mirror of
https://github.com/upx/upx
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138 lines
3.9 KiB
C++
138 lines
3.9 KiB
C++
/* filter.h --
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This file is part of the UPX executable compressor.
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Copyright (C) 1996-2003 Markus Franz Xaver Johannes Oberhumer
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Copyright (C) 1996-2003 Laszlo Molnar
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All Rights Reserved.
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UPX and the UCL library are free software; you can redistribute them
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and/or modify them under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; see the file COPYING.
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If not, write to the Free Software Foundation, Inc.,
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59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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Markus F.X.J. Oberhumer Laszlo Molnar
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markus@oberhumer.com ml1050@cdata.tvnet.hu
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*/
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#ifndef __UPX_FILTER_H
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#define __UPX_FILTER_H
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class Filter;
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class FilterImp;
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/*************************************************************************
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// A filter is a reversible operation that modifies a given
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// block of memory.
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//
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// A filter can fail and return false. In this case the buffer
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// must be unmodified (or otherwise restored).
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//
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// If a filter fails and somehow cannot restore the block it must
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// call throwFilterException() - this will cause the compression
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// to fail.
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//
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// Unfilters throw exceptions in case of errors.
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//
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// The main idea behind filters is to convert relative jumps and calls
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// to absolute addresses so that the buffer compresses better.
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**************************************************************************/
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class Filter
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{
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public:
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Filter(int level) { clevel = level; init(); }
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void init(int id=0, unsigned addvalue=0);
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bool filter(upx_byte *buf, unsigned buf_len);
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void unfilter(upx_byte *buf, unsigned buf_len, bool verify_checksum=false);
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void verifyUnfilter();
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bool scan(const upx_byte *buf, unsigned buf_len);
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static bool isValidFilter(int filter_id);
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public:
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// Will be set by each call to filter()/unfilter().
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// Read-only afterwards.
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upx_byte *buf;
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unsigned buf_len;
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// Checksum of the buffer before applying the filter
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// or after un-applying the filter.
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unsigned adler;
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// Input parameters used by various filters.
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unsigned addvalue;
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const int *preferred_ctos;
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// Input/output parameters used by various filters
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unsigned char cto; // call trick offset
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// Output used by various filters. Read only.
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unsigned calls;
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unsigned noncalls;
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unsigned wrongcalls;
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unsigned firstcall;
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unsigned lastcall;
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unsigned n_mru; // ctojr only
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// Read only.
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int id;
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private:
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int clevel; // compression level
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};
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/*************************************************************************
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// We don't want a full OO interface here because of
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// certain implementation speed reasons.
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//
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// This class is private to Filter - don't look.
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**************************************************************************/
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class FilterImp
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{
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friend class Filter;
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private:
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struct FilterEntry
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{
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int id; // 0 .. 255
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unsigned min_buf_len;
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unsigned max_buf_len;
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int (*do_filter)(Filter *); // filter a buffer
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int (*do_unfilter)(Filter *); // unfilter a buffer
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int (*do_scan)(Filter *); // scan a buffer
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};
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// get a specific filter entry
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static const FilterEntry *getFilter(int id);
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private:
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// strictly private filter database
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static const FilterEntry filters[];
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static const int n_filters; // number of filters[]
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};
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#endif /* already included */
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/*
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vi:ts=4:et
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*/
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