LTIOCallbackStream Class Reference

Stream driven entirely by user-defined callbacks. More...

#include <lt_ioCallbackStream.h>

Inheritance diagram for LTIOCallbackStream:

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Collaboration diagram for LTIOCallbackStream:

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List of all members.

Public Member Functions

 LTIOCallbackStream ()
virtual ~LTIOCallbackStream ()
virtual LT_STATUS initialize (LTIOCallbackStream_Open open, LTIOCallbackStream_Close close, LTIOCallbackStream_Read read, LTIOCallbackStream_Write write, LTIOCallbackStream_Seek seek, LTIOCallbackStream_Tell tell, LTIOCallbackStream_IsEOF isEOF, LTIOCallbackStream_IsOpen isOpen, LTIOCallbackStream_Duplicate duplicate, void *user)
 initialize
virtual bool isEOF ()
 Test for end-of-stream.
virtual bool isOpen ()
 Test for stream openness.
virtual LT_STATUS open ()
 Opens the stream.
virtual LT_STATUS close ()
 Closes the stream.
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.
virtual LT_STATUS seek (lt_int64 offset, LTIOSeekDir origin)
 Moves 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.
virtual LTIOStreamInfduplicate ()
 Clone the stream.
virtual LT_STATUS getLastError () const
 Get status code of last error event.
virtual const char * getID () const
 Get a URI describing the stream object.


Detailed Description

This class implements a stream whose operations -- read(), write(), open(), close(), etc -- are all defined by functions passed in from the user.

This class can be used as an alternative to deriving custom stream classes from LTIOStreamInf. This class also forms the basis for the C-callable stream defined in lt_ioCStream.h.

Definition at line 36 of file lt_ioCallbackStream.h.


Constructor & Destructor Documentation

LTIOCallbackStream::LTIOCallbackStream (  ) 

virtual LTIOCallbackStream::~LTIOCallbackStream (  )  [virtual]


Member Function Documentation

virtual LT_STATUS LTIOCallbackStream::initialize ( LTIOCallbackStream_Open  open,
LTIOCallbackStream_Close  close,
LTIOCallbackStream_Read  read,
LTIOCallbackStream_Write  write,
LTIOCallbackStream_Seek  seek,
LTIOCallbackStream_Tell  tell,
LTIOCallbackStream_IsEOF  isEOF,
LTIOCallbackStream_IsOpen  isOpen,
LTIOCallbackStream_Duplicate  duplicate,
void *  user 
) [virtual]

The parameters to this function are a set of function pointers which implement all the required operations needed to support a stream. Their semantics exactly mirror the semantics of the corresponding member functions in LTIOStreamInf.

The user parameter is a pointer to a user-defined area containing information about the stream itself, e.g. the filename and a FILE*. This pointer is passed as the first argument to each of the user's stream functions. This class never attempts to interpret this data directly.

Note that the implementation of the duplicate function is required to create a new copy of this user-defined data by whatever means appropriate. The user retains ownership of the copied user data.

Parameters:
open pointer to user's open function
close pointer to user's close function
read pointer to user's read function
write pointer to user's write function
seek pointer to user's seek function
tell pointer to user's tell function
isEOF pointer to user's isEOF function
isOpen pointer to user's isOpen function
duplicate pointer to user's duplicate function
user pointer to user-defined stream data
Returns:
status code indicating success or failure

virtual bool LTIOCallbackStream::isEOF (  )  [virtual]

Returns true after the first read operation that attempts to read past the end of the stream. It returns false if the current position is not end of stream.

Return values:
true end of stream
false otherwise

Implements LTIOStreamInf.

virtual bool LTIOCallbackStream::isOpen (  )  [virtual]

Return values:
true The stream is open
false otherwise

Implements LTIOStreamInf.

virtual LT_STATUS LTIOCallbackStream::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 stream is already open
LT_STS_Success On success.
LT_STS_Failure Failure.
other Implementations may return other codes

Implements LTIOStreamInf.

virtual LT_STATUS LTIOCallbackStream::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 lt_uint32 LTIOCallbackStream::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_uint32 LTIOCallbackStream::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.

virtual LT_STATUS LTIOCallbackStream::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
other Implementations may return other codes

Implements LTIOStreamInf.

virtual lt_int64 LTIOCallbackStream::tell (  )  [virtual]

Return values:
postion Number of bytes from the start of the data
-1 On error.
other Implementations may return other codes

Implements LTIOStreamInf.

virtual LTIOStreamInf* LTIOCallbackStream::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 LT_STATUS LTIOCallbackStream::getLastError (  )  const [virtual]

read(), write(), tell(), and duplicate() do not explicitly return status codes in the event of an error. When an error has occurred, this function returns the appropriate status code. Note calling this function after a successful I/O operation will return an undefined value.

Return values:
status the error code

Implements LTIOStreamInf.

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

This function returns a UTF-8, null-terminated string which is a URI describing the origin of the stream object -- for example, "file://foo.txt" or "lt_memstream:". This string is only intended for diagnostic purposes, i.e. it may not be valid to pass it to the ctor in an attempt to reopen the stream.

Return values:
uri the uri string

Implements LTIOStreamInf.


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

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