112 lines
2.4 KiB
C++
112 lines
2.4 KiB
C++
/*
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This file is part of Telegram Desktop,
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the official desktop application for the Telegram messaging service.
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For license and copyright information please follow this link:
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https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
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*/
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#include "storage/cache/storage_cache_binlog_reader.h"
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namespace Storage {
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namespace Cache {
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namespace details {
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BinlogWrapper::BinlogWrapper(
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File &binlog,
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const Settings &settings,
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int64 till)
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: _binlog(binlog)
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, _settings(settings)
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, _till(till ? till : _binlog.size())
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, _data(_settings.readBlockSize)
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, _full(_data) {
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}
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bool BinlogWrapper::finished() const {
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return _finished;
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}
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bool BinlogWrapper::failed() const {
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return _failed;
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}
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std::optional<BasicHeader> BinlogWrapper::ReadHeader(
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File &binlog,
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const Settings &settings) {
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auto result = BasicHeader();
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if (binlog.offset() != 0) {
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return {};
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} else if (binlog.read(bytes::object_as_span(&result)) != sizeof(result)) {
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return {};
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} else if (result.getFormat() != Format::Format_0) {
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return {};
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} else if (settings.trackEstimatedTime
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!= !!(result.flags & result.kTrackEstimatedTime)) {
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return {};
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}
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return result;
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}
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bool BinlogWrapper::readPart() {
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if (_finished) {
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return false;
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}
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const auto no = [&] {
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finish();
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return false;
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};
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const auto offset = _binlog.offset();
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const auto left = (_till - offset);
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if (!left) {
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return no();
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}
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if (!_part.empty() && _full.data() != _part.data()) {
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bytes::move(_full, _part);
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_part = _full.subspan(0, _part.size());
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}
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const auto amount = std::min(
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left,
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int64(_full.size() - _part.size()));
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Assert(amount > 0);
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const auto readBytes = _binlog.read(
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_full.subspan(_part.size(), amount));
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if (!readBytes) {
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return no();
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}
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_part = _full.subspan(0, _part.size() + readBytes);
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return true;
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}
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bytes::const_span BinlogWrapper::readRecord(ReadRecordSize readRecordSize) {
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if (_finished) {
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return {};
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}
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const auto size = readRecordSize(*this, _part);
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if (size == kRecordSizeUnknown || size > _part.size()) {
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return {};
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} else if (size == kRecordSizeInvalid) {
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finish();
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_finished = _failed = true;
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return {};
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}
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Assert(size >= 0);
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const auto result = _part.subspan(0, size);
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_part = _part.subspan(size);
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return result;
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}
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void BinlogWrapper::finish(size_type rollback) {
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Expects(rollback >= 0);
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if (rollback > 0) {
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_failed = true;
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}
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rollback += _part.size();
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_binlog.seek(_binlog.offset() - rollback);
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}
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} // namespace details
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} // namespace Cache
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} // namespace Storage
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