rpc: add new client, use it everywhere

The new client implementation supports concurrent requests,
subscriptions and replaces the various ad hoc RPC clients
throughout go-ethereum.

rpc/client_context_go1.7.go

@@ -0,0 +1,51 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build go1.7
+
+package rpc
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"time"
+)
+
+// In Go 1.7, context moved into the standard library and support
+// for cancelation via context was added to net.Dialer and http.Request.
+
+// contextDialer returns a dialer that applies the deadline value from the given context.
+func contextDialer(ctx context.Context) *net.Dialer {
+	dialer := &net.Dialer{Cancel: ctx.Done(), KeepAlive: tcpKeepAliveInterval}
+	if deadline, ok := ctx.Deadline(); ok {
+		dialer.Deadline = deadline
+	} else {
+		dialer.Deadline = time.Now().Add(defaultDialTimeout)
+	}
+	return dialer
+}
+
+// dialContext connects to the given address, aborting the dial if ctx is canceled.
+func dialContext(ctx context.Context, network, addr string) (net.Conn, error) {
+	d := &net.Dialer{KeepAlive: tcpKeepAliveInterval}
+	return d.DialContext(ctx, network, addr)
+}
+
+// requestWithContext copies req, adding the cancelation channel and deadline from ctx.
+func requestWithContext(c *http.Client, req *http.Request, ctx context.Context) (*http.Client, *http.Request) {
+	return c, req.WithContext(ctx)
+}