rocksdb abstraction layer

util/src/kvdb.rs

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+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Key-Value store abstraction with rocksb backend.
+
+use rocksdb::{DB, Writable, WriteBatch, IteratorMode, DBVector, DBIterator,
+	IndexType, Options, DBCompactionStyle, BlockBasedOptions, Direction};
+
+/// Write transaction. Batches a sequence of put/delete operations for efficiency.
+pub struct DBTransaction {
+	batch: WriteBatch,
+}
+
+impl DBTransaction {
+	/// Create new transaction.
+	pub fn new() -> DBTransaction {
+		DBTransaction { batch: WriteBatch::new() }
+	}
+
+	/// Insert a ket-value pair in the transaction. Any existing value value will be overwritten upon write.
+    pub fn put(&self, key: &[u8], value: &[u8]) -> Result<(), String> {
+		self.batch.put(key, value)
+	}
+
+	/// Delete value by key.
+    pub fn delete(&self, key: &[u8]) -> Result<(), String> {
+		self.batch.delete(key)
+	}
+}
+
+/// Database configuration
+pub struct DatabaseConfig {
+	/// Optional prefix size in bytes. Allows lookup by partial key.
+	pub prefix_size: Option<usize>
+}
+
+/// Database iterator
+pub struct DatabaseIterator<'a> {
+    iter: DBIterator<'a>,
+}
+
+impl<'a> Iterator for DatabaseIterator<'a> {
+    type Item = (Box<[u8]>, Box<[u8]>);
+
+	#[allow(type_complexity)]
+    fn next(&mut self) -> Option<(Box<[u8]>, Box<[u8]>)> {
+		self.iter.next()
+	}
+}
+
+/// Key-Value database.
+pub struct Database {
+	db: DB,
+}
+
+impl Database {
+	/// Open database with default settings.
+	pub fn open_default(path: &str) -> Result<Database, String> {
+		Database::open(DatabaseConfig { prefix_size: None }, path) 
+	}
+
+	/// Open database file. Creates if it does not exist.
+	pub fn open(config: DatabaseConfig, path: &str) -> Result<Database, String> {
+		let mut opts = Options::new();
+		opts.set_max_open_files(256);
+		opts.create_if_missing(true);
+		opts.set_use_fsync(false);
+		opts.set_compaction_style(DBCompactionStyle::DBUniversalCompaction);
+		/*
+		opts.set_bytes_per_sync(8388608);
+		opts.set_disable_data_sync(false);
+		opts.set_block_cache_size_mb(1024);
+		opts.set_table_cache_num_shard_bits(6);
+		opts.set_max_write_buffer_number(32);
+		opts.set_write_buffer_size(536870912);
+		opts.set_target_file_size_base(1073741824);
+		opts.set_min_write_buffer_number_to_merge(4);
+		opts.set_level_zero_stop_writes_trigger(2000);
+		opts.set_level_zero_slowdown_writes_trigger(0);
+		opts.set_compaction_style(DBUniversalCompaction);
+		opts.set_max_background_compactions(4);
+		opts.set_max_background_flushes(4);
+		opts.set_filter_deletes(false);
+		opts.set_disable_auto_compactions(false);*/
+
+		if let Some(size) = config.prefix_size {
+			let mut block_opts = BlockBasedOptions::new();
+			block_opts.set_index_type(IndexType::HashSearch);
+			opts.set_block_based_table_factory(&block_opts);
+			opts.set_prefix_extractor_fixed_size(size);
+		}
+		let db = try!(DB::open(&opts, path));
+		Ok(Database { db: db })
+	}
+
+	/// Insert a ket-value pair in the transaction. Any existing value value will be overwritten.
+    pub fn put(&self, key: &[u8], value: &[u8]) -> Result<(), String> {
+		self.db.put(key, value)
+	}
+
+	/// Delete value by key.
+    pub fn delete(&self, key: &[u8]) -> Result<(), String> {
+		self.db.delete(key)
+	}
+
+	/// Commit transaction to database.
+    pub fn write(&self, tr: DBTransaction) -> Result<(), String> {
+		self.db.write(tr.batch)
+	}
+	
+	/// Get value by key.
+    pub fn get(&self, key: &[u8]) -> Result<Option<DBVector>, String> {
+		self.db.get(key)
+	}
+
+	/// Get value by partial key. Prefix size should match configured prefix size.
+    pub fn get_by_prefix(&self, prefix: &[u8]) -> Option<Box<[u8]>> {
+		let mut iter = self.db.iterator(IteratorMode::From(prefix, Direction::forward));
+		match iter.next() {
+			// TODO: use prefix_same_as_start read option (not availabele in C API currently)
+			Some((k, v)) => if k[0 .. prefix.len()] == prefix[..] { Some(v) } else { None },
+			_ => None
+		}
+	}
+
+	/// Check if there is anything in the database.
+	pub fn is_empty(&self) -> bool {
+		self.db.iterator(IteratorMode::Start).next().is_none()
+	}
+
+	/// Check if there is anything in the database.
+	pub fn iter(&self) -> DatabaseIterator {
+		DatabaseIterator { iter: self.db.iterator(IteratorMode::Start) }
+	}
+}
+
+