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Improve performance when loading BackupMeta.

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* Use strtoul() and strtoull() instead of sscanf().
  glibc's sscanf() will do a implicit strlen().

* Move implicit construction of Slice("crc32 ") out of loop.
This commit is contained in:
Robert 2015-01-04 12:02:52 +08:00
parent e9ca358157
commit caa1fd0e0e
1 changed files with 13 additions and 10 deletions
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23
utilities/backupable/backupable_db.cc
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@ -20,6 +20,7 @@
#endif
#include <inttypes.h>
#include <stdlib.h>
#include <algorithm>
#include <vector>
#include <map>
@ -1163,16 +1164,18 @@ Status BackupEngineImpl::BackupMeta::LoadFromFile(
buf[data.size()] = 0;
uint32_t num_files = 0;
int bytes_read = 0;
sscanf(data.data(), "%" PRId64 "%n", &timestamp_, &bytes_read);
data.remove_prefix(bytes_read + 1); // +1 for '\n'
sscanf(data.data(), "%" PRIu64 "%n", &sequence_number_, &bytes_read);
data.remove_prefix(bytes_read + 1); // +1 for '\n'
sscanf(data.data(), "%u%n", &num_files, &bytes_read);
data.remove_prefix(bytes_read + 1); // +1 for '\n'
char *next;
timestamp_ = strtoull(data.data(), &next, 10);
data.remove_prefix(next - data.data() + 1); // +1 for '\n'
sequence_number_ = strtoull(data.data(), &next, 10);
data.remove_prefix(next - data.data() + 1); // +1 for '\n'
num_files = strtoul(data.data(), &next, 10);
data.remove_prefix(next - data.data() + 1); // +1 for '\n'
std::vector<FileInfo> files;
Slice checksum_prefix("crc32 ");
for (uint32_t i = 0; s.ok() && i < num_files; ++i) {
auto line = GetSliceUntil(&data, '\n');
std::string filename = GetSliceUntil(&line, ' ').ToString();
@ -1188,9 +1191,9 @@ Status BackupEngineImpl::BackupMeta::LoadFromFile(
}
uint32_t checksum_value = 0;
if (line.starts_with("crc32 ")) {
line.remove_prefix(6);
sscanf(line.data(), "%u", &checksum_value);
if (line.starts_with(checksum_prefix)) {
line.remove_prefix(checksum_prefix.size());
checksum_value = strtoul(line.data(), nullptr, 10);
if (memcmp(line.data(), std::to_string(checksum_value).c_str(),
line.size() - 1) != 0) {
return Status::Corruption("Invalid checksum value");