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

interface XInputStream

Base Interface
com::sun::star::uno::XInterface

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

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



Known Services which Export this Interface

com::sun::star::io::MarkableInputStream allows to set marks in an inputstream and to later jump back to these marks.
com::sun::star::io::Pipe the implementation of an output stream and an input stream.
com::sun::star::io::MarkableInputStream allows to set marks in an inputstream and to later jump back to these marks.
com::sun::star::io::Pipe the implementation of an output stream and an input stream.

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 ( com::sun::star::io::NotConnectedException, com::sun::star::io::BufferSizeExceededException, com::sun::star::io::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.
readSomeBytes
 
long
readSomeBytes(
[ out ] sequence< byte > aData,
[ in ] long nMaxBytesToRead )
raises ( com::sun::star::io::NotConnectedException, com::sun::star::io::BufferSizeExceededException, com::sun::star::io::IOException );

Description
reads the available number of bytes at maximum nMaxBytesToRead .

This method blocks the thread until at least one byte is available.

skipBytes
 
void
skipBytes(
[ in ] long nBytesToSkip )
raises ( com::sun::star::io::NotConnectedException, com::sun::star::io::BufferSizeExceededException, com::sun::star::io::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.

available
 
long
available( )
raises ( com::sun::star::io::NotConnectedException, com::sun::star::io::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 ( com::sun::star::io::NotConnectedException, com::sun::star::io::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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