Implement TextDecoder#decode.

components/script/dom/textdecoder.rs

@@ -7,16 +7,21 @@ use dom::bindings::codegen::Bindings::TextDecoderBinding::TextDecoderMethods;
 use dom::bindings::error::{Error, Fallible};
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::{JSRef, Temporary};
+use dom::bindings::str::USVString;
 use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::{Reflector, reflect_dom_object};
 
 use util::str::DOMString;
 
 use encoding::Encoding;
-use encoding::types::EncodingRef;
+use encoding::types::{EncodingRef, DecoderTrap};
 use encoding::label::encoding_from_whatwg_label;
+use js::jsapi::{JSContext, JSObject};
+use js::jsfriendapi::bindgen::JS_GetObjectAsArrayBufferView;
 
 use std::borrow::ToOwned;
+use std::ptr;
+use std::slice;
 
 #[dom_struct]
 pub struct TextDecoder {
@@ -62,4 +67,33 @@ impl<'a> TextDecoderMethods for JSRef<'a, TextDecoder> {
     fn Fatal(self) -> bool {
         self.fatal
     }
+
+    #[allow(unsafe_code)]
+    fn Decode(self, cx: *mut JSContext, input: Option<*mut JSObject>)
+              -> Fallible<USVString> {
+        let input = match input {
+            Some(input) => input,
+            None => return Ok(USVString("".to_owned())),
+        };
+
+        let mut length = 0;
+        let mut data = ptr::null_mut();
+        if unsafe { JS_GetObjectAsArrayBufferView(cx, input, &mut length, &mut data).is_null() } {
+            return Err(Error::Type("Argument to TextDecoder.decode is not an ArrayBufferView".to_owned()));
+        }
+
+        let buffer = unsafe {
+            slice::from_raw_parts(data as *const _, length as usize)
+        };
+        let trap = if self.fatal {
+            DecoderTrap::Strict
+        } else {
+            DecoderTrap::Replace
+        };
+        match self.encoding.decode(buffer, trap) {
+            Ok(s) => Ok(USVString(s)),
+            Err(_) => Err(Error::Type("Decoding failed".to_owned())),
+        }
+    }
+
 }

components/script/dom/webidls/TextDecoder.webidl

@@ -16,4 +16,6 @@ interface TextDecoder {
   readonly attribute boolean fatal;
   //readonly attribute boolean ignoreBOM;
   //USVString decode(optional BufferSource input, optional TextDecodeOptions options);
+  [Throws]
+  USVString decode(optional object input);
 };