Cleaner storage backend architecture

lib/src/storage/backend/fallback.rs

@@ -1,5 +1,6 @@
 //! TODO: This storage is dramatically naive.
 
+use crate::storage::backend::{ColumnFamilyDefinition, CompactionAction, CompactionFilter};
 use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
 use std::ffi::CString;
@@ -7,14 +8,6 @@ use std::io::Result;
 use std::iter::{once, Once};
 use std::sync::{Arc, RwLock};
 
-pub struct ColumnFamilyDefinition {
-    pub name: &'static str,
-    pub merge_operator: Option<MergeOperator>,
-    pub compaction_filter: Option<CompactionFilter>,
-    pub use_iter: bool,
-    pub min_prefix_size: usize,
-}
-
 #[derive(Clone)]
 pub struct Db(Arc<RwLock<BTreeMap<ColumnFamily, Tree>>>);
 
@@ -95,7 +88,6 @@ impl Db {
         match action {
             CompactionAction::Keep => tree.tree.insert(key.into(), value.into()),
             CompactionAction::Remove => tree.tree.remove(key),
-            CompactionAction::Replace(value) => tree.tree.insert(key.into(), value),
         };
         Ok(())
     }
@@ -152,9 +144,6 @@ impl Db {
                         e.insert(value);
                     }
                     CompactionAction::Remove => (),
-                    CompactionAction::Replace(value) => {
-                        e.insert(value);
-                    }
                 }
             }
             Entry::Occupied(mut e) => {
@@ -171,7 +160,6 @@ impl Db {
                 match action {
                     CompactionAction::Keep => e.insert(value),
                     CompactionAction::Remove => e.remove(),
-                    CompactionAction::Replace(value) => e.insert(value),
                 };
             }
         }
@@ -254,15 +242,3 @@ pub struct MergeOperator {
 }
 
 pub type SlicesIterator<'a> = Once<&'a [u8]>;
-
-pub struct CompactionFilter {
-    pub filter: fn(&[u8], &[u8]) -> CompactionAction,
-    pub name: CString,
-}
-
-#[allow(dead_code)]
-pub enum CompactionAction {
-    Keep,
-    Remove,
-    Replace(Vec<u8>),
-}

lib/src/storage/backend/mod.rs

@@ -0,0 +1,32 @@
+//! A storage backend
+//! RocksDB is available, if not in memory
+
+#[cfg(target_arch = "wasm32")]
+pub use fallback::{ColumnFamily, Db, Iter, MergeOperator};
+#[cfg(not(target_arch = "wasm32"))]
+pub use rocksdb::{ColumnFamily, Db, Iter, MergeOperator};
+use std::ffi::CString;
+
+#[cfg(target_arch = "wasm32")]
+mod fallback;
+#[cfg(not(target_arch = "wasm32"))]
+mod rocksdb;
+
+pub struct ColumnFamilyDefinition {
+    pub name: &'static str,
+    pub merge_operator: Option<MergeOperator>,
+    pub compaction_filter: Option<CompactionFilter>,
+    pub use_iter: bool,
+    pub min_prefix_size: usize,
+}
+
+pub struct CompactionFilter {
+    pub filter: fn(&[u8], &[u8]) -> CompactionAction,
+    pub name: CString,
+}
+
+#[warn(dead_code)]
+pub enum CompactionAction {
+    Keep,
+    Remove,
+}

lib/src/storage/backend/rocksdb.rs

@@ -5,6 +5,7 @@
 #![allow(unsafe_code)]
 
 use crate::error::invalid_input_error;
+use crate::storage::backend::{ColumnFamilyDefinition, CompactionAction, CompactionFilter};
 use libc::{self, c_char, c_int, c_uchar, c_void, size_t};
 use oxrocksdb_sys::*;
 use std::borrow::Borrow;
@@ -39,14 +40,6 @@ macro_rules! ffi_result_impl {
     }}
 }
 
-pub struct ColumnFamilyDefinition {
-    pub name: &'static str,
-    pub merge_operator: Option<MergeOperator>,
-    pub compaction_filter: Option<CompactionFilter>,
-    pub use_iter: bool,
-    pub min_prefix_size: usize,
-}
-
 #[derive(Clone)]
 pub struct Db(Arc<DbHandler>);
 
@@ -728,18 +721,6 @@ impl<'a> Iterator for SlicesIterator<'a> {
     }
 }
 
-pub struct CompactionFilter {
-    pub filter: fn(&[u8], &[u8]) -> CompactionAction,
-    pub name: CString,
-}
-
-#[allow(dead_code)]
-pub enum CompactionAction {
-    Keep,
-    Remove,
-    Replace(Vec<u8>),
-}
-
 unsafe extern "C" fn compactionfilter_destructor(filter: *mut c_void) {
     Box::from_raw(filter as *mut CompactionFilter);
 }
@@ -751,9 +732,9 @@ unsafe extern "C" fn compactionfilter_filter(
     key_length: size_t,
     existing_value: *const c_char,
     value_length: size_t,
-    new_value: *mut *mut c_char,
-    new_value_length: *mut size_t,
-    value_changed: *mut c_uchar,
+    _new_value: *mut *mut c_char,
+    _new_value_length: *mut size_t,
+    _value_changed: *mut c_uchar,
 ) -> c_uchar {
     let filter = &*(filter as *const CompactionFilter);
     match (filter.filter)(
@@ -762,12 +743,6 @@ unsafe extern "C" fn compactionfilter_filter(
     ) {
         CompactionAction::Keep => 0,
         CompactionAction::Remove => 1,
-        CompactionAction::Replace(new_val) => {
-            *new_value_length = new_val.len();
-            *value_changed = 1_u8;
-            *new_value = Box::into_raw(new_val.into_boxed_slice()) as *mut c_char;
-            0
-        }
     }
 }
 

lib/src/storage/mod.rs

@@ -9,13 +9,7 @@ use crate::storage::binary_encoder::{
 use crate::storage::numeric_encoder::{
     insert_term, remove_term, EncodedQuad, EncodedTerm, StrHash, StrLookup,
 };
-#[cfg(target_arch = "wasm32")]
-use fallback_backend::{
-    ColumnFamily, ColumnFamilyDefinition, CompactionAction, CompactionFilter, Db, Iter,
-    MergeOperator,
-};
-#[cfg(not(target_arch = "wasm32"))]
-use rocksdb_backend::{
+use backend::{
     ColumnFamily, ColumnFamilyDefinition, CompactionAction, CompactionFilter, Db, Iter,
     MergeOperator,
 };
@@ -24,13 +18,10 @@ use std::io::Result;
 #[cfg(not(target_arch = "wasm32"))]
 use std::path::Path;
 
+mod backend;
 mod binary_encoder;
-#[cfg(target_arch = "wasm32")]
-mod fallback_backend;
 pub mod io;
 pub mod numeric_encoder;
-#[cfg(not(target_arch = "wasm32"))]
-mod rocksdb_backend;
 pub mod small_string;
 
 const ID2STR_CF: &str = "id2str";