Make log crate dependency optional (issue #22)

Cargo.toml

@@ -12,11 +12,16 @@ repository = "https://github.com/ctz/rustls"
 untrusted = "0.3.1"
 time = "0.1.35"
 base64 = "~0.2.0"
-log = "0.3.6"
+log = { version = "0.3.6", optional = true }
 ring = { version = "0.4", features = ["rsa_signing"] }
 webpki = "0.3.0"
 
+[features]
+default = ["logging"]
+logging = ["log"]
+
 [dev-dependencies]
+log = "0.3.6"
 env_logger = "0.3.3"
 mio = "0.5.1"
 docopt = "0.6"

src/lib.rs

@@ -173,10 +173,20 @@ extern crate untrusted;
 /* rust-base64 for pemfile module. */
 extern crate base64;
 
-/* log for logging. */
+/* log for logging (optional). */
+#[cfg(feature = "logging")]
 #[macro_use]
 extern crate log;
 
+#[cfg(not(feature = "logging"))]
+#[macro_use]
+mod compile_out_log {
+  macro_rules! debug    ( ($($tt:tt)*) => {{}} );
+  macro_rules! info     ( ($($tt:tt)*) => {{}} );
+  macro_rules! warn     ( ($($tt:tt)*) => {{}} );
+  macro_rules! error    ( ($($tt:tt)*) => {{}} );
+}
+
 mod util;
 #[macro_use]
 mod msgs;