## wxStreamBuffer

Derived from

None

Include files

<wx/stream.h>

See also

wxStreamBase

Members

wxStreamBuffer::wxStreamBuffer
wxStreamBuffer::~wxStreamBuffer
wxStreamBuffer::Read
wxStreamBuffer::Write
wxStreamBuffer::GetChar
wxStreamBuffer::PutChar
wxStreamBuffer::Tell
wxStreamBuffer::Seek
wxStreamBuffer::ResetBuffer
wxStreamBuffer::SetBufferIO
wxStreamBuffer::GetBufferStart
wxStreamBuffer::GetBufferEnd
wxStreamBuffer::GetBufferPos
wxStreamBuffer::GetIntPosition
wxStreamBuffer::SetIntPosition
wxStreamBuffer::GetLastAccess
wxStreamBuffer::Fixed
wxStreamBuffer::Flushable
wxStreamBuffer::FlushBuffer
wxStreamBuffer::FillBuffer
wxStreamBuffer::GetDataLeft
wxStreamBuffer::Stream

### wxStreamBuffer::wxStreamBuffer

wxStreamBuffer(wxStreamBase& stream, BufMode mode)

Constructor, creates a new stream buffer using stream as a parent stream and mode as the IO mode. mode can 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'' */

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.

wxStreamBuffer(const wxStreamBuffer&buffer)

Constructor. It 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.

See also

wxStreamBuffer:SetBufferIO

### wxStreamBuffer::~wxStreamBuffer

wxStreamBuffer(~wxStreamBuffer)

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

### wxStreamBuffer::Read

size_t Read(void *buffer, size_t size)

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.

Return value

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 Read(wxStreamBuffer *buffer)

Reads a buffer. The function returns when buffer is full or when there isn't data anymore in the current buffer.

See also

wxStreamBuffer::Write

### wxStreamBuffer::Write

size_t Write(const void *buffer, size_t size)

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 Write(wxStreamBuffer *buffer)

See Read.

### wxStreamBuffer::GetChar

char GetChar()

Gets a single char from the stream buffer. It acts like the Read call.

Problem

You aren't directly notified if an error occurred during the IO call.

See also

wxStreamBuffer::Read

### wxStreamBuffer::PutChar

void PutChar(char c)

Puts a single char to the stream buffer.

Problem

You aren't directly notified if an error occurred during the IO call.

See also

wxStreamBuffer::Read

### wxStreamBuffer::Tell

off_t Tell() const

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.

Return value

Returns the current position in the stream if possible, wxInvalidOffset in the other case.

### wxStreamBuffer::Seek

off_t Seek(off_t pos, wxSeekMode mode)

Changes the current position.

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.

Return value

Upon successful completion, it returns the new offset as measured in bytes from the beginning of the stream. Otherwise, it returns wxInvalidOffset.

### wxStreamBuffer::ResetBuffer

void ResetBuffer()

Resets to the initial state variables concerning the buffer.

### wxStreamBuffer::SetBufferIO

void SetBufferIO(char* buffer_start, char* buffer_end)

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 constructor
wxStreamBuffer::Fixed
wxStreamBuffer::Flushable

void 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.

Remark

The created IO buffer is growable by the object.

See also

wxStreamBuffer::Fixed
wxStreamBuffer::Flushable

### wxStreamBuffer::GetBufferStart

void * GetBufferStart() const

Returns a pointer on the start of the stream buffer.

### wxStreamBuffer::GetBufferEnd

void * GetBufferEnd() const

Returns a pointer on the end of the stream buffer.

### wxStreamBuffer::GetBufferPos

void * GetBufferPos() const

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

### wxStreamBuffer::GetIntPosition

off_t GetIntPosition() const

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

### wxStreamBuffer::SetIntPosition

void 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.

### wxStreamBuffer::GetLastAccess

size_t GetLastAccess() const

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

### wxStreamBuffer::Fixed

void 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

wxStreamBuffer::SetBufferIO

### wxStreamBuffer::Flushable

void Flushable(bool flushable)

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

### wxStreamBuffer::FlushBuffer

bool FlushBuffer()

Flushes the IO buffer.

### wxStreamBuffer::FillBuffer

bool FillBuffer()

Fill the IO buffer.

### wxStreamBuffer::GetDataLeft

size_t GetDataLeft()

Returns the amount of available data in the buffer.

### wxStreamBuffer::Stream

wxStreamBase* Stream()

Returns the parent stream of the stream buffer.