Exiv2::BasicIo Class Reference

An interface for simple binary IO. More...

#include <basicio.hpp>

Inheritance diagram for Exiv2::BasicIo:

Inheritance graph
[legend]
List of all members.

Public Types

typedef std::auto_ptr< BasicIoAutoPtr
 BasicIo auto_ptr type.
enum  Position { beg, cur, end }
 Seek starting positions.

Public Member Functions

Creators
virtual ~BasicIo ()
 Destructor.
Manipulators
virtual int open ()=0
 Open the IO source using the default access mode. The default mode should allow for reading and writing.
virtual int close ()=0
 Close the IO source. After closing a BasicIo instance can not be read or written. Closing flushes any unwritten data. It is safe to call close on a closed instance.
virtual long write (const byte *data, long wcount)=0
 Write data to the IO source. Current IO position is advanced by the number of bytes written.
virtual long write (BasicIo &src)=0
 Write data that is read from another BasicIo instance to the IO source. Current IO position is advanced by the number of bytes written.
virtual int putb (byte data)=0
 Write one byte to the IO source. Current IO position is advanced by one byte.
virtual DataBuf read (long rcount)=0
 Read data from the IO source. Reading starts at the current IO position and the position is advanced by the number of bytes read.
virtual long read (byte *buf, long rcount)=0
 Read data from the IO source. Reading starts at the current IO position and the position is advanced by the number of bytes read.
virtual int getb ()=0
 Read one byte from the IO source. Current IO position is advanced by one byte.
virtual void transfer (BasicIo &src)=0
 Remove all data from this object's IO source and then transfer data from the src BasicIo object into this object.
virtual int seek (long offset, Position pos)=0
 Move the current IO position.
virtual bytemmap (bool isWriteable=false)=0
 Direct access to the IO data. For files, this is done by mapping the file into the process's address space; for memory blocks, this allows direct access to the memory block.
virtual int munmap ()=0
 Remove a mapping established with mmap(). If the mapped area is writeable, this ensures that changes are written back.
Accessors
virtual long tell () const =0
 Get the current IO position.
virtual long size () const =0
 Get the current size of the IO source in bytes.
virtual bool isopen () const =0
 Returns true if the IO source is open, otherwise false.
virtual int error () const =0
 Returns 0 if the IO source is in a valid state, otherwise nonzero.
virtual bool eof () const =0
 Returns true if the IO position has reach the end, otherwise false.
virtual std::string path () const =0
 Return the path to the IO resource. Often used to form comprehensive error messages where only a BasicIo instance is available.
virtual BasicIo::AutoPtr temporary () const =0
 Returns a temporary data storage location. This is often needed to rewrite an IO source.

Protected Member Functions

Creators
 BasicIo ()
 Default Constructor.

Detailed Description

An interface for simple binary IO.

Designed to have semantics and names similar to those of C style FILE* operations. Subclasses should all behave the same so that they can be interchanged.


Member Function Documentation

virtual int Exiv2::BasicIo::close  )  [pure virtual]
 

Close the IO source. After closing a BasicIo instance can not be read or written. Closing flushes any unwritten data. It is safe to call close on a closed instance.

Returns:
0 if successful;
Nonzero if failure.

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual int Exiv2::BasicIo::getb  )  [pure virtual]
 

Read one byte from the IO source. Current IO position is advanced by one byte.

Returns:
The byte read from the IO source if successful;
EOF if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual byte* Exiv2::BasicIo::mmap bool  isWriteable = false  )  [pure virtual]
 

Direct access to the IO data. For files, this is done by mapping the file into the process's address space; for memory blocks, this allows direct access to the memory block.

Parameters:
isWriteable Set to true if the mapped area should be writeable (default is false).
Returns:
A pointer to the mapped area.
Exceptions:
Error In case of failure.

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual int Exiv2::BasicIo::munmap  )  [pure virtual]
 

Remove a mapping established with mmap(). If the mapped area is writeable, this ensures that changes are written back.

Returns:
0 if successful;
Nonzero if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual int Exiv2::BasicIo::open  )  [pure virtual]
 

Open the IO source using the default access mode. The default mode should allow for reading and writing.

This method can also be used to "reopen" an IO source which will flush any unwritten data and reset the IO position to the start. Subclasses may provide custom methods to allow for opening IO sources differently.

Returns:
0 if successful;
Nonzero if failure.

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual int Exiv2::BasicIo::putb byte  data  )  [pure virtual]
 

Write one byte to the IO source. Current IO position is advanced by one byte.

Parameters:
data The single byte to be written.
Returns:
The value of the byte written if successful;
EOF if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual long Exiv2::BasicIo::read byte buf,
long  rcount
[pure virtual]
 

Read data from the IO source. Reading starts at the current IO position and the position is advanced by the number of bytes read.

Parameters:
buf Pointer to a block of memory into which the read data is stored. The memory block must be at least rcount bytes long.
rcount Maximum number of bytes to read. Fewer bytes may be read if rcount bytes are not available.
Returns:
Number of bytes read from IO source successfully;
0 if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual DataBuf Exiv2::BasicIo::read long  rcount  )  [pure virtual]
 

Read data from the IO source. Reading starts at the current IO position and the position is advanced by the number of bytes read.

Parameters:
rcount Maximum number of bytes to read. Fewer bytes may be read if rcount bytes are not available.
Returns:
DataBuf instance containing the bytes read. Use the DataBuf::size_ member to find the number of bytes read. DataBuf::size_ will be 0 on failure.

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual int Exiv2::BasicIo::seek long  offset,
Position  pos
[pure virtual]
 

Move the current IO position.

Parameters:
offset Number of bytes to move the position relative to the starting position specified by pos
pos Position from which the seek should start
Returns:
0 if successful;
Nonzero if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual long Exiv2::BasicIo::size  )  const [pure virtual]
 

Get the current size of the IO source in bytes.

Returns:
Size of the IO source in bytes;
-1 if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual long Exiv2::BasicIo::tell  )  const [pure virtual]
 

Get the current IO position.

Returns:
Offset from the start of IO if successful;
-1 if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual BasicIo::AutoPtr Exiv2::BasicIo::temporary  )  const [pure virtual]
 

Returns a temporary data storage location. This is often needed to rewrite an IO source.

For example, data may be read from the original IO source, modified in some way, and then saved to the temporary instance. After the operation is complete, the BasicIo::transfer method can be used to replace the original IO source with the modified version. Subclasses are free to return any class that derives from BasicIo.

Returns:
An instance of BasicIo on success
Exceptions:
Error In case of failure

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual void Exiv2::BasicIo::transfer BasicIo src  )  [pure virtual]
 

Remove all data from this object's IO source and then transfer data from the src BasicIo object into this object.

The source object is invalidated by this operation and should not be used after this method returns. This method exists primarily to be used with the BasicIo::temporary() method.

Parameters:
src Reference to another BasicIo instance. The entire contents of src are transferred to this object. The src object is invalidated by the method.
Exceptions:
Error In case of failure

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual long Exiv2::BasicIo::write BasicIo src  )  [pure virtual]
 

Write data that is read from another BasicIo instance to the IO source. Current IO position is advanced by the number of bytes written.

Parameters:
src Reference to another BasicIo instance. Reading start at the source's current IO position
Returns:
Number of bytes written to IO source successfully;
0 if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.

virtual long Exiv2::BasicIo::write const byte data,
long  wcount
[pure virtual]
 

Write data to the IO source. Current IO position is advanced by the number of bytes written.

Parameters:
data Pointer to data. Data must be at least wcount bytes long
wcount Number of bytes to be written.
Returns:
Number of bytes written to IO source successfully;
0 if failure;

Implemented in Exiv2::FileIo, and Exiv2::MemIo.


The documentation for this class was generated from the following file:
Generated on Thu Dec 31 03:57:57 2009 for Exiv2 by  doxygen 1.3.9.1