120ca87015
git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5000 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d
119 lines
4.1 KiB
C++
119 lines
4.1 KiB
C++
#ifndef BACKBUFFER_H
|
||
#define BACKBUFFER_H
|
||
|
||
#include "zipios-config.h"
|
||
|
||
#include <algorithm>
|
||
|
||
#include "meta-iostreams.h"
|
||
#include <vector>
|
||
|
||
#include "fcollexceptions.h"
|
||
#include "ziphead.h"
|
||
#include "zipheadio.h"
|
||
#include "virtualseeker.h"
|
||
#include "zipios_common.h"
|
||
|
||
namespace zipios {
|
||
|
||
using std::ios ;
|
||
using std::cerr ;
|
||
using std::endl ;
|
||
|
||
/** A BackBuffer instance is useful for reading the last part of a
|
||
file in an efficient manner, when it is not known exactly how far
|
||
back (towards the front!) to go, to find the start of the desired
|
||
data block. BackBuffer is a vector< unsigned char > that fills
|
||
itself with data from a file by reading chunks from the end of the
|
||
file progressing towards the start. Upon construction the
|
||
BackBuffer instance is associated with a file and a chunksize can
|
||
be specified. To read a chunk of the file into the BackBuffer call
|
||
readChunk(). */
|
||
class BackBuffer : public vector< unsigned char > {
|
||
public:
|
||
/** BackBuffer constructor.
|
||
@param is The istream to read the data from. The stream must be
|
||
seekable, as BackBuffer will reposition the file position to
|
||
read chunks from the back of the file.
|
||
@param vs
|
||
@param chunk_size specifies the size of the chunks to read the file
|
||
into the BackBuffer in.
|
||
@throw FCollException Thrown if the VirtualSeeker vs that has been
|
||
specified is invalid for the istream is. */
|
||
inline explicit BackBuffer( istream &is, VirtualSeeker vs = VirtualSeeker(),
|
||
int chunk_size = 1024 ) ;
|
||
/** Reads another chunk and returns the size of the chunk that has
|
||
been read. Returns 0 on I/O failure.
|
||
@param read_pointer When a new chunk is read in the already
|
||
stored bytes change position in the BackBuffer. read_pointer is
|
||
assumed by readChunk() to be a pointer into a position in the
|
||
BackBuffer, and is updated to point to the same position in the file
|
||
as it pointed to before the new chunk was read. */
|
||
inline int readChunk( int &read_pointer ) ;
|
||
|
||
private:
|
||
VirtualSeeker _vs ;
|
||
int _chunk_size ;
|
||
istream &_is ;
|
||
streampos _file_pos ;
|
||
|
||
};
|
||
|
||
BackBuffer::BackBuffer( istream &is, VirtualSeeker vs, int chunk_size )
|
||
: _vs ( vs ),
|
||
_chunk_size( chunk_size ),
|
||
_is ( is )
|
||
{
|
||
_vs.vseekg( is, 0, ios::end ) ;
|
||
_file_pos = _vs.vtellg( is ) ;
|
||
// Only happens if _vs.startOffset() is a position
|
||
// in the file that lies after _vs.endOffset(), which
|
||
// is clearly not a valid situation.
|
||
if ( _file_pos < 0 )
|
||
throw FCollException( "Invalid virtual file endings" ) ;
|
||
}
|
||
|
||
int BackBuffer::readChunk( int &read_pointer ) {
|
||
// Update chunk_size and file position
|
||
_chunk_size = min<int> ( static_cast< int >( _file_pos ), _chunk_size ) ;
|
||
_file_pos -= _chunk_size ;
|
||
_vs.vseekg( _is, _file_pos, ios::beg ) ;
|
||
// Make space for _chunk_size new bytes first in buffer
|
||
insert ( begin(), _chunk_size, static_cast< char > ( 0 ) ) ;
|
||
// Read in the next _chunk_size of bytes
|
||
|
||
readByteSeq ( _is, &( (*this)[ 0 ] ), _chunk_size ) ;
|
||
read_pointer += _chunk_size ;
|
||
|
||
if ( _is.good() )
|
||
return _chunk_size ;
|
||
else
|
||
return 0 ;
|
||
}
|
||
|
||
}
|
||
#endif
|
||
|
||
/** \file
|
||
The header file for BackBuffer
|
||
*/
|
||
|
||
/*
|
||
Zipios++ - a small C++ library that provides easy access to .zip files.
|
||
Copyright (C) 2000 Thomas S<>ndergaard
|
||
|
||
This library is free software; you can redistribute it and/or
|
||
modify it under the terms of the GNU Lesser General Public
|
||
License as published by the Free Software Foundation; either
|
||
version 2 of the License, or (at your option) any later version.
|
||
|
||
This library is distributed in the hope that it will be useful,
|
||
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Lesser General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Lesser General Public
|
||
License along with this library; if not, write to the Free Software
|
||
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
||
*/
|