Add a `--license` command line argument

Add a new argument that allows users to pass in the path to a license
file. Doing so should get picked up by the Objective-C code which will
copy and validate the license.

In order for the Objective-C code to pick up the path string, we add a
`license` field to the `Config.Args` struct.

The new `license` field is a `*mut c_char`, which means we can't derive
Default any more and need to implement a custom `Default` impl for
`Args`.

Additionally, 'getopts' gives us a Rust string (of course), which needs
to be converted into a raw `CString` before we can stick it in the
`license` field in `Args`. I previously wrote `dkeprintln` to be able to
print an error here at the conversion point between `CString` and raw C
string.

Since we used `CString#into_raw()`, we need to call `from_raw()` on the
pointer to free it, otherwise we end up with a memory leak. This
necessitated adding some additional code to `config_free()` to free the
`license` field if non-null.

In order to access `config.args.license` from within `config_free()`, I
also needed to make the `args` and `license` struct fields public, since
the free function is in a different module. Instead of making only those
two fields public, I decided to make them all public, as all the fields
are technically accessible from C code, and are needed by that C code.

Finally, move the module declaration of `prefix_println` to the top of
the module list instead of listing it alphabetically, because otherwise
any modules declared before it (like `config`) don't get access to its
macro. Also add a `#[macro_use]` attribute to the module declaration
because we do want to export its macro.
(https://stackoverflow.com/questions/26731243/how-do-i-use-a-macro-across-module-files#comment78329437_31749071)

3 files changed, 38 insertions, 8 deletions

diff --git a/src/cocoa_bridge.rs b/src/cocoa_bridge.rs
index 7b707de..cd1dafa 100644
--- a/src/cocoa_bridge.rs
+++ b/src/cocoa_bridge.rs
@@ -346,7 +346,10 @@ pub extern "C" fn config_get() -> *mut Config {
 #[no_mangle]
 pub extern "C" fn config_free(ptr: *mut Config) {
     if ptr.is_null() { return }
-    unsafe { Box::from_raw(ptr); }
+    let config = unsafe { Box::from_raw(ptr) };
+
+    if config.args.license.is_null() { return }
+    unsafe { CString::from_raw(config.args.license); }
 }
 
 
diff --git a/src/config.rs b/src/config.rs
index feaf578..b4cab10 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,18 +1,32 @@
+use std::ffi::CString;
 use std::fs;
+use std::ptr;
 
+use libc::c_char;
 use getopts::Options;
 use toml;
 use xdg;
 
 use errors::*;
+use prefix_println;
 
 type Milliseconds = u16;
 
 #[repr(C)]
-#[derive(Default)]
-struct Args {
-    reload: bool,
-    daemon: bool,
+pub struct Args {
+    pub reload: bool,
+    pub daemon: bool,
+    pub license: *mut c_char,
+}
+
+impl Default for Args {
+    fn default() -> Self {
+        Args {
+            reload: false,
+            daemon: false,
+            license: ptr::null_mut(),
+        }
+    }
 }
 
 #[repr(C)]
@@ -20,8 +34,8 @@ struct Args {
 #[serde(default)]
 pub struct Config {
     #[serde(skip)]
-    args: Args,
-    timeout: Milliseconds,
+    pub args: Args,
+    pub timeout: Milliseconds,
 }
 
 impl Default for Config {
@@ -43,6 +57,12 @@ pub fn parse_args<'a>(args: &[String], config: &'a mut Config) -> &'a mut Config
 
     opts.optflag("d", "daemon", "run the daemon in the current shell");
     opts.optflag("r", "reload-mappings", "reload the mappings file");
+    opts.optopt(
+        "",
+        "license",
+        "register the software using a license plist file",
+        "FILE"
+    );
     opts.optflag("h", "help", "print this help menu");
 
     let matches = match opts.parse(&args[1..]) {
@@ -59,6 +79,11 @@ pub fn parse_args<'a>(args: &[String], config: &'a mut Config) -> &'a mut Config
         config.args.reload = true;
     } else if matches.opt_present("d") {
         config.args.daemon = true;
+    } else if let Some(license_path) = matches.opt_str("license") {
+        match CString::new(license_path) {
+            Ok(str) => config.args.license = str.into_raw(),
+            Err(e) => dkeprintln!("{}", e),
+        }
     } else {
         print_usage(opts);
     }
diff --git a/src/lib.rs b/src/lib.rs
index 6a08e4b..1e0daa6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,13 +31,15 @@ extern crate stderrlog;
 extern crate toml;
 extern crate xdg;
 
+#[macro_use]
+mod prefix_println;
+
 mod autopilot_internal;
 mod cocoa_bridge;
 mod config;
 mod errors;
 mod key_code;
 mod parser;
-mod prefix_println;
 mod trial;
 
 use parser::{Action, HeadphoneButton, MapAction, MapGroup, MapKind};