block_hash method for LightChainClient

ethcore/light/src/client/header_chain.rs

@@ -355,6 +355,22 @@ impl HeaderChain {
 		}
 	}
 
+	/// Get a block's hash by ID. In the case of query by number, only canonical results
+	/// will be returned.
+	pub fn block_hash(&self, id: BlockId) -> Option<H256> {
+		match id {
+			BlockId::Earliest => Some(self.genesis_hash()),
+			BlockId::Hash(hash) => Some(hash),
+			BlockId::Number(num) => {
+				if self.best_block.read().number < num { return None }
+				self.candidates.read().get(&num).map(|entry| entry.canonical_hash)
+			}
+			BlockId::Latest | BlockId::Pending => {
+				Some(self.best_block.read().hash)
+			}
+		}
+	}
+
 	/// Get a block header. In the case of query by number, only canonical blocks
 	/// will be returned.
 	pub fn block_header(&self, id: BlockId) -> Option<encoded::Header> {

ethcore/light/src/client/mod.rs

@@ -65,6 +65,9 @@ pub trait LightChainClient: Send + Sync {
 	/// parent queued prior.
 	fn queue_header(&self, header: Header) -> Result<H256, BlockImportError>;
 
+	/// Attempt to get a block hash by block id.
+	fn block_hash(&self, id: BlockId) -> Option<H256>;
+
 	/// Attempt to get block header by block id.
 	fn block_header(&self, id: BlockId) -> Option<encoded::Header>;
 
@@ -181,6 +184,11 @@ impl Client {
 		self.queue.queue_info()
 	}
 
+	/// Attempt to get a block hash by block id.
+	pub fn block_hash(&self, id: BlockId) -> Option<H256> {
+		self.chain.block_hash(id)
+	}
+
 	/// Get a block header by Id.
 	pub fn block_header(&self, id: BlockId) -> Option<encoded::Header> {
 		self.chain.block_header(id)
@@ -308,6 +316,10 @@ impl LightChainClient for Client {
 		self.import_header(header)
 	}
 
+	fn block_hash(&self, id: BlockId) -> Option<H256> {
+		Client::block_hash(self, id)
+	}
+
 	fn block_header(&self, id: BlockId) -> Option<encoded::Header> {
 		Client::block_header(self, id)
 	}