Tkrzw
Public Member Functions | List of all members
tkrzw::PositionalAtomicFile Class Referencefinal

File implementation by positional access and locking for atomic operations. More...

#include <tkrzw_file_pos.h>

Public Member Functions

 PositionalAtomicFile ()
 Default constructor. More...
 
virtual ~PositionalAtomicFile ()
 Destructor. More...
 
 PositionalAtomicFile (const PositionalAtomicFile &rhs)=delete
 Copy and assignment are disabled. More...
 
PositionalAtomicFileoperator= (const PositionalAtomicFile &rhs)=delete
 
Status Open (const std::string &path, bool writable, int32_t options=OPEN_DEFAULT) override
 Opens a file. More...
 
Status Close () override
 Closes the file. More...
 
Status Read (int64_t off, void *buf, size_t size) override
 Reads data. More...
 
Status Write (int64_t off, const void *buf, size_t size) override
 Writes data. More...
 
Status Append (const void *buf, size_t size, int64_t *off=nullptr) override
 Appends data at the end of the file. More...
 
Status Expand (size_t inc_size, int64_t *old_size=nullptr) override
 Expands the file size without writing data. More...
 
Status Truncate (int64_t size) override
 Truncates the file. More...
 
Status Synchronize (bool hard) override
 Synchronizes the content of the file to the file system. More...
 
Status GetSize (int64_t *size) override
 Gets the size of the file. More...
 
Status SetAllocationStrategy (int64_t init_size, double inc_factor) override
 Sets allocation strategy. More...
 
bool IsMemoryMapping () const override
 Checks whether operations are done by memory mapping. More...
 
bool IsAtomic () const override
 Checks whether updating operations are atomic and thread-safe. More...
 
std::unique_ptr< FileMakeFile () const override
 Makes a new file object of the same concrete class. More...
 
- Public Member Functions inherited from tkrzw::File
virtual ~File ()=default
 Destructor. More...
 
virtual std::string ReadSimple (int64_t off, size_t size)
 Reads data, in a simple way. More...
 
virtual bool WriteSimple (int64_t off, std::string_view data)
 Writes data, in a simple way. More...
 
virtual int64_t AppendSimple (const std::string &data)
 Appends data at the end of the file, in a simple way. More...
 
virtual int64_t ExpandSimple (size_t inc_size)
 Expands the file size without writing data, in a simple way. More...
 
virtual int64_t GetSizeSimple ()
 Gets the size of the file, in a simple way. More...
 

Additional Inherited Members

- Public Types inherited from tkrzw::File
enum  OpenOption : int32_t {
  OPEN_DEFAULT = 0, OPEN_TRUNCATE = 1 << 0, OPEN_NO_CREATE = 1 << 1, OPEN_NO_WAIT = 1 << 2,
  OPEN_NO_LOCK = 1 << 3
}
 Enumeration of options for Open. More...
 
- Static Public Attributes inherited from tkrzw::File
static constexpr int64_t DEFAULT_ALLOC_INIT_SIZE = 1LL << 20
 The default value of initial allocation size. More...
 
static constexpr double DEFAULT_ALLOC_INC_FACTOR = 2.0
 The default value of allocation increment factor. More...
 

Detailed Description

File implementation by positional access and locking for atomic operations.

All operations are thread-safe; Multiple threads can access the same file concurrently. Also, locking assures that every operation is observed in an atomic manner.

Constructor & Destructor Documentation

◆ PositionalAtomicFile() [1/2]

tkrzw::PositionalAtomicFile::PositionalAtomicFile ( )

Default constructor.

◆ ~PositionalAtomicFile()

virtual tkrzw::PositionalAtomicFile::~PositionalAtomicFile ( )
virtual

Destructor.

◆ PositionalAtomicFile() [2/2]

tkrzw::PositionalAtomicFile::PositionalAtomicFile ( const PositionalAtomicFile rhs)
explicitdelete

Copy and assignment are disabled.

Member Function Documentation

◆ Open()

Status tkrzw::PositionalAtomicFile::Open ( const std::string &  path,
bool  writable,
int32_t  options = OPEN_DEFAULT 
)
overridevirtual

Opens a file.

Parameters
pathA path of the file.
writableIf true, the file is writable. If false, it is read-only.
optionsBit-sum options.
Returns
The result status.

By default, exclusive locking against other processes is done for a writer and shared locking against other processes is done for a reader.

Implements tkrzw::File.

◆ Close()

Status tkrzw::PositionalAtomicFile::Close ( )
overridevirtual

Closes the file.

Returns
The result status.

Implements tkrzw::File.

◆ Read()

Status tkrzw::PositionalAtomicFile::Read ( int64_t  off,
void *  buf,
size_t  size 
)
overridevirtual

Reads data.

Parameters
offThe offset of a source region.
bufThe pointer to the destination buffer.
sizeThe size of the data to be read.
Returns
The result status.

Implements tkrzw::File.

◆ Write()

Status tkrzw::PositionalAtomicFile::Write ( int64_t  off,
const void *  buf,
size_t  size 
)
overridevirtual

Writes data.

Parameters
offThe offset of the destination region.
bufThe pointer to the source buffer.
sizeThe size of the data to be written.
Returns
The result status.

Implements tkrzw::File.

◆ Append()

Status tkrzw::PositionalAtomicFile::Append ( const void *  buf,
size_t  size,
int64_t *  off = nullptr 
)
overridevirtual

Appends data at the end of the file.

Parameters
bufThe pointer to the source buffer.
sizeThe size of the data to be written.
offThe pointer to an integer object to contain the offset at which the data has been put. If it is nullptr, it is ignored.
Returns
The result status.

Implements tkrzw::File.

◆ Expand()

Status tkrzw::PositionalAtomicFile::Expand ( size_t  inc_size,
int64_t *  old_size = nullptr 
)
overridevirtual

Expands the file size without writing data.

Parameters
inc_sizeThe size to increment the file size by.
old_sizeThe pointer to an integer object to contain the old size of the file. put. If it is nullptr, it is ignored.
Returns
The result status.

Implements tkrzw::File.

◆ Truncate()

Status tkrzw::PositionalAtomicFile::Truncate ( int64_t  size)
overridevirtual

Truncates the file.

Parameters
sizeThe new size of the file.
Returns
The result status.

Implements tkrzw::File.

◆ Synchronize()

Status tkrzw::PositionalAtomicFile::Synchronize ( bool  hard)
overridevirtual

Synchronizes the content of the file to the file system.

Parameters
hardTrue to do physical synchronization with the hardware or false to do only logical synchronization with the file system.
Returns
The result status.

The pysical file size can be larger than the logical size in order to improve performance by reducing frequency of allocation. Thus, you should call this function before accessing the file with external tools.

Implements tkrzw::File.

◆ GetSize()

Status tkrzw::PositionalAtomicFile::GetSize ( int64_t *  size)
overridevirtual

Gets the size of the file.

Parameters
sizeThe pointer to an integer object to contain the result size.
Returns
The result status.

Implements tkrzw::File.

◆ SetAllocationStrategy()

Status tkrzw::PositionalAtomicFile::SetAllocationStrategy ( int64_t  init_size,
double  inc_factor 
)
overridevirtual

Sets allocation strategy.

Parameters
init_sizeAn initial size of allocation.
inc_factorA factor to increase the size of allocation.
Returns
The result status.

By default, the initial size is 1MB and the increasing factor is 2. This method must be called before the file is opened.

Implements tkrzw::File.

◆ IsMemoryMapping()

bool tkrzw::PositionalAtomicFile::IsMemoryMapping ( ) const
overridevirtual

Checks whether operations are done by memory mapping.

Returns
True if operations are done by memory mapping, or false if not.

Implements tkrzw::File.

◆ IsAtomic()

bool tkrzw::PositionalAtomicFile::IsAtomic ( ) const
overridevirtual

Checks whether updating operations are atomic and thread-safe.

Returns
Always true. Atomicity is assured. All operations are thread-safe.

Implements tkrzw::File.

◆ MakeFile()

std::unique_ptr<File> tkrzw::PositionalAtomicFile::MakeFile ( ) const
overridevirtual

Makes a new file object of the same concrete class.

Returns
The new file object.

Implements tkrzw::File.