rocksdb/db
Levi Tamasi 22655a398b Introduce a blob file reader class (#7461)
Summary:
The patch adds a class called `BlobFileReader` that can be used to retrieve blobs
using the information available in blob references (e.g. blob file number, offset, and
size). This will come in handy when implementing blob support for `Get`, `MultiGet`,
and iterators, and also for compaction/garbage collection.

When a `BlobFileReader` object is created (using the factory method `Create`),
it first checks whether the specified file is potentially valid by comparing the file
size against the combined size of the blob file header and footer (files smaller than
the threshold are considered malformed). Then, it opens the file, and reads and verifies
the header and footer. The verification involves magic number/CRC checks
as well as checking for unexpected header/footer fields, e.g. incorrect column family ID
or TTL blob files.

Blobs can be retrieved using `GetBlob`. `GetBlob` validates the offset and compression
type passed by the caller (because of the presence of the header and footer, the
specified offset cannot be too close to the start/end of the file; also, the compression type
has to match the one in the blob file header), and retrieves and potentially verifies and
uncompresses the blob. In particular, when `ReadOptions::verify_checksums` is set,
`BlobFileReader` reads the blob record header as well (as opposed to just the blob itself)
and verifies the key/value size, the key itself, as well as the CRC of the blob record header
and the key/value pair.

In addition, the patch exposes the compression type from `BlobIndex` (both using an
accessor and via `DebugString`), and adds a blob file read latency histogram to
`InternalStats` that can be used with `BlobFileReader`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7461

Test Plan: `make check`

Reviewed By: riversand963

Differential Revision: D23999219

Pulled By: ltamasi

fbshipit-source-id: deb6b1160d251258b308d5156e2ec063c3e12e5e
2020-10-07 15:44:53 -07:00
..
blob Introduce a blob file reader class (#7461) 2020-10-07 15:44:53 -07:00
compaction Make sure assert(false) handles failures too (#7483) 2020-10-06 13:52:42 -07:00
db_impl Disallow trivial move if BottommostLevelCompaction is kForce* (#7368) 2020-10-07 13:19:31 -07:00
arena_wrapped_db_iter.cc dedup ReadOptions in iterator hierarchy (#7210) 2020-08-03 15:23:04 -07:00
arena_wrapped_db_iter.h dedup ReadOptions in iterator hierarchy (#7210) 2020-08-03 15:23:04 -07:00
builder.cc Enforce status check for corruption_test (#7453) 2020-10-02 22:11:00 -07:00
builder.h Integrate blob file writing with the flush logic (#7345) 2020-09-14 21:11:43 -07:00
c_test.c Fix MSVC-related build issues (#7439) 2020-10-01 09:23:04 -07:00
c.cc RocksJava - Add errorIfLogFileExists parameter to RocksDB.openReadOnly (#7046) 2020-09-17 15:41:25 -07:00
column_family_test.cc Add status check enforcement for column_family_test.cc (#7484) 2020-10-02 13:35:15 -07:00
column_family.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
column_family.h Store FSRandomAccessPtr object in RandomAccessFileReader (#7192) 2020-08-27 11:21:52 -07:00
compact_files_test.cc Replace reinterpret_cast with static_cast_with_check (#7067) 2020-07-02 19:25:41 -07:00
compacted_db_impl.cc Periodically flush info log out of application buffer (#7488) 2020-10-01 19:14:14 -07:00
compacted_db_impl.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
comparator_db_test.cc More Makefile Cleanup (#7097) 2020-07-09 14:35:17 -07:00
convenience.cc sst_dump to reduce number of file reads (#6836) 2020-05-12 18:23:33 -07:00
corruption_test.cc Enforce status check for corruption_test (#7453) 2020-10-02 22:11:00 -07:00
cuckoo_table_db_test.cc Replace reinterpret_cast with static_cast_with_check (#7067) 2020-07-02 19:25:41 -07:00
db_basic_test.cc Add Stats for MultiGet (#7366) 2020-10-07 13:28:48 -07:00
db_block_cache_test.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
db_bloom_filter_test.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
db_compaction_filter_test.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
db_compaction_test.cc Disallow trivial move if BottommostLevelCompaction is kForce* (#7368) 2020-10-07 13:19:31 -07:00
db_dynamic_level_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_encryption_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_filesnapshot.cc Fix checkpoint file deletion race with avoid_unnecessary_blocking_io (#7369) 2020-09-10 22:35:25 -07:00
db_flush_test.cc Integrate blob file writing with the flush logic (#7345) 2020-09-14 21:11:43 -07:00
db_info_dumper.cc Add some simulator cache and block tracer tests to ASSERT_STATUS_CHECKED (#7305) 2020-08-24 16:43:31 -07:00
db_info_dumper.h Add a DB Session ID (#6959) 2020-06-15 10:47:02 -07:00
db_inplace_update_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_io_failure_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_iter_stress_test.cc Test CircleCI with CLANG-10 (#7025) 2020-06-24 16:22:49 -07:00
db_iter_test.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
db_iter.cc Make sure assert(false) handles failures too (#7483) 2020-10-06 13:52:42 -07:00
db_iter.h Make db_basic_test pass assert status checked (#7452) 2020-09-29 09:49:04 -07:00
db_iterator_test.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
db_log_iter_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_logical_block_size_cache_test.cc Get block size only in direct IO mode (#6522) 2020-03-20 15:26:10 -07:00
db_memtable_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_merge_operand_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_merge_operator_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_options_test.cc Add few unit test cases in ASSERT_STATUS_CHECKED build (#7427) 2020-09-24 21:48:57 -07:00
db_properties_test.cc Fix db_properties_test for ASSERT_STATUS_CHECKED (#7490) 2020-10-01 17:47:09 -07:00
db_range_del_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_sst_test.cc add Status check assertions for repair_test (#7455) 2020-09-29 16:30:08 -07:00
db_statistics_test.cc Add a new stats level to exclude tickers (#7329) 2020-09-04 23:25:03 -07:00
db_table_properties_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_tailing_iter_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_test2.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
db_test_util.cc Enable ASSERT_STATUS_CHECKED for db_universal_compaction_test (#7460) 2020-10-06 14:42:12 -07:00
db_test_util.h add Status check assertions for repair_test (#7455) 2020-09-29 16:30:08 -07:00
db_test.cc Reduce the number of iterations in DBTest.FileCreationRandomFailure (#7481) 2020-10-01 10:42:58 -07:00
db_universal_compaction_test.cc Enable ASSERT_STATUS_CHECKED for db_universal_compaction_test (#7460) 2020-10-06 14:42:12 -07:00
db_wal_test.cc Integrate blob file writing with recovery (#7388) 2020-09-15 17:14:10 -07:00
db_with_timestamp_basic_test.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
db_with_timestamp_compaction_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_write_test.cc Fix StallWrite crash with mixed of slowdown/no_slowdown writes (#7508) 2020-10-06 12:44:20 -07:00
dbformat_test.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
dbformat.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
dbformat.h Introduce options.check_flush_compaction_key_order (#7467) 2020-10-01 10:10:26 -07:00
deletefile_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
error_handler_fs_test.cc Status check enforcement for error_handler_fs_test (#7342) 2020-10-02 16:41:13 -07:00
error_handler.cc Status check enforcement for timestamp_basic_test (#7454) 2020-09-29 18:23:27 -07:00
error_handler.h Map retryable IO error during Flush without WAL to soft error and no switch memtable during resume (#7310) 2020-09-17 20:25:45 -07:00
event_helpers.cc Status check enforcement for error_handler_fs_test (#7342) 2020-10-02 16:41:13 -07:00
event_helpers.h Pass SST file checksum information through OnTableFileCreated (#7108) 2020-08-25 10:46:11 -07:00
experimental.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
external_sst_file_basic_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
external_sst_file_ingestion_job.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
external_sst_file_ingestion_job.h Store FSSequentialFilePtr object in SequenceFileReader (#7190) 2020-08-18 16:20:54 -07:00
external_sst_file_test.cc Disable fsync in some ExternalSSTFileTest tests (#7303) 2020-08-24 11:26:09 -07:00
fault_injection_test.cc More Makefile Cleanup (#7097) 2020-07-09 14:35:17 -07:00
file_indexer_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
file_indexer.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
file_indexer.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
filename_test.cc Add more tests to ASSERT_STATUS_CHECKED (#7211) 2020-08-06 17:19:41 -07:00
flush_job_test.cc Introduce options.check_flush_compaction_key_order (#7467) 2020-10-01 10:10:26 -07:00
flush_job.cc Add flush_job_test to the list of ASSERT_STATUS_CHECKED tests (#7445) 2020-09-28 14:59:02 -07:00
flush_job.h Store FSWritableFilePtr object in WritableFileWriter (#7193) 2020-09-08 10:56:08 -07:00
flush_scheduler.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
flush_scheduler.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
forward_iterator_bench.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
forward_iterator.cc Add status check enforcement for column_family_test.cc (#7484) 2020-10-02 13:35:15 -07:00
forward_iterator.h Properly report IO errors when IndexType::kBinarySearchWithFirstKey is used (#6621) 2020-04-15 17:40:44 -07:00
import_column_family_job.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
import_column_family_job.h Store FSSequentialFilePtr object in SequenceFileReader (#7190) 2020-08-18 16:20:54 -07:00
import_column_family_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
internal_stats.cc Introduce a blob file reader class (#7461) 2020-10-07 15:44:53 -07:00
internal_stats.h Introduce a blob file reader class (#7461) 2020-10-07 15:44:53 -07:00
job_context.h Expose the set of live blob files from Version/VersionSet (#6785) 2020-05-04 15:08:13 -07:00
listener_test.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
log_format.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
log_reader.cc Real fix for race in backup custom checksum checking (#7309) 2020-08-26 10:39:20 -07:00
log_reader.h Real fix for race in backup custom checksum checking (#7309) 2020-08-26 10:39:20 -07:00
log_test.cc Revert "Update googletest from 1.8.1 to 1.10.0 (#6808)" (#6923) 2020-06-03 15:55:03 -07:00
log_writer.cc Fail recovery when MANIFEST record checksum mismatch (#6996) 2020-06-18 10:09:12 -07:00
log_writer.h Pass IOStatus to write path and set retryable IO Error as hard error in BG jobs (#6487) 2020-03-27 16:04:43 -07:00
logs_with_prep_tracker.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
logs_with_prep_tracker.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
lookup_key.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
malloc_stats.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
malloc_stats.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
manual_compaction_test.cc Skip high levels with no key falling in the range in CompactRange (#6482) 2020-03-04 20:15:25 -08:00
memtable_list_test.cc Add few unit test cases in ASSERT_STATUS_CHECKED build (#7427) 2020-09-24 21:48:57 -07:00
memtable_list.cc Integrate blob file writing with the flush logic (#7345) 2020-09-14 21:11:43 -07:00
memtable_list.h Bug Fix for memtables not trimmed down. (#7296) 2020-08-21 13:29:05 -07:00
memtable.cc Introduce options.check_flush_compaction_key_order (#7467) 2020-10-01 10:10:26 -07:00
memtable.h Provide users with option to opt-in to get corrupt data in logs/messages (#7420) 2020-09-29 23:17:45 -07:00
merge_context.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_helper_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_helper.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
merge_helper.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_operator.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
obsolete_files_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
options_file_test.cc Add more tests to ASSERT_STATUS_CHECKED (#7367) 2020-09-16 15:48:07 -07:00
output_validator.cc Introduce options.check_flush_compaction_key_order (#7467) 2020-10-01 10:10:26 -07:00
output_validator.h Introduce options.check_flush_compaction_key_order (#7467) 2020-10-01 10:10:26 -07:00
perf_context_test.cc Fix MSVC-related build issues (#7439) 2020-10-01 09:23:04 -07:00
periodic_work_scheduler_test.cc Periodically flush info log out of application buffer (#7488) 2020-10-01 19:14:14 -07:00
periodic_work_scheduler.cc Periodically flush info log out of application buffer (#7488) 2020-10-01 19:14:14 -07:00
periodic_work_scheduler.h Periodically flush info log out of application buffer (#7488) 2020-10-01 19:14:14 -07:00
pinned_iterators_manager.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
plain_table_db_test.cc More Makefile Cleanup (#7097) 2020-07-09 14:35:17 -07:00
pre_release_callback.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
prefix_test.cc Fix prefix_test for status check (#7495) 2020-10-02 17:01:15 -07:00
range_del_aggregator_bench.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_del_aggregator_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_del_aggregator.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
range_del_aggregator.h Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
range_tombstone_fragmenter_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_tombstone_fragmenter.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_tombstone_fragmenter.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
read_callback.h Get() with timestamp should respect snapshot (#7227) 2020-08-14 19:20:58 -07:00
repair_test.cc add Status check assertions for repair_test (#7455) 2020-09-29 16:30:08 -07:00
repair.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
snapshot_checker.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
snapshot_impl.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
snapshot_impl.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
table_cache.cc Fix db_properties_test for ASSERT_STATUS_CHECKED (#7490) 2020-10-01 17:47:09 -07:00
table_cache.h Store FSRandomAccessPtr object in RandomAccessFileReader (#7192) 2020-08-27 11:21:52 -07:00
table_properties_collector_test.cc Bring the Configurable options together (#5753) 2020-09-14 17:01:01 -07:00
table_properties_collector.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
table_properties_collector.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
transaction_log_impl.cc Store FSSequentialFilePtr object in SequenceFileReader (#7190) 2020-08-18 16:20:54 -07:00
transaction_log_impl.h Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
trim_history_scheduler.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
trim_history_scheduler.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
version_builder_test.cc Add version_builder_test to the list of ASSERT_STATUS_CHECKED tests (#7444) 2020-09-28 12:12:40 -07:00
version_builder.cc Enforce status check for corruption_test (#7453) 2020-10-02 22:11:00 -07:00
version_builder.h make L0 index/filter pinned memory usage predictable (#6911) 2020-06-09 16:51:23 -07:00
version_edit_handler.cc Store FSWritableFilePtr object in WritableFileWriter (#7193) 2020-09-08 10:56:08 -07:00
version_edit_handler.h Store FSWritableFilePtr object in WritableFileWriter (#7193) 2020-09-08 10:56:08 -07:00
version_edit_test.cc Track WAL in MANIFEST: update WalMetadata for WAL syncing (#7414) 2020-09-22 14:35:14 -07:00
version_edit.cc Integrate blob file writing with the flush logic (#7345) 2020-09-14 21:11:43 -07:00
version_edit.h Integrate blob file writing with the flush logic (#7345) 2020-09-14 21:11:43 -07:00
version_set_test.cc Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
version_set.cc Add Stats for MultiGet (#7366) 2020-10-07 13:28:48 -07:00
version_set.h Fix TSAN build and re-enable the tests (#7386) 2020-09-25 14:46:28 -07:00
wal_edit_test.cc Track WAL in MANIFEST: add method to check WAL consistency (#7236) 2020-09-25 13:25:54 -07:00
wal_edit.cc Track WAL in MANIFEST: add method to check WAL consistency (#7236) 2020-09-25 13:25:54 -07:00
wal_edit.h Track WAL in MANIFEST: add method to check WAL consistency (#7236) 2020-09-25 13:25:54 -07:00
wal_manager_test.cc Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
wal_manager.cc add Status check assertions for repair_test (#7455) 2020-09-29 16:30:08 -07:00
wal_manager.h Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
write_batch_base.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_batch_internal.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_batch_test.cc Change ParseInternalKey() to return Status instead of bool (#7457) 2020-09-30 19:16:47 -07:00
write_batch.cc Add trace_analyzer_test to ASSERT_STATUS_CHECKED list (#7480) 2020-10-01 15:58:52 -07:00
write_callback_test.cc Divide WriteCallbackTest.WriteWithCallbackTest (#7037) 2020-06-30 12:31:30 -07:00
write_callback.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_controller_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_controller.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_controller.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_thread.cc Fix StallWrite crash with mixed of slowdown/no_slowdown writes (#7508) 2020-10-06 12:44:20 -07:00
write_thread.h Enforce status check for corruption_test (#7453) 2020-10-02 22:11:00 -07:00