Add the append method for the Headers API for the Fetch API

This commit will add the append method and associated helper functions, and introduce any necessary changes for it.

components/script/dom/headers.rs

@@ -0,0 +1,248 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::cell::DOMRefCell;
+use dom::bindings::codegen::Bindings::HeadersBinding;
+use dom::bindings::error::Error;
+use dom::bindings::global::GlobalRef;
+use dom::bindings::js::Root;
+use dom::bindings::reflector::{Reflector, reflect_dom_object};
+use dom::bindings::str::{ByteString, is_token};
+use hyper;
+use std::result::Result;
+
+#[dom_struct]
+pub struct Headers {
+    reflector_: Reflector,
+    guard: Guard,
+    #[ignore_heap_size_of = "Defined in hyper"]
+    header_list: DOMRefCell<hyper::header::Headers>
+}
+
+// https://fetch.spec.whatwg.org/#concept-headers-guard
+#[derive(JSTraceable, HeapSizeOf, PartialEq)]
+pub enum Guard {
+    Immutable,
+    Request,
+    RequestNoCors,
+    Response,
+    None,
+}
+
+impl Headers {
+    pub fn new_inherited() -> Headers {
+        Headers {
+            reflector_: Reflector::new(),
+            guard: Guard::None,
+            header_list: DOMRefCell::new(hyper::header::Headers::new()),
+        }
+    }
+
+    pub fn new(global: GlobalRef) -> Root<Headers> {
+        reflect_dom_object(box Headers::new_inherited(), global, HeadersBinding::Wrap)
+    }
+
+    // https://fetch.spec.whatwg.org/#concept-headers-append
+    pub fn Append(&self, name: ByteString, value: ByteString) -> Result<(), Error> {
+        // Step 1
+        let value = normalize_value(value);
+
+        // Step 2
+        let (valid_name, valid_value) = try!(validate_name_and_value(name, value));
+        // Step 3
+        if self.guard == Guard::Immutable {
+            return Err(Error::Type("Guard is immutable".to_string()));
+        }
+
+        // Step 4
+        if self.guard == Guard::Request && is_forbidden_header_name(&valid_name) {
+            return Ok(());
+        }
+
+        // Step 5
+        if self.guard == Guard::RequestNoCors && !is_cors_safelisted_request_header(&valid_name) {
+            return Ok(());
+        }
+
+        // Step 6
+        if self.guard == Guard::Response && is_forbidden_response_header(&valid_name) {
+            return Ok(());
+        }
+
+        // Step 7
+        self.header_list.borrow_mut().set_raw(valid_name, vec![valid_value]);
+        return Ok(());
+    }
+}
+
+// TODO
+// "Content-Type" once parsed, the value should be
+// `application/x-www-form-urlencoded`, `multipart/form-data`,
+// or `text/plain`.
+// "DPR", "Downlink", "Save-Data", "Viewport-Width", "Width":
+// once parsed, the value should not be failure.
+// https://fetch.spec.whatwg.org/#cors-safelisted-request-header
+fn is_cors_safelisted_request_header(name: &str) -> bool {
+    match name {
+        "accept" |
+        "accept-language" |
+        "content-language" => true,
+        _ => false,
+    }
+}
+
+// https://fetch.spec.whatwg.org/#forbidden-response-header-name
+fn is_forbidden_response_header(name: &str) -> bool {
+    match name {
+        "set-cookie" |
+        "set-cookie2"  => true,
+        _ => false,
+    }
+}
+
+// https://fetch.spec.whatwg.org/#forbidden-header-name
+fn is_forbidden_header_name(name: &str) -> bool {
+    let disallowed_headers =
+        ["accept-charset", "accept-encoding",
+         "access-control-request-headers",
+         "access-control-request-method",
+         "connection", "content-length",
+         "cookie", "cookie2", "date", "dnt",
+         "expect", "host", "keep-alive", "origin",
+         "referer", "te", "trailer", "transfer-encoding",
+         "upgrade", "via"];
+
+    let disallowed_header_prefixes = ["sec-", "proxy-"];
+
+    disallowed_headers.iter().any(|header| *header == name) ||
+        disallowed_header_prefixes.iter().any(|prefix| name.starts_with(prefix))
+}
+
+// There is some unresolved confusion over the definition of a name and a value.
+// The fetch spec [1] defines a name as "a case-insensitive byte
+// sequence that matches the field-name token production. The token
+// productions are viewable in [2]." A field-name is defined as a
+// token, which is defined in [3].
+// ISSUE 1:
+// It defines a value as "a byte sequence that matches the field-content token production."
+// To note, there is a difference between field-content and
+// field-value (which is made up of fied-content and obs-fold). The
+// current definition does not allow for obs-fold (which are white
+// space and newlines) in values. So perhaps a value should be defined
+// as "a byte sequence that matches the field-value token production."
+// However, this would then allow values made up entirely of white space and newlines.
+// RELATED ISSUE 2:
+// According to a previously filed Errata ID: 4189 in [4], "the
+// specified field-value rule does not allow single field-vchar
+// surrounded by whitespace anywhere". They provided a fix for the
+// field-content production, but ISSUE 1 has still not been resolved.
+// The production definitions likely need to be re-written.
+// [1] https://fetch.spec.whatwg.org/#concept-header-value
+// [2] https://tools.ietf.org/html/rfc7230#section-3.2
+// [3] https://tools.ietf.org/html/rfc7230#section-3.2.6
+// [4] https://www.rfc-editor.org/errata_search.php?rfc=7230
+fn validate_name_and_value(name: ByteString, value: ByteString)
+                           -> Result<(String, Vec<u8>), Error> {
+    if !is_field_name(&name) {
+        return Err(Error::Type("Name is not valid".to_string()));
+    }
+    if !is_field_content(&value) {
+        return Err(Error::Type("Value is not valid".to_string()));
+    }
+    match String::from_utf8(name.into()) {
+        Ok(ns) => Ok((ns, value.into())),
+        _ => Err(Error::Type("Non-UTF8 header name found".to_string())),
+    }
+}
+
+// Removes trailing and leading HTTP whitespace bytes.
+// https://fetch.spec.whatwg.org/#concept-header-value-normalize
+pub fn normalize_value(value: ByteString) -> ByteString {
+    match (index_of_first_non_whitespace(&value), index_of_last_non_whitespace(&value)) {
+        (Some(begin), Some(end)) => ByteString::new(value[begin..end + 1].to_owned()),
+        _ => ByteString::new(vec![]),
+    }
+}
+
+fn is_HTTP_whitespace(byte: u8) -> bool {
+    byte == b'\t' || byte == b'\n' || byte == b'\r' || byte == b' '
+}
+
+fn index_of_first_non_whitespace(value: &ByteString) -> Option<usize> {
+    for (index, &byte) in value.iter().enumerate() {
+        if !is_HTTP_whitespace(byte) {
+            return Some(index);
+        }
+    }
+    None
+}
+
+fn index_of_last_non_whitespace(value: &ByteString) -> Option<usize> {
+    for (index, &byte) in value.iter().enumerate().rev() {
+        if !is_HTTP_whitespace(byte) {
+            return Some(index);
+        }
+    }
+    None
+}
+
+// http://tools.ietf.org/html/rfc7230#section-3.2
+fn is_field_name(name: &ByteString) -> bool {
+    is_token(&*name)
+}
+
+// https://tools.ietf.org/html/rfc7230#section-3.2
+// http://www.rfc-editor.org/errata_search.php?rfc=7230
+// Errata ID: 4189
+// field-content = field-vchar [ 1*( SP / HTAB / field-vchar )
+//                               field-vchar ]
+fn is_field_content(value: &ByteString) -> bool {
+    if value.len() == 0 {
+        return false;
+    }
+    if !is_field_vchar(value[0]) {
+        return false;
+    }
+
+    for &ch in &value[1..value.len() - 1] {
+        if !is_field_vchar(ch) || !is_space(ch) || !is_htab(ch) {
+            return false;
+        }
+    }
+
+    if !is_field_vchar(value[value.len() - 1]) {
+        return false;
+    }
+
+    return true;
+}
+
+fn is_space(x: u8) -> bool {
+    x == b' '
+}
+
+fn is_htab(x: u8) -> bool {
+    x == b'\t'
+}
+
+// https://tools.ietf.org/html/rfc7230#section-3.2
+fn is_field_vchar(x: u8) -> bool {
+    is_vchar(x) || is_obs_text(x)
+}
+
+// https://tools.ietf.org/html/rfc5234#appendix-B.1
+fn is_vchar(x: u8) -> bool {
+    match x {
+        0x21...0x7E => true,
+        _ => false,
+    }
+}
+
+// http://tools.ietf.org/html/rfc7230#section-3.2.6
+fn is_obs_text(x: u8) -> bool {
+    match x {
+        0x80...0xFF => true,
+        _ => false,
+    }
+}