rocksdb: add get_compression_per_level method to Options

Signed-off-by: Cholerae Hu <huyingqian@pingcap.com>

librocksdb_sys/crocksdb/c.cc

@@ -1782,6 +1782,17 @@ void crocksdb_options_set_compression_per_level(crocksdb_options_t* opt,
   }
 }
 
+size_t crocksdb_options_get_compression_level_number(crocksdb_options_t* opt) {
+  return opt->rep.compression_per_level.size();
+}
+
+void crocksdb_options_get_compression_per_level(crocksdb_options_t* opt,
+                                               int* level_values) {
+  for (size_t i = 0; i < opt->rep.compression_per_level.size(); i++) {
+    level_values[i] = static_cast<int>(opt->rep.compression_per_level[i]);
+  }
+}
+
 void crocksdb_options_set_compression_options(crocksdb_options_t* opt, int w_bits,
                                              int level, int strategy,
                                              int max_dict_bytes) {

librocksdb_sys/crocksdb/rocksdb/c.h

@@ -624,6 +624,10 @@ extern C_ROCKSDB_LIBRARY_API void crocksdb_options_set_merge_operator(
     crocksdb_options_t*, crocksdb_mergeoperator_t*);
 extern C_ROCKSDB_LIBRARY_API void crocksdb_options_set_compression_per_level(
     crocksdb_options_t* opt, int* level_values, size_t num_levels);
+extern C_ROCKSDB_LIBRARY_API size_t crocksdb_options_get_compression_level_number(
+    crocksdb_options_t* opt);
+extern C_ROCKSDB_LIBRARY_API void crocksdb_options_get_compression_per_level(
+    crocksdb_options_t* opt, int *level_values);
 extern C_ROCKSDB_LIBRARY_API void crocksdb_options_set_create_if_missing(
     crocksdb_options_t*, unsigned char);
 extern C_ROCKSDB_LIBRARY_API void

librocksdb_sys/src/lib.rs

@@ -315,6 +315,9 @@ extern "C" {
     pub fn crocksdb_options_set_compression_per_level(options: *mut DBOptions,
                                                       level_values: *const DBCompressionType,
                                                       num_levels: size_t);
+    pub fn crocksdb_options_get_compression_level_number(options: *mut DBOptions) -> size_t;
+    pub fn crocksdb_options_get_compression_per_level(options: *mut DBOptions,
+                                                      level_values: *mut DBCompressionType);
     pub fn crocksdb_options_set_base_background_compactions(optinos: *mut DBOptions,
                                                             base_bg_compactions: c_int);
     pub fn crocksdb_options_set_max_background_compactions(options: *mut DBOptions,

src/rocksdb_options.rs

@@ -413,6 +413,21 @@ impl Options {
         }
     }
 
+    pub fn get_compression_level_number(&self) -> usize {
+        unsafe { crocksdb_ffi::crocksdb_options_get_compression_level_number(self.inner) as usize }
+    }
+
+    pub fn get_compression_per_level(&self) -> Vec<DBCompressionType> {
+        let size = self.get_compression_level_number();
+        unsafe {
+            let mut ret = Vec::with_capacity(size);
+            let pret = ret.as_mut_ptr();
+            crocksdb_ffi::crocksdb_options_get_compression_per_level(self.inner, pret);
+            ret.set_len(size);
+            ret
+        }
+    }
+
     pub fn add_merge_operator(&mut self, name: &str, merge_fn: MergeFn) {
         let cb = Box::new(MergeOperatorCallback {
             name: CString::new(name.as_bytes()).unwrap(),

tests/test_rocksdb_options.rs

@@ -360,3 +360,15 @@ fn test_get_compression() {
     opts.compression(DBCompressionType::DBSnappy);
     assert_eq!(opts.get_compression(), DBCompressionType::DBSnappy);
 }
+
+#[test]
+fn test_get_compression_per_level() {
+    let mut opts = Options::new();
+    let compressions = &[DBCompressionType::DBNo, DBCompressionType::DBSnappy];
+    opts.compression_per_level(compressions);
+    assert_eq!(opts.get_compression_level_number(), 2);
+    let v = opts.get_compression_per_level();
+    assert_eq!(v.len(), 2);
+    assert_eq!(v[0], DBCompressionType::DBNo);
+    assert_eq!(v[1], DBCompressionType::DBSnappy);
+}