accounts, p2p, rpc: make CGO_ENABLED=0 build again (#19593)

* p2p: remove direct import of cgo-library

* accounts, rpc: more nocgo alternatives

* rpc: move unix path constant into separate file

* accounts/scwallet: address review concerns, remove copy-pasta

3 files changed, 61 insertions, 13 deletions

diff --git a/rpc/constants_unix.go b/rpc/constants_unix.go
new file mode 100644
index 000000000..2f98d6499
--- /dev/null
+++ b/rpc/constants_unix.go
@@ -0,0 +1,33 @@
+// Copyright 2019 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 darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package rpc
+
+/*
+#include <sys/un.h>
+
+int max_socket_path_size() {
+struct sockaddr_un s;
+return sizeof(s.sun_path);
+}
+*/
+import "C"
+
+var (
+	max_path_size = C.max_socket_path_size()
+)
diff --git a/rpc/constants_unix_nocgo.go b/rpc/constants_unix_nocgo.go
new file mode 100644
index 000000000..ecb231f92
--- /dev/null
+++ b/rpc/constants_unix_nocgo.go
@@ -0,0 +1,25 @@
+// Copyright 2019 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 !cgo,!windows
+
+package rpc
+
+var (
+	//  On Linux, sun_path is 108 bytes in size
+	// see http://man7.org/linux/man-pages/man7/unix.7.html
+	max_path_size = 108
+)
diff --git a/rpc/ipc_unix.go b/rpc/ipc_unix.go
index 707b47fd7..da6ce294d 100644
--- a/rpc/ipc_unix.go
+++ b/rpc/ipc_unix.go
@@ -1,4 +1,4 @@
-// Copyright 2015 The go-ethereum Authors
+// Copyright 2019 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
@@ -28,20 +28,10 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
-/*
-#include <sys/un.h>
-
-int max_socket_path_size() {
-struct sockaddr_un s;
-return sizeof(s.sun_path);
-}
-*/
-import "C"
-
 // ipcListen will create a Unix socket on the given endpoint.
 func ipcListen(endpoint string) (net.Listener, error) {
-	if len(endpoint) > int(C.max_socket_path_size()) {
-		log.Warn(fmt.Sprintf("The ipc endpoint is longer than %d characters. ", C.max_socket_path_size()),
+	if len(endpoint) > int(max_path_size) {
+		log.Warn(fmt.Sprintf("The ipc endpoint is longer than %d characters. ", max_path_size),
 			"endpoint", endpoint)
 	}