Add initial support for JSON-RPC batching

contrib/client.py

@@ -7,13 +7,16 @@ class Client:
         self.f = self.s.makefile('r')
         self.id = 0
 
-    def call(self, method, *args):
-        req = {
+    def request(self, method, *args):
+        self.id += 1
+        return {
             'id': self.id,
             'method': method,
             'params': list(args),
             'jsonrpc': '2.0',
         }
-        msg = json.dumps(req) + '\n'
+
+    def call(self, *requests):
+        msg = json.dumps(requests) + '\n'
         self.s.sendall(msg.encode('ascii'))
         return json.loads(self.f.readline())

contrib/tx_fee.py

@@ -8,13 +8,18 @@ def main():
     args = parser.parse_args()
 
     conn = client.Client(("localhost", 50001))
-    tx = conn.call("blockchain.transaction.get", args.txid, True)["result"]
-    fee = 0
+    tx = conn.call(conn.request("blockchain.transaction.get", args.txid, True))[0]["result"]
+    requests = []
     for vin in tx["vin"]:
         prev_txid = vin["txid"]
-        prev_tx = conn.call("blockchain.transaction.get", prev_txid, True)["result"]
+        requests.append(conn.request("blockchain.transaction.get", prev_txid, True))
+
+    fee = 0
+    for vin, response in zip(tx["vin"], conn.call(*requests)):
+        prev_tx = response["result"]
         txo = prev_tx["vout"][vin["vout"]]
         fee += txo["value"]
+
     fee -= sum(vout["value"] for vout in tx["vout"])
 
     print(f'vSize = {tx["vsize"]}, Fee = {1e3 * fee:.2f} mBTC = {1e8 * fee / tx["vsize"]:.2f} sat/vB')

src/electrum.rs

@@ -38,6 +38,13 @@ struct Request {
     params: Value,
 }
 
+#[derive(Deserialize)]
+#[serde(untagged)]
+enum Requests {
+    Single(Request),
+    Batch(Vec<Request>),
+}
+
 #[derive(Deserialize, Debug, PartialEq, Eq)]
 #[serde(untagged)]
 enum Version {
@@ -127,12 +134,24 @@ impl Rpc {
     }
 
     pub fn handle_request(&self, client: &mut Client, value: Value) -> Result<Value> {
+        let requests: Requests = from_value(value).context("invalid request")?;
+        match requests {
+            Requests::Single(request) => self.handle_single_request(client, request),
+            Requests::Batch(requests) => requests
+                .into_iter()
+                .map(|request| self.handle_single_request(client, request))
+                .collect::<Result<Vec<_>>>()
+                .map(|results| json!(results)),
+        }
+    }
+
+    fn handle_single_request(&self, client: &mut Client, request: Request) -> Result<Value> {
         let Request {
             id,
             jsonrpc,
             method,
             params,
-        } = from_value(value).context("invalid request")?;
+        } = request;
         self.rpc_duration.observe_duration(&method, || {
             let result = match method.as_str() {
                 "blockchain.scripthash.get_history" => {