Allow codepoints 128-255 in fourc!!

Codepoints with those values will be interpreted as bytes with their
raw codepoint value. ('\xAB' -> 0xABu8, etc.) Codepoints > 255 remain
forbidden.

src/libfourcc/lib.rs

@@ -70,8 +70,6 @@ pub fn macro_registrar(register: |Name, SyntaxExtension|) {
         None));
 }
 
-use std::ascii::AsciiCast;
-
 pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) -> base::MacResult {
     let (expr, endian) = parse_tts(cx, tts);
 
@@ -93,9 +91,7 @@ pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) ->
         ast::ExprLit(lit) => match lit.node {
             // string literal
             ast::LitStr(ref s, _) => {
-                if !s.get().is_ascii() {
-                    cx.span_err(expr.span, "non-ascii string literal in fourcc!");
-                } else if s.get().len() != 4 {
+                if s.get().char_len() != 4 {
                     cx.span_err(expr.span, "string literal with len != 4 in fourcc!");
                 }
                 s
@@ -112,14 +108,19 @@ pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) ->
     };
 
     let mut val = 0u32;
-    if little {
-        for byte in s.get().bytes_rev().take(4) {
-            val = (val << 8) | (byte as u32);
-        }
-    } else {
-        for byte in s.get().bytes().take(4) {
-            val = (val << 8) | (byte as u32);
-        }
+    for codepoint in s.get().chars().take(4) {
+        let byte = if codepoint as u32 > 0xFF {
+            cx.span_err(expr.span, "fourcc! literal character out of range 0-255");
+            0u8
+        } else {
+            codepoint as u8
+        };
+
+        val = if little {
+            (val >> 8) | ((byte as u32) << 24)
+        } else {
+            (val << 8) | (byte as u32)
+        };
     }
     let e = cx.expr_lit(sp, ast::LitUint(val as u64, ast::TyU32));
     MRExpr(e)

src/test/compile-fail/syntax-extension-fourcc-non-ascii-str.rs

@@ -18,5 +18,5 @@
 extern mod fourcc;
 
 fn main() {
-    let v = fourcc!("fooλ"); //~ ERROR non-ascii string literal in fourcc!
+    let v = fourcc!("fooλ"); //~ ERROR fourcc! literal character out of range 0-255
 }

src/test/run-pass-fulldeps/syntax-extension-fourcc.rs

@@ -40,4 +40,6 @@ fn main() {
     assert_eq!(static_val_le, 0x206f6f66u32);
     let exp = if cfg!(target_endian = "big") { 0x666f6f20u32 } else { 0x206f6f66u32 };
     assert_eq!(static_val_target, exp);
+
+    assert_eq!(fourcc!("\xC0\xFF\xEE!"), 0xC0FFEE21);
 }