Auto merge of #15519 - gterzian:implement_structuredclone_callbacks, r=jdm

implement structured clone callbacks - support Blob cloning

<!-- Please describe your changes on the following line: -->
1. Implement stubs for structured clone callbacks.
2. Support Blob cloning.

Partial implementation of https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #15021 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/script/dom/bindings/structuredclone.rs

@@ -5,15 +5,164 @@
 //! This module implements structured cloning, as defined by [HTML]
 //! (https://html.spec.whatwg.org/multipage/#safe-passing-of-structured-data).
 
+use dom::bindings::conversions::root_from_handleobject;
 use dom::bindings::error::{Error, Fallible};
+use dom::bindings::js::Root;
+use dom::bindings::reflector::DomObject;
+use dom::blob::{Blob, BlobImpl};
 use dom::globalscope::GlobalScope;
-use js::jsapi::{HandleValue, MutableHandleValue};
-use js::jsapi::{JSContext, JS_ReadStructuredClone, JS_STRUCTURED_CLONE_VERSION};
-use js::jsapi::{JS_ClearPendingException, JS_WriteStructuredClone};
+use js::jsapi::{Handle, HandleObject, HandleValue, MutableHandleValue, JSAutoCompartment, JSContext};
+use js::jsapi::{JSStructuredCloneCallbacks, JSStructuredCloneReader, JSStructuredCloneWriter};
+use js::jsapi::{JS_ClearPendingException, JSObject, JS_ReadStructuredClone};
+use js::jsapi::{JS_ReadBytes, JS_WriteBytes};
+use js::jsapi::{JS_ReadUint32Pair, JS_WriteUint32Pair};
+use js::jsapi::{JS_STRUCTURED_CLONE_VERSION, JS_WriteStructuredClone};
+use js::jsapi::{MutableHandleObject, TransferableOwnership};
 use libc::size_t;
+use std::os::raw;
 use std::ptr;
 use std::slice;
 
+// TODO: Should we add Min and Max const to https://github.com/servo/rust-mozjs/blob/master/src/consts.rs?
+// TODO: Determine for sure which value Min and Max should have.
+// NOTE: Current values found at https://dxr.mozilla.org/mozilla-central/
+// rev/ff04d410e74b69acfab17ef7e73e7397602d5a68/js/public/StructuredClone.h#323
+#[repr(u32)]
+enum StructuredCloneTags {
+    /// To support additional types, add new tags with values incremented from the last one before Max.
+    Min = 0xFFFF8000,
+    DomBlob = 0xFFFF8001,
+    Max = 0xFFFFFFFF,
+}
+
+#[cfg(target_pointer_width = "64")]
+unsafe fn write_length(w: *mut JSStructuredCloneWriter,
+                       length: usize) {
+  let high: u32 = (length >> 32) as u32;
+  let low: u32 = length as u32;
+  assert!(JS_WriteUint32Pair(w, high, low));
+}
+
+#[cfg(target_pointer_width = "32")]
+unsafe fn write_length(w: *mut JSStructuredCloneWriter,
+                       length: usize) {
+  assert!(JS_WriteUint32Pair(w, length as u32, 0));
+}
+
+#[cfg(target_pointer_width = "64")]
+unsafe fn read_length(r: *mut JSStructuredCloneReader)
+                      -> usize {
+  let mut high: u32 = 0;
+  let mut low: u32 = 0;
+  assert!(JS_ReadUint32Pair(r, &mut high as *mut u32, &mut low as *mut u32));
+  return (low << high) as usize;
+}
+
+#[cfg(target_pointer_width = "32")]
+unsafe fn read_length(r: *mut JSStructuredCloneReader)
+                      -> usize {
+  let mut length: u32 = 0;
+  let mut zero: u32 = 0;
+  assert!(JS_ReadUint32Pair(r, &mut length as *mut u32, &mut zero as *mut u32));
+  return length as usize;
+}
+
+unsafe fn read_blob(cx: *mut JSContext,
+                    r: *mut JSStructuredCloneReader)
+                    -> *mut JSObject {
+    let blob_length = read_length(r);
+    let type_str_length = read_length(r);
+    let mut blob_buffer = vec![0u8; blob_length];
+    assert!(JS_ReadBytes(r, blob_buffer.as_mut_ptr() as *mut raw::c_void, blob_length));
+    let mut type_str_buffer = vec![0u8; type_str_length];
+    assert!(JS_ReadBytes(r, type_str_buffer.as_mut_ptr() as *mut raw::c_void, type_str_length));
+    let type_str = String::from_utf8_unchecked(type_str_buffer);
+    let target_global = GlobalScope::from_context(cx);
+    let blob = Blob::new(&target_global, BlobImpl::new_from_bytes(blob_buffer), type_str);
+    return blob.reflector().get_jsobject().get()
+}
+
+unsafe fn write_blob(blob: Root<Blob>,
+                     w: *mut JSStructuredCloneWriter)
+                     -> Result<(), ()> {
+    let blob_vec = try!(blob.get_bytes());
+    let blob_length = blob_vec.len();
+    let type_string_bytes = blob.get_type_string().as_bytes().to_vec();
+    let type_string_length = type_string_bytes.len();
+    assert!(JS_WriteUint32Pair(w, StructuredCloneTags::DomBlob as u32, 0));
+    write_length(w, blob_length);
+    write_length(w, type_string_length);
+    assert!(JS_WriteBytes(w, blob_vec.as_ptr() as *const raw::c_void, blob_length));
+    assert!(JS_WriteBytes(w, type_string_bytes.as_ptr() as *const raw::c_void, type_string_length));
+    return Ok(())
+}
+
+unsafe extern "C" fn read_callback(cx: *mut JSContext,
+                                   r: *mut JSStructuredCloneReader,
+                                   tag: u32,
+                                   _data: u32,
+                                   _closure: *mut raw::c_void)
+                                   -> *mut JSObject {
+    assert!(tag < StructuredCloneTags::Max as u32, "tag should be lower than StructuredCloneTags::Max");
+    assert!(tag > StructuredCloneTags::Min as u32, "tag should be higher than StructuredCloneTags::Min");
+    if tag == StructuredCloneTags::DomBlob as u32 {
+        return read_blob(cx, r)
+    }
+    return ptr::null_mut()
+}
+
+unsafe extern "C" fn write_callback(_cx: *mut JSContext,
+                                    w: *mut JSStructuredCloneWriter,
+                                    obj: HandleObject,
+                                    _closure: *mut raw::c_void)
+                                    -> bool {
+    if let Ok(blob) = root_from_handleobject::<Blob>(obj) {
+        return write_blob(blob, w).is_ok()
+    }
+    return false
+}
+
+unsafe extern "C" fn read_transfer_callback(_cx: *mut JSContext,
+                                            _r: *mut JSStructuredCloneReader,
+                                            _tag: u32,
+                                            _content: *mut raw::c_void,
+                                            _extra_data: u64,
+                                            _closure: *mut raw::c_void,
+                                            _return_object: MutableHandleObject)
+                                            -> bool {
+    false
+}
+
+unsafe extern "C" fn write_transfer_callback(_cx: *mut JSContext,
+                                             _obj: Handle<*mut JSObject>,
+                                             _closure: *mut raw::c_void,
+                                             _tag: *mut u32,
+                                             _ownership: *mut TransferableOwnership,
+                                             _content:  *mut *mut raw::c_void,
+                                             _extra_data: *mut u64)
+                                             -> bool {
+    false
+}
+
+unsafe extern "C" fn free_transfer_callback(_tag: u32,
+                                            _ownership: TransferableOwnership,
+                                            _content: *mut raw::c_void,
+                                            _extra_data: u64,
+                                            _closure: *mut raw::c_void) {
+}
+
+unsafe extern "C" fn report_error_callback(_cx: *mut JSContext, _errorid: u32) {
+}
+
+static STRUCTURED_CLONE_CALLBACKS: JSStructuredCloneCallbacks = JSStructuredCloneCallbacks {
+    read: Some(read_callback),
+    write: Some(write_callback),
+    reportError: Some(report_error_callback),
+    readTransfer: Some(read_transfer_callback),
+    writeTransfer: Some(write_transfer_callback),
+    freeTransfer: Some(free_transfer_callback),
+};
+
 /// A buffer for a structured clone.
 pub enum StructuredCloneData {
     /// A non-serializable (default) variant
@@ -32,7 +181,7 @@ impl StructuredCloneData {
                                     message,
                                     &mut data,
                                     &mut nbytes,
-                                    ptr::null(),
+                                    &STRUCTURED_CLONE_CALLBACKS,
                                     ptr::null_mut(),
                                     HandleValue::undefined())
         };
@@ -60,14 +209,20 @@ impl StructuredCloneData {
     /// Reads a structured clone.
     ///
     /// Panics if `JS_ReadStructuredClone` fails.
-    fn read_clone(global: &GlobalScope, data: *mut u64, nbytes: size_t, rval: MutableHandleValue) {
+    fn read_clone(global: &GlobalScope,
+                  data: *mut u64,
+                  nbytes: size_t,
+                  rval: MutableHandleValue) {
+        let cx = global.get_cx();
+        let globalhandle = global.reflector().get_jsobject();
+        let _ac = JSAutoCompartment::new(cx, globalhandle.get());
         unsafe {
-            assert!(JS_ReadStructuredClone(global.get_cx(),
+            assert!(JS_ReadStructuredClone(cx,
                                            data,
                                            nbytes,
                                            JS_STRUCTURED_CLONE_VERSION,
                                            rval,
-                                           ptr::null(),
+                                           &STRUCTURED_CLONE_CALLBACKS,
                                            ptr::null_mut()));
         }
     }

components/script/dom/blob.rs

@@ -163,6 +163,11 @@ impl Blob {
         }
     }
 
+    /// Get a copy of the type_string
+    pub fn get_type_string(&self) -> String {
+        self.type_string.clone()
+    }
+
     /// Get a FileID representing the Blob content,
     /// used by URL.createObjectURL
     pub fn get_blob_url_id(&self) -> Uuid {