std: add str.to_c_str()

Author: erickt

src/libstd/os.rs

@@ -1948,7 +1948,7 @@ mod tests {
           };
           assert!((ostream as uint != 0u));
           let s = ~"hello";
-          let mut buf = s.as_bytes_with_null().to_owned();
+          let mut buf = s.to_owned().to_c_str();
           let len = buf.len();
           do buf.as_mut_buf |b, _len| {
               assert_eq!(libc::fwrite(b as *c_void, 1u as size_t,

src/libstd/str.rs

@@ -2024,6 +2024,13 @@ pub trait OwnedStr {
     fn capacity(&self) -> uint;
     fn to_bytes_with_null(self) -> ~[u8];
 
+    /// Allocates a null terminate byte array.
+    ///
+    /// # Failure
+    ///
+    /// Fails if there are any null characters inside the byte array.
+    fn to_c_str(self) -> ~[u8];
+
     /// Work with the mutable byte buffer and length of a slice.
     ///
     /// The given length is one byte longer than the 'official' indexable
@@ -2215,6 +2222,13 @@ impl OwnedStr for ~str {
         unsafe { cast::transmute(self) }
     }
 
+    #[inline]
+    fn to_c_str(self) -> ~[u8] {
+        let bytes = self.to_bytes_with_null();
+        assert!(bytes.slice(0, bytes.len() - 1).iter().all(|byte| *byte != 0));
+        bytes
+    }
+
     #[inline]
     fn as_mut_buf<T>(&mut self, f: &fn(*mut u8, uint) -> T) -> T {
         let v: &mut ~[u8] = unsafe { cast::transmute(self) };
@@ -3059,6 +3073,18 @@ mod tests {
     }
 
     #[test]
+    fn test_to_c_str() {
+        let s = ~"ศไทย中华Việt Nam";
+        let v = ~[
+            224, 184, 168, 224, 185, 132, 224, 184, 151, 224, 184, 162, 228,
+            184, 173, 229, 141, 142, 86, 105, 225, 187, 135, 116, 32, 78, 97,
+            109, 0
+        ];
+        assert_eq!((~"").to_c_str(), ~[0]);
+        assert_eq!((~"abc").to_c_str(), ~['a' as u8, 'b' as u8, 'c' as u8, 0]);
+        assert_eq!(s.to_c_str(), v);
+    }
+
     fn test_subslice_offset() {
         let a = "kernelsprite";
         let b = a.slice(7, a.len());