Blocks and snapshot compression (#1687)

* new Compressible rlp trait

* new Compressible rlp trait

* make compressed rlp iterable

* make compressed rlp iterable

* invalid rlp slice swapper

* switch compress to swapper, add reverse swapper test case

* add basic account compression test

* add new rlp trait

* new Compressible rlp trait

* make compressed rlp iterable

* invalid rlp slice swapper

* invalid rlp slice swapper

* switch compress to swapper, add reverse swapper test case

* switch compress to swapper, add reverse swapper test case

* add account compress/ decompress test

* make compressor cleaner, use hashmaps for swapper

* improve compression tests

* add a DecompressingDecoder, change Decoder to take refernce

* separate rlp compression related stuff

* new Compressible rlp trait

* new Compressible rlp trait

* new Compressible rlp trait

* make compressed rlp iterable

* make compressed rlp iterable

* make compressed rlp iterable

* invalid rlp slice swapper

* invalid rlp slice swapper

* invalid rlp slice swapper

* switch compress to swapper, add reverse swapper test case

* switch compress to swapper, add reverse swapper test case

* switch compress to swapper, add reverse swapper test case

* add basic account compression test

* add new rlp trait

* add account compress/ decompress test

* make compressor cleaner, use hashmaps for swapper

* improve compression tests

* add a DecompressingDecoder, change Decoder to take refernce

* separate rlp compression related stuff

* DecompressingDecoder test

* initial compressing HashDB wrapper

* remove unused test

* change CompressedDB to struct wrapper with overlay

* simplify compressor

* failed RefCell attempt

* use denote to return reference

* compiled compresseddb

* compressdb test, add overlay emplace

* fix overlay reference count handling

* add immutable compresseddb, make account use hashdb

* simplify using trait objects

* enable hashdb for account

* initial state compression attempt

* wrap state db

* add tests for analyzing db

* add account predicate

* try to compress data fields as rlp too

* remove compression for storage trie

* add a compressing migration

* more compression stats tests

* fix migration import

* nested encoding compression test

* fix decompression, move db stats tests to rlpcompression

* added malformed rlp tests, cover a few edge cases

* new CompressingEncoder struct

* extend migrations to state

* first version working on the whole db

* clean up Compressible impl

* tests cleanup

* add a testing migration

* refactor deep compression using option, add simple compression

* put tests in a module

* fix compressed overlay loading

* simple compression for snapshots

* remove unused DecompressingDecoder

* add a general compressing migration

* add more common rlps to compress

* use static slices for swapper

* add precomputed hashes and invalid rlps

* make decoder private again

* cover more cases with tests

* style

* fix weird indentation

* remove possible panic in payload_info

* make prefix checking safe

* fix db existence check

* remove db dir from test

* pass usize by value [ci skip]

* Improve comment on panic removal.

* add common blocks db rlps

* add compression to blockchain db

* add blocks db migration

* fix the migrations

* remove state compression

* add a separate snapshot swapper

* ability to use different swappers and traversal

* update tests to new interface

* clean up code ordering

* update usage

* fix compilation

* remove unnecessary changes

* move methods to functions to reduce interface

* move test to module

* update common rlps to blocks db

* move tests to tests modules

* remove redundant &

ethcore/src/account.rs

@@ -288,6 +288,16 @@ mod tests {
 	use super::*;
 	use account_db::*;
 
+	#[test]
+	fn account_compress() {
+		let raw = Account::new_basic(2.into(), 4.into()).rlp();
+		let rlp = UntrustedRlp::new(&raw);
+		let compact_vec = rlp.compress(RlpType::Snapshot).to_vec();
+		assert!(raw.len() > compact_vec.len());
+		let again_raw = UntrustedRlp::new(&compact_vec).decompress(RlpType::Snapshot);
+		assert_eq!(raw, again_raw.to_vec());
+    }
+
 	#[test]
 	fn storage_at() {
 		let mut db = MemoryDB::new();

ethcore/src/blockchain/blockchain.rs

@@ -183,7 +183,7 @@ impl BlockProvider for BlockChain {
 
 		match opt {
 			Some(b) => {
-				let bytes: Bytes = b.to_vec();
+				let bytes: Bytes = UntrustedRlp::new(&b).decompress(RlpType::Blocks).to_vec();
 				let mut write = self.blocks.write();
 				write.insert(hash.clone(), bytes.clone());
 				Some(bytes)
@@ -510,9 +510,11 @@ impl BlockChain {
 			return ImportRoute::none();
 		}
 
+		let compressed = UntrustedRlp::new(bytes).compress(RlpType::Blocks).to_vec();
+
 		let _lock = self.insert_lock.lock();
 		// store block in db
-		self.blocks_db.put(&hash, bytes).unwrap();
+		self.blocks_db.put(&hash, &compressed).unwrap();
 
 		let info = self.block_info(bytes);
 

ethcore/src/migrations/blocks/mod.rs

@@ -0,0 +1,21 @@
+// 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/>.
+
+//! Blocks database migrations.
+
+mod v8;
+
+pub use self::v8::V8;

ethcore/src/migrations/blocks/v8.rs

@@ -0,0 +1,34 @@
+// 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/>.
+
+//! This migration compresses the state db.
+
+use util::migration::SimpleMigration;
+use util::rlp::{Compressible, UntrustedRlp, View, RlpType};
+
+/// Compressing migration.
+#[derive(Default)]
+pub struct V8;
+
+impl SimpleMigration for V8 {
+	fn version(&self) -> u32 {
+		8
+	}
+
+	fn simple_migrate(&mut self, key: Vec<u8>, value: Vec<u8>) -> Option<(Vec<u8>, Vec<u8>)> {
+		Some((key,UntrustedRlp::new(&value).compress(RlpType::Blocks).to_vec()))
+	}
+}

ethcore/src/migrations/mod.rs

@@ -1,4 +1,5 @@
 //! Database migrations.
 
-pub mod extras;
 pub mod state;
+pub mod blocks;
+pub mod extras;

ethcore/src/snapshot/mod.rs

@@ -29,7 +29,7 @@ use views::{BlockView, HeaderView};
 
 use util::{Bytes, Hashable, HashDB, JournalDB, snappy, TrieDB, TrieDBMut, TrieMut};
 use util::hash::{FixedHash, H256};
-use util::rlp::{DecoderError, RlpStream, Stream, UntrustedRlp, View};
+use util::rlp::{DecoderError, RlpStream, Stream, UntrustedRlp, View, Compressible, RlpType};
 
 use self::account::Account;
 use self::block::AbridgedBlock;
@@ -261,7 +261,8 @@ pub fn chunk_state(db: &HashDB, root: &H256, path: &Path) -> Result<Vec<H256>, E
 		let account_db = AccountDB::from_hash(db, account_key_hash);
 
 		let fat_rlp = try!(account.to_fat_rlp(&account_db));
-		try!(chunker.push(account_key, fat_rlp));
+		let compressed_rlp = UntrustedRlp::new(&fat_rlp).compress(RlpType::Snapshot).to_vec();
+		try!(chunker.push(account_key, compressed_rlp));
 	}
 
 	if chunker.cur_size != 0 {
@@ -400,7 +401,8 @@ fn rebuild_account_trie(db: &mut HashDB, account_chunk: &[&[u8]], out_chunk: &mu
 		let account_rlp = UntrustedRlp::new(account_pair);
 
 		let hash: H256 = try!(account_rlp.val_at(0));
-		let fat_rlp = try!(account_rlp.at(1));
+		let decompressed = try!(account_rlp.at(1)).decompress(RlpType::Snapshot);
+		let fat_rlp = UntrustedRlp::new(&decompressed[..]);
 
 		let thin_rlp = {
 			let mut acct_db = AccountDBMut::from_hash(db.as_hashdb_mut(), hash);

parity/migration.rs

@@ -26,7 +26,7 @@ use ethcore::migrations;
 /// Database is assumed to be at default version, when no version file is found.
 const DEFAULT_VERSION: u32 = 5;
 /// Current version of database models.
-const CURRENT_VERSION: u32 = 7;
+const CURRENT_VERSION: u32 = 8;
 /// Defines how many items are migrated to the new version of database at once.
 const BATCH_SIZE: usize = 1024;
 /// Version file name.
@@ -110,6 +110,13 @@ fn update_version(path: &Path) -> Result<(), Error> {
 	Ok(())
 }
 
+/// State database path.
+fn state_database_path(path: &Path) -> PathBuf {
+	let mut state_path = path.to_owned();
+	state_path.push("state");
+	state_path
+}
+
 /// Blocks database path.
 fn blocks_database_path(path: &Path) -> PathBuf {
 	let mut blocks_path = path.to_owned();
@@ -124,13 +131,6 @@ fn extras_database_path(path: &Path) -> PathBuf {
 	extras_path
 }
 
-/// State database path.
-fn state_database_path(path: &Path) -> PathBuf {
-	let mut state_path = path.to_owned();
-	state_path.push("state");
-	state_path
-}
-
 /// Database backup
 fn backup_database_path(path: &Path) -> PathBuf {
 	let mut backup_path = path.to_owned();
@@ -148,7 +148,8 @@ fn default_migration_settings() -> MigrationConfig {
 
 /// Migrations on the blocks database.
 fn blocks_database_migrations() -> Result<MigrationManager, Error> {
-	let manager = MigrationManager::new(default_migration_settings());
+	let mut manager = MigrationManager::new(default_migration_settings());
+	try!(manager.add_migration(migrations::blocks::V8::default()).map_err(|_| Error::MigrationImpossible));
 	Ok(manager)
 }
 
@@ -167,8 +168,8 @@ fn state_database_migrations(pruning: Algorithm) -> Result<MigrationManager, Err
 		Algorithm::OverlayRecent => manager.add_migration(migrations::state::OverlayRecentV7::default()),
 		_ => return Err(Error::UnsuportedPruningMethod),
 	};
-
 	try!(res.map_err(|_| Error::MigrationImpossible));
+
 	Ok(manager)
 }
 

util/src/kvdb.rs

@@ -275,4 +275,3 @@ mod tests {
 		test_db(&DatabaseConfig::default());
 	}
 }
-

util/src/rlp/commonrlps.rs

@@ -0,0 +1,106 @@
+// 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/>.
+
+//! Contains RLPs used for compression.
+
+use rlp::rlpcompression::InvalidRlpSwapper;
+
+lazy_static! {
+	/// Swapper for snapshot compression.
+	pub static ref SNAPSHOT_RLP_SWAPPER: InvalidRlpSwapper<'static> = InvalidRlpSwapper::new(EMPTY_RLPS, INVALID_RLPS);
+}
+
+lazy_static! {
+	/// Swapper with common long RLPs, up to 127 can be added.
+	pub static ref BLOCKS_RLP_SWAPPER: InvalidRlpSwapper<'static> = InvalidRlpSwapper::new(COMMON_RLPS, INVALID_RLPS);
+}
+
+static EMPTY_RLPS: &'static [&'static [u8]] = &[
+	// RLP of SHA3_NULL_RLP
+	&[160, 86, 232, 31, 23, 27, 204, 85, 166, 255, 131, 69, 230, 146, 192, 248, 110, 91, 72, 224, 27, 153, 108, 173, 192, 1, 98, 47, 181, 227, 99, 180, 33],
+	// RLP of SHA3_EMPTY
+	&[160, 197, 210, 70, 1, 134, 247, 35, 60, 146, 126, 125, 178, 220, 199, 3, 192, 229, 0, 182, 83, 202, 130, 39, 59, 123, 250, 216, 4, 93, 133, 164, 112]
+];
+
+static COMMON_RLPS: &'static [&'static [u8]] = &[
+	// RLP of SHA3_NULL_RLP
+	&[160, 86, 232, 31, 23, 27, 204, 85, 166, 255, 131, 69, 230, 146, 192, 248, 110, 91, 72, 224, 27, 153, 108, 173, 192, 1, 98, 47, 181, 227, 99, 180, 33],
+	// RLP of SHA3_EMPTY
+	&[160, 197, 210, 70, 1, 134, 247, 35, 60, 146, 126, 125, 178, 220, 199, 3, 192, 229, 0, 182, 83, 202, 130, 39, 59, 123, 250, 216, 4, 93, 133, 164, 112],
+	// Other RLPs found in blocks DB using the test below.
+	&[160, 29, 204, 77, 232, 222, 199, 93, 122, 171, 133, 181, 103, 182, 204, 212, 26, 211, 18, 69, 27, 148, 138, 116, 19, 240, 161, 66, 253, 64, 212, 147, 71],
+	&[148, 50, 190, 52, 59, 148, 248, 96, 18, 77, 196, 254, 226, 120, 253, 203, 211, 140, 16, 45, 136],
+	&[148, 82, 188, 68, 213, 55, 131, 9, 238, 42, 191, 21, 57, 191, 113, 222, 27, 125, 123, 227, 181],
+	&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+]; 
+
+static INVALID_RLPS: &'static [&'static [u8]] = &[&[0x81, 0x0], &[0x81, 0x1], &[0x81, 0x2], &[0x81, 0x3], &[0x81, 0x4], &[0x81, 0x5], &[0x81, 0x6], &[0x81, 0x7], &[0x81, 0x8], &[0x81, 0x9], &[0x81, 0xa], &[0x81, 0xb], &[0x81, 0xc], &[0x81, 0xd], &[0x81, 0xe], &[0x81, 0xf], &[0x81, 0x10], &[0x81, 0x11], &[0x81, 0x12], &[0x81, 0x13], &[0x81, 0x14], &[0x81, 0x15], &[0x81, 0x16], &[0x81, 0x17], &[0x81, 0x18], &[0x81, 0x19], &[0x81, 0x1a], &[0x81, 0x1b], &[0x81, 0x1c], &[0x81, 0x1d], &[0x81, 0x1e], &[0x81, 0x1f], &[0x81, 0x20], &[0x81, 0x21], &[0x81, 0x22], &[0x81, 0x23], &[0x81, 0x24], &[0x81, 0x25], &[0x81, 0x26], &[0x81, 0x27], &[0x81, 0x28], &[0x81, 0x29], &[0x81, 0x2a], &[0x81, 0x2b], &[0x81, 0x2c], &[0x81, 0x2d], &[0x81, 0x2e], &[0x81, 0x2f], &[0x81, 0x30], &[0x81, 0x31], &[0x81, 0x32], &[0x81, 0x33], &[0x81, 0x34], &[0x81, 0x35], &[0x81, 0x36], &[0x81, 0x37], &[0x81, 0x38], &[0x81, 0x39], &[0x81, 0x3a], &[0x81, 0x3b], &[0x81, 0x3c], &[0x81, 0x3d], &[0x81, 0x3e], &[0x81, 0x3f], &[0x81, 0x40], &[0x81, 0x41], &[0x81, 0x42], &[0x81, 0x43], &[0x81, 0x44], &[0x81, 0x45], &[0x81, 0x46], &[0x81, 0x47], &[0x81, 0x48], &[0x81, 0x49], &[0x81, 0x4a], &[0x81, 0x4b], &[0x81, 0x4c], &[0x81, 0x4d], &[0x81, 0x4e], &[0x81, 0x4f], &[0x81, 0x50], &[0x81, 0x51], &[0x81, 0x52], &[0x81, 0x53], &[0x81, 0x54], &[0x81, 0x55], &[0x81, 0x56], &[0x81, 0x57], &[0x81, 0x58], &[0x81, 0x59], &[0x81, 0x5a], &[0x81, 0x5b], &[0x81, 0x5c], &[0x81, 0x5d], &[0x81, 0x5e], &[0x81, 0x5f], &[0x81, 0x60], &[0x81, 0x61], &[0x81, 0x62], &[0x81, 0x63], &[0x81, 0x64], &[0x81, 0x65], &[0x81, 0x66], &[0x81, 0x67], &[0x81, 0x68], &[0x81, 0x69], &[0x81, 0x6a], &[0x81, 0x6b], &[0x81, 0x6c], &[0x81, 0x6d], &[0x81, 0x6e], &[0x81, 0x6f], &[0x81, 0x70], &[0x81, 0x71], &[0x81, 0x72], &[0x81, 0x73], &[0x81, 0x74], &[0x81, 0x75], &[0x81, 0x76], &[0x81, 0x77], &[0x81, 0x78], &[0x81, 0x79], &[0x81, 0x7a], &[0x81, 0x7b], &[0x81, 0x7c], &[0x81, 0x7d], &[0x81, 0x7e]];
+
+#[cfg(test)]
+mod tests {
+	#[test]
+	#[ignore]
+	fn analyze_db() {
+		use rlp::{UntrustedRlp, View};
+		use std::collections::HashMap;
+		use kvdb::*;
+
+		let path =  "db path".to_string();
+		let values: Vec<_> = Database::open_default(&path).unwrap().iter().map(|(_, v)| v).collect();
+		let mut rlp_counts: HashMap<_, u32> = HashMap::new();
+		let mut rlp_sizes: HashMap<_, u32> = HashMap::new();
+
+		fn flat_rlp<'a>(acc: &mut Vec<UntrustedRlp<'a>>, rlp: UntrustedRlp<'a>) {
+			match rlp.is_data() {
+				true => if rlp.size()>=70 {
+					match rlp.data() {
+						Ok(x) => flat_rlp(acc, UntrustedRlp::new(x)),
+						_ => acc.push(rlp),
+					}
+				} else {
+					acc.push(rlp);
+				},
+				false => for r in rlp.iter() { flat_rlp(acc, r); },
+			}
+		}
+
+		fn space_saving(bytes: &[u8]) -> u32 {
+			let l = bytes.len() as u32;
+			match l >= 2 {
+				true => l-2,
+				false => 0,
+			}
+		}
+
+		for v in values.iter() {
+			let rlp = UntrustedRlp::new(&v);
+			let mut flat = Vec::new();
+			flat_rlp(&mut flat, rlp);
+			for r in flat.iter() {
+				*rlp_counts.entry(r.as_raw()).or_insert(0) += 1;
+				*rlp_sizes.entry(r.as_raw()).or_insert(0) += space_saving(r.as_raw());
+			}
+		}
+		let mut size_vec: Vec<_> = rlp_sizes.iter().collect();
+		size_vec.sort_by(|a, b| b.1.cmp(a.1));
+
+		// Exclude rare large RLPs.
+		for v in size_vec.iter().filter(|v| rlp_counts.get(v.0).unwrap()>&100).take(20) {
+			println!("{:?}, {:?}", v, rlp_counts.get(v.0).unwrap());
+		}
+		println!("DONE");
+	}
+}

util/src/rlp/mod.rs

@@ -51,16 +51,19 @@ mod rlperrors;
 mod rlpin;
 mod untrusted_rlp;
 mod rlpstream;
+mod rlpcompression;
+mod commonrlps;
 mod bytes;
 
 #[cfg(test)]
 mod tests;
 
 pub use self::rlperrors::DecoderError;
-pub use self::rlptraits::{Decoder, Decodable, View, Stream, Encodable, Encoder, RlpEncodable, RlpDecodable};
+pub use self::rlptraits::{Decoder, Decodable, View, Stream, Encodable, Encoder, RlpEncodable, RlpDecodable, Compressible};
 pub use self::untrusted_rlp::{UntrustedRlp, UntrustedRlpIterator, PayloadInfo, Prototype};
 pub use self::rlpin::{Rlp, RlpIterator};
-pub use self::rlpstream::{RlpStream};
+pub use self::rlpstream::RlpStream;
+pub use self::rlpcompression::RlpType;
 pub use elastic_array::ElasticArray1024;
 use super::hash::H256;
 

util/src/rlp/rlpcompression.rs

@@ -0,0 +1,245 @@
+// 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 rlp::{UntrustedRlp, View, Compressible, encode, ElasticArray1024, Stream, RlpStream};
+use rlp::commonrlps::{BLOCKS_RLP_SWAPPER, SNAPSHOT_RLP_SWAPPER};
+use std::collections::HashMap;
+
+/// Stores RLPs used for compression
+pub struct InvalidRlpSwapper<'a> {
+	invalid_to_valid: HashMap<&'a [u8], &'a [u8]>,
+	valid_to_invalid: HashMap<&'a [u8], &'a [u8]>,
+}
+
+impl<'a> InvalidRlpSwapper<'a> {
+	/// Construct a swapper from a list of common RLPs
+	pub fn new(rlps_to_swap: &[&'a [u8]], invalid_rlps: &[&'a [u8]]) -> Self {
+		if rlps_to_swap.len() > 0x7e {
+			panic!("Invalid usage, only 127 RLPs can be swappable.");
+		}
+		let mut invalid_to_valid = HashMap::new();
+		let mut valid_to_invalid = HashMap::new();
+		for (&rlp, &invalid) in rlps_to_swap.iter().zip(invalid_rlps.iter()) {
+			invalid_to_valid.insert(invalid, rlp);
+			valid_to_invalid.insert(rlp, invalid);
+		}
+		InvalidRlpSwapper {
+			invalid_to_valid: invalid_to_valid,
+			valid_to_invalid: valid_to_invalid
+		}
+	}
+	/// Get a valid RLP corresponding to an invalid one
+	fn get_valid(&self, invalid_rlp: &[u8]) -> Option<&[u8]> {
+		self.invalid_to_valid.get(invalid_rlp).map(|r| r.clone())
+	}
+	/// Get an invalid RLP corresponding to a valid one
+	fn get_invalid(&self, valid_rlp: &[u8]) -> Option<&[u8]> {
+		self.valid_to_invalid.get(valid_rlp).map(|r| r.clone())
+	}
+}
+
+/// Type of RLP indicating its origin database.
+pub enum RlpType {
+	/// RLP used in blocks database.
+	Blocks,
+	/// RLP used in snapshots.
+	Snapshot,
+}
+
+fn to_elastic(slice: &[u8]) -> ElasticArray1024<u8> {
+	let mut out = ElasticArray1024::new();
+	out.append_slice(slice);
+	out
+}
+
+fn map_rlp<F>(rlp: &UntrustedRlp, f: F) -> Option<ElasticArray1024<u8>> where
+	F: Fn(&UntrustedRlp) -> Option<ElasticArray1024<u8>> {
+	match rlp.iter()
+	.fold((false, RlpStream::new_list(rlp.item_count())),
+		|(is_some, mut acc), subrlp| {
+  		let new = f(&subrlp);
+  		if let Some(ref insert) = new {
+  			acc.append_raw(&insert[..], 1);
+  		} else {
+  			acc.append_raw(subrlp.as_raw(), 1);
+  		}
+  		(is_some || new.is_some(), acc)
+  	  }) {
+  	(true, s) => Some(s.drain()),
+  	_ => None,
+  }
+}
+
+/// Replace common RLPs with invalid shorter ones.
+fn simple_compress(rlp: &UntrustedRlp, swapper: &InvalidRlpSwapper) -> ElasticArray1024<u8> {
+	if rlp.is_data() {
+		to_elastic(swapper.get_invalid(rlp.as_raw()).unwrap_or(rlp.as_raw()))
+	} else {
+		map_rlp(rlp, |r| Some(simple_compress(r, swapper))).unwrap_or(to_elastic(rlp.as_raw()))
+	}
+}
+
+/// Recover valid RLP from a compressed form.
+fn simple_decompress(rlp: &UntrustedRlp, swapper: &InvalidRlpSwapper) -> ElasticArray1024<u8> {
+	if rlp.is_data() {
+		to_elastic(swapper.get_valid(rlp.as_raw()).unwrap_or(rlp.as_raw()))
+	} else {
+		map_rlp(rlp, |r| Some(simple_decompress(r, swapper))).unwrap_or(to_elastic(rlp.as_raw()))
+	}
+}
+
+/// Replace common RLPs with invalid shorter ones, None if no compression achieved.
+/// Tries to compress data insides.
+fn deep_compress(rlp: &UntrustedRlp, swapper: &InvalidRlpSwapper) -> Option<ElasticArray1024<u8>> {
+	let simple_swap = ||
+		swapper.get_invalid(rlp.as_raw()).map(|b| to_elastic(&b));
+	if rlp.is_data() {
+		// Try to treat the inside as RLP.
+		return match rlp.payload_info() {
+			// Shortest decompressed account is 70, so simply try to swap the value.
+			Ok(ref p) if p.value_len < 70 => simple_swap(),
+			_ => {
+				if let Ok(d) = rlp.data() {
+					let internal_rlp = UntrustedRlp::new(d);
+					if let Some(new_d) = deep_compress(&internal_rlp, swapper) {
+						// If compressed put in a special list, with first element being invalid code.
+						let mut rlp = RlpStream::new_list(2);
+						rlp.append_raw(&[0x81, 0x7f], 1);
+						rlp.append_raw(&new_d[..], 1);
+						return Some(rlp.drain());
+					}
+				}
+				simple_swap()
+			},
+		};
+	}
+	// Iterate through RLP while checking if it has been compressed.
+	map_rlp(rlp, |r| deep_compress(r, swapper))
+}
+
+/// Recover valid RLP from a compressed form, None if no decompression achieved.
+/// Tries to decompress compressed data insides.
+fn deep_decompress(rlp: &UntrustedRlp, swapper: &InvalidRlpSwapper) -> Option<ElasticArray1024<u8>> {
+	let simple_swap = ||
+		swapper.get_valid(rlp.as_raw()).map(|b| to_elastic(&b));
+	// Simply decompress data.
+	if rlp.is_data() { return simple_swap(); }
+	match rlp.item_count() {
+		// Look for special compressed list, which contains nested data.
+		2 if rlp.at(0).map(|r| r.as_raw() == &[0x81, 0x7f]).unwrap_or(false) =>
+			rlp.at(1).ok().map_or(simple_swap(),
+			|r| deep_decompress(&r, swapper).map(|d| { let v = d.to_vec(); encode(&v) })),
+		// Iterate through RLP while checking if it has been compressed.
+		_ => map_rlp(rlp, |r| deep_decompress(r, swapper)),
+  	}
+}
+
+
+
+impl<'a> Compressible for UntrustedRlp<'a> {
+	type DataType = RlpType;
+
+	fn compress(&self, t: RlpType) -> ElasticArray1024<u8> { 
+		match t {
+			RlpType::Snapshot => simple_compress(self, &SNAPSHOT_RLP_SWAPPER),
+			RlpType::Blocks => deep_compress(self, &BLOCKS_RLP_SWAPPER).unwrap_or(to_elastic(self.as_raw())),
+		}
+	}
+
+	fn decompress(&self, t: RlpType) -> ElasticArray1024<u8> {
+		match t {
+			RlpType::Snapshot => simple_decompress(self, &SNAPSHOT_RLP_SWAPPER),
+			RlpType::Blocks => deep_decompress(self, &BLOCKS_RLP_SWAPPER).unwrap_or(to_elastic(self.as_raw())),
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use rlp::{UntrustedRlp, Compressible, View, RlpType};
+	use rlp::rlpcompression::InvalidRlpSwapper;
+
+	#[test]
+	fn invalid_rlp_swapper() {
+		let to_swap: &[&[u8]] = &[&[0x83, b'c', b'a', b't'], &[0x83, b'd', b'o', b'g']];
+		let invalid_rlp: &[&[u8]] = &[&[0x81, 0x00], &[0x81, 0x01]];
+		let swapper = InvalidRlpSwapper::new(to_swap, invalid_rlp);
+		assert_eq!(Some(invalid_rlp[0]), swapper.get_invalid(&[0x83, b'c', b'a', b't']));
+		assert_eq!(None, swapper.get_invalid(&[0x83, b'b', b'a', b't']));
+		assert_eq!(Some(to_swap[1]), swapper.get_valid(invalid_rlp[1]));
+	}
+
+	#[test]
+	fn simple_compression() {
+		let basic_account_rlp = vec![248, 68, 4, 2, 160, 86, 232, 31, 23, 27, 204, 85, 166, 255, 131, 69, 230, 146, 192, 248, 110, 91, 72, 224, 27, 153, 108, 173, 192, 1, 98, 47, 181, 227, 99, 180, 33, 160, 197, 210, 70, 1, 134, 247, 35, 60, 146, 126, 125, 178, 220, 199, 3, 192, 229, 0, 182, 83, 202, 130, 39, 59, 123, 250, 216, 4, 93, 133, 164, 112];
+		let rlp = UntrustedRlp::new(&basic_account_rlp);
+		let compressed = rlp.compress(RlpType::Snapshot).to_vec();
+		assert_eq!(compressed, vec![198, 4, 2, 129, 0, 129, 1]);
+		let compressed_rlp = UntrustedRlp::new(&compressed);
+		assert_eq!(compressed_rlp.decompress(RlpType::Snapshot).to_vec(), basic_account_rlp);
+	}
+
+	#[test]
+	fn data_compression() {
+		let data_basic_account_rlp = vec![184, 70, 248, 68, 4, 2, 160, 86, 232, 31, 23, 27, 204, 85, 166, 255, 131, 69, 230, 146, 192, 248, 110, 91, 72, 224, 27, 153, 108, 173, 192, 1, 98, 47, 181, 227, 99, 180, 33, 160, 197, 210, 70, 1, 134, 247, 35, 60, 146, 126, 125, 178, 220, 199, 3, 192, 229, 0, 182, 83, 202, 130, 39, 59, 123, 250, 216, 4, 93, 133, 164, 112];
+		let data_rlp = UntrustedRlp::new(&data_basic_account_rlp);
+		let compressed = data_rlp.compress(RlpType::Blocks).to_vec();
+		assert_eq!(compressed, vec![201, 129, 127, 198, 4, 2, 129, 0, 129, 1]);
+		let compressed_rlp = UntrustedRlp::new(&compressed);
+		assert_eq!(compressed_rlp.decompress(RlpType::Blocks).to_vec(), data_basic_account_rlp);
+	}
+
+	#[test]
+	fn nested_list_rlp() {
+		let nested_basic_account_rlp = vec![228, 4, 226, 2, 160, 86, 232, 31, 23, 27, 204, 85, 166, 255, 131, 69, 230, 146, 192, 248, 110, 91, 72, 224, 27, 153, 108, 173, 192, 1, 98, 47, 181, 227, 99, 180, 33];
+		let nested_rlp = UntrustedRlp::new(&nested_basic_account_rlp);
+		let compressed = nested_rlp.compress(RlpType::Blocks).to_vec();
+		assert_eq!(compressed, vec![197, 4, 195, 2, 129, 0]);
+		let compressed_rlp = UntrustedRlp::new(&compressed);
+		assert_eq!(compressed_rlp.decompress(RlpType::Blocks).to_vec(), nested_basic_account_rlp);
+		let compressed = nested_rlp.compress(RlpType::Snapshot).to_vec();
+		assert_eq!(compressed, vec![197, 4, 195, 2, 129, 0]);
+		let compressed_rlp = UntrustedRlp::new(&compressed);
+		assert_eq!(compressed_rlp.decompress(RlpType::Snapshot).to_vec(), nested_basic_account_rlp);
+	}
+
+	#[test]
+	fn malformed_rlp() {
+		let malformed = vec![248, 81, 128, 128, 128, 128, 128, 160, 12, 51, 241, 93, 69, 218, 74, 138, 79, 115, 227, 44, 216, 81, 46, 132, 85, 235, 96, 45, 252, 48, 181, 29, 75, 141, 217, 215, 86, 160, 109, 130, 160, 140, 36, 93, 200, 109, 215, 100, 241, 246, 99, 135, 92, 168, 149, 170, 114, 9, 143, 4, 93, 25, 76, 54, 176, 119, 230, 170, 154, 105, 47, 121, 10, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128];
+		let malformed_rlp = UntrustedRlp::new(&malformed);
+		assert_eq!(malformed_rlp.decompress(RlpType::Blocks).to_vec(), malformed);
+	}
+
+	#[test]
+	#[ignore]
+	fn test_compression() {
+		use kvdb::*;
+		let path = "db to test".to_string();
+		let values: Vec<_> = Database::open_default(&path).unwrap().iter().map(|(_, v)| v).collect();
+		let mut decomp_size = 0;
+		let mut comp_size = 0;
+
+		for v in values.iter() {
+			let rlp = UntrustedRlp::new(&v);
+			let compressed = rlp.compress(RlpType::Blocks).to_vec();
+			comp_size += compressed.len();
+			let decompressed = rlp.decompress(RlpType::Blocks).to_vec();
+			decomp_size += decompressed.len();
+		}
+		println!("Decompressed bytes {:?}, compressed bytes: {:?}", decomp_size, comp_size);
+		assert!(decomp_size > comp_size);
+	}
+}

util/src/rlp/rlptraits.rs

@@ -26,8 +26,8 @@ use sha3::*;
 /// Type is able to decode RLP.
 pub trait Decoder: Sized {
 	/// Read a value from the RLP into a given type.
-	fn read_value<T, F>(&self, f: F) -> Result<T, DecoderError>
+	fn read_value<T, F>(&self, f: &F) -> Result<T, DecoderError>
-		where F: FnOnce(&[u8]) -> Result<T, DecoderError>;
+		where F: Fn(&[u8]) -> Result<T, DecoderError>;
 
 	/// Get underlying `UntrustedRLP` object.
 	fn as_rlp(&self) -> &UntrustedRlp;
@@ -63,7 +63,7 @@ pub trait View<'a, 'view>: Sized {
 	/// Creates a new instance of `Rlp` reader
 	fn new(bytes: &'a [u8]) -> Self;
 
-	/// The raw data of the RLP.
+	/// The raw data of the RLP as slice.
 	///
 	/// ```rust
 	/// extern crate ethcore_util as util;
@@ -365,3 +365,14 @@ pub trait Stream: Sized {
 	/// panic! if stream is not finished.
 	fn out(self) -> Vec<u8>;
 }
+
+/// Trait for compressing and decompressing RLP by replacement of common terms.
+pub trait Compressible: Sized {
+	/// Indicates the origin of RLP to be compressed.
+	type DataType;
+
+	/// Compress given RLP type using appropriate methods.
+	fn compress(&self, t: Self::DataType) -> ElasticArray1024<u8>;
+	/// Decompress given RLP type using appropriate methods.
+	fn decompress(&self, t: Self::DataType) -> ElasticArray1024<u8>;
+}

util/src/rlp/untrusted_rlp.rs

@@ -55,6 +55,18 @@ pub struct PayloadInfo {
 	pub value_len: usize,
 }
 
+fn calculate_payload_info(header_bytes: &[u8], len_of_len: usize) -> Result<PayloadInfo, DecoderError> {
+	let header_len = 1 + len_of_len;
+	match header_bytes.get(1) {
+		Some(&0) => return Err(DecoderError::RlpDataLenWithZeroPrefix),
+		None => return Err(DecoderError::RlpIsTooShort),
+		_ => (),
+	}
+	if header_bytes.len() < header_len { return Err(DecoderError::RlpIsTooShort); }
+	let value_len = try!(usize::from_bytes(&header_bytes[1..header_len]));
+	Ok(PayloadInfo::new(header_len, value_len))
+}
+
 impl PayloadInfo {
 	fn new(header_len: usize, value_len: usize) -> PayloadInfo {
 		PayloadInfo {
@@ -68,28 +80,22 @@ impl PayloadInfo {
 
 	/// Create a new object from the given bytes RLP. The bytes
 	pub fn from(header_bytes: &[u8]) -> Result<PayloadInfo, DecoderError> {
-		Ok(match header_bytes.first().cloned() {
+		match header_bytes.first().cloned() {
-			None => return Err(DecoderError::RlpIsTooShort),
+			None => Err(DecoderError::RlpIsTooShort),
-			Some(0...0x7f) => PayloadInfo::new(0, 1),
+			Some(0...0x7f) => Ok(PayloadInfo::new(0, 1)),
-			Some(l @ 0x80...0xb7) => PayloadInfo::new(1, l as usize - 0x80),
+			Some(l @ 0x80...0xb7) => Ok(PayloadInfo::new(1, l as usize - 0x80)),
 			Some(l @ 0xb8...0xbf) => {
 				let len_of_len = l as usize - 0xb7;
-				let header_len = 1 + len_of_len;
+				calculate_payload_info(header_bytes, len_of_len)
-				if header_bytes[1] == 0 { return Err(DecoderError::RlpDataLenWithZeroPrefix); }
-				let value_len = try!(usize::from_bytes(&header_bytes[1..header_len]));
-				PayloadInfo::new(header_len, value_len)
 			}
-			Some(l @ 0xc0...0xf7) => PayloadInfo::new(1, l as usize - 0xc0),
+			Some(l @ 0xc0...0xf7) => Ok(PayloadInfo::new(1, l as usize - 0xc0)),
 			Some(l @ 0xf8...0xff) => {
 				let len_of_len = l as usize - 0xf7;
-				let header_len = 1 + len_of_len;
+				calculate_payload_info(header_bytes, len_of_len)
-				let value_len = try!(usize::from_bytes(&header_bytes[1..header_len]));
-				if header_bytes[1] == 0 { return Err(DecoderError::RlpListLenWithZeroPrefix); }
-				PayloadInfo::new(header_len, value_len)
 			},
 			// we cant reach this place, but rust requires _ to be implemented
 			_ => { unreachable!(); }
-		})
+		}
 	}
 }
 
@@ -190,8 +196,8 @@ impl<'a, 'view> View<'a, 'view> for UntrustedRlp<'a> where 'a: 'view {
 
 	fn size(&self) -> usize {
 		match self.is_data() {
-			// we can safely unwrap (?) cause its data
+			// TODO: No panic on malformed data, but ideally would Err on no PayloadInfo.
-			true => BasicDecoder::payload_info(self.bytes).unwrap().value_len,
+			true => BasicDecoder::payload_info(self.bytes).map(|b| b.value_len).unwrap_or(0),
 			false => 0
 		}
 	}
@@ -342,15 +348,15 @@ impl<'a> BasicDecoder<'a> {
 }
 
 impl<'a> Decoder for BasicDecoder<'a> {
-	fn read_value<T, F>(&self, f: F) -> Result<T, DecoderError>
+	fn read_value<T, F>(&self, f: &F) -> Result<T, DecoderError>
-		where F: FnOnce(&[u8]) -> Result<T, DecoderError> {
+		where F: Fn(&[u8]) -> Result<T, DecoderError> {
 
 		let bytes = self.rlp.as_raw();
 
 		match bytes.first().cloned() {
-			// rlp is too short
+			// RLP is too short.
 			None => Err(DecoderError::RlpIsTooShort),
-			// single byt value
+			// Single byte value.
 			Some(l @ 0...0x7f) => Ok(try!(f(&[l]))),
 			// 0-55 bytes
 			Some(l @ 0x80...0xb7) => {
@@ -362,10 +368,9 @@ impl<'a> Decoder for BasicDecoder<'a> {
 				if l == 0x81 && d[0] < 0x80 {
 					return Err(DecoderError::RlpInvalidIndirection);
 				}
-
 				Ok(try!(f(d)))
 			},
-			// longer than 55 bytes
+			// Longer than 55 bytes.
 			Some(l @ 0xb8...0xbf) => {
 				let len_of_len = l as usize - 0xb7;
 				let begin_of_value = 1 as usize + len_of_len;
@@ -380,7 +385,7 @@ impl<'a> Decoder for BasicDecoder<'a> {
 				}
 				Ok(try!(f(&bytes[begin_of_value..last_index_of_value])))
 			}
-			// we are reading value, not a list!
+			// We are reading value, not a list!
 			_ => Err(DecoderError::RlpExpectedToBeData)
 		}
 	}
@@ -396,9 +401,7 @@ impl<'a> Decoder for BasicDecoder<'a> {
 
 impl<T> Decodable for T where T: FromBytes {
 	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
-		decoder.read_value(| bytes | {
+		decoder.read_value(&|bytes: &[u8]| Ok(try!(T::from_bytes(bytes))))
-			Ok(try!(T::from_bytes(bytes)))
-		})
 	}
 }
 
@@ -416,11 +419,7 @@ impl<T> Decodable for Option<T> where T: Decodable {
 
 impl Decodable for Vec<u8> {
 	fn decode<D>(decoder: &D) -> Result<Self, DecoderError> where D: Decoder {
-		decoder.read_value(| bytes | {
+		decoder.read_value(&|bytes: &[u8]| Ok(bytes.to_vec()))
-			let mut res = vec![];
-			res.extend_from_slice(bytes);
-			Ok(res)
-		})
 	}
 }
 
@@ -489,11 +488,14 @@ impl RlpDecodable for u8 {
 	}
 }
 
-#[test]
+#[cfg(test)]
-fn test_rlp_display() {
+mod tests {
+	use rlp::{UntrustedRlp, View};
+	#[test]
+	fn test_rlp_display() {
 		use rustc_serialize::hex::FromHex;
 		let data = "f84d0589010efbef67941f79b2a056e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421a0c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470".from_hex().unwrap();
 		let rlp = UntrustedRlp::new(&data);
 		assert_eq!(format!("{}", rlp), "[\"0x05\", \"0x010efbef67941f79b2\", \"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421\", \"0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470\"]");
+	}
 }
-