Add new line after writing block to hex file. (#10984)

* add new line after writing block to hex file.

* refactor for testability

* correct import

* better error reporting, code formatting

* multiline imports

* docs

* better docs, move type to common types, merge ImportBlocks and ExportBlocks

* tabs over spaces

* correct test imports

* Apply suggestions from code review

Co-Authored-By: David <[email protected]>

* correct typo

* fixed test import

ethcore/blockchain/src/blockchain.rs

@@ -614,7 +614,7 @@ impl BlockChain {
 			let best_block_rlp = bc.block(&best_block_hash)
 				.expect("Best block is from a known block hash; qed");
 
-			// and write them
+			// and write them to the cache.
 			let mut best_block = bc.best_block.write();
 			*best_block = BestBlock {
 				total_difficulty: best_block_total_difficulty,
@@ -877,12 +877,31 @@ impl BlockChain {
 		}
 	}
 
-	/// clears all caches for testing purposes
+	/// clears all caches, re-loads best block from disk for testing purposes
 	pub fn clear_cache(&self) {
 		self.block_bodies.write().clear();
 		self.block_details.write().clear();
 		self.block_hashes.write().clear();
 		self.block_headers.write().clear();
+		// Fetch best block details from disk
+		let best_block_hash = self.db.key_value().get(db::COL_EXTRA, b"best")
+			.expect("Low-level database error when fetching 'best' block. Some issue with disk?")
+			.as_ref()
+			.map(|r| H256::from_slice(r))
+			.unwrap();
+		let best_block_total_difficulty = self.block_details(&best_block_hash)
+			.expect("Best block is from a known block hash; a known block hash always comes with a known block detail; qed")
+			.total_difficulty;
+		let best_block_rlp = self.block(&best_block_hash)
+			.expect("Best block is from a known block hash; qed");
+
+		// and write them to the cache
+		let mut best_block = self.best_block.write();
+		*best_block = BestBlock {
+			total_difficulty: best_block_total_difficulty,
+			header: best_block_rlp.decode_header(),
+			block: best_block_rlp,
+		};
 	}
 
 	/// Update the best ancient block to the given hash, after checking that

ethcore/client-traits/src/lib.rs

@@ -55,6 +55,7 @@ use trace::{
 	localized::LocalizedTrace,
 	VMTrace,
 };
+use common_types::data_format::DataFormat;
 use vm::{LastHashes, Schedule};
 
 use common_types::snapshot::Progress;
@@ -510,3 +511,29 @@ pub trait ChainNotify: Send + Sync {
 		// does nothing by default
 	}
 }
+
+/// Provides a method for importing/exporting blocks
+pub trait ImportExportBlocks {
+    /// Export blocks to destination, with the given from, to and format argument.
+    /// destination could be a file or stdout.
+    /// If the format is hex, each block is written on a new line.
+    /// For binary exports, all block data is written to the same line.
+	fn export_blocks<'a>(
+        &self,
+        destination: Box<dyn std::io::Write + 'a>,
+        from: BlockId,
+        to: BlockId,
+        format: Option<DataFormat>
+    ) -> Result<(), String>;
+
+	/// Import blocks from destination, with the given format argument
+	/// Source could be a file or stdout.
+	/// For hex format imports, it attempts to read the blocks on a line by line basis.
+	/// For binary format imports, reads the 8 byte RLP header in order to decode the block
+	/// length to be read.
+	fn import_blocks<'a>(
+		&self,
+		source: Box<dyn std::io::Read + 'a>,
+		format: Option<DataFormat>
+	) -> Result<(), String>;
+}