ByteInputStream Class Reference

ByteInputStream defines an interface for reading from a stream of bytes. More...

#include <ByteInputStream.h>

Inheritance diagram for ByteInputStream:

List of all members.

Public Member Functions
uint	readBytes (void *pData, uint cbRequested)
	Reads bytes from the stream.
template<class T>
uint	readValue (T &value)
	Reads a fixed-size value from the stream.
PConstBuffer	getReadPointer (uint cbRequested, uint *pcbActual=NULL)
	Copyless alternative for reading bytes from the stream.
void	consumeReadPointer (uint cbUsed)
	Advances stream position after a call to getReadPointer.
void	seekForward (uint cb)
	Skips forward in stream.
void	seekBackward (uint cb)
	Skips backward in stream.
virtual SharedByteStreamMarker	newMarker ()
	Creates a new uninitialized marker for this stream.
virtual void	mark (ByteStreamMarker &marker)
	Marks the current stream position in preparation for a future call to reset().
virtual void	reset (ByteStreamMarker const &marker)
	Resets stream to a previously marked position.
FileSize	getOffset () const
	Returns: current offset from beginning of stream
bool	isClosed () const
	Returns: whether the object has been closed
void	close ()
	Closes this object, releasing any unallocated resources.
Protected Member Functions
	ByteInputStream ()
virtual void	readNextBuffer ()=0
	Must be implemented by derived class by calling either setBuffer or nullifyBuffer.
virtual void	readPrevBuffer ()
	Must be implemented by derived class if seekBackward is to be supported.
void	setBuffer (PConstBuffer pBuffer, uint cbBuffer)
	Sets the current buffer to be read.
void	nullifyBuffer ()
	Nullifies the current buffer, indicating no more data is available.
uint	getBytesAvailable () const
	Returns: number of bytes remaining in current buffer
uint	getBytesConsumed () const
	Returns: number of bytes already consumed from current buffer
virtual void	closeImpl ()=0
	Must be implemented by derived class to release any resources.
Protected Attributes
FileSize	cbOffset
	Byte position in stream.
bool	needsClose
Private Attributes
PConstBuffer	pFirstByte
	First buffered byte of data.
PConstBuffer	pNextByte
	Next buffered byte of data.
PConstBuffer	pEndByte
	End of buffer (one past last byte of data in buffer).

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Detailed Description

ByteInputStream defines an interface for reading from a stream of bytes.

Definition at line 34 of file ByteInputStream.h.

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Constructor & Destructor Documentation

ByteInputStream::ByteInputStream

(

)

[explicit, protected]

Definition at line 29 of file ByteInputStream.cpp.

References nullifyBuffer().

{
    nullifyBuffer();
}

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Member Function Documentation

virtual void ByteInputStream::readNextBuffer

(

)

[protected, pure virtual]

Must be implemented by derived class by calling either setBuffer or nullifyBuffer.

Implemented in ByteArrayInputStream, and SegInputStream.

Referenced by getReadPointer(), and readBytes().

void ByteInputStream::readPrevBuffer

(

)

[protected, virtual]

Must be implemented by derived class if seekBackward is to be supported.

Reimplemented in ByteArrayInputStream, and SegInputStream.

Definition at line 66 of file ByteInputStream.cpp.

Referenced by seekBackward().

{
    permAssert(false);
}

void ByteInputStream::setBuffer	(	PConstBuffer	pBuffer,
		uint	cbBuffer
	)			[inline, protected]

Sets the current buffer to be read.

Parameters:

	pBuffer	receives start address of new buffer
	cbBuffer	number of bytes in buffer

Definition at line 241 of file ByteInputStream.h.

References pEndByte, pFirstByte, and pNextByte.

Referenced by ByteArrayInputStream::ByteArrayInputStream(), SegInputStream::lockBuffer(), CrcSegInputStream::lockBufferParanoid(), nullifyBuffer(), and ByteArrayInputStream::resetArray().

{
    pFirstByte = pBuffer;
    pEndByte = pBuffer + cbBuffer;
    pNextByte = pFirstByte;
}

void ByteInputStream::nullifyBuffer

(

)

[inline, protected]

Nullifies the current buffer, indicating no more data is available.

Definition at line 250 of file ByteInputStream.h.

References setBuffer().

Referenced by ByteInputStream(), CrcSegInputStream::lockBuffer(), SegInputStream::readNextBuffer(), ByteArrayInputStream::readNextBuffer(), SegInputStream::readPrevBuffer(), and ByteArrayInputStream::readPrevBuffer().

{
    setBuffer(NULL,0);
}

uint ByteInputStream::getBytesAvailable

(

)

const [inline, protected]

Returns:

number of bytes remaining in current buffer

Definition at line 199 of file ByteInputStream.h.

References pEndByte, and pNextByte.

Referenced by consumeReadPointer(), getReadPointer(), readBytes(), and SegInputStream::seekSegPos().

{
    return static_cast<uint>(pEndByte - pNextByte);
}

uint ByteInputStream::getBytesConsumed

(

)

const [inline, protected]

Returns:

number of bytes already consumed from current buffer

Definition at line 204 of file ByteInputStream.h.

References pFirstByte, and pNextByte.

Referenced by SegInputStream::getSegPos(), and seekBackward().

{
    return static_cast<uint>(pNextByte - pFirstByte);
}

uint ByteInputStream::readBytes	(	void *	pData,
		uint	cbRequested
	)

Reads bytes from the stream.

Parameters:

	pData	target buffer to read into
	cbRequested	number of bytes to read

Returns:

number of bytes actually read; 0 indicates end-of-stream

Definition at line 34 of file ByteInputStream.cpp.

References ByteStream::cbOffset, getBytesAvailable(), pEndByte, pNextByte, and readNextBuffer().

Referenced by FtrsTableWriter::redoLogicalAction(), and seekForward().

{
    uint cbActual = 0;
    if (pNextByte == pEndByte) {
        readNextBuffer();
    }
    for (;;) {
        uint cbAvailable = getBytesAvailable();
        if (!cbAvailable) {
            break;
        }
        if (cbRequested <= cbAvailable) {
            if (pData) {
                memcpy(pData,pNextByte,cbRequested);
            }
            pNextByte += cbRequested;
            cbActual += cbRequested;
            break;
        }
        if (pData) {
            memcpy(pData,pNextByte,cbAvailable);
            pData = static_cast<char *>(pData) + cbAvailable;
        }
        cbRequested -= cbAvailable;
        cbActual += cbAvailable;
        readNextBuffer();
    }
    cbOffset += cbActual;
    return cbActual;
}

template<class T>

uint ByteInputStream::readValue

(

T &

value

)

[inline]

Reads a fixed-size value from the stream.

Parameters:

value

value to write; type must be memcpy-safe

Returns:

number of bytes actually read

Definition at line 112 of file ByteInputStream.h.

Referenced by FtrsTableWriterFactory::loadIndex(), LogicalTxnTest::loadParticipant(), FtrsTableWriterFactory::loadParticipant(), BTreeRecoveryFactory::loadParticipant(), TupleProjection::readPersistent(), TupleDescriptor::readPersistent(), LogicalTxnTest::redoLogicalAction(), DatabaseTest::redoLogicalAction(), LogicalTxnTest::undoLogicalAction(), and DatabaseTest::undoLogicalAction().

    {
        return readBytes(&value,sizeof(value));
    }

PConstBuffer ByteInputStream::getReadPointer	(	uint	cbRequested,
		uint *	pcbActual = NULL
	)			[inline]

Copyless alternative for reading bytes from the stream.

Provides direct access to the stream's internal buffer, but doesn't move the stream position (see consumeReadPointer).

Note that it is in general dangerous to assume that getReadPointer will be able to access desired data items contiguously. For example, a stream created by calling ByteOutputStream::write is likely to have data items split across buffers. The assumption MAY be valid for streams created by calling ByteOutputStream::getWritePointer with matching values for cbRequested; it depends on the stream implementation.

Parameters:

	cbRequested	number of contiguous bytes to access; if a non-zero number of bytes are currently available in the buffer, cbRequested must be no greater than the number of available bytes (otherwise an assertion violation will result)
	pcbActual	if non-NULL, receives actual number of contiguous bytes available, which will always be greater than or equal to cbRequested except 0 for end-of-stream

Returns:

pointer to cbActual bytes of available data, or NULL for end-of-stream

Definition at line 209 of file ByteInputStream.h.

References getBytesAvailable(), pEndByte, pNextByte, and readNextBuffer().

Referenced by BTreeWriter::deleteLogged(), BTreeWriter::insertLogged(), and BTreeBuildLevel::processInput().

{
    if (getBytesAvailable() < cbRequested) {
        assert(pNextByte == pEndByte);
        readNextBuffer();
        if (pNextByte == pEndByte) {
            if (pcbActual) {
                *pcbActual = 0;
            }
            return NULL;
        }
    }
    if (pcbActual) {
        *pcbActual = getBytesAvailable();
    }
    return pNextByte;
}

void ByteInputStream::consumeReadPointer

(

uint

cbUsed

)

[inline]

Advances stream position after a call to getReadPointer.

Parameters:

cbUsed

number of bytes to advance; must be less than or equal to the value of cbActual returned by the last call to getReadPointer

Definition at line 234 of file ByteInputStream.h.

References ByteStream::cbOffset, getBytesAvailable(), and pNextByte.

Referenced by BTreeWriter::deleteLogged(), BTreeWriter::insertLogged(), BTreeBuildLevel::processInput(), and SegInputStream::seekSegPos().

{
    assert(cbUsed <= getBytesAvailable());
    pNextByte += cbUsed;
    cbOffset += cbUsed;
}

void ByteInputStream::seekForward

(

uint

cb

)

[inline]

Skips forward in stream.

Parameters:

cb

number of bytes to advance

Definition at line 228 of file ByteInputStream.h.

References readBytes().

Referenced by reset().

{
    uint cbActual = readBytes(NULL,cb);
    assert(cbActual == cb);
}

void ByteInputStream::seekBackward

(

uint

cb

)

Skips backward in stream.

Not all stream implementations support this behavior.

Parameters:

cb

number of bytes backward to seek

Definition at line 71 of file ByteInputStream.cpp.

References ByteStream::cbOffset, getBytesConsumed(), pEndByte, pFirstByte, pNextByte, and readPrevBuffer().

Referenced by reset().

{
    assert(cb <= cbOffset);
    cbOffset -= cb;
    if (pNextByte == pFirstByte) {
        readPrevBuffer();
        pNextByte = pEndByte;
    }
    for (;;) {
        uint cbAvailable = getBytesConsumed();
        assert(cbAvailable);
        if (cb <= cbAvailable) {
            pNextByte -= cb;
            break;
        }
        cb -= cbAvailable;
        readPrevBuffer();
        pNextByte = pEndByte;
    }
}

SharedByteStreamMarker ByteInputStream::newMarker

(

)

[virtual]

Creates a new uninitialized marker for this stream.

The returned marker must be passed to mark() in order to initialize it.

Returns:

shared pointer to new marker

Reimplemented in SegInputStream.

Definition at line 92 of file ByteInputStream.cpp.

{
    return SharedByteStreamMarker(new SequentialByteStreamMarker(*this));
}

void ByteInputStream::mark

(

ByteStreamMarker &

marker

)

[virtual]

Marks the current stream position in preparation for a future call to reset().

How long this marker remains valid depends upon the implementation of the ByteInputStream.

Parameters:

marker

memento object created with newMarker() on the same stream; receives the marked position (forgetting any previously marked position)

Reimplemented in SegInputStream.

Definition at line 97 of file ByteInputStream.cpp.

References SequentialByteStreamMarker::cbOffset, ByteStream::getOffset(), and ByteStreamMarker::getStream().

{
    assert(&(marker.getStream()) == this);

    SequentialByteStreamMarker &seqMarker =
        dynamic_cast<SequentialByteStreamMarker &>(marker);
    seqMarker.cbOffset = getOffset();
}

void ByteInputStream::reset

(

ByteStreamMarker const &

marker

)

[virtual]

Resets stream to a previously marked position.

The base implementation uses seekForward/seekBackward (i.e. sequential access), making it inefficient for large streams. Derived classes may override with more efficient implementations such as random access.

Parameters:

marker

memento previously memorized with mark()

Reimplemented in SegInputStream.

Definition at line 106 of file ByteInputStream.cpp.

References ByteStream::cbOffset, SequentialByteStreamMarker::cbOffset, ByteStreamMarker::getStream(), isMAXU(), seekBackward(), and seekForward().

{
    assert(&(marker.getStream()) == this);

    SequentialByteStreamMarker const &seqMarker =
        dynamic_cast<SequentialByteStreamMarker const &>(marker);
    assert(!isMAXU(seqMarker.cbOffset));
    if (cbOffset == seqMarker.cbOffset) {
        // expedite common case where stream has not moved since mark
        return;
    } else if (cbOffset > seqMarker.cbOffset) {
        seekBackward(cbOffset - seqMarker.cbOffset);
    } else {
        seekForward(seqMarker.cbOffset - cbOffset);
    }
}

FileSize ByteStream::getOffset

(

)

const [inline, inherited]

Returns:

current offset from beginning of stream

Definition at line 110 of file ByteStream.h.

References ByteStream::cbOffset.

Referenced by SpillOutputStream::getInputStream(), and mark().

{
    return cbOffset;
}

virtual void ClosableObject::closeImpl

(

)

[protected, pure virtual, inherited]

Must be implemented by derived class to release any resources.

Implemented in CacheImpl< PageT, VictimPolicyT >, ByteArrayInputStream, ByteArrayOutputStream, ByteOutputStream, CheckpointThread, Database, BarrierExecStream, DoubleBufferExecStream, ExecStream, ExecStreamGraphImpl, MockResourceExecStream, ReshapeExecStream, ScratchBufferExecStream, SegBufferExecStream, SegBufferReader, SegBufferReaderExecStream, SegBufferWriter, SegBufferWriterExecStream, JavaSinkExecStream, JavaTransformExecStream, FlatFileBuffer, FlatFileExecStreamImpl, BTreeExecStream, BTreeInsertExecStream, BTreePrefetchSearchExecStream, BTreeReadExecStream, BTreeSearchExecStream, FtrsTableWriterExecStream, LhxAggExecStream, LhxJoinExecStream, LbmBitOpExecStream, LbmChopperExecStream, LbmGeneratorExecStream, LbmIntersectExecStream, LbmMinusExecStream, LbmSplicerExecStream, LbmUnionExecStream, LcsClusterAppendExecStream, LcsRowScanBaseExecStream, LcsRowScanExecStream, DelegatingSegment, DynamicDelegatingSegment, ScratchSegment, SegInputStream, Segment, SegOutputStream, SegPageBackupRestoreDevice, SegStream, SegStreamAllocation, SpillOutputStream, and ExternalSortExecStreamImpl.

Referenced by ClosableObject::close().

bool ClosableObject::isClosed

(

)

const [inline, inherited]

Returns:

whether the object has been closed

Definition at line 58 of file ClosableObject.h.

    {
        return !needsClose;
    }

void ClosableObject::close

(

)

[inherited]

Closes this object, releasing any unallocated resources.

Reimplemented in CollectExecStream, CorrelationJoinExecStream, LcsClusterAppendExecStream, and LcsClusterReplaceExecStream.

Definition at line 39 of file ClosableObject.cpp.

References ClosableObject::closeImpl(), and ClosableObject::needsClose.

Referenced by CacheImpl< PageT, VictimPolicyT >::allocatePages(), LcsRowScanBaseExecStream::closeImpl(), ExecStreamGraphImpl::closeImpl(), FlatFileBuffer::open(), ClosableObjectDestructor::operator()(), and Segment::~Segment().

{
    if (!needsClose) {
        return;
    }
    needsClose = false;
    closeImpl();
}

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Member Data Documentation

PConstBuffer ByteInputStream::pFirstByte [private]

First buffered byte of data.

Definition at line 39 of file ByteInputStream.h.

Referenced by getBytesConsumed(), SegInputStream::lockBuffer(), CrcSegInputStream::lockBufferParanoid(), seekBackward(), and setBuffer().

PConstBuffer ByteInputStream::pNextByte [private]

Next buffered byte of data.

Definition at line 44 of file ByteInputStream.h.

Referenced by consumeReadPointer(), getBytesAvailable(), getBytesConsumed(), getReadPointer(), readBytes(), seekBackward(), and setBuffer().

PConstBuffer ByteInputStream::pEndByte [private]

End of buffer (one past last byte of data in buffer).

Definition at line 49 of file ByteInputStream.h.

Referenced by getBytesAvailable(), getReadPointer(), readBytes(), seekBackward(), and setBuffer().

FileSize ByteStream::cbOffset [protected, inherited]

Byte position in stream.

Definition at line 41 of file ByteStream.h.

Referenced by ByteStream::ByteStream(), consumeReadPointer(), ByteOutputStream::consumeWritePointer(), ByteStream::getOffset(), SegOutputStream::getSegPos(), SegInputStream::getSegPos(), readBytes(), reset(), ByteArrayInputStream::resetArray(), seekBackward(), SegInputStream::seekSegPos(), and ByteOutputStream::writeBytes().

bool ClosableObject::needsClose [protected, inherited]

Definition at line 44 of file ClosableObject.h.

Referenced by SegStreamAllocation::beginWrite(), ExecStreamGraphImpl::clear(), ClosableObject::ClosableObject(), ClosableObject::close(), FlatFileBuffer::open(), ExecStreamGraphImpl::open(), ExecStream::open(), and ClosableObject::~ClosableObject().

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

• /home/pub/open/dev/fennel/common/ByteInputStream.h
• /home/pub/open/dev/fennel/common/ByteInputStream.cpp

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