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:: com :: sun :: star :: io ::

interface XInputStream
Description
This is the basic interface to read data from a stream.

See the streaming document for further information on chaining and piping streams.


Methods' Summary
readBytes reads the specified number of bytes in the given sequence.  
readSomeBytes reads the available number of bytes, at maximum nMaxBytesToRead.  
skipBytes skips the next nBytesToSkip bytes (must be positive).  
available states how many bytes can be read or skipped without blocking.  
closeInput closes the stream.  
Methods' Details
readBytes
long
readBytes( [out] sequence< byte >  aData,
[in] long  nBytesToRead )
raises( NotConnectedException,
BufferSizeExceededException,
IOException );

Description
reads the specified number of bytes in the given sequence.

The return value specifies the number of bytes which have been put into the sequence. A difference between nBytesToRead and the return value indicates that EOF has been reached. This means that the method blocks until the specified number of bytes are available or the EOF is reached.

Parameter aData
after the call, the byte sequence contains the requested number of bytes (or less as a sign of EOF).

C++ only : Note that for unbridged (e.g., in-process) calls, using the same sequence for repetive readBytes()-calls can bear a performance advantage. The callee can put the data directly into the sequence so that no buffer reallocation is necessary. But this holds only when

  1. neither caller nor callee keep a second reference to the same sequence.
  2. the sequence is pre-allocated with the requested number of bytes.
  3. the same sequence is reused ( simply preallocationg a new sequence for every call bears no advantage ).
  4. the call is not bridged (e.g., betweeen different compilers or different processes ).
If the same 'optimized' code runs against an interface in a different process, there is an unnecessary memory allocation/deallocation (the out parameter is of course NOT transported over the connection), but this should be negligible compared to a synchron call.
Parameter nBytesToRead
the total number of bytes to read
readSomeBytes
long
readSomeBytes( [out] sequence< byte >  aData,
[in] long  nMaxBytesToRead )
raises( NotConnectedException,
BufferSizeExceededException,
IOException );

Description
reads the available number of bytes, at maximum nMaxBytesToRead.

This method is very similar to the readBytes method, except that it has different blocking behaviour. The method blocks as long as at least 1 byte is available or EOF has been reached. EOF has only been reached, when the method returns 0 and the corresponding byte sequence is empty. Otherwise, after the call, aData contains the available, but no more than nMaxBytesToRead, bytes.

Parameter aData
contains the data read from the stream.
Parameter nMaxBytesToRead
The maximum number of bytes to be read from this stream during the call.
See also
XInputStream::readBytes
skipBytes
void
skipBytes( [in] long  nBytesToSkip )
raises( NotConnectedException,
BufferSizeExceededException,
IOException );

Description
skips the next nBytesToSkip bytes (must be positive).

It is up to the implementation whether this method is blocking the thread or not.

Parameter nBytesToSkip
number of bytes to skip
available
long
available()
raises( NotConnectedException,
IOException );

Description
states how many bytes can be read or skipped without blocking.

Note: This method offers no information on whether the EOF has been reached.

closeInput
void
closeInput()
raises( NotConnectedException,
IOException );

Description
closes the stream.

Users must close the stream explicitly when no further reading should be done. (There may exist ring references to chained objects that can only be released during this call. Thus not calling this method would result in a leak of memory or external resources.)

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