This class supports the writing of recordings to disk. More...

#include <libmythbase/threadedfilewriter.h>

Collaboration diagram for ThreadedFileWriter:

Classes
class	TFWBuffer

Public Member Functions
	ThreadedFileWriter (QString fname, int flags, mode_t mode)
	Creates a threaded file writer. More...

	~ThreadedFileWriter ()
	Commits all writes and closes the file. More...

bool	Open (void)
	Opens the file we will be writing to. More...

bool	ReOpen (const QString &newFilename="")
	Reopens the file we are writing to or opens a new file. More...

long long	Seek (long long pos, int whence)
	Seek to a position within stream; May be unsafe. More...

int	Write (const void *data, uint count)
	Writes data to the end of the write buffer. More...

void	SetWriteBufferMinWriteSize (uint newMinSize=kMinWriteSize)
	Sets the minumum number of bytes to write to disk in a single write. This is ignored during a Flush(void) More...

void	Sync (void) const
	Flush data written to the file descriptor to disk. More...

void	Flush (void)
	Allow DiskLoop() to flush buffer completely ignoring low watermark. More...

bool	SetBlocking (bool block=true)
	Set write blocking mode While in blocking mode, ThreadedFileWriter::Write will wait for buffers to be freed as required, so there's never any data loss. More...

bool	WritesFailing (void) const

Protected Member Functions
void	DiskLoop (void)
	The thread run method that actually calls writes to disk. More...

void	SyncLoop (void)
	The thread run method that calls Sync(void). More...

void	TrimEmptyBuffers (void)

Private Attributes
QString	m_filename

int	m_flags

mode_t	m_mode

int	m_fd {-1}

bool	m_flush {false}

bool	m_inDtor {false}

bool	m_ignoreWrites {false}

uint	m_tfwMinWriteSize {kMinWriteSize}

uint	m_totalBufferUse {0}

QMutex	m_bufLock

QList< TFWBuffer * >	m_writeBuffers

QList< TFWBuffer * >	m_emptyBuffers

TFWWriteThread *	m_writeThread {nullptr}

TFWSyncThread *	m_syncThread {nullptr}

QWaitCondition	m_bufferEmpty

QWaitCondition	m_bufferHasData

QWaitCondition	m_bufferSyncWait

QWaitCondition	m_bufferWasFreed

bool	m_warned {false}

bool	m_blocking {false}

bool	m_registered {false}

Static Private Attributes
static const uint	kMaxBufferSize = 8 * 1024 * 1024

static const uint	kMinWriteSize = 64 * 1024
	Minimum to write to disk in a single write, when not flushing buffer. More...

static const uint	kMaxBlockSize = 1 * 1024 * 1024
	Maximum block size to write at a time. More...

Friends
class	TFWWriteThread

class	TFWSyncThread

Detailed Description

This class supports the writing of recordings to disk.

This class allows us manage the buffering when writing to disk. We write to the kernel image of the disk using one thread, and sync the kernel's image of the disk to hardware using another thread. The goal here so to block as little as possible when the classes using this class want to add data to the stream.

Definition at line 42 of file threadedfilewriter.h.

Constructor & Destructor Documentation

◆ ThreadedFileWriter()

ThreadedFileWriter::ThreadedFileWriter	(	QString	fname,
		int	flags,
		mode_t	mode
	)

inline

Creates a threaded file writer.

Definition at line 50 of file threadedfilewriter.h.

◆ ~ThreadedFileWriter()

ThreadedFileWriter::~ThreadedFileWriter ( )

Commits all writes and closes the file.

Definition at line 137 of file threadedfilewriter.cpp.

Member Function Documentation

◆ Open()

bool ThreadedFileWriter::Open ( void )

Opens the file we will be writing to.

Returns: true if we successfully open the file.

Definition at line 92 of file threadedfilewriter.cpp.

Referenced by StreamHandler::AddNamedOutputFile(), MythFileBuffer::MythFileBuffer(), RemoteFile::OpenInternal(), and ReOpen().

◆ ReOpen()

bool ThreadedFileWriter::ReOpen ( const QString & newFilename = "" )

Reopens the file we are writing to or opens a new file.

Returns: true if we successfully open the file.

Parameters

newFilename optional name of new file to open

Definition at line 63 of file threadedfilewriter.cpp.

Referenced by MythFileBuffer::ReOpen().

◆ Seek()

long long ThreadedFileWriter::Seek	(	long long	pos,
		int	whence
	)

Seek to a position within stream; May be unsafe.

This method is unsafe if Start() has been called and the call us not preceeded by StopReads(). You probably want to follow Seek() with a StartReads() in this case.

This method assumes that we don't seek very often. It does not use a high performance approach... we just block until the write thread empties the buffer.

Definition at line 297 of file threadedfilewriter.cpp.

Referenced by RemoteFile::SeekInternal(), and MythMediaBuffer::WriterSeek().

◆ Write()

int ThreadedFileWriter::Write	(	const void *	data,
		uint	count
	)

Writes data to the end of the write buffer.

Parameters

data	pointer to data to write to disk
count	size of data in bytes

Definition at line 190 of file threadedfilewriter.cpp.

Referenced by RemoteFile::Write(), MythMediaBuffer::Write(), and StreamHandler::WriteMPTS().

◆ SetWriteBufferMinWriteSize()

void ThreadedFileWriter::SetWriteBufferMinWriteSize ( uint newMinSize = kMinWriteSize )

Sets the minumum number of bytes to write to disk in a single write. This is ignored during a Flush(void)

Definition at line 374 of file threadedfilewriter.cpp.

◆ Sync()

void ThreadedFileWriter::Sync ( void ) const

Flush data written to the file descriptor to disk.

This prevents freezing up Linux disk access on a running CFQ, AS, or Deadline as the disk write schedulers. It does this via two mechanism. One is a data sync using the best mechanism available (fdatasync then fsync). The second is by telling the kernel we do not intend to use the data just written anytime soon so other processes time-slices will not be used to deal with our excess dirty pages.

Note: We used to also use sync_file_range on Linux, however this is incompatible with newer filesystems such as BRTFS and does not actually sync any blocks that have not been allocated yet so it was never really appropriate for ThreadedFileWriter.; We use standard posix calls for this, so any operating system supporting the calls will benefit, but this has been designed with Linux in mind. Other OS's may benefit from revisiting this function.

Definition at line 355 of file threadedfilewriter.cpp.

Referenced by MythMediaBuffer::Sync(), and SyncLoop().

◆ Flush()

void ThreadedFileWriter::Flush ( void )

Allow DiskLoop() to flush buffer completely ignoring low watermark.

Definition at line 318 of file threadedfilewriter.cpp.

Referenced by RemoteFile::GetFileSize(), ReOpen(), MythMediaBuffer::WriterFlush(), MythMediaBuffer::~MythMediaBuffer(), and ~ThreadedFileWriter().

◆ SetBlocking()

bool ThreadedFileWriter::SetBlocking ( bool block = true )

Set write blocking mode While in blocking mode, ThreadedFileWriter::Write will wait for buffers to be freed as required, so there's never any data loss.

Returns: old mode value

Parameters

block False if not blocking, true if blocking

Definition at line 613 of file threadedfilewriter.cpp.

Referenced by RemoteFile::SetBlocking(), and MythMediaBuffer::WriterSetBlocking().

◆ WritesFailing()

bool ThreadedFileWriter::WritesFailing ( void ) const

inline

Definition at line 65 of file threadedfilewriter.h.

◆ DiskLoop()

void ThreadedFileWriter::DiskLoop ( void )

protected

The thread run method that actually calls writes to disk.

Definition at line 409 of file threadedfilewriter.cpp.

Referenced by TFWWriteThread::run().

◆ SyncLoop()

void ThreadedFileWriter::SyncLoop ( void )

protected

The thread run method that calls Sync(void).

Definition at line 385 of file threadedfilewriter.cpp.

Referenced by TFWSyncThread::run().

◆ TrimEmptyBuffers()

void ThreadedFileWriter::TrimEmptyBuffers ( void )

protected

Definition at line 586 of file threadedfilewriter.cpp.

Referenced by DiskLoop().

Friends And Related Function Documentation

◆ TFWWriteThread

friend class TFWWriteThread

friend

Definition at line 44 of file threadedfilewriter.h.

Referenced by Open().

◆ TFWSyncThread

friend class TFWSyncThread

friend

Definition at line 45 of file threadedfilewriter.h.

Referenced by Open().

Member Data Documentation

◆ m_filename

QString ThreadedFileWriter::m_filename

private

Definition at line 74 of file threadedfilewriter.h.

Referenced by DiskLoop(), Open(), ReOpen(), SyncLoop(), and ~ThreadedFileWriter().

◆ m_flags

int ThreadedFileWriter::m_flags

private

Definition at line 75 of file threadedfilewriter.h.

Referenced by Open().

◆ m_mode

mode_t ThreadedFileWriter::m_mode

private

Definition at line 76 of file threadedfilewriter.h.

Referenced by Open().

◆ m_fd

int ThreadedFileWriter::m_fd {-1}

private

Definition at line 77 of file threadedfilewriter.h.

Referenced by DiskLoop(), Open(), ReOpen(), Seek(), Sync(), and ~ThreadedFileWriter().

◆ m_flush

bool ThreadedFileWriter::m_flush {false}

private

Definition at line 80 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), and Seek().

◆ m_inDtor

bool ThreadedFileWriter::m_inDtor {false}

private

Definition at line 81 of file threadedfilewriter.h.

Referenced by DiskLoop(), SyncLoop(), and ~ThreadedFileWriter().

◆ m_ignoreWrites

bool ThreadedFileWriter::m_ignoreWrites {false}

private

Definition at line 82 of file threadedfilewriter.h.

Referenced by DiskLoop(), Open(), SyncLoop(), and Write().

◆ m_tfwMinWriteSize

uint ThreadedFileWriter::m_tfwMinWriteSize {kMinWriteSize}

private

Definition at line 83 of file threadedfilewriter.h.

Referenced by SetWriteBufferMinWriteSize().

◆ m_totalBufferUse

uint ThreadedFileWriter::m_totalBufferUse {0}

private

Definition at line 84 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), Seek(), and Write().

◆ m_bufLock

QMutex ThreadedFileWriter::m_bufLock

mutableprivate

Definition at line 93 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), ReOpen(), Seek(), SetWriteBufferMinWriteSize(), SyncLoop(), Write(), and ~ThreadedFileWriter().

◆ m_writeBuffers

QList<TFWBuffer*> ThreadedFileWriter::m_writeBuffers

private

Definition at line 94 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), Seek(), Write(), and ~ThreadedFileWriter().

◆ m_emptyBuffers

QList<TFWBuffer*> ThreadedFileWriter::m_emptyBuffers

private

Definition at line 95 of file threadedfilewriter.h.

Referenced by DiskLoop(), TrimEmptyBuffers(), Write(), and ~ThreadedFileWriter().

◆ m_writeThread

TFWWriteThread* ThreadedFileWriter::m_writeThread {nullptr}

private

Definition at line 98 of file threadedfilewriter.h.

Referenced by Open(), and ~ThreadedFileWriter().

◆ m_syncThread

TFWSyncThread* ThreadedFileWriter::m_syncThread {nullptr}

private

Definition at line 99 of file threadedfilewriter.h.

Referenced by Open(), and ~ThreadedFileWriter().

◆ m_bufferEmpty

QWaitCondition ThreadedFileWriter::m_bufferEmpty

private

Definition at line 102 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), and Seek().

◆ m_bufferHasData

QWaitCondition ThreadedFileWriter::m_bufferHasData

private

Definition at line 103 of file threadedfilewriter.h.

Referenced by DiskLoop(), Flush(), Seek(), SetWriteBufferMinWriteSize(), Write(), and ~ThreadedFileWriter().

◆ m_bufferSyncWait

QWaitCondition ThreadedFileWriter::m_bufferSyncWait

private

Definition at line 104 of file threadedfilewriter.h.

Referenced by SyncLoop(), and ~ThreadedFileWriter().

◆ m_bufferWasFreed

QWaitCondition ThreadedFileWriter::m_bufferWasFreed

private

Definition at line 105 of file threadedfilewriter.h.

Referenced by DiskLoop(), and Write().

◆ kMaxBufferSize

const uint ThreadedFileWriter::kMaxBufferSize = 8 * 1024 * 1024

staticprivate

Definition at line 108 of file threadedfilewriter.h.

Referenced by Write().

◆ kMinWriteSize

const uint ThreadedFileWriter::kMinWriteSize = 64 * 1024

staticprivate

Minimum to write to disk in a single write, when not flushing buffer.

Definition at line 110 of file threadedfilewriter.h.

Referenced by DiskLoop(), and Write().

◆ kMaxBlockSize

const uint ThreadedFileWriter::kMaxBlockSize = 1 * 1024 * 1024

staticprivate

Maximum block size to write at a time.

Definition at line 112 of file threadedfilewriter.h.

Referenced by Write().

◆ m_warned

bool ThreadedFileWriter::m_warned {false}

private

Definition at line 114 of file threadedfilewriter.h.

Referenced by Write().

◆ m_blocking

bool ThreadedFileWriter::m_blocking {false}

private

Definition at line 115 of file threadedfilewriter.h.

Referenced by SetBlocking(), and Write().

◆ m_registered

bool ThreadedFileWriter::m_registered {false}

private

Definition at line 116 of file threadedfilewriter.h.

Referenced by DiskLoop(), Open(), ReOpen(), SyncLoop(), and ~ThreadedFileWriter().

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

mythtv/libs/libmythbase/threadedfilewriter.h
mythtv/libs/libmythbase/threadedfilewriter.cpp

Classes

Public Member Functions

Protected Member Functions

Private Attributes

Static Private Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

◆ ThreadedFileWriter()

◆ ~ThreadedFileWriter()

Member Function Documentation

◆ Open()

◆ ReOpen()

◆ Seek()

◆ Write()

◆ SetWriteBufferMinWriteSize()

◆ Sync()

◆ Flush()

◆ SetBlocking()

◆ WritesFailing()

◆ DiskLoop()

◆ SyncLoop()

◆ TrimEmptyBuffers()

Friends And Related Function Documentation

◆ TFWWriteThread

◆ TFWSyncThread

Member Data Documentation

◆ m_filename

◆ m_flags

◆ m_mode

◆ m_fd

◆ m_flush

◆ m_inDtor

◆ m_ignoreWrites

◆ m_tfwMinWriteSize

◆ m_totalBufferUse

◆ m_bufLock

◆ m_writeBuffers

◆ m_emptyBuffers

◆ m_writeThread

◆ m_syncThread

◆ m_bufferEmpty

◆ m_bufferHasData

◆ m_bufferSyncWait

◆ m_bufferWasFreed

◆ kMaxBufferSize

◆ kMinWriteSize

◆ kMaxBlockSize

◆ m_warned

◆ m_blocking

◆ m_registered