hardcoresushi/libcryfs
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Speed up writing back of DirBlobs by another factor of 3 (so 9 in total) by serializing the whole blob and writing it back with one write() call

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This commit is contained in:
Sebastian Messmer 2015-10-05 02:55:04 +02:00
parent af70891d27
commit 7e54d284e1
2 changed files with 25 additions and 21 deletions
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42
src/filesystem/fsblobstore/DirBlob.cpp
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@ -47,47 +47,51 @@ unique_ref<DirBlob> DirBlob::InitializeEmptyDir(unique_ref<Blob> blob, std::func
return make_unique_ref<DirBlob>(std::move(blob), getLstatSize);
}
Data DirBlob::_writeEntry(const DirBlob::Entry & entry) {
size_t DirBlob::_serializedSizeOfEntry(const DirBlob::Entry &entry) {
return 1 + (entry.name.size() + 1) + (entry.key.STRING_LENGTH + 1) + sizeof(uid_t) + sizeof(gid_t) + sizeof(mode_t);
}
void DirBlob::_serializeEntry(const DirBlob::Entry & entry, uint8_t *dest) {
//TODO Write key as binary?
string keystr = entry.key.ToString();
unsigned int size = 1 + (entry.name.size() + 1) + (keystr.size() + 1) + sizeof(uid_t) + sizeof(gid_t) + sizeof(mode_t);
Data result(size);
unsigned int offset = 0;
*static_cast<uint8_t*>(result.dataOffset(offset)) = static_cast<uint8_t>(entry.type);
*(dest+offset) = static_cast<uint8_t>(entry.type);
offset += 1;
std::memcpy(result.dataOffset(offset), entry.name.c_str(), entry.name.size()+1);
std::memcpy(dest+offset, entry.name.c_str(), entry.name.size()+1);
offset += entry.name.size() + 1;
std::memcpy(result.dataOffset(offset), keystr.c_str(), keystr.size() + 1);
std::memcpy(dest+offset, keystr.c_str(), keystr.size() + 1);
offset += keystr.size() + 1;
*reinterpret_cast<uid_t*>(result.dataOffset(offset)) = entry.uid;
*reinterpret_cast<uid_t*>(dest+offset) = entry.uid;
offset += sizeof(uid_t);
*reinterpret_cast<gid_t*>(result.dataOffset(offset)) = entry.gid;
*reinterpret_cast<gid_t*>(dest+offset) = entry.gid;
offset += sizeof(gid_t);
*reinterpret_cast<mode_t*>(result.dataOffset(offset)) = entry.mode;
*reinterpret_cast<mode_t*>(dest+offset) = entry.mode;
offset += sizeof(mode_t);
ASSERT(offset == size, "Didn't write correct number of elements");
return result;
ASSERT(offset == _serializedSizeOfEntry(entry), "Didn't write correct number of elements");
}
void DirBlob::_writeEntriesToBlob() {
std::unique_lock<std::mutex> lock(_mutex);
if (_changed) {
//TODO Resizing is imperformant
baseBlob().resize(1);
unsigned int offset = 1;
size_t serializedSize = 0;
for (const auto &entry : _entries) {
Data serializedEntry = _writeEntry(entry);
baseBlob().write(serializedEntry.data(), offset, serializedEntry.size());
offset += serializedEntry.size();
serializedSize += _serializedSizeOfEntry(entry);
}
Data serialized(serializedSize);
unsigned int offset = 0;
for (const auto &entry : _entries) {
_serializeEntry(entry, static_cast<uint8_t*>(serialized.dataOffset(offset)));
offset += _serializedSizeOfEntry(entry);
}
baseBlob().resize(1 + serializedSize);
baseBlob().write(serialized.data(), 1, serializedSize);
_changed = false;
}
}

4
src/filesystem/fsblobstore/DirBlob.h
View File

@ -4,7 +4,6 @@
#include <messmer/blockstore/utils/Key.h>
#include <messmer/cpp-utils/macros.h>
#include <messmer/cpp-utils/data/Data.h>
#include <messmer/fspp/fs_interface/Dir.h>
#include "FsBlob.h"
#include <vector>
@ -91,7 +90,8 @@ namespace cryfs {
void _readEntriesFromBlob();
void _writeEntriesToBlob();
static cpputils::Data _writeEntry(const DirBlob::Entry & entry);
static size_t _serializedSizeOfEntry(const DirBlob::Entry &entry);
static void _serializeEntry(const DirBlob::Entry &entry, uint8_t *dest);
std::vector<DirBlob::Entry>::iterator _findChild(const blockstore::Key &key);