File Processing

[jimin-kiim]

• File Stream Class
• File Processing Overview
• Text mode and Binary mode
• open()
• Get and Put stream positioning
• Binary file processing and memblock

[jimin-kiim]

File Processing Overview

1. opening a file
   • text file? or binary file?
   • in the case of writing, is it appending mode? or truncating?
   • is file position automatic? or user-control?
2. processing(reading/writing) file
3. closing the file

[jimin-kiim]

Text mode and Binary mode

• generally, binary file processing method is used.
• text mode is a kind of exceptional case
• 129 in text mode : stored as 3 character, 3 bytes of memory (3 ASCII code; ASCII code 1 character : 1 byte)
• 129 in binary mode(image, video, sound) : stored as 10000001, 1 byte of memory

[jimin-kiim]

Specifying modes for member function 'open'

• either using only one mode or combination of several modes( with 'or operator' | ) are available

Different Modes

• ios::in
  opening the file as 'read-only' mode (considering the file as an input)
• ios::out
  opening the file as 'write-only' mode (considering the file as a destination for output)
• ios::binary
  opening the file in binay mode
• ios::ate
  setting the initial position as the end of the file.
  unless this flag is set, the initial position is the beginning of the file.
• ios::app
  performing output operation at the end of the file.
  appending the content to the current content of the file.
• ios:: trunc
  if the file is opened for output operations and it already existed,
  then its previous content is deleted and replaced by the new one.

Default mode

ofstream : ios::out
ifstream : ios::in
fstream : ios::in|ios::out

[jimin-kiim]

Get and Put Stream Positioning

reading - get, writing - put

• tellg(), tellp()
  • returns the current get/put position
• seekg(), seekp()
  • changes the location of the get/put position
  • seekg(position) or seekg(offset, direction)
  • modes
    • ios::beg : offset counted from the beginning of the stream
    • ios::cur : offset counted from the current position
    • ios::end : offset counted from the end of the stream

[jimin-kiim]

Binary file processing and memblock

• write( memory_block, size );
• read( memory_block, size ); // the file is read as much as the 'size' bytes and stored into the 'memory_block'
• memory block: is a pointer that points to some memory block
• size: the unit of size if bytes

[jimin-kiim]

File Stream Class

• ofstream(output file stream) : stream class to write on files
• ifstream(input file stream) : stream class to read from files
• fstream(file stream) : stream class to read and write from/to files