Use apple's native ObjC APIs to produce the right paths

Cargo.toml

@@ -11,6 +11,9 @@ maintenance = { status = "as-is" }
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
 
+[target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies]
+objc = "0.2"
+
 [target.'cfg(target_os = "redox")'.dependencies]
 redox_users = "0.3.0"
 

src/apple.rs

@@ -0,0 +1,117 @@
+use objc::rc::autoreleasepool;
+use objc::runtime::Object;
+use std::ffi::CStr;
+use std::os::raw::c_char;
+use std::path::PathBuf;
+
+// We need to link to Foundation to access the NSFileManager class
+#[link(name = "Foundation", kind = "framework")]
+extern "C" {}
+
+/// Type of directory to lookup from macOS/iOS
+#[repr(u64)]
+pub enum SearchPathDirectory {
+    /// Applications directory, depending on domain. /Applications or ~/Applications typically
+    Application = 1,
+    AdminApplication = 4,
+    /// Library folder, can be /Library (system) or ~/Library (user)
+    Library = 5,
+    /// Location of usere's home directories, typically /Users
+    Users = 7,
+    /// Documentation, not sure if used...
+    Documentation = 8,
+    /// Documents folder, typically ~/Documents
+    Documents = 9,
+    AutosavedInformation = 11,
+    /// User's desktop folder, typically ~/Desktop
+    Desktop = 12,
+    /// Caches folder, Library/Caches
+    Caches = 13,
+    /// Applicatino support, Library/Application Support
+    ///
+    /// Typical home of non-userdefaults app data & settings
+    ApplicationSupport = 14,
+    /// Downloads folder, ~/Downloads
+    Downloads = 15,
+    /// Movies folder, ~/Movies
+    Movies = 17,
+    /// Music folder, ~/Music
+    Music = 18,
+    /// Pictures folder, ~/Pictures
+    Pictures = 19,
+    /// PPDs folder, Library/Printers/PPDs
+    PrinterDescription = 20,
+    /// Public folder, ~/Public
+    SharedPublic = 21,
+    /// Preference Panes, Library/PreferencePanes
+    PreferencePanes = 22,
+    /// User scripts folder for calling application, ~/Library/Application Scripts/code-signing-id
+    ApplicationScripts = 23,
+    /// Trash folder
+    Trash = 102,
+}
+
+/// Domain for path to return, dirs currently mostly deals with user dirs so likely want UserDomain
+#[repr(u64)]
+pub enum SearchPathDomainMask {
+    /// Looks up directory in user's domain, so ~
+    UserDomain = 1,
+    /// Local system domain, which is folders typically found in /Library
+    LocalDomain = 2,
+    /// Publically available locations on the local network
+    NetworkDomain = 4,
+    /// Read only system locations, /System (may be completely unavailable on newer systems?)
+    SystemDomain = 8,
+    /// Looks up directories in all of the current domains and future ones apple may add
+    AllDomains = 65535,
+}
+
+/// Returns first path found on macOS/iOS systems given the requested type of path, within given domain
+///
+/// Even if a path is returned, it may not exist yet and require creation
+pub fn path_for_dir(dir: SearchPathDirectory, domain: SearchPathDomainMask) -> Option<PathBuf> {
+    let mut result = None;
+    autoreleasepool(|| {
+        let cls = class!(NSFileManager);
+        unsafe {
+            let obj: *mut Object = msg_send![cls, defaultManager];
+            let url: *mut Object = msg_send![obj, URLForDirectory:dir inDomain:domain as u64 appropriateForURL:0 create:false error:0];
+            if !url.is_null() {
+                let path: *mut Object = msg_send![url, path];
+                let s: *const c_char = msg_send![path, UTF8String];
+                let c_str = CStr::from_ptr(s);
+                match c_str.to_str() {
+                    Err(error) => {
+                        println!("Error getting home dir string: {}", error);
+                    }
+                    Ok(string) => result = Some(PathBuf::from(string.to_owned())),
+                };
+            } else {
+                println!("Failed to get dir");
+            }
+        }
+    });
+    result
+}
+
+/// Returns user's home directory, or sandbox if called within sandboxed app
+pub fn home_dir() -> Option<PathBuf> {
+    unsafe {
+        let mut result = None;
+        autoreleasepool(|| {
+            let cls = class!(NSFileManager);
+            let obj: *mut Object = msg_send![cls, defaultManager];
+            let url: *mut Object = msg_send![obj, homeDirectoryForCurrentUser];
+            let path: *mut Object = msg_send![url, path];
+            let s: *const c_char = msg_send![path, UTF8String];
+            let c_str = CStr::from_ptr(s);
+            match c_str.to_str() {
+                Err(error) => {
+                    println!("Error getting home dir string: {}", error);
+                }
+                Ok(string) => result = Some(PathBuf::from(string.to_owned())),
+            };
+        });
+        result
+    }
+}