diff -r 000000000000 -r 6474c204b198 netwerk/base/src/nsUnicharStreamLoader.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/netwerk/base/src/nsUnicharStreamLoader.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,238 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "mozilla/DebugOnly.h"
+
+#include "nsUnicharStreamLoader.h"
+#include "nsIInputStream.h"
+#include "nsICharsetConverterManager.h"
+#include "nsServiceManagerUtils.h"
+#include <algorithm>
+
+// 1024 bytes is specified in
+// http://www.whatwg.org/specs/web-apps/current-work/#charset for HTML; for
+// other resource types (e.g. CSS) typically fewer bytes are fine too, since
+// they only look at things right at the beginning of the data.
+#define SNIFFING_BUFFER_SIZE 1024
+
+using namespace mozilla;
+
+NS_IMETHODIMP
+nsUnicharStreamLoader::Init(nsIUnicharStreamLoaderObserver *aObserver)
+{
+  NS_ENSURE_ARG_POINTER(aObserver);
+
+  mObserver = aObserver;
+
+  if (!mRawData.SetCapacity(SNIFFING_BUFFER_SIZE, fallible_t()))
+    return NS_ERROR_OUT_OF_MEMORY;
+
+  return NS_OK;
+}
+
+nsresult
+nsUnicharStreamLoader::Create(nsISupports *aOuter,
+                              REFNSIID aIID,
+                              void **aResult)
+{
+  if (aOuter) return NS_ERROR_NO_AGGREGATION;
+
+  nsUnicharStreamLoader* it = new nsUnicharStreamLoader();
+  NS_ADDREF(it);
+  nsresult rv = it->QueryInterface(aIID, aResult);
+  NS_RELEASE(it);
+  return rv;
+}
+
+NS_IMPL_ISUPPORTS(nsUnicharStreamLoader, nsIUnicharStreamLoader,
+                  nsIRequestObserver, nsIStreamListener)
+
+/* readonly attribute nsIChannel channel; */
+NS_IMETHODIMP
+nsUnicharStreamLoader::GetChannel(nsIChannel **aChannel)
+{
+  NS_IF_ADDREF(*aChannel = mChannel);
+  return NS_OK;
+}
+
+/* readonly attribute nsACString charset */
+NS_IMETHODIMP
+nsUnicharStreamLoader::GetCharset(nsACString& aCharset)
+{
+  aCharset = mCharset;
+  return NS_OK;
+}
+
+/* nsIRequestObserver implementation */
+NS_IMETHODIMP
+nsUnicharStreamLoader::OnStartRequest(nsIRequest*, nsISupports*)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsUnicharStreamLoader::OnStopRequest(nsIRequest *aRequest,
+                                     nsISupports *aContext,
+                                     nsresult aStatus)
+{
+  if (!mObserver) {
+    NS_ERROR("nsUnicharStreamLoader::OnStopRequest called before ::Init");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mContext = aContext;
+  mChannel = do_QueryInterface(aRequest);
+
+  nsresult rv = NS_OK;
+  if (mRawData.Length() > 0 && NS_SUCCEEDED(aStatus)) {
+    NS_ABORT_IF_FALSE(mBuffer.Length() == 0,
+                      "should not have both decoded and raw data");
+    rv = DetermineCharset();
+  }
+
+  if (NS_FAILED(rv)) {
+    // Call the observer but pass it no data.
+    mObserver->OnStreamComplete(this, mContext, rv, EmptyString());
+  } else {
+    mObserver->OnStreamComplete(this, mContext, aStatus, mBuffer);
+  }
+
+  mObserver = nullptr;
+  mDecoder = nullptr;
+  mContext = nullptr;
+  mChannel = nullptr;
+  mCharset.Truncate();
+  mBuffer.Truncate();
+  return rv;
+}
+
+/* nsIStreamListener implementation */
+NS_IMETHODIMP
+nsUnicharStreamLoader::OnDataAvailable(nsIRequest *aRequest,
+                                       nsISupports *aContext,
+                                       nsIInputStream *aInputStream,
+                                       uint64_t aSourceOffset,
+                                       uint32_t aCount)
+{
+  if (!mObserver) {
+    NS_ERROR("nsUnicharStreamLoader::OnDataAvailable called before ::Init");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mContext = aContext;
+  mChannel = do_QueryInterface(aRequest);
+
+  nsresult rv = NS_OK;
+  if (mDecoder) {
+    // process everything we've got
+    uint32_t dummy;
+    aInputStream->ReadSegments(WriteSegmentFun, this, aCount, &dummy);
+  } else {
+    // no decoder yet.  Read up to SNIFFING_BUFFER_SIZE octets into
+    // mRawData (this is the cutoff specified in
+    // draft-abarth-mime-sniff-06).  If we can get that much, then go
+    // ahead and fire charset detection and read the rest.  Otherwise
+    // wait for more data.
+
+    uint32_t haveRead = mRawData.Length();
+    uint32_t toRead = std::min(SNIFFING_BUFFER_SIZE - haveRead, aCount);
+    uint32_t n;
+    char *here = mRawData.BeginWriting() + haveRead;
+
+    rv = aInputStream->Read(here, toRead, &n);
+    if (NS_SUCCEEDED(rv)) {
+      mRawData.SetLength(haveRead + n);
+      if (mRawData.Length() == SNIFFING_BUFFER_SIZE) {
+        rv = DetermineCharset();
+        if (NS_SUCCEEDED(rv)) {
+          // process what's left
+          uint32_t dummy;
+          aInputStream->ReadSegments(WriteSegmentFun, this, aCount - n, &dummy);
+        }
+      } else {
+        NS_ABORT_IF_FALSE(n == aCount, "didn't read as much as was available");
+      }
+    }
+  }
+
+  mContext = nullptr;
+  mChannel = nullptr;
+  return rv;
+}
+
+/* internal */
+static NS_DEFINE_CID(kCharsetConverterManagerCID,
+                     NS_ICHARSETCONVERTERMANAGER_CID);
+
+nsresult
+nsUnicharStreamLoader::DetermineCharset()
+{
+  nsresult rv = mObserver->OnDetermineCharset(this, mContext,
+                                              mRawData, mCharset);
+  if (NS_FAILED(rv) || mCharset.IsEmpty()) {
+    // The observer told us nothing useful
+    mCharset.AssignLiteral("UTF-8");
+  }
+
+  // Create the decoder for this character set
+  nsCOMPtr<nsICharsetConverterManager> ccm =
+    do_GetService(kCharsetConverterManagerCID, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  // Sadly, nsIUnicharStreamLoader is exposed to extensions, so we can't
+  // assume mozilla::css::Loader to be the only caller. Since legacy
+  // charset alias code doesn't know about the replacement encoding,
+  // special-case it here, but let other stuff go through legacy alias
+  // resolution for now.
+  if (mCharset.EqualsLiteral("replacement")) {
+    rv = ccm->GetUnicodeDecoderRaw(mCharset.get(), getter_AddRefs(mDecoder));
+  } else {
+    rv = ccm->GetUnicodeDecoder(mCharset.get(), getter_AddRefs(mDecoder));
+  }
+  if (NS_FAILED(rv)) return rv;
+
+  // Process the data into mBuffer
+  uint32_t dummy;
+  rv = WriteSegmentFun(nullptr, this,
+                       mRawData.BeginReading(),
+                       0, mRawData.Length(),
+                       &dummy);
+  mRawData.Truncate();
+  return rv;
+}
+
+NS_METHOD
+nsUnicharStreamLoader::WriteSegmentFun(nsIInputStream *,
+                                       void *aClosure,
+                                       const char *aSegment,
+                                       uint32_t,
+                                       uint32_t aCount,
+                                       uint32_t *aWriteCount)
+{
+  nsUnicharStreamLoader* self = static_cast<nsUnicharStreamLoader*>(aClosure);
+
+  uint32_t haveRead = self->mBuffer.Length();
+  int32_t srcLen = aCount;
+  int32_t dstLen;
+  self->mDecoder->GetMaxLength(aSegment, srcLen, &dstLen);
+
+  uint32_t capacity = haveRead + dstLen;
+  if (!self->mBuffer.SetCapacity(capacity, fallible_t())) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  DebugOnly<nsresult> rv =
+    self->mDecoder->Convert(aSegment,
+                            &srcLen,
+                            self->mBuffer.BeginWriting() + haveRead,
+                            &dstLen);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  MOZ_ASSERT(srcLen == static_cast<int32_t>(aCount));
+  haveRead += dstLen;
+
+  self->mBuffer.SetLength(haveRead);
+  *aWriteCount = aCount;
+  return NS_OK;
+}