1 files changed, 50 insertions, 0 deletions
diff --git a/src/components/script/dom/bindings/str.rs b/src/components/script/dom/bindings/str.rs
index e0ac5e57a2e..a662470aeab 100644
--- a/src/components/script/dom/bindings/str.rs
+++ b/src/components/script/dom/bindings/str.rs
@@ -37,6 +37,7 @@ impl ByteString {
             }
         }).collect())
     }
+
     pub fn is_token(&self) -> bool {
         let ByteString(ref vec) = *self;
         vec.iter().all(|&x| {
@@ -51,6 +52,55 @@ impl ByteString {
             }
         })
     }
+
+    pub fn is_field_value(&self) -> bool {
+        // Classifications of characters necessary for the [CRLF] (SP|HT) rule
+        #[deriving(Eq)]
+        enum PreviousCharacter {
+            Other,
+            CR,
+            LF,
+            SP_HT // SP or HT
+        }
+        let ByteString(ref vec) = *self;
+        let mut prev = Other; // The previous character
+        vec.iter().all(|&x| {
+            // http://tools.ietf.org/html/rfc2616#section-2.2
+            match x {
+                13  => { // CR
+                    if prev == Other || prev == SP_HT {
+                        prev = CR;
+                        true
+                    } else {
+                        false
+                    }
+                },
+                10 => { // LF
+                    if prev == CR {
+                        prev = LF;
+                        true
+                    } else {
+                        false
+                    }
+                },
+                32 | 9 => { // SP | HT
+                    if prev == LF || prev == SP_HT {
+                        prev = SP_HT;
+                        true
+                    } else {
+                        false
+                    }
+                },
+                0..31 | 127 => false, // CTLs
+                x if x > 127 => false, // non ASCII
+                _ if prev == Other || prev == SP_HT => {
+                    prev = Other;
+                    true
+                },
+                _ => false // Previous character was a CR/LF but not part of the [CRLF] (SP|HT) rule
+            }
+        })
+    }
 }
 
 impl Hash for ByteString {