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/* Copyright 2021 Ján Sučan <jan@jansucan.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "restore.h"
#include "buffered_file.h"
#include <filesystem>
#include <fstream>
static void
check_diff_file(const OptionsRestore &opts)
{
size_t diff_size{0};
try {
diff_size = std::filesystem::file_size(opts.getDiffFilePath());
} catch (const std::exception &e) {
throw RestoreError("cannot get size of diff file: " +
std::string(e.what()));
}
if (diff_size == 0) {
throw RestoreError("diff file is empty");
} else if ((diff_size % (sizeof(uint64_t) + opts.getSectorSize())) != 0) {
/* The diff file must hold equally sized sectors and the
* offset of each of them
*/
throw RestoreError(
"diff file has size that cannot contain valid diff data");
}
size_t out_size{0};
try {
out_size = std::filesystem::file_size(opts.getOutFilePath());
} catch (const std::exception &e) {
throw RestoreError("cannot get size of output file: " +
std::string(e.what()));
}
std::ifstream diff_file;
diff_file.open(opts.getDiffFilePath(), std::ios::in | std::ios::binary);
if (!diff_file) {
throw RestoreError("cannot open diff file");
}
uint64_t prev_out_offset = 0;
bool is_first_reading = true;
/* Scan the diff file and check */
for (;;) {
uint64_t out_offset;
/* Read the next offset */
diff_file.read(reinterpret_cast<char *>(&out_offset),
sizeof(out_offset));
if (diff_file.eof() && diff_file.fail() && !diff_file.bad()) {
break;
} else if (!diff_file.good() && !diff_file.eof()) {
throw RestoreError("cannot read from file");
}
out_offset = le64toh(out_offset);
if (!is_first_reading && (out_offset <= prev_out_offset)) {
throw RestoreError(
"a sector offset points behind the previous offset");
} else if ((out_offset + opts.getSectorSize()) > out_size) {
throw RestoreError(
"a sector offset points past the end of the output file");
} else if (!diff_file.seekg(opts.getSectorSize(), std::ios_base::cur)) {
throw RestoreError("cannot seek in diff file");
}
is_first_reading = false;
prev_out_offset = out_offset;
}
/* The diff file must be read completely */
char c;
diff_file.read(&c, 1);
if (diff_file.gcount() != 0) {
throw RestoreError("diff file is not valid");
}
diff_file.clear();
diff_file.close();
}
void
restore(const OptionsRestore &opts)
{
check_diff_file(opts);
BufferedFileReader diff_file(opts.getDiffFilePath(), opts.getBufferSize());
std::fstream out_file;
out_file.open(opts.getOutFilePath(),
std::ios::in | std::ios::out | std::ios::binary);
if (!out_file) {
throw RestoreError("cannot open output file");
}
const size_t diff_buffer_size = sizeof(uint64_t) + opts.getSectorSize();
std::unique_ptr<char[]> diff_buffer;
try {
diff_buffer = std::make_unique<char[]>(diff_buffer_size);
} catch (const std::bad_alloc &e) {
throw RestoreError("cannot allocate sector buffer for diff file data");
}
/* Restore data from the differential image */
size_t diff_read_size = {0};
for (;;) {
diff_read_size = diff_file.read(diff_buffer.get(), diff_buffer_size);
if (diff_read_size == 0) {
break;
} else if (diff_read_size != diff_buffer_size) {
throw RestoreError("cannot read from diff file");
}
const uint64_t out_offset =
le64toh(*reinterpret_cast<uint64_t *>(diff_buffer.get()));
if (!out_file.seekp(out_offset, std::ios_base::beg)) {
throw RestoreError("cannot seek in output file");
}
if (!out_file.write(reinterpret_cast<char *>(diff_buffer.get()) +
sizeof(uint64_t),
opts.getSectorSize())) {
throw RestoreError("cannot write to output file");
}
}
out_file.close();
/* The diff file must be read completely */
char c;
diff_read_size = diff_file.read(&c, 1);
if (diff_read_size != 0) {
throw RestoreError("diff file is not valid");
}
}
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