Add SyncClient and use from BankClient

sdk/src/lib.rs

@@ -13,6 +13,7 @@ pub mod pubkey;
 pub mod rpc_port;
 pub mod short_vec;
 pub mod signature;
+pub mod sync_client;
 pub mod system_instruction;
 pub mod system_program;
 pub mod system_transaction;

sdk/src/sync_client.rs

@@ -0,0 +1,33 @@
+//! Defines a trait for blocking (synchronous) communication with a Solana server.
+//! Implementations are expected to create tranasctions, sign them, and send
+//! them with multiple retries, updating blockhashes and resigning as-needed.
+
+use crate::instruction::Instruction;
+use crate::message::Message;
+use crate::pubkey::Pubkey;
+use crate::signature::Keypair;
+use crate::transaction::TransactionError;
+
+pub trait SyncClient {
+    /// Create a transaction from the given message, and send it to the
+    /// server, retrying as-needed.
+    fn send_message(&self, keypairs: &[&Keypair], message: Message)
+        -> Result<(), TransactionError>;
+
+    /// Create a transaction from a single instruction that only requires
+    /// a single signer. Then send it to the server, retrying as-needed.
+    fn send_instruction(
+        &self,
+        keypair: &Keypair,
+        instruction: Instruction,
+    ) -> Result<(), TransactionError>;
+
+    /// Transfer lamports from `keypair` to `pubkey`, retrying until the
+    /// transfer completes or produces and error.
+    fn transfer(
+        &self,
+        lamports: u64,
+        keypair: &Keypair,
+        pubkey: &Pubkey,
+    ) -> Result<(), TransactionError>;
+}