Jumptable cache (#2435)

* v1.3.3

* Jumptable cache

ethcore/src/evm/interpreter/shared_cache.rs

@@ -0,0 +1,84 @@
+// 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/>.
+
+use std::sync::Arc;
+use lru_cache::LruCache;
+use util::{H256, Mutex};
+use util::sha3::*;
+use bit_set::BitSet;
+use super::super::instructions;
+
+const CACHE_CODE_ITEMS: usize = 4096;
+
+/// GLobal cache for EVM interpreter
+pub struct SharedCache {
+	jump_destinations: Mutex<LruCache<H256, Arc<BitSet>>>
+}
+
+impl SharedCache {
+	/// Get jump destincations bitmap for a contract.
+	pub fn jump_destinations(&self, code_hash: &H256, code: &[u8]) -> Arc<BitSet> {
+		if code_hash == &SHA3_EMPTY {
+			return Self::find_jump_destinations(code);
+		}
+		if let Some(d) = self.jump_destinations.lock().get_mut(code_hash) {
+			return d.clone();
+		}
+
+		let d = Self::find_jump_destinations(code);
+		self.jump_destinations.lock().insert(code_hash.clone(), d.clone());
+		d
+	}
+
+	fn find_jump_destinations(code: &[u8]) -> Arc<BitSet> {
+		let mut jump_dests = BitSet::with_capacity(code.len());
+		let mut position = 0;
+
+		while position < code.len() {
+			let instruction = code[position];
+
+			if instruction == instructions::JUMPDEST {
+				jump_dests.insert(position);
+			} else if instructions::is_push(instruction) {
+				position += instructions::get_push_bytes(instruction);
+			}
+			position += 1;
+		}
+		Arc::new(jump_dests)
+	}
+}
+
+impl Default for SharedCache {
+	fn default() -> SharedCache {
+		SharedCache {
+			jump_destinations: Mutex::new(LruCache::new(CACHE_CODE_ITEMS)),
+		}
+	}
+}
+
+
+#[test]
+fn test_find_jump_destinations() {
+	use util::FromHex;
+	// given
+	let code = "7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff5b01600055".from_hex().unwrap();
+
+	// when
+	let valid_jump_destinations = SharedCache::find_jump_destinations(&code);
+
+	// then
+	assert!(valid_jump_destinations.contains(66));
+}