Exiv2::FileIo Class Reference

Provides binary file IO by implementing the BasicIo interface. More...

#include <basicio.hpp>

Inheritance diagram for Exiv2::FileIo:

Public Member Functions

Creators
 FileIo (const std::string &path)
 Constructor that accepts the file path on which IO will be performed. The constructor does not open the file, and therefore never fails. More...
 
 ~FileIo () override
 Destructor. Flushes and closes an open file.
 
Manipulators
int open (const std::string &mode)
 Open the file using the specified mode. More...
 
int open () override
 Open the file using the default access mode of "rb". This method can also be used to "reopen" a file which will flush any unwritten data and reset the IO position to the start. More...
 
int close () override
 Flush and unwritten data and close the file . It is safe to call close on an already closed instance. More...
 
size_t write (const byte *data, size_t wcount) override
 Write data to the file. The file position is advanced by the number of bytes written. More...
 
size_t write (BasicIo &src) override
 Write data that is read from another BasicIo instance to the file. The file position is advanced by the number of bytes written. More...
 
int putb (byte data) override
 Write one byte to the file. The file position is advanced by one byte. More...
 
DataBuf read (size_t rcount) override
 Read data from the file. Reading starts at the current file position and the position is advanced by the number of bytes read. More...
 
size_t read (byte *buf, size_t rcount) override
 Read data from the file. Reading starts at the current file position and the position is advanced by the number of bytes read. More...
 
int getb () override
 Read one byte from the file. The file position is advanced by one byte. More...
 
void transfer (BasicIo &src) override
 Remove the contents of the file and then transfer data from the src BasicIo object into the empty file. More...
 
int seek (int64_t offset, Position pos) override
 Move the current IO position. More...
 
bytemmap (bool isWriteable=false) override
 Map the file into the process's address space. The file must be open before mmap() is called. If the mapped area is writeable, changes may not be written back to the underlying file until munmap() is called. The pointer is valid only as long as the FileIo object exists. More...
 
int munmap () override
 Remove a mapping established with mmap(). If the mapped area is writeable, this ensures that changes are written back to the underlying file. More...
 
virtual void setPath (const std::string &path)
 close the file source and set a new path.
 
- Public Member Functions inherited from Exiv2::BasicIo
virtual ~BasicIo ()=default
 Destructor.
 
void readOrThrow (byte *buf, size_t rcount, ErrorCode err=ErrorCode::kerCorruptedMetadata)
 Safe version of read() that checks for errors and throws an exception if the read was unsuccessful. More...
 
void seekOrThrow (int64_t offset, Position pos, ErrorCode err)
 Safe version of seek() that checks for errors and throws an exception if the seek was unsuccessful. More...
 

Accessors

size_t tell () const override
 Get the current file position. More...
 
size_t size () const override
 Flush any buffered writes and get the current file size in bytes. More...
 
bool isopen () const override
 Returns true if the file is open, otherwise false.
 
int error () const override
 Returns 0 if the file is in a valid state, otherwise nonzero.
 
bool eof () const override
 Returns true if the file position has reached the end, otherwise false.
 
const std::string & path () const noexcept override
 Returns the path of the file.
 
void populateFakeData () override
 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...
 
 FileIo (const FileIo &)=delete
 Copy constructor.
 
FileIooperator= (const FileIo &)=delete
 Assignment operator.
 

Additional Inherited Members

- Public Types inherited from Exiv2::BasicIo
enum  Position { beg, cur, end }
 Seek starting positions.
 
using UniquePtr = std::unique_ptr< BasicIo >
 BasicIo auto_ptr type.
 
- Public Attributes inherited from Exiv2::BasicIo
bytebigBlock_ {}
 this is allocated and populated by mmap()
 

Detailed Description

Provides binary file IO by implementing the BasicIo interface.

Examples
metacopy.cpp, and mrwthumb.cpp.

Constructor & Destructor Documentation

◆ FileIo()

Exiv2::FileIo::FileIo ( const std::string &  path)
explicit

Constructor that accepts the file path on which IO will be performed. The constructor does not open the file, and therefore never fails.

Parameters
pathThe full path of a file

Member Function Documentation

◆ close()

int Exiv2::FileIo::close ( )
overridevirtual

Flush and unwritten data and close the file . It is safe to call close on an already closed instance.

Returns
0 if successful;
Nonzero if failure;

Implements Exiv2::BasicIo.

Examples
mrwthumb.cpp.

◆ getb()

int Exiv2::FileIo::getb ( )
overridevirtual

Read one byte from the file. The file position is advanced by one byte.

Returns
The byte read from the file if successful;
EOF if failure;

Implements Exiv2::BasicIo.

◆ mmap()

byte* Exiv2::FileIo::mmap ( bool  isWriteable = false)
overridevirtual

Map the file into the process's address space. The file must be open before mmap() is called. If the mapped area is writeable, changes may not be written back to the underlying file until munmap() is called. The pointer is valid only as long as the FileIo object exists.

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.

Implements Exiv2::BasicIo.

◆ munmap()

int Exiv2::FileIo::munmap ( )
overridevirtual

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

Returns
0 if successful;
Nonzero if failure;

Implements Exiv2::BasicIo.

◆ open() [1/2]

int Exiv2::FileIo::open ( )
overridevirtual

Open the file using the default access mode of "rb". This method can also be used to "reopen" a file which will flush any unwritten data and reset the IO position to the start.

Returns
0 if successful;
Nonzero if failure.

Implements Exiv2::BasicIo.

◆ open() [2/2]

int Exiv2::FileIo::open ( const std::string &  mode)

Open the file using the specified mode.

This method can also be used to "reopen" a file which will flush any unwritten data and reset the IO position to the start. Although files can be opened in binary or text mode, this class has only been tested carefully in binary mode.

Parameters
modeSpecified that type of access allowed on the file. Valid values match those of the C fopen command exactly.
Returns
0 if successful;
Nonzero if failure.
Examples
mrwthumb.cpp.

◆ populateFakeData()

void Exiv2::FileIo::populateFakeData ( )
overridevirtual

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.

Implements Exiv2::BasicIo.

◆ putb()

int Exiv2::FileIo::putb ( byte  data)
overridevirtual

Write one byte to the file. The file 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;

Implements Exiv2::BasicIo.

◆ read() [1/2]

size_t Exiv2::FileIo::read ( byte buf,
size_t  rcount 
)
overridevirtual

Read data from the file. Reading starts at the current file 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 the file successfully;
0 if failure;

Implements Exiv2::BasicIo.

◆ read() [2/2]

DataBuf Exiv2::FileIo::read ( size_t  rcount)
overridevirtual

Read data from the file. Reading starts at the current file 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.

Implements Exiv2::BasicIo.

◆ seek()

int Exiv2::FileIo::seek ( int64_t  offset,
Position  pos 
)
overridevirtual

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;

Implements Exiv2::BasicIo.

◆ size()

size_t Exiv2::FileIo::size ( ) const
overridevirtual

Flush any buffered writes and get the current file size in bytes.

Returns
Size of the file in bytes;
-1 if failure;

Implements Exiv2::BasicIo.

◆ tell()

size_t Exiv2::FileIo::tell ( ) const
overridevirtual

Get the current file position.

Returns
Offset from the start of the file

Implements Exiv2::BasicIo.

◆ transfer()

void Exiv2::FileIo::transfer ( BasicIo src)
overridevirtual

Remove the contents of the file and then transfer data from the src BasicIo object into the empty file.

This method is optimized to simply rename the source file if the source object is another FileIo instance. The source BasicIo 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.

Note
If the caller doesn't have permissions to write to the file, an exception is raised and src is deleted.
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

Implements Exiv2::BasicIo.

Reimplemented in Exiv2::XPathIo.

◆ write() [1/2]

size_t Exiv2::FileIo::write ( BasicIo src)
overridevirtual

Write data that is read from another BasicIo instance to the file. The file 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 the file successfully;
0 if failure;

Implements Exiv2::BasicIo.

◆ write() [2/2]

size_t Exiv2::FileIo::write ( const byte data,
size_t  wcount 
)
overridevirtual

Write data to the file. The file 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 the file successfully;
0 if failure;

Implements Exiv2::BasicIo.

Examples
mrwthumb.cpp.

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