auto merge of #7027 : sstewartgallus/rust/dynamic_lib, r=graydon

I would appreciate if someone could help out with the Windows code on this pull request. I tried to test it using WINE but I couldn't figure out a way to set that up.

src/libstd/unstable/dynamic_lib.rs

@@ -0,0 +1,199 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/*!
+
+Dynamic library facilities.
+
+A simple wrapper over the platforms dynamic library facilities
+
+*/
+use ptr;
+use cast;
+use path;
+use libc;
+use ops::*;
+use option::*;
+use result::*;
+
+pub struct DynamicLibrary { priv handle: *libc::c_void }
+
+impl Drop for DynamicLibrary {
+    fn finalize(&self) {
+        match do dl::check_for_errors_in {
+            unsafe {
+                dl::close(self.handle)
+            }
+        } {
+            Ok(()) => { },
+            Err(str) => fail!(str)
+        }
+    }
+}
+
+impl DynamicLibrary {
+    /// Lazily open a dynamic library. When passed None it gives a
+    /// handle to the calling process
+    pub fn open(filename: Option<&path::Path>) -> Result<DynamicLibrary, ~str> {
+        let open_wrapper = |raw_ptr| {
+            do dl::check_for_errors_in {
+                unsafe {
+                    DynamicLibrary { handle: dl::open(raw_ptr) }
+                }
+            }
+        };
+
+        match filename {
+            Some(name) => do name.to_str().as_c_str |raw_name| {
+                open_wrapper(raw_name)
+            },
+            None => open_wrapper(ptr::null())
+        }
+    }
+
+    /// Access the value at the symbol of the dynamic library
+    pub unsafe fn symbol<T>(&self, symbol: &str) -> Result<T, ~str> {
+        // This function should have a lifetime constraint of 'self on
+        // T but that feature is still unimplemented
+
+        do dl::check_for_errors_in {
+            let symbol_value = do symbol.as_c_str |raw_string| {
+                dl::symbol(self.handle, raw_string)
+            };
+
+            cast::transmute(symbol_value)
+        }
+    }
+}
+
+#[test]
+priv fn test_loading_cosine () {
+    // The math library does not need to be loaded since it is already
+    // statically linked in
+    let libm = match DynamicLibrary::open(None) {
+        Err (error) => fail!("Could not load self as module: %s", error),
+        Ok (libm) => libm
+    };
+
+    // Unfortunately due to issue #6194 it is not possible to call
+    // this as a C function
+    let cosine: extern fn(libc::c_double) -> libc::c_double = unsafe {
+        match libm.symbol("cos") {
+            Err (error) => fail!("Could not load function cos: %s", error),
+            Ok (cosine) => cosine
+        }
+    };
+
+    let argument = 0.0;
+    let expected_result = 1.0;
+    let result = cosine(argument);
+    if result != expected_result {
+        fail!("cos(%?) != %? but equaled %? instead", argument,
+              expected_result, result)
+    }
+}
+
+#[cfg(target_os = "linux")]
+#[cfg(target_os = "android")]
+#[cfg(target_os = "macos")]
+#[cfg(target_os = "freebsd")]
+mod dl {
+    use libc;
+    use ptr;
+    use str;
+    use task;
+    use result::*;
+
+    pub unsafe fn open(filename: *libc::c_char) -> *libc::c_void {
+        dlopen(filename, Lazy as libc::c_int)
+    }
+
+    pub fn check_for_errors_in<T>(f: &fn()->T) -> Result<T, ~str> {
+        unsafe {
+            do task::atomically {
+                let _old_error = dlerror();
+
+                let result = f();
+
+                let last_error = dlerror();
+                if ptr::null() == last_error {
+                    Ok(result)
+                } else {
+                    Err(str::raw::from_c_str(last_error))
+                }
+            }
+        }
+    }
+
+    pub unsafe fn symbol(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void {
+        dlsym(handle, symbol)
+    }
+    pub unsafe fn close(handle: *libc::c_void) {
+        dlclose(handle); ()
+    }
+
+    pub enum RTLD {
+        Lazy = 1,
+        Now = 2,
+        Global = 256,
+        Local = 0,
+    }
+
+    #[link_name = "dl"]
+    extern {
+        fn dlopen(filename: *libc::c_char, flag: libc::c_int) -> *libc::c_void;
+        fn dlerror() -> *libc::c_char;
+        fn dlsym(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void;
+        fn dlclose(handle: *libc::c_void) -> libc::c_int;
+    }
+}
+
+#[cfg(target_os = "win32")]
+mod dl {
+    use os;
+    use libc;
+    use task;
+    use result::*;
+
+    pub unsafe fn open(filename: *libc::c_char) -> *libc::c_void {
+        LoadLibrary(filename)
+    }
+
+    pub fn check_for_errors_in<T>(f: &fn()->T) -> Result<T, ~str> {
+        unsafe {
+            do task::atomically {
+                SetLastError(0);
+
+                let result = f();
+
+                let error = os::errno();
+                if 0 == error {
+                    Ok(result)
+                } else {
+                    Err(fmt!("Error code %?", error))
+                }
+            }
+        }
+    }
+    pub unsafe fn symbol(handle: *libc::c_void, symbol: *libc::c_char) -> *libc::c_void {
+        GetProcAddress(handle, symbol)
+    }
+    pub unsafe fn close(handle: *libc::c_void) {
+        FreeLibrary(handle); ()
+    }
+
+    #[link_name = "kernel32"]
+    extern "stdcall" {
+        fn SetLastError(error: u32);
+        fn LoadLibrary(name: *libc::c_char) -> *libc::c_void;
+        fn GetProcAddress(handle: *libc::c_void, name: *libc::c_char) -> *libc::c_void;
+        fn FreeLibrary(handle: *libc::c_void);
+    }
+}

src/libstd/unstable/mod.rs

@@ -17,6 +17,14 @@ use prelude::*;
 use task;
 
 pub mod at_exit;
+
+// Currently only works for *NIXes
+#[cfg(target_os = "linux")]
+#[cfg(target_os = "android")]
+#[cfg(target_os = "macos")]
+#[cfg(target_os = "freebsd")]
+pub mod dynamic_lib;
+
 pub mod global;
 pub mod finally;
 pub mod weak_task;