory(parent),
        m_entry(info),
        m_first_cluster((info->first_cluster_high << 16) | info->first_cluster_low) {
 
    m_name = name;
    m_size = info->size;
    m_offset = 0;
}

References MaxOS::filesystem::File::m_name, MaxOS::filesystem::File::m_offset, MaxOS::filesystem::File::m_size, and MaxOS::filesystem::File::name().

Member Function Documentation

first_cluster()

uint32_t MaxOS::filesystem::format::Fat32File::first_cluster ( ) const

inline

Get the first cluster of the directory.

Returns

The first cluster of the directory

Definition at line 228 of file fat32.h.

{ return m_first_cluster; }

flush()

void Fat32File::flush ( )

finalvirtual

Flush the file to the disk.

Reimplemented from MaxOS::filesystem::File.

Definition at line 413 of file fat32.cpp.

                      {
    File::flush();
}

References MaxOS::filesystem::File::flush().

read()

void Fat32File::read ( common::buffer_t *  data, size_t  amount  )

finalvirtual

read data from the file (at the current seek position, updated to be += amount)

Parameters

data	The byte buffer to read into
amount	The amount of data to read

Reimplemented from MaxOS::filesystem::File.

Definition at line 361 of file fat32.cpp.

                                                  {
    size_t buffer_space = m_volume->bpb.bytes_per_sector * m_volume->bpb.sectors_per_cluster;
    buffer_t buffer(buffer_space);
    buffer.clear();
 
    uint64_t current_offset = 0;
    uint64_t bytes_read = 0;
 
    // Read the file
    for(uint32_t cluster = m_first_cluster;
        cluster != (uint32_t) ClusterState::END_OF_CHAIN; cluster = m_volume->next_cluster(cluster)) {
 
        // Skip clusters before the offset
        if((current_offset + buffer_space) < m_offset) {
            current_offset += buffer_space;
            continue;
        }
 
        // Read each sector in the cluster
        lba_t lba = m_volume->data_lba + (cluster - 2) * m_volume->bpb.sectors_per_cluster;
        for(size_t sector = 0; sector < m_volume->bpb.sectors_per_cluster; sector++)
            m_volume->disk->read(lba + sector, &buffer, m_volume->bpb.bytes_per_sector);
        buffer.set_offset(0);
 
        // If the offset is in the middle of the cluster
        size_t buffer_offset = 0;
        if(m_offset > current_offset)
            buffer_offset = m_offset - current_offset;
 
        // Calculate how many bytes are being copied (read from cluster at offset? or read part of cluster?)
        size_t cluster_remaining_bytes = buffer_space - buffer_offset;
        size_t data_remaining_bytes = amount - bytes_read;
        size_t bytes_to_copy = (cluster_remaining_bytes < data_remaining_bytes) ? cluster_remaining_bytes
                                                                                : data_remaining_bytes;
        bytes_to_copy = (bytes_to_copy > buffer_space) ? buffer_space : bytes_to_copy;
 
        // Read the data
        buffer.copy_from(data, bytes_to_copy, buffer_offset, bytes_read);
        bytes_read += bytes_to_copy;
        current_offset += buffer_space;
 
        // Dont read more than needed
        if(bytes_read >= amount)
            break;
    }
 
    m_offset += bytes_read;
}

References MaxOS::filesystem::format::Fat32Volume::bpb, MaxOS::common::Buffer::clear(), MaxOS::common::Buffer::copy_from(), MaxOS::filesystem::format::Fat32Volume::data_lba, MaxOS::filesystem::format::Fat32Volume::disk, MaxOS::filesystem::File::m_offset, MaxOS::filesystem::format::Fat32Volume::next_cluster(), MaxOS::drivers::disk::Disk::read(), and MaxOS::common::Buffer::set_offset().

write()

void Fat32File::write ( common::buffer_t *  data, size_t  amount  )

finalvirtual

write data to the file (at the current seek position, updated to be += amount)

Parameters

data	The byte buffer to write
amount	The amount of data to write

Todo:

When in userspace: save timestamps

Reimplemented from MaxOS::filesystem::File.

Definition at line 260 of file fat32.cpp.

                                                   {
 
    size_t buffer_space = m_volume->bpb.bytes_per_sector * m_volume->bpb.sectors_per_cluster;
    buffer_t buffer(buffer_space);
    buffer.clear();
 
    uint64_t current_offset = 0;
    uint64_t bytes_written = 0;
    uint32_t last = m_first_cluster;
 
    // Read the file
    for(uint32_t cluster = last;
        cluster != (uint32_t) ClusterState::END_OF_CHAIN; cluster = m_volume->next_cluster(cluster)) {
        last = cluster;
 
        // No cluster to read from (blank file)
        if(cluster == 0)
            break;
 
        // Skip clusters before the offset
        if((current_offset + buffer_space) < m_offset) {
            current_offset += buffer_space;
            continue;
        }
 
        // Read each sector in the cluster (prevent overwriting the data)
        lba_t lba = m_volume->data_lba + (cluster - 2) * m_volume->bpb.sectors_per_cluster;
        for(size_t sector = 0; sector < m_volume->bpb.sectors_per_cluster; sector++)
            m_volume->disk->read(lba + sector, &buffer, m_volume->bpb.bytes_per_sector);
        buffer.set_offset(0);
 
        // If the offset is in the middle of the cluster
        size_t buffer_offset = 0;
        if(m_offset > current_offset)
            buffer_offset = m_offset - current_offset;
 
        // Calculate how many bytes are being copied (read from cluster at offset?
        // or read part of cluster?)
        size_t cluster_remaining_bytes = buffer_space - buffer_offset;
        size_t data_remaining_bytes = amount - bytes_written;
        size_t bytes_to_copy = (cluster_remaining_bytes < data_remaining_bytes) ? cluster_remaining_bytes
                                                                                : data_remaining_bytes;
        bytes_to_copy = (bytes_to_copy > buffer_space) ? buffer_space : bytes_to_copy;
 
        // Update the data
        buffer.copy_from(data, bytes_to_copy, buffer_offset, bytes_written);
        bytes_written += bytes_to_copy;
        current_offset += bytes_to_copy;
        buffer.set_offset(0);
 
        // Write the data back to the disk
        for(size_t sector = 0; sector < m_volume->bpb.sectors_per_cluster; sector++)
            m_volume->disk->write(lba + sector, &buffer, m_volume->bpb.bytes_per_sector);
    }
 
    // Extend the file
    while(bytes_written < amount) {
        // Allocate a new cluster
        uint32_t new_cluster = m_volume->allocate_cluster(last);
        if(new_cluster == 0)
            break;
 
        if(last == 0)
            m_first_cluster = new_cluster;
 
        // Update the data
        size_t bytes_to_copy = (amount - bytes_written) > buffer_space ? buffer_space : (amount - bytes_written);
        buffer.copy_from(data, bytes_to_copy, 0, bytes_written);
        bytes_written += bytes_to_copy;
        current_offset += bytes_to_copy;
        buffer.set_offset(0);
 
        // Write the data back to the disk
        lba_t lba = m_volume->data_lba + (new_cluster - 2) * m_volume->bpb.sectors_per_cluster;
        for(size_t sector = 0; sector < m_volume->bpb.sectors_per_cluster; sector++)
            m_volume->disk->write(lba + sector, &buffer, m_volume->bpb.bytes_per_sector);
 
        // Go to the next cluster
        last = new_cluster;
    }
 
    // Update file size
    m_offset += bytes_written;
    if(m_offset > m_size)
        m_size = m_offset;
 
    // Update entry info
    m_entry->size = m_size;
    m_entry->first_cluster_high = (m_first_cluster >> 16) & 0xFFFF;
    m_entry->first_cluster_low = m_first_cluster & 0xFFFF;
 
    m_parent_directory->save_entry_to_disk(m_entry);
 
}

References MaxOS::filesystem::format::Fat32Volume::allocate_cluster(), MaxOS::filesystem::format::Fat32Volume::bpb, MaxOS::common::Buffer::clear(), MaxOS::common::Buffer::copy_from(), MaxOS::filesystem::format::Fat32Volume::data_lba, MaxOS::filesystem::format::Fat32Volume::disk, MaxOS::filesystem::File::m_offset, MaxOS::filesystem::File::m_size, MaxOS::filesystem::format::Fat32Volume::next_cluster(), MaxOS::drivers::disk::Disk::read(), MaxOS::filesystem::format::Fat32Directory::save_entry_to_disk(), MaxOS::common::Buffer::set_offset(), and MaxOS::drivers::disk::Disk::write().

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The documentation for this class was generated from the following files:

• /home/runner/work/MaxOS/MaxOS/kernel/include/filesystem/format/fat32.h
• /home/runner/work/MaxOS/MaxOS/kernel/src/filesystem/format/fat32.cpp