Add as_c_str method on strings

src/libstd/prelude.rs

@@ -45,7 +45,7 @@ pub use path::PosixPath;
 pub use path::WindowsPath;
 pub use ptr::Ptr;
 pub use ascii::{Ascii, AsciiCast, OwnedAsciiCast, AsciiStr};
-pub use str::{StrSlice, OwnedStr};
+pub use str::{StrSlice, OwnedStr, StrUtil};
 pub use from_str::{FromStr};
 pub use to_bytes::IterBytes;
 pub use to_str::{ToStr, ToStrConsume};

src/libstd/str.rs

@@ -2165,6 +2165,10 @@ pub fn as_bytes_slice<'a>(s: &'a str) -> &'a [u8] {
 }
 
 /**
+ * A dummy trait to hold all the utility methods that we implement on strings.
+ */
+pub trait StrUtil {
+    /**
      * Work with the byte buffer of a string as a null-terminated C string.
      *
      * Allows for unsafe manipulation of strings, which is useful for foreign
@@ -2176,20 +2180,33 @@ pub fn as_bytes_slice<'a>(s: &'a str) -> &'a [u8] {
      * # Example
      *
      * ~~~ {.rust}
- * let s = str::as_c_str("PATH", { |path| libc::getenv(path) });
+     * let s = "PATH".as_c_str(|path| libc::getenv(path));
      * ~~~
      */
-#[inline]
+    fn as_c_str<T>(self, f: &fn(*libc::c_char) -> T) -> T;
-pub fn as_c_str<T>(s: &str, f: &fn(*libc::c_char) -> T) -> T {
+}
-    do as_buf(s) |buf, len| {
+
+impl<'self> StrUtil for &'self str {
+    #[inline]
+    fn as_c_str<T>(self, f: &fn(*libc::c_char) -> T) -> T {
+        do as_buf(self) |buf, len| {
             // NB: len includes the trailing null.
             assert!(len > 0);
             if unsafe { *(ptr::offset(buf,len-1)) != 0 } {
-            as_c_str(to_owned(s), f)
+                to_owned(self).as_c_str(f)
             } else {
                 f(buf as *libc::c_char)
             }
         }
+    }
+}
+
+/**
+ * Deprecated. Use the `as_c_str` method on strings instead.
+ */
+#[inline(always)]
+pub fn as_c_str<T>(s: &str, f: &fn(*libc::c_char) -> T) -> T {
+    s.as_c_str(f)
 }
 
 /**