/* filter.cpp --

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2025 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2025 Laszlo Molnar
   All Rights Reserved.

   UPX and the UCL library are free software; you can redistribute them
   and/or modify them under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer              Laszlo Molnar
   <markus@oberhumer.com>               <ezerotven+github@gmail.com>
 */

#include "conf.h"
#include "filter.h"
#include "file.h"

/*************************************************************************
// util
**************************************************************************/

static void initFilter(Filter *f, byte *buf, unsigned buf_len) noexcept {
    f->buf = buf;
    f->buf_len = buf_len;
    // clear output parameters
    f->calls = f->wrongcalls = f->noncalls = f->firstcall = f->lastcall = 0;
}

/*************************************************************************
// get a FilterEntry
**************************************************************************/

/*static*/ const FilterImpl::FilterEntry *FilterImpl::getFilter(int id) {
    static upx_uint8_t filter_map[256];
    static upx_std_once_flag init_done;

    upx_std_call_once(init_done, []() noexcept {
        // init the filter_map[] (using a lambda function)
        assert_noexcept(n_filters <= 254); // as 0xff means "empty slot"
        memset(filter_map, 0xff, sizeof(filter_map));
        for (int i = 0; i < n_filters; i++) {
            int filter_id = filters[i].id;
            assert_noexcept(filter_id >= 0 && filter_id <= 255);
            assert_noexcept(filter_map[filter_id] == 0xff);
            filter_map[filter_id] = (upx_uint8_t) i;
        }
    });

    if (id < 0 || id > 255)
        return nullptr;
    unsigned index = filter_map[id];
    if (index == 0xff) // empty slot
        return nullptr;
    assert_noexcept(filters[index].id == id);
    return &filters[index];
}

/*static*/ bool Filter::isValidFilter(int filter_id) {
    const FilterImpl::FilterEntry *const fe = FilterImpl::getFilter(filter_id);
    return fe != nullptr;
}

/*static*/ bool Filter::isValidFilter(int filter_id, const int *allowed_filters) {
    if (!isValidFilter(filter_id))
        return false;
    if (filter_id == 0)
        return true;
    if (allowed_filters == nullptr)
        return false;
    while (*allowed_filters != FT_END)
        if (*allowed_filters++ == filter_id)
            return true;
    return false;
}

/*************************************************************************
// high level API
**************************************************************************/

Filter::Filter(int level) noexcept : clevel(level) { init(); }

void Filter::init(int id_, unsigned addvalue_) noexcept {
    this->id = id_;
    initFilter(this, nullptr, 0);
    // clear input parameters
    this->addvalue = addvalue_;
    this->preferred_ctos = nullptr;
    // clear input/output parameters
    this->cto = 0;
    this->n_mru = 0;
}

bool Filter::filter(SPAN_0(byte) xbuf, unsigned buf_len_) {
    byte *const buf_ = raw_bytes(xbuf, buf_len_);
    initFilter(this, buf_, buf_len_);

    const FilterImpl::FilterEntry *const fe = FilterImpl::getFilter(id);
    if (fe == nullptr)
        throwInternalError("filter-1");
    if (fe->id == 0)
        return true;
    if (buf_len < fe->min_buf_len)
        return false;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return false;
    if (!fe->do_filter)
        throwInternalError("filter-2");

    // save checksum
    this->adler = 0;
    if (clevel != 1)
        this->adler = upx_adler32(this->buf, this->buf_len);

    NO_printf("filter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    // OutputFile::dump("filter.dat", buf, buf_len);
    int r = (*fe->do_filter)(this);
    NO_printf("filter: %02x %d\n", fe->id, r);
    if (r > 0)
        throwFilterException();
    if (r == 0)
        return true;
    return false;
}

void Filter::unfilter(SPAN_0(byte) xbuf, unsigned buf_len_, bool verify_checksum) {
    byte *const buf_ = raw_bytes(xbuf, buf_len_);
    initFilter(this, buf_, buf_len_);

    const FilterImpl::FilterEntry *const fe = FilterImpl::getFilter(id);
    if (fe == nullptr)
        throwInternalError("unfilter-1");
    if (fe->id == 0)
        return;
    if (buf_len < fe->min_buf_len)
        return;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return;
    if (!fe->do_unfilter)
        throwInternalError("unfilter-2");

    NO_printf("unfilter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    int r = (*fe->do_unfilter)(this);
    NO_printf("unfilter: %02x %d\n", fe->id, r);
    if (r != 0)
        throwInternalError("unfilter-3");
    // OutputFile::dump("unfilter.dat", buf, buf_len);

    // verify checksum
    if (verify_checksum && clevel != 1) {
        if (this->adler != upx_adler32(this->buf, this->buf_len))
            throwInternalError("unfilter-4");
    }
}

void Filter::verifyUnfilter() {
    // Note:
    //   This verify is just because of complete paranoia that there
    //   could be a hidden bug in the filter implementation, and
    //   it should not be necessary at all.
    //   Maybe we will remove it at some future point.
    //
    // See also:
    //   Packer::verifyOverlappingDecompression()

    NO_printf("verifyUnfilter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    if (clevel != 1)
        unfilter(this->buf, this->buf_len, true);
}

bool Filter::scan(SPAN_0(const byte) xbuf, unsigned buf_len_) {
    const byte *const buf_ = raw_bytes(xbuf, buf_len_);
    // Note: must use const_cast here. This is fine as the scan
    //   implementations (fe->do_scan) actually don't change the buffer.
    byte *const b = const_cast<byte *>(buf_);
    initFilter(this, b, buf_len_);

    const FilterImpl::FilterEntry *const fe = FilterImpl::getFilter(id);
    if (fe == nullptr)
        throwInternalError("scan-1");
    if (fe->id == 0)
        return true;
    if (buf_len < fe->min_buf_len)
        return false;
    if (fe->max_buf_len && buf_len > fe->max_buf_len)
        return false;
    if (!fe->do_scan)
        throwInternalError("scan-2");

    NO_printf("filter: %02x %p %d\n", this->id, this->buf, this->buf_len);
    int r = (*fe->do_scan)(this);
    NO_printf("filter: %02x %d\n", fe->id, r);
    if (r > 0)
        throwFilterException();
    if (r == 0)
        return true;
    return false;
}

/* vim:set ts=4 sw=4 et: */
