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wxStreamBuffer

Derived from

None

Include files

<wx/stream.h>

See also

wxStreamBase

Members

wxStreamBuffer::wxStreamBuffer
wxStreamBuffer::~wxStreamBuffer
wxStreamBuffer::Read
wxStreamBuffer::Write
wxStreamBuffer::WriteBack
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.

Warning

All errors and messages linked to the stream are stored in the stream object.

   streambuffer.Read(...);
   streambuffer2.Read(...); /* This one 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 may not work: it isn't completely finished. You can create "memory" streams by this way:

  wxStreamBuffer *sb = new wxStreamBuffer(wxStreamBuffer::read)
  wxInputStream *input = new wxInputStream(sb);

  sb->Fixed(FALSE); // It can change the size of the buffer.

  // input is now a read-only memory stream.
But you should take care when destroying the stream buffer yourself.

wxStreamBuffer(const wxStreamBuffer&buffer)

Constructor. It initializes the stream buffer with the data of the specified stream buffer. The new stream buffer is nearly exactly the same as the original: it has the same attributes, the same size, the same position, shares the same internal buffer. The interresting point is that they can differ in the future but the root is the same.

Warning

The fact that the two stream buffers shared the same buffer could generate segmentation violation if the parent is destroyed and the children continues operating. 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. In the case of a children stream buffer, the internal buffer isn't freed, this is the job of the parent. The "Write-Back" buffer is freed.


wxStreamBuffer::Read

size_t Read(void *buffer, size_t size)

Reads a block of the specified size and stores datas in buffer. This function uses also the "Write-Back" buffer: in the case there are datas waiting in this buffer, they are used before anything else. After that, if there are still datas to be read, the stream is read and the stream buffer position is incremented.

Return value

It returns the real read size. If returned size is different of the specified size, an error occured and should be tested using LastError.

See also

wxStreamBuffer::WriteBack

size_t Read(wxStreamBuffer *buffer)

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


wxStreamBuffer::Write

size_t Write(const void *buffer, size_t size)

Writes a block of the specified size using datas of buffer. The datas are cached in a buffer before being sent in one block to the stream.

size_t Write(wxStreamBuffer *buffer)

See Read.


wxStreamBuffer::WriteBack

size_t WriteBack(const char* buffer, size_t size)

This function is only useful in read mode. It is the manager of the "Write-Back" buffer. This buffer acts like a temporary buffer where datas which has to be read during the next read IO call are put. This is useful when you get a big block of data which you didn't want to read: you can replace them at the top of the input queue by this way.

Return value

Returns the amount of bytes saved in the Write-Back buffer.

size_t WriteBack(char c)

This function acts like the previous one except that it takes only one character: it is sometimes shorter to use than the generic function.


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 occured 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 occured 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'll 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 grow 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

char * GetBufferStart() const

Returns a pointer on the start of the stream buffer.


wxStreamBuffer::GetBufferEnd

char * GetBufferEnd() const

Returns a pointer on the end of the stream buffer.


wxStreamBuffer::GetBufferPos

char * 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()

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: specify 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 datas 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 datas in the buffer.


wxStreamBuffer::Stream

wxStreamBase* Stream()

Returns the parent stream of the stream buffer.