LTIOSubStream Class Reference

LTIOSubStream. More...

#include <lt_ioSubStream.h>

Inheritance diagram for LTIOSubStream:
LTIOStreamInf

List of all members.

Public Member Functions

Construction, destruction, initialization



 LTIOSubStream ()
 Default Constructor.
virtual ~LTIOSubStream ()
 Destructor.
virtual LT_STATUS initialize (LTIOStreamInf *stream, lt_int64 start, lt_int64 end, bool takeOwnership=false)
 Initializes the stream.
Status accessors



virtual bool isEOF ()
 Indicates whether the stream is at the end of its data or not.
Opening and closing



virtual bool isOpen ()
 Is the stream open?
virtual LT_STATUS open ()
 Opens the stream.
virtual LT_STATUS close ()
 Closes the stream.
Data access



virtual lt_uint32 read (lt_uint8 *pDest, lt_uint32 numBytes)
 Retrieve the specified number of bytes from the data source and place them in pDest.
virtual lt_uint32 write (const lt_uint8 *pSrc, lt_uint32 numBytes)
 Store the specified number of bytes in the data source.
Positioning



virtual LT_STATUS seek (lt_int64 offset, LTIOSeekDir origin)
 Moves the the data access position to origin + offset.
virtual lt_int64 tell ()
 Returns the current data access position as an offset from the start of the data.
Other operations



virtual LTIOStreamInfduplicate ()
 Clone the stream.
virtual LT_STATUS getLastError () const
 Clone the stream.
virtual const char * getID () const
 Clone the stream.

Protected Member Functions

void cleanup ()
 cleanup method

Protected Attributes

LTIOStreamInfm_stream
bool m_ownsStream
lt_int64 m_startOffset
lt_int64 m_endOffset
bool m_isEOF

Detailed Description

A SubStream is a stream which wraps another stream, but provides access to only a (contiguous) subset of the bytes of the parent stream -- without revealing any of the surrounding bytes.

Consider the following situation: the MG2 decoder always assumes byte 0 of the image stream given to it is the start of the image, but you have an image embedded in some larger stream -- say from byte offset 100 to 2100. By creating a substream from the larger stream and giving that to the decoder, the decoder will be doing the right thing when it naively issues a "seek-to-beginning" request.

Note that the SubStream does NOT take ownership of the stream given to it. The caller should duplicate() the main stream first, if needed. Closing the substream will close the parent stream, but deleting the substream will not delete the parent stream.

Note that the results might be undefined if the parent or child stream is modified at any point -- try to avoid such situations.

Examples:

UsingStreams.cpp.

Definition at line 46 of file lt_ioSubStream.h.


Constructor & Destructor Documentation

LTIOSubStream::LTIOSubStream (  ) 
virtual LTIOSubStream::~LTIOSubStream (  )  [virtual]

Member Function Documentation

void LTIOSubStream::cleanup (  )  [protected]
virtual LT_STATUS LTIOSubStream::close (  )  [virtual]

Puts the stream in a state that does not allow data access. May free up resources, but only in such a way that doesn't inhibit successful future calls to open()

Return values:
LT_STS_Success On success, or if the stream is already closed.
LT_STS_Failure Otherwise.

Implements LTIOStreamInf.

virtual LTIOStreamInf* LTIOSubStream::duplicate (  )  [virtual]

Create new stream of the same type with the same initialization parameters. The transmission of these parameters is the responsibility of the derived type. The new stream should initially return false for isOpen().

Return values:
NULL the stream could not be duplicated; valid LTIOStreamInf* otherwise.

Implements LTIOStreamInf.

virtual const char* LTIOSubStream::getID (  )  const [virtual]

Create new stream of the same type with the same initialization parameters. The transmission of these parameters is the responsibility of the derived type. The new stream should initially return false for isOpen().

Return values:
NULL the stream could not be duplicated; valid LTIOStreamInf* otherwise.

Implements LTIOStreamInf.

virtual LT_STATUS LTIOSubStream::getLastError (  )  const [virtual]

Create new stream of the same type with the same initialization parameters. The transmission of these parameters is the responsibility of the derived type. The new stream should initially return false for isOpen().

Return values:
NULL the stream could not be duplicated; valid LTIOStreamInf* otherwise.

Implements LTIOStreamInf.

virtual LT_STATUS LTIOSubStream::initialize ( LTIOStreamInf stream,
lt_int64  start,
lt_int64  end,
bool  takeOwnership = false 
) [virtual]
Parameters:
stream the parent stream to be subsetted
start the byte offset to be byte 0 of the subset stream
end the byte offset to be the last byte of the subset stream: reading or writing past this byte will be handled as an EOF condition
takeOwnership if true, this object will take ownership of stream and delete it
virtual bool LTIOSubStream::isEOF (  )  [virtual]
Returns:
true the stream is valid and at the end of its data.
Return values:
false otherwise

Implements LTIOStreamInf.

virtual bool LTIOSubStream::isOpen (  )  [virtual]
Return values:
true the stream is valid and in a state that allows data access.
false otherwise

Implements LTIOStreamInf.

virtual LT_STATUS LTIOSubStream::open (  )  [virtual]

Opening a stream puts it in a state that allows data access based on cached initialization parameters.

Return values:
LT_STS_IOStreamUninitialized The stream has not been initialized with enough information to open the stream
LT_STS_IOStreamInvalidState The the stream is already open
LT_STS_Success On success.
LT_STS_Failure Otherwise.

Implements LTIOStreamInf.

virtual lt_uint32 LTIOSubStream::read ( lt_uint8 pDest,
lt_uint32  numBytes 
) [virtual]
Parameters:
pDest buffer in which to store read data
numBytes number of bytes to read from stream
Return values:
numBytes The number of bytes actually read

Implements LTIOStreamInf.

virtual LT_STATUS LTIOSubStream::seek ( lt_int64  offset,
LTIOSeekDir  origin 
) [virtual]
Parameters:
offset number of bytes from origin at which to the next read or write will take place
origin place in stream from which to seek
Return values:
LT_STS_IOStreamUnsupported The stream is not seekable
LT_STS_IOStreamInvalidArgs The offset and origin do not specify a valid location in the stream
LT_STS_Success On success
LT_STS_Failure Otherwise

Implements LTIOStreamInf.

virtual lt_int64 LTIOSubStream::tell (  )  [virtual]
Return values:
postion Number of bytes from the start of the data
-1 On error.

Implements LTIOStreamInf.

virtual lt_uint32 LTIOSubStream::write ( const lt_uint8 pSrc,
lt_uint32  numBytes 
) [virtual]
Parameters:
pSrc buffer from which to store data
numBytes number of bytes to write to stream
Return values:
numBytes number of bytes actually written

Implements LTIOStreamInf.


Member Data Documentation

lt_int64 LTIOSubStream::m_endOffset [protected]

Definition at line 223 of file lt_ioSubStream.h.

bool LTIOSubStream::m_isEOF [protected]

Definition at line 225 of file lt_ioSubStream.h.

bool LTIOSubStream::m_ownsStream [protected]

Definition at line 221 of file lt_ioSubStream.h.

lt_int64 LTIOSubStream::m_startOffset [protected]

Definition at line 222 of file lt_ioSubStream.h.

Definition at line 220 of file lt_ioSubStream.h.


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

LizardTech