Version: 3.1.1
wxStreamBuffer Class Reference

#include <wx/stream.h>

Detailed Description

wxStreamBuffer is a cache manager for wxStreamBase: it manages a stream buffer linked to a stream.

Each stream always has one autoinitialized stream buffer, but you may attach more of them to the same stream.

Library:  wxBase
Category:  Streams
See also
wxStreamBase, Stream Classes Overview

Public Types

enum  BufMode {
  read,
  write,
  read_write
}
 BufMode flags. More...
 

Public Member Functions

 wxStreamBuffer (wxStreamBase &stream, BufMode mode)
 Constructor, creates a new stream buffer using stream as a parent stream and mode as the IO mode. More...
 
 wxStreamBuffer (size_t bufsize, wxInputStream &stream)
 Constructor for an input buffer of the specified size. More...
 
 wxStreamBuffer (size_t bufsize, wxOutputStream &stream)
 Constructor for an output buffer of the specified size. More...
 
 wxStreamBuffer (BufMode mode)
 Constructor; creates a new empty stream buffer which won't flush any data to a stream. More...
 
 wxStreamBuffer (const wxStreamBuffer &buffer)
 Copy constructor. More...
 
 ~wxStreamBuffer ()
 Destructor. More...
 
bool FillBuffer ()
 Fill the IO buffer. More...
 
void Fixed (bool fixed)
 Toggles the fixed flag. More...
 
bool FlushBuffer ()
 Flushes the IO buffer. More...
 
void Flushable (bool flushable)
 Toggles the flushable flag. More...
 
void * GetBufferEnd () const
 Returns a pointer on the end of the stream buffer. More...
 
void * GetBufferPos () const
 Returns a pointer on the current position of the stream buffer. More...
 
size_t GetBufferSize () const
 Returns the size of the buffer. More...
 
void * GetBufferStart () const
 Returns a pointer on the start of the stream buffer. More...
 
virtual char GetChar ()
 Gets a single char from the stream buffer. More...
 
size_t GetDataLeft ()
 Returns the amount of available data in the buffer. More...
 
size_t GetIntPosition () const
 Returns the current position (counted in bytes) in the stream buffer. More...
 
size_t GetLastAccess () const
 Returns the amount of bytes read during the last IO call to the parent stream. More...
 
virtual void PutChar (char c)
 Puts a single char to the stream buffer. More...
 
virtual size_t Read (void *buffer, size_t size)
 Reads a block of the specified size and stores the data in buffer. More...
 
size_t Read (wxStreamBuffer *buffer)
 Copies data to buffer. More...
 
void ResetBuffer ()
 Resets to the initial state variables concerning the buffer. More...
 
virtual wxFileOffset Seek (wxFileOffset pos, wxSeekMode mode)
 Changes the current position. More...
 
void SetBufferIO (void *start, void *end, bool takeOwnership=false)
 Specifies which pointers to use for stream buffering. More...
 
void SetBufferIO (size_t bufsize)
 Destroys or invalidates the previous IO buffer and allocates a new one of the specified size. More...
 
void SetIntPosition (size_t pos)
 Sets the current position (in bytes) in the stream buffer. More...
 
wxStreamBaseStream ()
 Returns the parent stream of the stream buffer. More...
 
virtual wxFileOffset Tell () const
 Gets the current position in the stream. More...
 
void Truncate ()
 Truncates the buffer to the current position. More...
 
virtual size_t Write (const void *buffer, size_t size)
 Writes a block of the specified size using data of buffer. More...
 
size_t Write (wxStreamBuffer *buffer)
 See Read(). More...
 

Member Enumeration Documentation

BufMode flags.

Enumerator
read 
write 
read_write 

Constructor & Destructor Documentation

wxStreamBuffer::wxStreamBuffer ( wxStreamBase stream,
BufMode  mode 
)

Constructor, creates a new stream buffer using stream as a parent stream and mode as the IO mode.

Parameters
streamThe parent stream.
modeCan be: wxStreamBuffer::read, wxStreamBuffer::write, wxStreamBuffer::read_write.

One stream can have many stream buffers but only one is used internally to pass IO call (e.g. wxInputStream::Read() -> wxStreamBuffer::Read()), but you can call directly wxStreamBuffer::Read without any problems. Note that all errors and messages linked to the stream are stored in the stream, not the stream buffers:

streambuffer.Read(...);
streambuffer2.Read(...);
// This call erases previous error messages set by 'streambuffer'
// assuming that both instances are stream buffers for the same stream
See also
SetBufferIO()
wxStreamBuffer::wxStreamBuffer ( size_t  bufsize,
wxInputStream stream 
)

Constructor for an input buffer of the specified size.

Using it is equivalent to using the constructor above with read mode and calling SetBufferIO() but is more convenient.

Since
2.9.0
Parameters
bufsizeThe size of buffer in bytes.
streamThe associated input stream, the buffer will be used in read mode.
wxStreamBuffer::wxStreamBuffer ( size_t  bufsize,
wxOutputStream stream 
)

Constructor for an output buffer of the specified size.

Using it is equivalent to using the constructor above with write mode and calling SetBufferIO() but is more convenient.

Since
2.9.0
Parameters
bufsizeThe size of buffer in bytes.
streamThe associated output stream, the buffer will be used in write mode.
wxStreamBuffer::wxStreamBuffer ( BufMode  mode)

Constructor; creates a new empty stream buffer which won't flush any data to a stream.

mode specifies the type of the buffer (read, write, read_write).

This stream buffer has the advantage to be stream independent and to work only on memory buffers but it is still compatible with the rest of the wxStream classes. You can write, read to this special stream and it will grow (if it is allowed by the user) its internal buffer. Briefly, it has all functionality of a "normal" stream.

Warning
The "read_write" mode doesn't currently work for standalone stream buffers.
See also
SetBufferIO()
wxStreamBuffer::wxStreamBuffer ( const wxStreamBuffer buffer)

Copy constructor.

This method initializes the stream buffer with the data of the specified stream buffer. The new stream buffer has the same attributes, size, position and they share the same buffer. This will cause problems if the stream to which the stream buffer belong is destroyed and the newly cloned stream buffer continues to be used, trying to call functions in the (destroyed) stream. It is advised to use this feature only in very local area of the program.

wxStreamBuffer::~wxStreamBuffer ( )

Destructor.

It finalizes all IO calls and frees all internal buffers if necessary.

Member Function Documentation

bool wxStreamBuffer::FillBuffer ( )

Fill the IO buffer.

void wxStreamBuffer::Fixed ( bool  fixed)

Toggles the fixed flag.

Usually this flag is toggled at the same time as flushable. This flag allows (when it has the false value) or forbids (when it has the true value) the stream buffer to resize dynamically the IO buffer.

See also
SetBufferIO()
void wxStreamBuffer::Flushable ( bool  flushable)

Toggles the flushable flag.

If flushable is disabled, no data are sent to the parent stream.

bool wxStreamBuffer::FlushBuffer ( )

Flushes the IO buffer.

void* wxStreamBuffer::GetBufferEnd ( ) const

Returns a pointer on the end of the stream buffer.

void* wxStreamBuffer::GetBufferPos ( ) const

Returns a pointer on the current position of the stream buffer.

size_t wxStreamBuffer::GetBufferSize ( ) const

Returns the size of the buffer.

void* wxStreamBuffer::GetBufferStart ( ) const

Returns a pointer on the start of the stream buffer.

virtual char wxStreamBuffer::GetChar ( )
virtual

Gets a single char from the stream buffer.

It acts like the Read() call.

Warning
You aren't directly notified if an error occurred during the IO call.
See also
Read()
size_t wxStreamBuffer::GetDataLeft ( )

Returns the amount of available data in the buffer.

size_t wxStreamBuffer::GetIntPosition ( ) const

Returns the current position (counted in bytes) in the stream buffer.

size_t wxStreamBuffer::GetLastAccess ( ) const

Returns the amount of bytes read during the last IO call to the parent stream.

virtual void wxStreamBuffer::PutChar ( char  c)
virtual

Puts a single char to the stream buffer.

Warning
You aren't directly notified if an error occurred during the IO call.
See also
Read()
virtual size_t wxStreamBuffer::Read ( void *  buffer,
size_t  size 
)
virtual

Reads a block of the specified size and stores the data in buffer.

This function tries to read from the buffer first and if more data has been requested, reads more data from the associated stream and updates the buffer accordingly until all requested data is read.

Returns
It returns the size of the data read. If the returned size is different of the specified size, an error has occurred and should be tested using GetLastError().
size_t wxStreamBuffer::Read ( wxStreamBuffer buffer)

Copies data to buffer.

The function returns when buffer is full or when there isn't any more data in the current buffer.

See also
Write()
void wxStreamBuffer::ResetBuffer ( )

Resets to the initial state variables concerning the buffer.

virtual wxFileOffset wxStreamBuffer::Seek ( wxFileOffset  pos,
wxSeekMode  mode 
)
virtual

Changes the current position.

Parameter mode may be one of the following:

  • wxFromStart: The position is counted from the start of the stream.
  • wxFromCurrent: The position is counted from the current position of the stream.
  • wxFromEnd: The position is counted from the end of the stream.
Returns
Upon successful completion, it returns the new offset as measured in bytes from the beginning of the stream. Otherwise, it returns wxInvalidOffset.
void wxStreamBuffer::SetBufferIO ( void *  start,
void *  end,
bool  takeOwnership = false 
)

Specifies which pointers to use for stream buffering.

You need to pass a pointer on the start of the buffer end and another on the end. The object will use this buffer to cache stream data. It may be used also as a source/destination buffer when you create an empty stream buffer (See wxStreamBuffer::wxStreamBuffer).

Remarks
When you use this function, you will have to destroy the IO buffers yourself after the stream buffer is destroyed or don't use it anymore. In the case you use it with an empty buffer, the stream buffer will not resize it when it is full.
See also
wxStreamBuffer(), Fixed(), Flushable()
void wxStreamBuffer::SetBufferIO ( size_t  bufsize)

Destroys or invalidates the previous IO buffer and allocates a new one of the specified size.

Warning
All previous pointers aren't valid anymore.
Remarks
The created IO buffer is growable by the object.
See also
Fixed(), Flushable()
void wxStreamBuffer::SetIntPosition ( size_t  pos)

Sets the current position (in bytes) in the stream buffer.

Warning
Since it is a very low-level function, there is no check on the position: specifying an invalid position can induce unexpected results.
wxStreamBase* wxStreamBuffer::Stream ( )

Returns the parent stream of the stream buffer.

Deprecated:
use GetStream() instead
virtual wxFileOffset wxStreamBuffer::Tell ( ) const
virtual

Gets the current position in the stream.

This position is calculated from the real position in the stream and from the internal buffer position: so it gives you the position in the real stream counted from the start of the stream.

Returns
Returns the current position in the stream if possible, wxInvalidOffset in the other case.
void wxStreamBuffer::Truncate ( )

Truncates the buffer to the current position.

Note
Truncate() cannot be used to enlarge the buffer. This is usually not needed since the buffer expands automatically.
virtual size_t wxStreamBuffer::Write ( const void *  buffer,
size_t  size 
)
virtual

Writes a block of the specified size using data of buffer.

The data are cached in a buffer before being sent in one block to the stream.

size_t wxStreamBuffer::Write ( wxStreamBuffer buffer)

See Read().