layout/style/StreamLoader.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/css/StreamLoader.h"
   8
   9 #include "mozilla/Encoding.h"
  10 #include "mozilla/TaskQueue.h"
  11 #include "nsContentUtils.h"
  12 #include "nsIChannel.h"
  13 #include "nsIInputStream.h"
  14 #include "nsIThreadRetargetableRequest.h"
  15 #include "nsIStreamTransportService.h"
  16 #include "nsNetCID.h"
  17 #include "nsServiceManagerUtils.h"
  18
  19 #include <limits>
  20
  21 namespace mozilla::css {
  22
  23 StreamLoader::StreamLoader(SheetLoadData& aSheetLoadData)
  24     : mSheetLoadData(&aSheetLoadData), mStatus(NS_OK) {}
  25
  26 StreamLoader::~StreamLoader() {
  27 #ifdef NIGHTLY_BUILD
  28   MOZ_RELEASE_ASSERT(mOnStopRequestCalled || mChannelOpenFailed);
  29 #endif
  30 }
  31
  32 NS_IMPL_ISUPPORTS(StreamLoader, nsIStreamListener,
  33                   nsIThreadRetargetableStreamListener)
  34
  35 /* nsIRequestObserver implementation */
  36 NS_IMETHODIMP
  37 StreamLoader::OnStartRequest(nsIRequest* aRequest) {
  38   MOZ_ASSERT(aRequest);
  39   mSheetLoadData->NotifyStart(aRequest);
  40
  41   // It's kinda bad to let Web content send a number that results
  42   // in a potentially large allocation directly, but efficiency of
  43   // compression bombs is so great that it doesn't make much sense
  44   // to require a site to send one before going ahead and allocating.
  45   if (nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest)) {
  46     int64_t length;
  47     nsresult rv = channel->GetContentLength(&length);
  48     if (NS_SUCCEEDED(rv) && length > 0) {
  49       CheckedInt<nsACString::size_type> checkedLength(length);
  50       if (!checkedLength.isValid()) {
  51         return (mStatus = NS_ERROR_OUT_OF_MEMORY);
  52       }
  53       if (!mBytes.SetCapacity(checkedLength.value(), fallible)) {
  54         return (mStatus = NS_ERROR_OUT_OF_MEMORY);
  55       }
  56     }
  57   }
  58   if (nsCOMPtr<nsIThreadRetargetableRequest> rr = do_QueryInterface(aRequest)) {
  59     nsCOMPtr<nsIEventTarget> sts =
  60         do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
  61     RefPtr queue =
  62         TaskQueue::Create(sts.forget(), "css::StreamLoader Delivery Queue");
  63     rr->RetargetDeliveryTo(queue);
  64   }
  65
  66   mSheetLoadData->mExpirationTime = [&] {
  67     auto info = nsContentUtils::GetSubresourceCacheValidationInfo(
  68         aRequest, mSheetLoadData->mURI);
  69
  70     // For now, we never cache entries that we have to revalidate, or whose
  71     // channel don't support caching.
  72     if (info.mMustRevalidate || !info.mExpirationTime) {
  73       return nsContentUtils::SecondsFromPRTime(PR_Now()) - 1;
  74     }
  75     return *info.mExpirationTime;
  76   }();
  77
  78   return NS_OK;
  79 }
  80
  81 NS_IMETHODIMP
  82 StreamLoader::CheckListenerChain() { return NS_OK; }
  83
  84 NS_IMETHODIMP
  85 StreamLoader::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
  86 #ifdef NIGHTLY_BUILD
  87   MOZ_RELEASE_ASSERT(!mOnStopRequestCalled);
  88   mOnStopRequestCalled = true;
  89 #endif
  90
  91   nsresult rv = mStatus;
  92   // Decoded data
  93   nsCString utf8String;
  94   {
  95     // Hold the nsStringBuffer for the bytes from the stack to ensure release
  96     // no matter which return branch is taken.
  97     nsCString bytes = std::move(mBytes);
  98
  99     nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
 100
 101     if (NS_FAILED(mStatus)) {
 102       mSheetLoadData->VerifySheetReadyToParse(mStatus, ""_ns, ""_ns, channel);
 103       return mStatus;
 104     }
 105
 106     rv = mSheetLoadData->VerifySheetReadyToParse(aStatus, mBOMBytes, bytes,
 107                                                  channel);
 108     if (rv != NS_OK_PARSE_SHEET) {
 109       return rv;
 110     }
 111
 112     // BOM detection generally happens during the write callback, but that won't
 113     // have happened if fewer than three bytes were received.
 114     if (mEncodingFromBOM.isNothing()) {
 115       HandleBOM();
 116       MOZ_ASSERT(mEncodingFromBOM.isSome());
 117     }
 118
 119     // The BOM handling has happened, but we still may not have an encoding if
 120     // there was no BOM. Ensure we have one.
 121     const Encoding* encoding = mEncodingFromBOM.value();
 122     if (!encoding) {
 123       // No BOM
 124       encoding = mSheetLoadData->DetermineNonBOMEncoding(bytes, channel);
 125     }
 126     mSheetLoadData->mEncoding = encoding;
 127
 128     size_t validated = 0;
 129     if (encoding == UTF_8_ENCODING) {
 130       validated = Encoding::UTF8ValidUpTo(bytes);
 131     }
 132
 133     if (validated == bytes.Length()) {
 134       // Either this is UTF-8 and all valid, or it's not UTF-8 but is an empty
 135       // string. This assumes that an empty string in any encoding decodes to
 136       // empty string, which seems like a plausible assumption.
 137       utf8String = std::move(bytes);
 138     } else {
 139       rv = encoding->DecodeWithoutBOMHandling(bytes, utf8String, validated);
 140       NS_ENSURE_SUCCESS(rv, rv);
 141     }
 142   }  // run destructor for `bytes`
 143
 144   // For reasons I don't understand, factoring the below lines into
 145   // a method on SheetLoadData resulted in a linker error. Hence,
 146   // accessing fields of mSheetLoadData from here.
 147   mSheetLoadData->mLoader->ParseSheet(utf8String, *mSheetLoadData,
 148                                       Loader::AllowAsyncParse::Yes);
 149
 150   return NS_OK;
 151 }
 152
 153 /* nsIStreamListener implementation */
 154 NS_IMETHODIMP
 155 StreamLoader::OnDataAvailable(nsIRequest*, nsIInputStream* aInputStream,
 156                               uint64_t, uint32_t aCount) {
 157   if (NS_FAILED(mStatus)) {
 158     return mStatus;
 159   }
 160   uint32_t dummy;
 161   return aInputStream->ReadSegments(WriteSegmentFun, this, aCount, &dummy);
 162 }
 163
 164 void StreamLoader::HandleBOM() {
 165   MOZ_ASSERT(mEncodingFromBOM.isNothing());
 166   MOZ_ASSERT(mBytes.IsEmpty());
 167
 168   auto [encoding, bomLength] = Encoding::ForBOM(mBOMBytes);
 169   mEncodingFromBOM.emplace(encoding);  // Null means no BOM.
 170
 171   // BOMs are three bytes at most, but may be fewer. Copy over anything
 172   // that wasn't part of the BOM to mBytes. Note that we need to track
 173   // any BOM bytes as well for SRI handling.
 174   mBytes.Append(Substring(mBOMBytes, bomLength));
 175   mBOMBytes.Truncate(bomLength);
 176 }
 177
 178 nsresult StreamLoader::WriteSegmentFun(nsIInputStream*, void* aClosure,
 179                                        const char* aSegment, uint32_t,
 180                                        uint32_t aCount, uint32_t* aWriteCount) {
 181   *aWriteCount = 0;
 182   StreamLoader* self = static_cast<StreamLoader*>(aClosure);
 183   if (NS_FAILED(self->mStatus)) {
 184     return self->mStatus;
 185   }
 186
 187   // If we haven't done BOM detection yet, divert bytes into the special buffer.
 188   if (self->mEncodingFromBOM.isNothing()) {
 189     size_t bytesToCopy = std::min<size_t>(3 - self->mBOMBytes.Length(), aCount);
 190     self->mBOMBytes.Append(aSegment, bytesToCopy);
 191     aSegment += bytesToCopy;
 192     *aWriteCount += bytesToCopy;
 193     aCount -= bytesToCopy;
 194
 195     if (self->mBOMBytes.Length() == 3) {
 196       self->HandleBOM();
 197     } else {
 198       return NS_OK;
 199     }
 200   }
 201
 202   if (!self->mBytes.Append(aSegment, aCount, fallible)) {
 203     self->mBytes.Truncate();
 204     return (self->mStatus = NS_ERROR_OUT_OF_MEMORY);
 205   }
 206
 207   *aWriteCount += aCount;
 208   return NS_OK;
 209 }
 210
 211 }  // namespace mozilla::css