Convert properties to &CStr (#643)

src/properties.rs

@@ -3,36 +3,46 @@
 //! Full list of valid properties and descriptions pulled from
 //! [here](https:///github.com/facebook/rocksdb/blob/08809f5e6cd9cc4bc3958dd4d59457ae78c76660/include/rocksdb/db.h#L428-L634).
 
+use std::ffi::{CStr, CString};
+
 macro_rules! property {
     ($suffix: literal) => {
-        concat!("rocksdb.", $suffix)
+        // SAFETY: We’re appending terminating NUL byte and this macro is always
+        // called with values without interior NUL bytes.
+        unsafe {
+            CStr::from_bytes_with_nul_unchecked(concat!("rocksdb.", $suffix, "\0").as_bytes())
+        }
     };
 }
 
 /// "rocksdb.num-files-at-level<N>" - returns string containing the number
 /// of files at level <N>, where <N> is an ASCII representation of a
 /// level number (e.g., "0").
-pub const NUM_FILES_AT_LEVEL_PREFIX: &str = property!("num-files-at-level");
+pub fn num_files_at_level(level: usize) -> CString {
+    unsafe { level_property("num-files-at-level", level) }
+}
 
 /// "rocksdb.compression-ratio-at-level<N>" - returns string containing the
 /// compression ratio of data at level <N>, where <N> is an ASCII
 /// representation of a level number (e.g., "0"). Here, compression
 /// ratio is defined as uncompressed data size / compressed file size.
 /// Returns "-1.0" if no open files at level <N>.
-pub const COMPRESSION_RATIO_AT_LEVEL: &str = property!("compression-ratio-at-level");
+pub fn compression_ratio_at_level(level: usize) -> CString {
+    unsafe { level_property("compression-ratio-at-level", level) }
+}
 
 /// "rocksdb.stats" - returns a multi-line string containing the data
 /// described by kCFStats followed by the data described by kDBStats.
-pub const STATS: &str = property!("stats");
+pub const STATS: &CStr = property!("stats");
 
 /// "rocksdb.sstables" - returns a multi-line string summarizing current
 /// SST files.
-pub const SSTABLES: &str = property!("sstables");
+pub const SSTABLES: &CStr = property!("sstables");
 
 /// "rocksdb.cfstats" - Both of "rocksdb.cfstats-no-file-histogram" and
 /// "rocksdb.cf-file-histogram" together. See below for description
 /// of the two.
-pub const CFSTATS: &str = property!("CFSTATS");
+pub const CFSTATS: &CStr = property!("CFSTATS");
 
 /// "rocksdb.cfstats-no-file-histogram" - returns a multi-line string with
 /// general columm family stats per-level over db's lifetime ("L<n>"),
@@ -42,176 +52,200 @@ pub const CFSTATS: &str = property!("CFSTATS");
 /// In this case there will a pair of string to array of double for
 /// each level as well as for "Sum". "Int" stats will not be affected
 /// when this form of stats are retrieved.
-pub const CFSTATS_NO_FILE_HISTOGRAM: &str = property!("cfstats-no-file-histogram");
+pub const CFSTATS_NO_FILE_HISTOGRAM: &CStr = property!("cfstats-no-file-histogram");
 
 /// "rocksdb.cf-file-histogram" - print out how many file reads to every
 /// level, as well as the histogram of latency of single requests.
-pub const CF_FILE_HISTOGRAM: &str = property!("cf-file-histogram");
+pub const CF_FILE_HISTOGRAM: &CStr = property!("cf-file-histogram");
 
 /// "rocksdb.dbstats" - returns a multi-line string with general database
 /// stats, both cumulative (over the db's lifetime) and interval (since
 /// the last retrieval of kDBStats).
-pub const DBSTATS: &str = property!("dbstats");
+pub const DBSTATS: &CStr = property!("dbstats");
 
 /// "rocksdb.levelstats" - returns multi-line string containing the number
 /// of files per level and total size of each level (MB).
-pub const LEVELSTATS: &str = property!("levelstats");
+pub const LEVELSTATS: &CStr = property!("levelstats");
 
 /// "rocksdb.num-immutable-mem-table" - returns number of immutable
 /// memtables that have not yet been flushed.
-pub const NUM_IMMUTABLE_MEM_TABLE: &str = property!("num-immutable-mem-table");
+pub const NUM_IMMUTABLE_MEM_TABLE: &CStr = property!("num-immutable-mem-table");
 
 /// "rocksdb.num-immutable-mem-table-flushed" - returns number of immutable
 /// memtables that have already been flushed.
-pub const NUM_IMMUTABLE_MEM_TABLE_FLUSHED: &str = property!("num-immutable-mem-table-flushed");
+pub const NUM_IMMUTABLE_MEM_TABLE_FLUSHED: &CStr = property!("num-immutable-mem-table-flushed");
 
 /// "rocksdb.mem-table-flush-pending" - returns 1 if a memtable flush is
 /// pending; otherwise, returns 0.
-pub const MEM_TABLE_FLUSH_PENDING: &str = property!("mem-table-flush-pending");
+pub const MEM_TABLE_FLUSH_PENDING: &CStr = property!("mem-table-flush-pending");
 
 /// "rocksdb.num-running-flushes" - returns the number of currently running
 /// flushes.
-pub const NUM_RUNNING_FLUSHES: &str = property!("num-running-flushes");
+pub const NUM_RUNNING_FLUSHES: &CStr = property!("num-running-flushes");
 
 /// "rocksdb.compaction-pending" - returns 1 if at least one compaction is
 /// pending; otherwise, returns 0.
-pub const COMPACTION_PENDING: &str = property!("compaction-pending");
+pub const COMPACTION_PENDING: &CStr = property!("compaction-pending");
 
 /// "rocksdb.num-running-compactions" - returns the number of currently
 /// running compactions.
-pub const NUM_RUNNING_COMPACTIONS: &str = property!("num-running-compactions");
+pub const NUM_RUNNING_COMPACTIONS: &CStr = property!("num-running-compactions");
 
 /// "rocksdb.background-errors" - returns accumulated number of background
 /// errors.
-pub const BACKGROUND_ERRORS: &str = property!("background-errors");
+pub const BACKGROUND_ERRORS: &CStr = property!("background-errors");
 
 /// "rocksdb.cur-size-active-mem-table" - returns approximate size of active
 /// memtable (bytes).
-pub const CUR_SIZE_ACTIVE_MEM_TABLE: &str = property!("cur-size-active-mem-table");
+pub const CUR_SIZE_ACTIVE_MEM_TABLE: &CStr = property!("cur-size-active-mem-table");
 
 /// "rocksdb.cur-size-all-mem-tables" - returns approximate size of active
 /// and unflushed immutable memtables (bytes).
-pub const CUR_SIZE_ALL_MEM_TABLES: &str = property!("cur-size-all-mem-tables");
+pub const CUR_SIZE_ALL_MEM_TABLES: &CStr = property!("cur-size-all-mem-tables");
 
 /// "rocksdb.size-all-mem-tables" - returns approximate size of active,
 /// unflushed immutable, and pinned immutable memtables (bytes).
-pub const SIZE_ALL_MEM_TABLES: &str = property!("size-all-mem-tables");
+pub const SIZE_ALL_MEM_TABLES: &CStr = property!("size-all-mem-tables");
 
 /// "rocksdb.num-entries-active-mem-table" - returns total number of entries
 /// in the active memtable.
-pub const NUM_ENTRIES_ACTIVE_MEM_TABLE: &str = property!("num-entries-active-mem-table");
+pub const NUM_ENTRIES_ACTIVE_MEM_TABLE: &CStr = property!("num-entries-active-mem-table");
 
 /// "rocksdb.num-entries-imm-mem-tables" - returns total number of entries
 /// in the unflushed immutable memtables.
-pub const NUM_ENTRIES_IMM_MEM_TABLES: &str = property!("num-entries-imm-mem-tables");
+pub const NUM_ENTRIES_IMM_MEM_TABLES: &CStr = property!("num-entries-imm-mem-tables");
 
 /// "rocksdb.num-deletes-active-mem-table" - returns total number of delete
 /// entries in the active memtable.
-pub const NUM_DELETES_ACTIVE_MEM_TABLE: &str = property!("num-deletes-active-mem-table");
+pub const NUM_DELETES_ACTIVE_MEM_TABLE: &CStr = property!("num-deletes-active-mem-table");
 
 /// "rocksdb.num-deletes-imm-mem-tables" - returns total number of delete
 /// entries in the unflushed immutable memtables.
-pub const NUM_DELETES_IMM_MEM_TABLES: &str = property!("num-deletes-imm-mem-tables");
+pub const NUM_DELETES_IMM_MEM_TABLES: &CStr = property!("num-deletes-imm-mem-tables");
 
 /// "rocksdb.estimate-num-keys" - returns estimated number of total keys in
 /// the active and unflushed immutable memtables and storage.
-pub const ESTIMATE_NUM_KEYS: &str = property!("estimate-num-keys");
+pub const ESTIMATE_NUM_KEYS: &CStr = property!("estimate-num-keys");
 
 /// "rocksdb.estimate-table-readers-mem" - returns estimated memory used for
 /// reading SST tables, excluding memory used in block cache (e.g.,
 /// filter and index blocks).
-pub const ESTIMATE_TABLE_READERS_MEM: &str = property!("estimate-table-readers-mem");
+pub const ESTIMATE_TABLE_READERS_MEM: &CStr = property!("estimate-table-readers-mem");
 
 /// "rocksdb.is-file-deletions-enabled" - returns 0 if deletion of obsolete
 /// files is enabled; otherwise, returns a non-zero number.
-pub const IS_FILE_DELETIONS_ENABLED: &str = property!("is-file-deletions-enabled");
+pub const IS_FILE_DELETIONS_ENABLED: &CStr = property!("is-file-deletions-enabled");
 
 /// "rocksdb.num-snapshots" - returns number of unreleased snapshots of the
 /// database.
-pub const NUM_SNAPSHOTS: &str = property!("num-snapshots");
+pub const NUM_SNAPSHOTS: &CStr = property!("num-snapshots");
 
 /// "rocksdb.oldest-snapshot-time" - returns number representing unix
 /// timestamp of oldest unreleased snapshot.
-pub const OLDEST_SNAPSHOT_TIME: &str = property!("oldest-snapshot-time");
+pub const OLDEST_SNAPSHOT_TIME: &CStr = property!("oldest-snapshot-time");
 
 /// "rocksdb.num-live-versions" - returns number of live versions. `Version`
 /// is an internal data structure. See version_set.h for details. More
 /// live versions often mean more SST files are held from being deleted,
 /// by iterators or unfinished compactions.
-pub const NUM_LIVE_VERSIONS: &str = property!("num-live-versions");
+pub const NUM_LIVE_VERSIONS: &CStr = property!("num-live-versions");
 
 /// "rocksdb.current-super-version-number" - returns number of current LSM
 /// version. It is a uint64_t integer number, incremented after there is
 /// any change to the LSM tree. The number is not preserved after restarting
 /// the DB. After DB restart, it will start from 0 again.
-pub const CURRENT_SUPER_VERSION_NUMBER: &str = property!("current-super-version-number");
+pub const CURRENT_SUPER_VERSION_NUMBER: &CStr = property!("current-super-version-number");
 
 /// "rocksdb.estimate-live-data-size" - returns an estimate of the amount of
 /// live data in bytes.
-pub const ESTIMATE_LIVE_DATA_SIZE: &str = property!("estimate-live-data-size");
+pub const ESTIMATE_LIVE_DATA_SIZE: &CStr = property!("estimate-live-data-size");
 
 /// "rocksdb.min-log-number-to-keep" - return the minimum log number of the
 /// log files that should be kept.
-pub const MIN_LOG_NUMBER_TO_KEEP: &str = property!("min-log-number-to-keep");
+pub const MIN_LOG_NUMBER_TO_KEEP: &CStr = property!("min-log-number-to-keep");
 
 /// "rocksdb.min-obsolete-sst-number-to-keep" - return the minimum file
 /// number for an obsolete SST to be kept. The max value of `uint64_t`
 /// will be returned if all obsolete files can be deleted.
-pub const MIN_OBSOLETE_SST_NUMBER_TO_KEEP: &str = property!("min-obsolete-sst-number-to-keep");
+pub const MIN_OBSOLETE_SST_NUMBER_TO_KEEP: &CStr = property!("min-obsolete-sst-number-to-keep");
 
 /// "rocksdb.total-sst-files-size" - returns total size (bytes) of all SST
 /// files.
 /// WARNING: may slow down online queries if there are too many files.
-pub const TOTAL_SST_FILES_SIZE: &str = property!("total-sst-files-size");
+pub const TOTAL_SST_FILES_SIZE: &CStr = property!("total-sst-files-size");
 
 /// "rocksdb.live-sst-files-size" - returns total size (bytes) of all SST
 /// files belong to the latest LSM tree.
-pub const LIVE_SST_FILES_SIZE: &str = property!("live-sst-files-size");
+pub const LIVE_SST_FILES_SIZE: &CStr = property!("live-sst-files-size");
 
 /// "rocksdb.base-level" - returns number of level to which L0 data will be
 /// compacted.
-pub const BASE_LEVEL: &str = property!("base-level");
+pub const BASE_LEVEL: &CStr = property!("base-level");
 
 /// "rocksdb.estimate-pending-compaction-bytes" - returns estimated total
 /// number of bytes compaction needs to rewrite to get all levels down
 /// to under target size. Not valid for other compactions than level-
 /// based.
-pub const ESTIMATE_PENDING_COMPACTION_BYTES: &str = property!("estimate-pending-compaction-bytes");
+pub const ESTIMATE_PENDING_COMPACTION_BYTES: &CStr = property!("estimate-pending-compaction-bytes");
 
 /// "rocksdb.aggregated-table-properties" - returns a string representation
 /// of the aggregated table properties of the target column family.
-pub const AGGREGATED_TABLE_PROPERTIES: &str = property!("aggregated-table-properties");
+pub const AGGREGATED_TABLE_PROPERTIES: &CStr = property!("aggregated-table-properties");
 
 /// "rocksdb.aggregated-table-properties-at-level<N>", same as the previous
 /// one but only returns the aggregated table properties of the
 /// specified level "N" at the target column family.
-pub const AGGREGATED_TABLE_PROPERTIES_AT_LEVEL: &str =
+pub fn aggregated_table_properties_at_level(level: usize) -> CString {
-    property!("aggregated-table-properties-at-level");
+    unsafe { level_property("aggregated-table-properties-at-level", level) }
+}
 
 /// "rocksdb.actual-delayed-write-rate" - returns the current actual delayed
 /// write rate. 0 means no delay.
-pub const ACTUAL_DELAYED_WRITE_RATE: &str = property!("actual-delayed-write-rate");
+pub const ACTUAL_DELAYED_WRITE_RATE: &CStr = property!("actual-delayed-write-rate");
 
 /// "rocksdb.is-write-stopped" - Return 1 if write has been stopped.
-pub const IS_WRITE_STOPPED: &str = property!("is-write-stopped");
+pub const IS_WRITE_STOPPED: &CStr = property!("is-write-stopped");
 
 /// "rocksdb.estimate-oldest-key-time" - returns an estimation of
 /// oldest key timestamp in the DB. Currently only available for
 /// FIFO compaction with
 /// compaction_options_fifo.allow_compaction = false.
-pub const ESTIMATE_OLDEST_KEY_TIME: &str = property!("estimate-oldest-key-time");
+pub const ESTIMATE_OLDEST_KEY_TIME: &CStr = property!("estimate-oldest-key-time");
 
 /// "rocksdb.block-cache-capacity" - returns block cache capacity.
-pub const BLOCK_CACHE_CAPACITY: &str = property!("block-cache-capacity");
+pub const BLOCK_CACHE_CAPACITY: &CStr = property!("block-cache-capacity");
 
 /// "rocksdb.block-cache-usage" - returns the memory size for the entries
 /// residing in block cache.
-pub const BLOCK_CACHE_USAGE: &str = property!("block-cache-usage");
+pub const BLOCK_CACHE_USAGE: &CStr = property!("block-cache-usage");
 
 /// "rocksdb.block-cache-pinned-usage" - returns the memory size for the
 /// entries being pinned.
-pub const BLOCK_CACHE_PINNED_USAGE: &str = property!("block-cache-pinned-usage");
+pub const BLOCK_CACHE_PINNED_USAGE: &CStr = property!("block-cache-pinned-usage");
 
 /// "rocksdb.options-statistics" - returns multi-line string
 /// of options.statistics
-pub const OPTIONS_STATISTICS: &str = property!("options-statistics");
+pub const OPTIONS_STATISTICS: &CStr = property!("options-statistics");
+
+/// Constructs a property name for an ‘at level’ property.
+///
+/// `name` is the infix of the property name (e.g. `"num-files-at-level"`) and
+/// `level` is level to get statistics of.  The property name is constructed as
+/// `"rocksdb.<name><level>"`.
+///
+/// Expects `name` not to contain any interior NUL bytes.
+unsafe fn level_property(name: &str, level: usize) -> CString {
+    let bytes = format!("rocksdb.{}{}\0", name, level).into_bytes();
+    // SAFETY: We’re appending terminating NUL and all our call sites pass
+    // a string without interior NUL bytes.
+    CString::from_vec_with_nul_unchecked(bytes)
+}
+
+#[test]
+fn sanity_checks() {
+    let want = CString::new("rocksdb.cfstats-no-file-histogram".to_string()).unwrap();
+    assert_eq!(want.as_c_str(), CFSTATS_NO_FILE_HISTOGRAM);
+
+    let want = CString::new("rocksdb.num-files-at-level5".to_string()).unwrap();
+    assert_eq!(want, num_files_at_level(5));
+}

tests/test_property.rs

@@ -24,21 +24,22 @@ fn property_test() {
     let n = DBPath::new("_rust_rocksdb_property_test");
     {
         let db = DB::open_default(&n).unwrap();
-        let value = db.property_value(properties::STATS).unwrap().unwrap();
+        let prop_name: &std::ffi::CStr = properties::STATS;
+        let value = db.property_value(prop_name).unwrap().unwrap();
         assert!(value.contains("Stats"));
     }
 
     {
         let db = DB::open_default(&n).unwrap();
-        let prop_name = std::ffi::CString::new(properties::STATS).unwrap();
+        let prop_name: std::ffi::CString = properties::STATS.to_owned();
-        let value = db.property_value(prop_name).unwrap().unwrap();
+        let value = db.property_value(&prop_name).unwrap().unwrap();
         assert!(value.contains("Stats"));
     }
 
     {
         let db = DB::open_default(&n).unwrap();
-        let prop_name = std::ffi::CString::new(properties::STATS).unwrap();
+        let prop_name: String = properties::STATS.to_owned().into_string().unwrap();
-        let value = db.property_value(prop_name.as_ref()).unwrap().unwrap();
+        let value = db.property_value(&prop_name).unwrap().unwrap();
         assert!(value.contains("Stats"));
     }
 }