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Location:
s32buf.h
Link against: estor.lib
MStreamBuf
Supported from 5.0
A stream buffer that provides a generic I/O interface for streamed data.
A stream buffer:
may be buffered or unbuffered
may provide read-only, write-only or read/write capability
may be seekable, or unseekable.
A seekable stream buffer maintains independent read and write pointers, which can be manipulated separately. This is unlike the RFile interface which maintains a single current position in the file. For example, file streams and memory streams are seekable streams, but socket, serial-comms, and filtered streams are not.
Objects of this type are used by the stream interface classes derived from RReadStream and RWriteStream.
The class has no member data.
Derive from this class, if the stream has no intermediate buffering capabilities, otherwise derive from TStreamBuf.
Defined in MStreamBuf:
SeekL(), Close(), DoReadL(), DoRelease(), DoSeekL(), DoSynchL(), DoWriteL(), ERead, EWrite, PushL(), Read(), ReadL(), Release(), SeekL(), SizeL(), Synch(), SynchL(), TMark, TRead, TWrite, TellL(), Write(), WriteL()
RReadStream::Source()RWriteStream::Sink()TInt ReadL(TAny* aPtr,TInt aMaxLength);
Reads data from the stream buffer into the specified memory location.
The function calls the virtual function DoReadL(TAny*,TInt) to implement this behaviour.
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TInt ReadL(TDes8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Reads data, asynchronously, from the stream buffer into the specified descriptor.
The function calls the virtual function DoReadL(TDes8&,TInt,TRequestStatus&) to implement this behaviour.
If the function leaves, then no read request will have been initiated.
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TInt ReadL(TDes8& aDes,TRequestStatus& aStatus);
Reads data, asynchronously, from the stream buffer into the specified descriptor.
The function calls the virtual function DoReadL(TDes8&,TInt,TRequestStatus&) to implement this behaviour. The maximum number of bytes to be read is the maximum length of the descriptor.
If the function leaves, then no read request will have been initiated.
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TStreamTransfer ReadL(MStreamInput& anInput,TStreamTransfer aTransfer);
Reads data from the stream buffer into the specified data sink.
The function calls the virtual function DoReadL(MStreamInput&,TStreamTransfer) to implement this behaviour.
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TInt ReadL(MStreamInput& anInput,TInt aMaxLength);
Reads data from the stream buffer into the specified data sink.
The function uses the virtual function DoReadL(MStreamInput&,TStreamTransfer) to implement this behaviour.
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void ReadL(MStreamInput& anInput);
Reads data from the stream buffer into the specified data sink.
The function uses the virtual function DoReadL(MStreamInput&,TStreamTransfer) to implement this behaviour.
No explicit limit is placed on the amount of data that can be read.
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TInt Read(TDes8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Reads data, asynchronously, from the stream buffer into the specified descriptor; request completion is guaranteed, even if request initiation fails.
The function calls the virtual function DoReadL(TDes8&,TInt,TRequestStatus&) to implement this behaviour.
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TInt Read(TDes8& aDes,TRequestStatus& aStatus);
Reads data, asynchronously, from the stream buffer into the specified descriptor; request completion is guaranteed, even if request initiation fails.
The function calls the virtual function DoReadL(TDes8&,TInt,TRequestStatus&) to implement this behaviour. The maximum number of bytes to be read is the value of the maximum length of the descriptor.
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void WriteL(const TAny* aPtr,TInt aLength);
Writes data from the specified memory location into the stream buffer.
The function calls the virtual function DoWriteL(TAny*,TInt) to implement this behaviour.
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TInt WriteL(const TDesC8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Writes data, asynchronously, from the specified descriptor into the stream buffer.
The function calls the virtual function DoWriteL(const TDesC8&,TInt,TRequestStatus&) to implement this behaviour.
If the function leaves, then no write request will have been initiated.
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TInt WriteL(const TDesC8& aDes,TRequestStatus& aStatus);
Writes data, asynchronously, from the specified descriptor into the stream buffer.
The function calls the virtual function DoWriteL(const TDesC8&,TInt,TRequestStatus&) to implement this behaviour. The maximum number of bytes to be written is the value of the maximum length of the descriptor.
If the function leaves, then no write request will have been initiated.
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TStreamTransfer WriteL(MStreamOutput& anOutput,TStreamTransfer aTransfer);
Writes data into the stream buffer from the specified data source.
The function calls the virtual function DoWriteL(MStreamOutput&,TStreamTransfer) to implement this behaviour.
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TInt WriteL(MStreamOutput& anOutput,TInt aMaxLength);
Writes data into the stream buffer from the specified data source.
The function calls the virtual function DoWriteL(MStreamOutput&,TStreamTransfer) to implement this behaviour.
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void WriteL(MStreamOutput& anOutput);
Writes data into the stream buffer from the specified data source.
The function calls the virtual function DoWriteL(MStreamOutput&,TStreamTransfer) to implement this behaviour.
No explicit limit is placed on the amount of data that can be written.
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TInt Write(const TDesC8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Writes data, asynchronously, from the specified descriptor into the stream buffer; request completion is guaranteed, even if request initiation fails.
The function calls the virtual function DoWriteL(const TDesC8&,TInt,TRequestStatus&) to implement this behaviour.
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TInt Write(const TDesC8& aDes,TRequestStatus& aStatus);
Writes data, asynchronously, from the specified descriptor into the stream buffer; request completion is guaranteed, even if request initiation fails.
The function calls the virtual function DoWriteL(const TDesC8&,TInt,TRequestStatus&) to implement this behaviour. The maximum number of bytes to be written is the value of the maximum length of the descriptor.
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void SeekL(TMark aMark,TStreamPos aPos);
Moves the position of the read or write mark in the stream.
The new position is calculated by adding the specified value to the position of the beginning of the stream.
The function calls virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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SeekL() to move both the read and write marks.TStreamPos SeekL(TMark aMark,TStreamLocation aLocation,TInt anOffset=0);
Moves the position of the read mark or the write mark in the stream.
The new position is calculated by adding the specified offset to one of:
the position of the beginning of the stream
the position of the end of the stream
the position of the current read mark or write mark.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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SeekL() to move both the read and write marks.TStreamPos SeekL(TRead,TStreamLocation aLocation,TInt anOffset=0);
Moves the position of the read mark in the stream.
The new position is calculated by adding the specified offset to one of:
the position of the beginning of the stream
the position of the end of the stream
the position of the current read mark.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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TStreamPos SeekL(TWrite,TStreamLocation aLocation,TInt anOffset=0);
Moves the position of the write mark in the stream.
The new position is calculated by adding the specified offset to one of:
the position of the beginning of the stream
the position of the end of the stream
the position of the current write mark.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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TStreamPos SeekL(TRead,TInt anOffset);
Moves the position of the read mark in the stream by the specified offset.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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TStreamPos SeekL(TWrite,TInt anOffset);
Moves the position of the write mark in the stream by the specified offset.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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TInt Synch();
Synchronises the stream buffer with the stream, returning any error.
In effect, this ensures that buffered data is delivered to the stream.
This function calls SynchL() inside a TRAPD harness and returns the leave code if a leave occurs.
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void SynchL();
Synchronises the stream buffer with the stream, leaving if any error occurs.
In effect, this ensures that buffered data is delivered to the stream.
The function calls the virtual function DoSynchL() to implement this behaviour.
void Release();
Frees resources before abandoning the stream buffer.
The function calls the virtual function DoRelease() to implement this behaviour.
Release() is called by both RReadStream::Release() and RWriteStream::Release().
void Close();
Closes the stream buffer.
This function attempts to synchronise buffered data with the stream before freeing any resources. All errors are ignored.
void PushL();
Puts a cleanup item for this object onto the cleanup stack.
This allows allocated resources to be cleaned up if a subsequent leave occurs.
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TStreamPos TellL(TRead) const;
Gets the position of the read mark within the stream.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this behaviour.
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TStreamPos TellL(TWrite)
const;
Gets the position of the write mark within the stream.
The function calls the virtual function DoSeekL(TMark,TStreamLocation,TInt) to implement this
behaviour.
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TInt SizeL() const;
Gets the size of the stream.
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private : virtual TInt DoReadL(TAny* aPtr,TInt aMaxLength);
Reads data from the stream buffer into the specified memory location.
This is called by ReadL(TAny*,TInt).
This class does not provide buffering capabilities and, therefore, this implementation raises a STORE-Stream 10 panic. Buffering capabilities are supported by the derived class, TStreamBuf, which provides an implementation.
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private : virtual TInt DoReadL(TDes8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Reads data from the stream buffer into the specified descriptor.
This function is called by ReadL(TDes8&,TInt,TRequestStatus&).
This implementation deals with the request synchronously, and completes the request with KErrNone. Other implementations may choose to deal with this in a true asynchronous manner.
In addition, the read operation itself uses the DoReadL(TAny*,TInt) variant.
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private : virtual TStreamTransfer DoReadL(MStreamInput& anInput,TStreamTransfer aTransfer);
Reads data from the stream into the specified data sink.
It is called by ReadL(MStreamInput&,TStreamTransfer).
This implementation calls the sink's ReadFromL() function, which performs the read (transfer) operation.
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DoReadL() is called for streams that do not have buffering capabilities, and that are derived directly from this class.private : virtual void DoWriteL(const TAny* aPtr,TInt aLength);
Writes data from the specified memory location into the stream buffer.
This is called by WriteL(const TAny*,TInt).
This class does not provide buffering capabilities and, therefore, this implementation raises a STORE-Stream 11 panic. Buffering capabilities are supported by the derived class, TStreamBuf, which provides an implementation.
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private : virtual TInt DoWriteL(const TDesC8& aDes,TInt aMaxLength,TRequestStatus& aStatus);
Writes data from the specified descriptor into this stream buffer.
This function is called by WriteL(const TDesC8&,TInt,TRequestStatus&).
This implementation deals with the request synchronously, and completes the request with KErrNone. Other implementations may choose to deal with this in a true asynchronous manner.
In addition, the write operation itself uses the DoWriteL(TAny*,TInt) variant.
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private : virtual TStreamTransfer DoWriteL(MStreamOutput& anOutput,TStreamTransfer aTransfer);
Writes data to the stream from the specified data source.
It is called by WriteL(MStreamOutput&,TStreamTransfer).
This implementation calls the target stream output object's WriteToL() function, which performs the write (transfer) operation.
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DoReadL() is called for streams that do not have buffering capabilities, and that are derived directly from this class.private : virtual TStreamPos DoSeekL(TMark aMark,TStreamLocation aLocation,TInt anOffset);
Moves the position of the read/write mark in the stream.
The new position is calculated by adding the specified offset to one of:
the beginning of the stream
the end of the stream
the current position of the read/write mark.
It is called by all variations of SeekL() and Seek().
Not all streams are seekable, and this default implementation raises a STORE-Stream 12 panic. Streams that are seekable must provide a suitable implementation.
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private : virtual void DoRelease();
Frees resources before abandoning the stream buffer.
It is called by Release().
This implementation is empty, but classes derived from MStreamBuf can provide their own implementation, if necessary.
private : virtual void DoSynchL();
Synchronises the stream buffer with the stream, leaving if any error occurs.
In effect, this ensures that buffered data is delivered to the stream.
It is called by SynchL().
This implementation is empty, but classes derived from MStreamBuf can provide their own implementation, if necessary.
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TRead
Indicates that an operation applies to the read mark in a stream or to the read area in an stream buffer.
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TWrite
Indicates that an operation applies to the write mark in a stream or to the write area in an stream buffer.
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typedef TInt TMark;
Used to identify the type of mark in a stream.
The type is used by functions of this class and derived classes that perform seek operations to marks within a stream.
The type uses the ERead and EWrite enumeration values, as bit flags, to identify the read and write marks respectively.
ERead is an MStreamBuf::TRead enumerator. EWrite is an MStreamBuf::EWrite enumerator.
Copyright ©2002 Symbian Ltd. 6.1-00174 |
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