Source manager that allow us to read from a std::istream. More...

#include <jpeg.hpp>

Public Member Functions
	source_manager (std::istream &is)
	Constructor.
	~source_manager ()
	Destructor.
boolean	fill_input_buffer ()
	Fill the input buffer with new data.
void	skip_input_data (long num_bytes)
	Skip some bytes in the input buffer.
Public Attributes
struct jpeg_source_mgr	pub
	"public" fields, needed by the jpeg library.
Private Attributes
std::istream &	m_input
	The stream from which we get data.
const JOCTET *	m_buffer
	Pointer on the begining of the buffer.
const unsigned int	m_buffer_size
	Number of bytes in the buffer.
unsigned int	m_stream_size
	The size of the stream.
unsigned int	m_stream_position
	The current position in the stream.

Detailed Description

Source manager that allow us to read from a std::istream.

Author:: Julien Jorge

Definition at line 88 of file jpeg.hpp.

Constructor & Destructor Documentation

claw::graphic::jpeg::reader::source_manager::source_manager ( std::istream & is )

Constructor.

Parameters:

is	The stream we read from.

Definition at line 97 of file jpeg_reader.cpp.

References m_buffer, m_buffer_size, m_stream_size, and pub.

  : m_input(is), m_buffer_size(1024), m_stream_position(0)
{
  std::istream::pos_type pos = is.tellg();

  is.seekg( 0 , std::ios_base::end );
  m_stream_size = is.tellg() ;

  is.seekg( pos, std::ios_base::beg ) ;

  m_buffer = new JOCTET[m_buffer_size];
  pub.bytes_in_buffer = 0;
} // jpeg::reader::source_manager::source_manager()

claw::graphic::jpeg::reader::source_manager::~source_manager ( )

Destructor.

Definition at line 115 of file jpeg_reader.cpp.

{
  delete[] m_buffer;
} // jpeg::reader::source_manager::~source_manager()

Member Function Documentation

boolean claw::graphic::jpeg::reader::source_manager::fill_input_buffer ( )

Fill the input buffer with new data.

Definition at line 125 of file jpeg_reader.cpp.

{
  unsigned int n = std::min( m_buffer_size, m_stream_size - m_stream_position );
  m_input.read( (char*)m_buffer, n );

  pub.next_input_byte = m_buffer;
  pub.bytes_in_buffer = n;

  m_stream_position += n;

  if (m_input)
    return TRUE;
  else
    return FALSE;
} // jpeg::reader::source_manager::fill_input_buffer()

void claw::graphic::jpeg::reader::source_manager::skip_input_data ( long num_bytes )

Skip some bytes in the input buffer.

Parameters:

num_bytes The number of bytes to skip.

Definition at line 147 of file jpeg_reader.cpp.

References CLAW_PRECOND.

{
  CLAW_PRECOND(num_bytes >=0);

  if ( (size_t)num_bytes <= pub.bytes_in_buffer )
    {
      pub.next_input_byte += num_bytes;
      pub.bytes_in_buffer -= num_bytes;
    }
  else
    {
      num_bytes -= pub.bytes_in_buffer;
      
      long div = num_bytes / m_buffer_size;
      long rest = num_bytes % m_buffer_size;

      for (long i=0; i!=(div+1); ++i)
        fill_input_buffer();

      pub.next_input_byte += rest;
      pub.bytes_in_buffer -= rest;
    }
} // jpeg::reader::source_manager::skip_input_data()