Improve c++ example client and clang-format with sane options.

rpc/documentation/clientusage.md

@@ -93,8 +93,8 @@ func main() {
 <a name="cpp"/>
 ## C++
 
-**Note:** Protocol Buffers and gRPC require at least C++11.  The example client
-is written using C++14.
+**Note:** Protocol Buffers and gRPC require at least C++11.  The
+example client is written using modern C++ as well.
 
 **Note:** The following instructions assume the client is being written on a
 Unix-like platform (with instructions using the `sh` shell and Unix-isms in the
@@ -127,55 +127,55 @@ thread on all gRPC IO.
 
 #include "api.grpc.pb.h"
 
-using namespace std::string_literals;
-
 struct NoHomeDirectoryException : std::exception {
-    char const* what() const noexcept override {
-        return "Failed to lookup home directory";
-    }
+    char const *what() const noexcept override { return "Failed to lookup home directory"; }
 };
 
-auto read_file(std::string const& file_path) -> std::string {
+auto unix_home_directory() -> std::string {
+    auto const pw = getpwuid(getuid());
+    if (pw == nullptr || pw->pw_dir == nullptr) {
+        throw NoHomeDirectoryException{};
+    }
+    return std::string{pw->pw_dir};
+}
+
+auto read_file(std::string const &file_path) -> std::string {
     std::ifstream in{file_path};
     std::stringstream ss{};
     ss << in.rdbuf();
     return ss.str();
 }
 
 auto main() -> int {
-    // Before the gRPC native library (gRPC Core) is lazily loaded and
-    // initialized, an environment variable must be set so OpenSSL is
-    // configured to use ECDSA TLS certificates (required by btcwallet).
+    // Before the gRPC native library is lazily loaded and initialized, an environment variable must
+    // be set so OpenSSL is configured to use ECDSA TLS certificates (required by btcwallet).
     setenv("GRPC_SSL_CIPHER_SUITES", "HIGH+ECDSA", 1);
 
-    // Note: This path is operating system-dependent.  This can be created
-    // portably using boost::filesystem or the experimental filesystem class
-    // expected to ship in C++17.
-    auto wallet_tls_cert_file = []{
-        auto pw = getpwuid(getuid());
-        if (pw == nullptr || pw->pw_dir == nullptr) {
-            throw NoHomeDirectoryException{};
-        }
-        return pw->pw_dir + "/.btcwallet/rpc.cert"s;
+    auto const stub = [] {
+        grpc::SslCredentialsOptions const cred_options{
+            // Note: This path used in this example is specific to non-OS X Unix systems.
+            // On Windows, this should be: %LOCALAPPDATA%\Btcwallet\rpc.cert
+            // On Mac OS X, this should be: $HOME/Library/Application Support/Btcwallet/rpc.cert
+            .pem_root_certs = read_file(unix_home_directory() + "/.btcwallet/rpc.cert"),
+        };
+        auto const creds = grpc::SslCredentials(cred_options);
+        auto const channel = grpc::CreateChannel("localhost:18332", creds);
+        return walletrpc::WalletService::NewStub(channel);
     }();
 
-    grpc::SslCredentialsOptions cred_options{
-        .pem_root_certs = read_file(wallet_tls_cert_file),
-    };
-    auto creds = grpc::SslCredentials(cred_options);
-    auto channel = grpc::CreateChannel("localhost:18332", creds);
-    auto stub = walletrpc::WalletService::NewStub(channel);
-
     grpc::ClientContext context{};
 
-    walletrpc::BalanceRequest request{};
-    request.set_account_number(0);
-    request.set_required_confirmations(1);
+    auto const request = [] {
+        walletrpc::BalanceRequest request{};
+        request.set_account_number(0);
+        request.set_required_confirmations(1);
+        return request;
+    }();
 
     walletrpc::BalanceResponse response{};
-    auto status = stub->Balance(&context, request, &response);
+    auto const status = stub->Balance(&context, request, &response);
     if (!status.ok()) {
-        std::cout << status.error_message() << std::endl;
+        std::cerr << status.error_code() << ": " << status.error_message() << std::endl;
     } else {
         std::cout << "Spendable balance: " << response.spendable() << " Satoshis" << std::endl;
     }
@@ -185,9 +185,9 @@ auto main() -> int {
 The example can then be built with the following commands:
 
 ```bash
-$ c++ -std=c++14 -I/usr/local/include -pthread -c -o api.pb.o api.pb.cc
-$ c++ -std=c++14 -I/usr/local/include -pthread -c -o api.grpc.pb.o api.grpc.pb.cc
-$ c++ -std=c++14 -I/usr/local/include -pthread -c -o example.o example.cc
+$ c++ -std=c++11 -I/usr/local/include -pthread -c -o api.pb.o api.pb.cc
+$ c++ -std=c++11 -I/usr/local/include -pthread -c -o api.grpc.pb.o api.grpc.pb.cc
+$ c++ -std=c++11 -I/usr/local/include -pthread -c -o example.o example.cc
 $ c++ *.o -L/usr/local/lib -lgrpc++ -lgrpc -lgpr -lprotobuf -lpthread -ldl -o example
 ```