Add chain_getRawHeaderByNumber RPC

To create a light client we need raw bytes of a header. It will be
included in the CreateClient datagram.

Author: majecty

rpc/src/v1/impls/chain.rs

@@ -26,6 +26,7 @@ use ctypes::transaction::Action;
 use ctypes::{BlockHash, BlockNumber, ShardId, Tracker, TxHash};
 use jsonrpc_core::Result;
 use primitives::H256;
+use rustc_hex::ToHex;
 use std::convert::TryFrom;
 use std::sync::Arc;
 
@@ -172,6 +173,11 @@ where
         }))
     }
 
+    fn get_raw_header_by_number(&self, block_number: u64) -> Result<Option<String>> {
+        let id = BlockId::Number(block_number);
+        Ok(self.client.block_header(&id).map(|header| header.into_inner().as_slice().to_hex()))
+    }
+
     fn get_block_transaction_count_by_hash(&self, block_hash: BlockHash) -> Result<Option<usize>> {
         Ok(self.client.block(&BlockId::Hash(block_hash)).map(|block| block.transactions_count()))
     }

rpc/src/v1/traits/chain.rs

@@ -107,6 +107,10 @@ pub trait Chain {
     #[rpc(name = "chain_getBlockTransactionCountByHash")]
     fn get_block_transaction_count_by_hash(&self, block_hash: BlockHash) -> Result<Option<usize>>;
 
+    ///Gets the raw bytes of a header with given number.
+    #[rpc(name = "chain_getRawHeaderByNumber")]
+    fn get_raw_header_by_number(&self, block_number: u64) -> Result<Option<String>>;
+
     ///Gets the minimum transaction fee of the given name.
     #[rpc(name = "chain_getMinTransactionFee")]
     fn get_min_transaction_fee(&self, action_type: String, block_number: Option<u64>) -> Result<Option<u64>>;