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    // Copyright 2015-2017 Parity Technologies (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/>.

    //! Block RLP compression.

    use block::Block;
    use header::Header;

    use views::BlockView;
    use rlp::{DecoderError, RlpStream, Stream, UntrustedRlp, View};
    use util::{Bytes, Hashable, H256};
    use util::triehash::ordered_trie_root;

    const HEADER_FIELDS: usize = 8;
    const BLOCK_FIELDS: usize = 2;

    pub struct AbridgedBlock {
    	rlp: Bytes,
    }

    impl AbridgedBlock {
    	/// Create from rlp-compressed bytes. Does no verification.
    	pub fn from_raw(compressed: Bytes) -> Self {
    		AbridgedBlock {
    			rlp: compressed,
    		}
    	}

    	/// Return the inner bytes.
    	pub fn into_inner(self) -> Bytes {
    		self.rlp
    	}

    	/// Given a full block view, trim out the parent hash and block number,
    	/// producing new rlp.
    	pub fn from_block_view(block_view: &BlockView) -> Self {
    		let header = block_view.header_view();
    		let seal_fields = header.seal();

    		// 10 header fields, unknown number of seal fields, and 2 block fields.
    		let mut stream = RlpStream::new_list(
    			HEADER_FIELDS +
    			seal_fields.len() +
    			BLOCK_FIELDS
    		);

    		// write header values.
    		stream
    			.append(&header.author())
    			.append(&header.state_root())
    			.append(&header.log_bloom())
    			.append(&header.difficulty())
    			.append(&header.gas_limit())
    			.append(&header.gas_used())
    			.append(&header.timestamp())
    			.append(&header.extra_data());

    		// write block values.
    		stream.append(&block_view.transactions()).append(&block_view.uncles());

    		// write seal fields.
    		for field in seal_fields {
    			stream.append_raw(&field, 1);
    		}

    		AbridgedBlock {
    			rlp: stream.out(),
    		}
    	}

    	/// Flesh out an abridged block view with the provided parent hash and block number.
    	///
    	/// Will fail if contains invalid rlp.
    	pub fn to_block(&self, parent_hash: H256, number: u64, receipts_root: H256) -> Result<Block, DecoderError> {
    		let rlp = UntrustedRlp::new(&self.rlp);

    		let mut header: Header = Default::default();
    		header.set_parent_hash(parent_hash);
    		header.set_author(rlp.val_at(0)?);
    		header.set_state_root(rlp.val_at(1)?);
    		header.set_log_bloom(rlp.val_at(2)?);
    		header.set_difficulty(rlp.val_at(3)?);
    		header.set_number(number);
    		header.set_gas_limit(rlp.val_at(4)?);
    		header.set_gas_used(rlp.val_at(5)?);
    		header.set_timestamp(rlp.val_at(6)?);
    		header.set_extra_data(rlp.val_at(7)?);

    		let transactions = rlp.val_at(8)?;
    		let uncles: Vec<Header> = rlp.val_at(9)?;

    		header.set_transactions_root(ordered_trie_root(
    			rlp.at(8)?.iter().map(|r| r.as_raw().to_owned())
    		));
    		header.set_receipts_root(receipts_root);

    		let mut uncles_rlp = RlpStream::new();
    		uncles_rlp.append(&uncles);
    		header.set_uncles_hash(uncles_rlp.as_raw().sha3());

    		let mut seal_fields = Vec::new();
    		for i in (HEADER_FIELDS + BLOCK_FIELDS)..rlp.item_count() {
    			let seal_rlp = rlp.at(i)?;
    			seal_fields.push(seal_rlp.as_raw().to_owned());
    		}

    		header.set_seal(seal_fields);

    		Ok(Block {
    			header: header,
    			transactions: transactions,
    			uncles: uncles,
    		})
    	}
    }

    #[cfg(test)]
    mod tests {
    	use views::BlockView;
    	use block::Block;
    	use super::AbridgedBlock;
    	use types::transaction::{Action, Transaction};

    	use util::{Address, H256, FixedHash, U256, Bytes};

    	fn encode_block(b: &Block) -> Bytes {
    		b.rlp_bytes(::basic_types::Seal::With)
    	}

    	#[test]
    	fn empty_block_abridging() {
    		let b = Block::default();
    		let receipts_root = b.header.receipts_root().clone();
    		let encoded = encode_block(&b);

    		let abridged = AbridgedBlock::from_block_view(&BlockView::new(&encoded));
    		assert_eq!(abridged.to_block(H256::new(), 0, receipts_root).unwrap(), b);
    	}

    	#[test]
    	#[should_panic]
    	fn wrong_number() {
    		let b = Block::default();
    		let receipts_root = b.header.receipts_root().clone();
    		let encoded = encode_block(&b);

    		let abridged = AbridgedBlock::from_block_view(&BlockView::new(&encoded));
    		assert_eq!(abridged.to_block(H256::new(), 2, receipts_root).unwrap(), b);
    	}

    	#[test]
    	fn with_transactions() {
    		let mut b = Block::default();

    		let t1 = Transaction {
    			action: Action::Create,
    			nonce: U256::from(42),
    			gas_price: U256::from(3000),
    			gas: U256::from(50_000),
    			value: U256::from(1),
    			data: b"Hello!".to_vec()
    		}.fake_sign(Address::from(0x69));

    		let t2 = Transaction {
    			action: Action::Create,
    			nonce: U256::from(88),
    			gas_price: U256::from(12345),
    			gas: U256::from(300000),
    			value: U256::from(1000000000),
    			data: "Eep!".into(),
    		}.fake_sign(Address::from(0x55));

    		b.transactions.push(t1.into());
    		b.transactions.push(t2.into());

    		let receipts_root = b.header.receipts_root().clone();
    		b.header.set_transactions_root(::util::triehash::ordered_trie_root(
    			b.transactions.iter().map(::rlp::encode).map(|out| out.to_vec())
    		));

    		let encoded = encode_block(&b);

    		let abridged = AbridgedBlock::from_block_view(&BlockView::new(&encoded[..]));
    		assert_eq!(abridged.to_block(H256::new(), 0, receipts_root).unwrap(), b);
    	}
    }

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