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    use clap::ArgMatches;
    use storage::BlockRef;
    use config::Config;
    use primitives::hash::H256;
    use util::init_db;

    pub fn rollback(cfg: Config, matches: &ArgMatches) -> Result<(), String> {
    	try!(init_db(&cfg));

    	let block_ref = matches.value_of("BLOCK").expect("BLOCK is required in cli.yml; qed");
    	let block_ref = if block_ref.len() == 64 {
    		BlockRef::Hash({
    			let hash: H256 = block_ref.parse().map_err(|e| format!("Invalid block number: {}", e))?;
    			hash.reversed()
    		})
    	} else {
    		BlockRef::Number(block_ref.parse().map_err(|e| format!("Invalid block hash: {}", e))?)
    	};

    	let required_block_hash = cfg.db.block_header(block_ref.clone()).ok_or(format!("Block {:?} is unknown", block_ref))?.hash();
    	let genesis_hash = cfg.network.genesis_block().hash();

    	let mut best_block_hash = cfg.db.best_block().hash;
    	debug_assert!(best_block_hash != H256::default()); // genesis inserted in init_db

    	loop {
    		if best_block_hash == required_block_hash {
    			info!("Reverted to block {:?}", block_ref);
    			return Ok(());
    		}

    		if best_block_hash == genesis_hash {
    			return Err(format!("Failed to revert to block {:?}. Reverted to genesis", block_ref));
    		}

    		best_block_hash = cfg.db.rollback_best().map_err(|e| format!("{:?}", e))?;
    	}
    }

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