Exiv2::BasicIo Class Referenceabstract

An interface for simple binary IO. More...

#include <basicio.hpp>

Inheritance diagram for Exiv2::BasicIo:

Public Types

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

Public Member Functions

Manipulators
virtual int open ()=0
 Open the IO source using the default access mode. The default mode should allow for reading and writing. More...
 
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. More...
 
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. More...
 
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. More...
 
virtual int putb (byte data)=0
 Write one byte to the IO source. Current IO position is advanced by one byte. More...
 
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. More...
 
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. More...
 
virtual int getb ()=0
 Read one byte from the IO source. Current IO position is advanced by one byte. More...
 
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. More...
 
virtual int seek (long offset, Position pos)=0
 Move the current IO position. More...
 
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. More...
 
virtual int munmap ()=0
 Remove a mapping established with mmap(). If the mapped area is writeable, this ensures that changes are written back. More...
 

Creators

virtual ~BasicIo ()
 Destructor.
 
 BasicIo ()
 Default Constructor.
 

Accessors

bytebigBlock_
 this is allocated and populated by mmap()
 
virtual long tell () const =0
 Get the current IO position. More...
 
virtual size_t size () const =0
 Get the current size of the IO source in bytes. More...
 
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 reached 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 void populateFakeData ()
 Mark all the bNone blocks to bKnow. This avoids allocating memory for parts of the file that contain image-date (non-metadata/pixel data) More...
 

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

◆ close()

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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ getb()

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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ mmap()

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
isWriteableSet to true if the mapped area should be writeable (default is false).
Returns
A pointer to the mapped area.
Exceptions
ErrorIn case of failure.

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

◆ munmap()

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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ open()

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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ populateFakeData()

virtual void Exiv2::BasicIo::populateFakeData ( )
inlinevirtual

Mark all the bNone blocks to bKnow. This avoids allocating memory for parts of the file that contain image-date (non-metadata/pixel data)

Note
This method should be only called after the concerned data (metadata) are all downloaded from the remote file to memory.

Reimplemented in Exiv2::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ putb()

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

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

◆ read() [1/2]

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
rcountMaximum 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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ read() [2/2]

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
bufPointer to a block of memory into which the read data is stored. The memory block must be at least rcount bytes long.
rcountMaximum 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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ seek()

virtual int Exiv2::BasicIo::seek ( long  offset,
Position  pos 
)
pure virtual

Move the current IO position.

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

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

◆ size()

virtual size_t 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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ tell()

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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.

◆ transfer()

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
srcReference to another BasicIo instance. The entire contents of src are transferred to this object. The src object is invalidated by the method.
Exceptions
ErrorIn case of failure

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

◆ write() [1/2]

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

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

◆ write() [2/2]

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
srcReference 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::RemoteIo, Exiv2::MemIo, and Exiv2::FileIo.


The documentation for this class was generated from the following file: