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Speed up block loading/storing by issuing only one read/write syscall to the base file system

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This commit is contained in:
Sebastian Messmer 2016-07-06 15:35:51 -07:00
parent 7348f7c64d
commit 0d860fa4f0
2 changed files with 14 additions and 32 deletions
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44
src/blockstore/implementations/ondisk/OnDiskBlock.cpp
View File

@ -99,56 +99,38 @@ void OnDiskBlock::RemoveFromDisk(const bf::path &rootdir, const Key &key) {
}
void OnDiskBlock::_storeToDisk() const {
std::ofstream file(_filepath.c_str(), std::ios::binary | std::ios::trunc);
if (!file.good()) {
throw std::runtime_error("Could not open file for writing");
}
file.write(FORMAT_VERSION_HEADER.c_str(), formatVersionHeaderSize());
if (!file.good()) {
throw std::runtime_error("Error writing block header");
}
_data.StoreToStream(file);
if (!file.good()) {
throw std::runtime_error("Error writing block data");
}
Data fileContent(formatVersionHeaderSize() + _data.size());
std::memcpy(fileContent.data(), FORMAT_VERSION_HEADER.c_str(), formatVersionHeaderSize());
std::memcpy(fileContent.dataOffset(formatVersionHeaderSize()), _data.data(), _data.size());
fileContent.StoreToFile(_filepath);
}
optional<Data> OnDiskBlock::_loadFromDisk(const bf::path &filepath) {
//If it isn't a file, ifstream::good() would return false. We still need this extra check
//upfront, because ifstream::good() doesn't crash if we give it the path of a directory
//instead the path of a file.
if(!bf::is_regular_file(filepath)) {
auto fileContent = Data::LoadFromFile(filepath);
if (fileContent == none) {
return none;
}
ifstream file(filepath.c_str(), ios::binary);
if (!file.good()) {
return none;
}
_checkHeader(&file);
Data result = Data::LoadFromStream(file);
//TODO With newer compilers, "return result;" would be enough
return boost::optional<Data>(std::move(result));
return _checkAndRemoveHeader(std::move(*fileContent));
}
void OnDiskBlock::_checkHeader(istream *str) {
Data header(formatVersionHeaderSize());
str->read(reinterpret_cast<char*>(header.data()), formatVersionHeaderSize());
if (!_isAcceptedCryfsHeader(header)) {
if (_isOtherCryfsHeader(header)) {
Data OnDiskBlock::_checkAndRemoveHeader(Data data) {
if (!_isAcceptedCryfsHeader(data)) {
if (_isOtherCryfsHeader(data)) {
throw std::runtime_error("This block is not supported yet. Maybe it was created with a newer version of CryFS?");
} else {
throw std::runtime_error("This is not a valid block.");
}
}
Data result(data.size() - formatVersionHeaderSize());
std::memcpy(result.data(), data.dataOffset(formatVersionHeaderSize()), result.size());
return result;
}
bool OnDiskBlock::_isAcceptedCryfsHeader(const Data &data) {
ASSERT(data.size() == formatVersionHeaderSize(), "We extracted the wrong header size from the block.");
return 0 == std::memcmp(data.data(), FORMAT_VERSION_HEADER.c_str(), formatVersionHeaderSize());
}
bool OnDiskBlock::_isOtherCryfsHeader(const Data &data) {
ASSERT(data.size() >= FORMAT_VERSION_HEADER_PREFIX.size(), "We extracted the wrong header size from the block.");
return 0 == std::memcmp(data.data(), FORMAT_VERSION_HEADER_PREFIX.c_str(), FORMAT_VERSION_HEADER_PREFIX.size());
}

2
src/blockstore/implementations/ondisk/OnDiskBlock.h
View File

@ -40,7 +40,7 @@ private:
static bool _isAcceptedCryfsHeader(const cpputils::Data &data);
static bool _isOtherCryfsHeader(const cpputils::Data &data);
static void _checkHeader(std::istream *str);
static cpputils::Data _checkAndRemoveHeader(cpputils::Data data);
static boost::filesystem::path _getFilepath(const boost::filesystem::path &rootdir, const Key &key);
const boost::filesystem::path _filepath;