gecko-dev/image/imgRequest.cpp

/* -*- 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 "imgRequest.h"
#include "ImageLogging.h"

#include "imgLoader.h"
#include "imgRequestProxy.h"
#include "DecodePool.h"
#include "ProgressTracker.h"
#include "ImageFactory.h"
#include "Image.h"
#include "MultipartImage.h"
#include "RasterImage.h"

#include "nsIChannel.h"
#include "nsICacheInfoChannel.h"
#include "mozilla/dom/Document.h"
#include "nsIThreadRetargetableRequest.h"
#include "nsIInputStream.h"
#include "nsIMultiPartChannel.h"
#include "nsIHttpChannel.h"
#include "nsIApplicationCache.h"
#include "nsIApplicationCacheChannel.h"
#include "nsMimeTypes.h"

#include "nsIInterfaceRequestorUtils.h"
#include "nsISupportsPrimitives.h"
#include "nsIScriptSecurityManager.h"
#include "nsContentUtils.h"

#include "plstr.h"   // PL_strcasestr(...)
#include "prtime.h"  // for PR_Now
#include "nsNetUtil.h"
#include "nsIProtocolHandler.h"
#include "imgIRequest.h"
#include "nsProperties.h"

#include "mozilla/IntegerPrintfMacros.h"
#include "mozilla/SizeOfState.h"

using namespace mozilla;
using namespace mozilla::image;

#define LOG_TEST(level) (MOZ_LOG_TEST(gImgLog, (level)))

NS_IMPL_ISUPPORTS(imgRequest, nsIStreamListener, nsIRequestObserver,
                  nsIThreadRetargetableStreamListener, nsIChannelEventSink,
                  nsIInterfaceRequestor, nsIAsyncVerifyRedirectCallback)

imgRequest::imgRequest(imgLoader* aLoader, const ImageCacheKey& aCacheKey)
    : mLoader(aLoader),
      mCacheKey(aCacheKey),
      mLoadId(nullptr),
      mFirstProxy(nullptr),
      mValidator(nullptr),
      mInnerWindowId(0),
      mCORSMode(imgIRequest::CORS_NONE),
      mImageErrorCode(NS_OK),
      mImageAvailable(false),
      mMutex("imgRequest"),
      mProgressTracker(new ProgressTracker()),
      mIsMultiPartChannel(false),
      mIsInCache(false),
      mDecodeRequested(false),
      mNewPartPending(false),
      mHadInsecureRedirect(false) {
  LOG_FUNC(gImgLog, "imgRequest::imgRequest()");
}

imgRequest::~imgRequest() {
  if (mLoader) {
    mLoader->RemoveFromUncachedImages(this);
  }
  if (mURI) {
    LOG_FUNC_WITH_PARAM(gImgLog, "imgRequest::~imgRequest()", "keyuri", mURI);
  } else
    LOG_FUNC(gImgLog, "imgRequest::~imgRequest()");
}

nsresult imgRequest::Init(nsIURI* aURI, nsIURI* aFinalURI,
                          bool aHadInsecureRedirect, nsIRequest* aRequest,
                          nsIChannel* aChannel, imgCacheEntry* aCacheEntry,
                          nsISupports* aCX, nsIPrincipal* aTriggeringPrincipal,
                          int32_t aCORSMode, nsIReferrerInfo* aReferrerInfo) {
  MOZ_ASSERT(NS_IsMainThread(), "Cannot use nsIURI off main thread!");

  LOG_FUNC(gImgLog, "imgRequest::Init");

  MOZ_ASSERT(!mImage, "Multiple calls to init");
  MOZ_ASSERT(aURI, "No uri");
  MOZ_ASSERT(aFinalURI, "No final uri");
  MOZ_ASSERT(aRequest, "No request");
  MOZ_ASSERT(aChannel, "No channel");

  mProperties = new nsProperties();
  mURI = aURI;
  mFinalURI = aFinalURI;
  mRequest = aRequest;
  mChannel = aChannel;
  mTimedChannel = do_QueryInterface(mChannel);
  mTriggeringPrincipal = aTriggeringPrincipal;
  mCORSMode = aCORSMode;
  mReferrerInfo = aReferrerInfo;

  // If the original URI and the final URI are different, check whether the
  // original URI is secure. We deliberately don't take the final URI into
  // account, as it needs to be handled using more complicated rules than
  // earlier elements of the redirect chain.
  if (aURI != aFinalURI) {
    bool schemeLocal = false;
    if (NS_FAILED(NS_URIChainHasFlags(
            aURI, nsIProtocolHandler::URI_IS_LOCAL_RESOURCE, &schemeLocal)) ||
        (!aURI->SchemeIs("https") && !aURI->SchemeIs("chrome") &&
         !schemeLocal)) {
      mHadInsecureRedirect = true;
    }
  }

  // imgCacheValidator may have handled redirects before we were created, so we
  // allow the caller to let us know if any redirects were insecure.
  mHadInsecureRedirect = mHadInsecureRedirect || aHadInsecureRedirect;

  mChannel->GetNotificationCallbacks(getter_AddRefs(mPrevChannelSink));

  NS_ASSERTION(mPrevChannelSink != this,
               "Initializing with a channel that already calls back to us!");

  mChannel->SetNotificationCallbacks(this);

  mCacheEntry = aCacheEntry;
  mCacheEntry->UpdateLoadTime();

  SetLoadId(aCX);

  // Grab the inner window ID of the loading document, if possible.
  nsCOMPtr<dom::Document> doc = do_QueryInterface(aCX);
  if (doc) {
    mInnerWindowId = doc->InnerWindowID();
  }

  return NS_OK;
}

void imgRequest::ClearLoader() { mLoader = nullptr; }

already_AddRefed<ProgressTracker> imgRequest::GetProgressTracker() const {
  MutexAutoLock lock(mMutex);

  if (mImage) {
    MOZ_ASSERT(!mProgressTracker,
               "Should have given mProgressTracker to mImage");
    return mImage->GetProgressTracker();
  }
  MOZ_ASSERT(mProgressTracker,
             "Should have mProgressTracker until we create mImage");
  RefPtr<ProgressTracker> progressTracker = mProgressTracker;
  MOZ_ASSERT(progressTracker);
  return progressTracker.forget();
}

void imgRequest::SetCacheEntry(imgCacheEntry* entry) { mCacheEntry = entry; }

bool imgRequest::HasCacheEntry() const { return mCacheEntry != nullptr; }

void imgRequest::ResetCacheEntry() {
  if (HasCacheEntry()) {
    mCacheEntry->SetDataSize(0);
  }
}

void imgRequest::AddProxy(imgRequestProxy* proxy) {
  MOZ_ASSERT(proxy, "null imgRequestProxy passed in");
  LOG_SCOPE_WITH_PARAM(gImgLog, "imgRequest::AddProxy", "proxy", proxy);

  if (!mFirstProxy) {
    // Save a raw pointer to the first proxy we see, for use in the network
    // priority logic.
    mFirstProxy = proxy;
  }

  // If we're empty before adding, we have to tell the loader we now have
  // proxies.
  RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
  if (progressTracker->ObserverCount() == 0) {
    MOZ_ASSERT(mURI, "Trying to SetHasProxies without key uri.");
    if (mLoader) {
      mLoader->SetHasProxies(this);
    }
  }

  progressTracker->AddObserver(proxy);
}

nsresult imgRequest::RemoveProxy(imgRequestProxy* proxy, nsresult aStatus) {
  LOG_SCOPE_WITH_PARAM(gImgLog, "imgRequest::RemoveProxy", "proxy", proxy);

  // This will remove our animation consumers, so after removing
  // this proxy, we don't end up without proxies with observers, but still
  // have animation consumers.
  proxy->ClearAnimationConsumers();

  // Let the status tracker do its thing before we potentially call Cancel()
  // below, because Cancel() may result in OnStopRequest being called back
  // before Cancel() returns, leaving the image in a different state then the
  // one it was in at this point.
  RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
  if (!progressTracker->RemoveObserver(proxy)) {
    return NS_OK;
  }

  if (progressTracker->ObserverCount() == 0) {
    // If we have no observers, there's nothing holding us alive. If we haven't
    // been cancelled and thus removed from the cache, tell the image loader so
    // we can be evicted from the cache.
    if (mCacheEntry) {
      MOZ_ASSERT(mURI, "Removing last observer without key uri.");

      if (mLoader) {
        mLoader->SetHasNoProxies(this, mCacheEntry);
      }
    } else {
      LOG_MSG_WITH_PARAM(gImgLog, "imgRequest::RemoveProxy no cache entry",
                         "uri", mURI);
    }

    /* If |aStatus| is a failure code, then cancel the load if it is still in
       progress.  Otherwise, let the load continue, keeping 'this' in the cache
       with no observers.  This way, if a proxy is destroyed without calling
       cancel on it, it won't leak and won't leave a bad pointer in the observer
       list.
     */
    if (!(progressTracker->GetProgress() & FLAG_LAST_PART_COMPLETE) &&
        NS_FAILED(aStatus)) {
      LOG_MSG(gImgLog, "imgRequest::RemoveProxy",
              "load in progress.  canceling");

      this->Cancel(NS_BINDING_ABORTED);
    }

    /* break the cycle from the cache entry. */
    mCacheEntry = nullptr;
  }

  return NS_OK;
}

void imgRequest::CancelAndAbort(nsresult aStatus) {
  LOG_SCOPE(gImgLog, "imgRequest::CancelAndAbort");

  Cancel(aStatus);

  // It's possible for the channel to fail to open after we've set our
  // notification callbacks. In that case, make sure to break the cycle between
  // the channel and us, because it won't.
  if (mChannel) {
    mChannel->SetNotificationCallbacks(mPrevChannelSink);
    mPrevChannelSink = nullptr;
  }
}

class imgRequestMainThreadCancel : public Runnable {
 public:
  imgRequestMainThreadCancel(imgRequest* aImgRequest, nsresult aStatus)
      : Runnable("imgRequestMainThreadCancel"),
        mImgRequest(aImgRequest),
        mStatus(aStatus) {
    MOZ_ASSERT(!NS_IsMainThread(), "Create me off main thread only!");
    MOZ_ASSERT(aImgRequest);
  }

  NS_IMETHOD Run() override {
    MOZ_ASSERT(NS_IsMainThread(), "I should be running on the main thread!");
    mImgRequest->ContinueCancel(mStatus);
    return NS_OK;
  }

 private:
  RefPtr<imgRequest> mImgRequest;
  nsresult mStatus;
};

void imgRequest::Cancel(nsresult aStatus) {
  /* The Cancel() method here should only be called by this class. */
  LOG_SCOPE(gImgLog, "imgRequest::Cancel");

  if (NS_IsMainThread()) {
    ContinueCancel(aStatus);
  } else {
    RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
    nsCOMPtr<nsIEventTarget> eventTarget = progressTracker->GetEventTarget();
    nsCOMPtr<nsIRunnable> ev = new imgRequestMainThreadCancel(this, aStatus);
    eventTarget->Dispatch(ev.forget(), NS_DISPATCH_NORMAL);
  }
}

void imgRequest::ContinueCancel(nsresult aStatus) {
  MOZ_ASSERT(NS_IsMainThread());

  RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
  progressTracker->SyncNotifyProgress(FLAG_HAS_ERROR);

  RemoveFromCache();

  if (mRequest && !(progressTracker->GetProgress() & FLAG_LAST_PART_COMPLETE)) {
    mRequest->Cancel(aStatus);
  }
}

class imgRequestMainThreadEvict : public Runnable {
 public:
  explicit imgRequestMainThreadEvict(imgRequest* aImgRequest)
      : Runnable("imgRequestMainThreadEvict"), mImgRequest(aImgRequest) {
    MOZ_ASSERT(!NS_IsMainThread(), "Create me off main thread only!");
    MOZ_ASSERT(aImgRequest);
  }

  NS_IMETHOD Run() override {
    MOZ_ASSERT(NS_IsMainThread(), "I should be running on the main thread!");
    mImgRequest->ContinueEvict();
    return NS_OK;
  }

 private:
  RefPtr<imgRequest> mImgRequest;
};

// EvictFromCache() is written to allowed to get called from any thread
void imgRequest::EvictFromCache() {
  /* The EvictFromCache() method here should only be called by this class. */
  LOG_SCOPE(gImgLog, "imgRequest::EvictFromCache");

  if (NS_IsMainThread()) {
    ContinueEvict();
  } else {
    NS_DispatchToMainThread(new imgRequestMainThreadEvict(this));
  }
}

// Helper-method used by EvictFromCache()
void imgRequest::ContinueEvict() {
  MOZ_ASSERT(NS_IsMainThread());

  RemoveFromCache();
}

void imgRequest::StartDecoding() {
  MutexAutoLock lock(mMutex);
  mDecodeRequested = true;
}

bool imgRequest::IsDecodeRequested() const {
  MutexAutoLock lock(mMutex);
  return mDecodeRequested;
}

nsresult imgRequest::GetURI(nsIURI** aURI) {
  MOZ_ASSERT(aURI);

  LOG_FUNC(gImgLog, "imgRequest::GetURI");

  if (mURI) {
    *aURI = mURI;
    NS_ADDREF(*aURI);
    return NS_OK;
  }

  return NS_ERROR_FAILURE;
}

nsresult imgRequest::GetFinalURI(nsIURI** aURI) {
  MOZ_ASSERT(aURI);

  LOG_FUNC(gImgLog, "imgRequest::GetFinalURI");

  if (mFinalURI) {
    *aURI = mFinalURI;
    NS_ADDREF(*aURI);
    return NS_OK;
  }

  return NS_ERROR_FAILURE;
}

bool imgRequest::IsChrome() const { return mURI->SchemeIs("chrome"); }

bool imgRequest::IsData() const { return mURI->SchemeIs("data"); }

nsresult imgRequest::GetImageErrorCode() { return mImageErrorCode; }

void imgRequest::RemoveFromCache() {
  LOG_SCOPE(gImgLog, "imgRequest::RemoveFromCache");

  bool isInCache = false;

  {
    MutexAutoLock lock(mMutex);
    isInCache = mIsInCache;
  }

  if (isInCache && mLoader) {
    // mCacheEntry is nulled out when we have no more observers.
    if (mCacheEntry) {
      mLoader->RemoveFromCache(mCacheEntry);
    } else {
      mLoader->RemoveFromCache(mCacheKey);
    }
  }

  mCacheEntry = nullptr;
}

bool imgRequest::HasConsumers() const {
  RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
  return progressTracker && progressTracker->ObserverCount() > 0;
}

already_AddRefed<image::Image> imgRequest::GetImage() const {
  MutexAutoLock lock(mMutex);
  RefPtr<image::Image> image = mImage;
  return image.forget();
}

int32_t imgRequest::Priority() const {
  int32_t priority = nsISupportsPriority::PRIORITY_NORMAL;
  nsCOMPtr<nsISupportsPriority> p = do_QueryInterface(mRequest);
  if (p) {
    p->GetPriority(&priority);
  }
  return priority;
}

void imgRequest::AdjustPriority(imgRequestProxy* proxy, int32_t delta) {
  // only the first proxy is allowed to modify the priority of this image load.
  //
  // XXX(darin): this is probably not the most optimal algorithm as we may want
  // to increase the priority of requests that have a lot of proxies.  the key
  // concern though is that image loads remain lower priority than other pieces
  // of content such as link clicks, CSS, and JS.
  //
  if (!mFirstProxy || proxy != mFirstProxy) {
    return;
  }

  AdjustPriorityInternal(delta);
}

void imgRequest::AdjustPriorityInternal(int32_t aDelta) {
  nsCOMPtr<nsISupportsPriority> p = do_QueryInterface(mChannel);
  if (p) {
    p->AdjustPriority(aDelta);
  }
}

void imgRequest::BoostPriority(uint32_t aCategory) {
  if (!StaticPrefs::image_layout_network_priority()) {
    return;
  }

  uint32_t newRequestedCategory =
      (mBoostCategoriesRequested & aCategory) ^ aCategory;
  if (!newRequestedCategory) {
    // priority boost for each category can only apply once.
    return;
  }

  MOZ_LOG(gImgLog, LogLevel::Debug,
          ("[this=%p] imgRequest::BoostPriority for category %x", this,
           newRequestedCategory));

  int32_t delta = 0;

  if (newRequestedCategory & imgIRequest::CATEGORY_FRAME_INIT) {
    --delta;
  }

  if (newRequestedCategory & imgIRequest::CATEGORY_FRAME_STYLE) {
    --delta;
  }

  if (newRequestedCategory & imgIRequest::CATEGORY_SIZE_QUERY) {
    --delta;
  }

  if (newRequestedCategory & imgIRequest::CATEGORY_DISPLAY) {
    delta += nsISupportsPriority::PRIORITY_HIGH;
  }

  AdjustPriorityInternal(delta);
  mBoostCategoriesRequested |= newRequestedCategory;
}

void imgRequest::SetIsInCache(bool aInCache) {
  LOG_FUNC_WITH_PARAM(gImgLog, "imgRequest::SetIsCacheable", "aInCache",
                      aInCache);
  MutexAutoLock lock(mMutex);
  mIsInCache = aInCache;
}

void imgRequest::UpdateCacheEntrySize() {
  if (!mCacheEntry) {
    return;
  }

  RefPtr<Image> image = GetImage();
  SizeOfState state(moz_malloc_size_of);
  size_t size = image->SizeOfSourceWithComputedFallback(state);
  mCacheEntry->SetDataSize(size);
}

void imgRequest::SetCacheValidation(imgCacheEntry* aCacheEntry,
                                    nsIRequest* aRequest) {
  /* get the expires info */
  if (aCacheEntry) {
    // Expiration time defaults to 0. We set the expiration time on our
    // entry if it hasn't been set yet.
    if (aCacheEntry->GetExpiryTime() == 0) {
      uint32_t expiration = 0;
      nsCOMPtr<nsICacheInfoChannel> cacheChannel(do_QueryInterface(aRequest));
      if (cacheChannel) {
        /* get the expiration time from the caching channel's token */
        cacheChannel->GetCacheTokenExpirationTime(&expiration);
      }
      if (expiration == 0) {
        // If the channel doesn't support caching, then ensure this expires the
        // next time it is used.
        expiration = imgCacheEntry::SecondsFromPRTime(PR_Now()) - 1;
      }
      aCacheEntry->SetExpiryTime(expiration);
    }

    // Determine whether the cache entry must be revalidated when we try to use
    // it. Currently, only HTTP specifies this information...
    nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(aRequest));
    if (httpChannel) {
      bool bMustRevalidate = false;

      Unused << httpChannel->IsNoStoreResponse(&bMustRevalidate);

      if (!bMustRevalidate) {
        Unused << httpChannel->IsNoCacheResponse(&bMustRevalidate);
      }

      if (!bMustRevalidate) {
        nsAutoCString cacheHeader;

        Unused << httpChannel->GetResponseHeader(
            NS_LITERAL_CSTRING("Cache-Control"), cacheHeader);
        if (PL_strcasestr(cacheHeader.get(), "must-revalidate")) {
          bMustRevalidate = true;
        }
      }

      // Cache entries default to not needing to validate. We ensure that
      // multiple calls to this function don't override an earlier decision to
      // validate by making validation a one-way decision.
      if (bMustRevalidate) {
        aCacheEntry->SetMustValidate(bMustRevalidate);
      }
    }
  }
}

namespace {

already_AddRefed<nsIApplicationCache> GetApplicationCache(
    nsIRequest* aRequest) {
  nsresult rv;

  nsCOMPtr<nsIApplicationCacheChannel> appCacheChan =
      do_QueryInterface(aRequest);
  if (!appCacheChan) {
    return nullptr;
  }

  bool fromAppCache;
  rv = appCacheChan->GetLoadedFromApplicationCache(&fromAppCache);
  NS_ENSURE_SUCCESS(rv, nullptr);

  if (!fromAppCache) {
    return nullptr;
  }

  nsCOMPtr<nsIApplicationCache> appCache;
  rv = appCacheChan->GetApplicationCache(getter_AddRefs(appCache));
  NS_ENSURE_SUCCESS(rv, nullptr);

  return appCache.forget();
}

}  // namespace

bool imgRequest::CacheChanged(nsIRequest* aNewRequest) {
  nsCOMPtr<nsIApplicationCache> newAppCache = GetApplicationCache(aNewRequest);

  // Application cache not involved at all or the same app cache involved
  // in both of the loads (original and new).
  if (newAppCache == mApplicationCache) {
    return false;
  }

  // In a rare case it may happen that two objects still refer
  // the same application cache version.
  if (newAppCache && mApplicationCache) {
    nsresult rv;

    nsAutoCString oldAppCacheClientId, newAppCacheClientId;
    rv = mApplicationCache->GetClientID(oldAppCacheClientId);
    NS_ENSURE_SUCCESS(rv, true);
    rv = newAppCache->GetClientID(newAppCacheClientId);
    NS_ENSURE_SUCCESS(rv, true);

    if (oldAppCacheClientId == newAppCacheClientId) {
      return false;
    }
  }

  // When we get here, app caches differ or app cache is involved
  // just in one of the loads what we also consider as a change
  // in a loading cache.
  return true;
}

bool imgRequest::GetMultipart() const {
  MutexAutoLock lock(mMutex);
  return mIsMultiPartChannel;
}

bool imgRequest::HadInsecureRedirect() const {
  MutexAutoLock lock(mMutex);
  return mHadInsecureRedirect;
}

/** nsIRequestObserver methods **/

NS_IMETHODIMP
imgRequest::OnStartRequest(nsIRequest* aRequest) {
  LOG_SCOPE(gImgLog, "imgRequest::OnStartRequest");

  RefPtr<Image> image;

  // Figure out if we're multipart.
  nsCOMPtr<nsIMultiPartChannel> multiPartChannel = do_QueryInterface(aRequest);
  MOZ_ASSERT(multiPartChannel || !mIsMultiPartChannel,
             "Stopped being multipart?");
  {
    MutexAutoLock lock(mMutex);
    mNewPartPending = true;
    image = mImage;
    mIsMultiPartChannel = bool(multiPartChannel);
  }

  // If we're not multipart, we shouldn't have an image yet.
  if (image && !multiPartChannel) {
    MOZ_ASSERT_UNREACHABLE("Already have an image for a non-multipart request");
    Cancel(NS_IMAGELIB_ERROR_FAILURE);
    return NS_ERROR_FAILURE;
  }

  /*
   * If mRequest is null here, then we need to set it so that we'll be able to
   * cancel it if our Cancel() method is called.  Note that this can only
   * happen for multipart channels.  We could simply not null out mRequest for
   * non-last parts, if GetIsLastPart() were reliable, but it's not.  See
   * https://bugzilla.mozilla.org/show_bug.cgi?id=339610
   */
  if (!mRequest) {
    MOZ_ASSERT(multiPartChannel, "Should have mRequest unless we're multipart");
    nsCOMPtr<nsIChannel> baseChannel;
    multiPartChannel->GetBaseChannel(getter_AddRefs(baseChannel));
    mRequest = baseChannel;
  }

  nsCOMPtr<nsIChannel> channel(do_QueryInterface(aRequest));
  if (channel) {
    /* Get our principal */
    nsCOMPtr<nsIScriptSecurityManager> secMan =
        nsContentUtils::GetSecurityManager();
    if (secMan) {
      nsresult rv = secMan->GetChannelResultPrincipal(
          channel, getter_AddRefs(mPrincipal));
      if (NS_FAILED(rv)) {
        return rv;
      }
    }
  }

  SetCacheValidation(mCacheEntry, aRequest);

  mApplicationCache = GetApplicationCache(aRequest);

  // Shouldn't we be dead already if this gets hit?
  // Probably multipart/x-mixed-replace...
  RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
  if (progressTracker->ObserverCount() == 0) {
    this->Cancel(NS_IMAGELIB_ERROR_FAILURE);
  }

  // Try to retarget OnDataAvailable to a decode thread. We must process data
  // URIs synchronously as per the spec however.
  if (!channel || IsData()) {
    return NS_OK;
  }

  nsCOMPtr<nsIThreadRetargetableRequest> retargetable =
      do_QueryInterface(aRequest);
  if (retargetable) {
    nsAutoCString mimeType;
    nsresult rv = channel->GetContentType(mimeType);
    if (NS_SUCCEEDED(rv) && !mimeType.EqualsLiteral(IMAGE_SVG_XML)) {
      // Retarget OnDataAvailable to the DecodePool's IO thread.
      nsCOMPtr<nsIEventTarget> target =
          DecodePool::Singleton()->GetIOEventTarget();
      rv = retargetable->RetargetDeliveryTo(target);
    }
    MOZ_LOG(gImgLog, LogLevel::Warning,
            ("[this=%p] imgRequest::OnStartRequest -- "
             "RetargetDeliveryTo rv %" PRIu32 "=%s\n",
             this, static_cast<uint32_t>(rv),
             NS_SUCCEEDED(rv) ? "succeeded" : "failed"));
  }

  return NS_OK;
}

NS_IMETHODIMP
imgRequest::OnStopRequest(nsIRequest* aRequest, nsresult status) {
  LOG_FUNC(gImgLog, "imgRequest::OnStopRequest");
  MOZ_ASSERT(NS_IsMainThread(), "Can't send notifications off-main-thread");

  RefPtr<Image> image = GetImage();

  RefPtr<imgRequest> strongThis = this;

  if (mIsMultiPartChannel && mNewPartPending) {
    OnDataAvailable(aRequest, nullptr, 0, 0);
  }

  // XXXldb What if this is a non-last part of a multipart request?
  // xxx before we release our reference to mRequest, lets
  // save the last status that we saw so that the
  // imgRequestProxy will have access to it.
  if (mRequest) {
    mRequest = nullptr;  // we no longer need the request
  }

  // stop holding a ref to the channel, since we don't need it anymore
  if (mChannel) {
    mChannel->SetNotificationCallbacks(mPrevChannelSink);
    mPrevChannelSink = nullptr;
    mChannel = nullptr;
  }

  bool lastPart = true;
  nsCOMPtr<nsIMultiPartChannel> mpchan(do_QueryInterface(aRequest));
  if (mpchan) {
    mpchan->GetIsLastPart(&lastPart);
  }

  bool isPartial = false;
  if (image && (status == NS_ERROR_NET_PARTIAL_TRANSFER)) {
    isPartial = true;
    status = NS_OK;  // fake happy face
  }

  // Tell the image that it has all of the source data. Note that this can
  // trigger a failure, since the image might be waiting for more non-optional
  // data and this is the point where we break the news that it's not coming.
  if (image) {
    nsresult rv =
        image->OnImageDataComplete(aRequest, nullptr, status, lastPart);

    // If we got an error in the OnImageDataComplete() call, we don't want to
    // proceed as if nothing bad happened. However, we also want to give
    // precedence to failure status codes from necko, since presumably they're
    // more meaningful.
    if (NS_FAILED(rv) && NS_SUCCEEDED(status)) {
      status = rv;
    }
  }

  // If the request went through, update the cache entry size. Otherwise,
  // cancel the request, which removes us from the cache.
  if (image && NS_SUCCEEDED(status) && !isPartial) {
    // We update the cache entry size here because this is where we finish
    // loading compressed source data, which is part of our size calculus.
    UpdateCacheEntrySize();

  } else if (isPartial) {
    // Remove the partial image from the cache.
    this->EvictFromCache();

  } else {
    mImageErrorCode = status;

    // if the error isn't "just" a partial transfer
    // stops animations, removes from cache
    this->Cancel(status);
  }

  if (!image) {
    // We have to fire the OnStopRequest notifications ourselves because there's
    // no image capable of doing so.
    Progress progress =
        LoadCompleteProgress(lastPart, /* aError = */ false, status);

    RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
    progressTracker->SyncNotifyProgress(progress);
  }

  mTimedChannel = nullptr;
  return NS_OK;
}

struct mimetype_closure {
  nsACString* newType;
};

/* prototype for these defined below */
static nsresult sniff_mimetype_callback(nsIInputStream* in, void* closure,
                                        const char* fromRawSegment,
                                        uint32_t toOffset, uint32_t count,
                                        uint32_t* writeCount);

/** nsThreadRetargetableStreamListener methods **/
NS_IMETHODIMP
imgRequest::CheckListenerChain() {
  // TODO Might need more checking here.
  NS_ASSERTION(NS_IsMainThread(), "Should be on the main thread!");
  return NS_OK;
}

/** nsIStreamListener methods **/

struct NewPartResult final {
  explicit NewPartResult(image::Image* aExistingImage)
      : mImage(aExistingImage),
        mIsFirstPart(!aExistingImage),
        mSucceeded(false),
        mShouldResetCacheEntry(false) {}

  nsAutoCString mContentType;
  nsAutoCString mContentDisposition;
  RefPtr<image::Image> mImage;
  const bool mIsFirstPart;
  bool mSucceeded;
  bool mShouldResetCacheEntry;
};

static NewPartResult PrepareForNewPart(nsIRequest* aRequest,
                                       nsIInputStream* aInStr, uint32_t aCount,
                                       nsIURI* aURI, bool aIsMultipart,
                                       image::Image* aExistingImage,
                                       ProgressTracker* aProgressTracker,
                                       uint32_t aInnerWindowId) {
  NewPartResult result(aExistingImage);

  if (aInStr) {
    mimetype_closure closure;
    closure.newType = &result.mContentType;

    // Look at the first few bytes and see if we can tell what the data is from
    // that since servers tend to lie. :(
    uint32_t out;
    aInStr->ReadSegments(sniff_mimetype_callback, &closure, aCount, &out);
  }

  nsCOMPtr<nsIChannel> chan(do_QueryInterface(aRequest));
  if (result.mContentType.IsEmpty()) {
    nsresult rv =
        chan ? chan->GetContentType(result.mContentType) : NS_ERROR_FAILURE;
    if (NS_FAILED(rv)) {
      MOZ_LOG(gImgLog, LogLevel::Error,
              ("imgRequest::PrepareForNewPart -- "
               "Content type unavailable from the channel\n"));
      if (!aIsMultipart) {
        return result;
      }
    }
  }

  if (chan) {
    chan->GetContentDispositionHeader(result.mContentDisposition);
  }

  MOZ_LOG(gImgLog, LogLevel::Debug,
          ("imgRequest::PrepareForNewPart -- Got content type %s\n",
           result.mContentType.get()));

  // XXX If server lied about mimetype and it's SVG, we may need to copy
  // the data and dispatch back to the main thread, AND tell the channel to
  // dispatch there in the future.

  // Create the new image and give it ownership of our ProgressTracker.
  if (aIsMultipart) {
    // Create the ProgressTracker and image for this part.
    RefPtr<ProgressTracker> progressTracker = new ProgressTracker();
    RefPtr<image::Image> partImage = image::ImageFactory::CreateImage(
        aRequest, progressTracker, result.mContentType, aURI,
        /* aIsMultipart = */ true, aInnerWindowId);

    if (result.mIsFirstPart) {
      // First part for a multipart channel. Create the MultipartImage wrapper.
      MOZ_ASSERT(aProgressTracker, "Shouldn't have given away tracker yet");
      aProgressTracker->SetIsMultipart();
      result.mImage = image::ImageFactory::CreateMultipartImage(
          partImage, aProgressTracker);
    } else {
      // Transition to the new part.
      auto multipartImage = static_cast<MultipartImage*>(aExistingImage);
      multipartImage->BeginTransitionToPart(partImage);

      // Reset our cache entry size so it doesn't keep growing without bound.
      result.mShouldResetCacheEntry = true;
    }
  } else {
    MOZ_ASSERT(!aExistingImage, "New part for non-multipart channel?");
    MOZ_ASSERT(aProgressTracker, "Shouldn't have given away tracker yet");

    // Create an image using our progress tracker.
    result.mImage = image::ImageFactory::CreateImage(
        aRequest, aProgressTracker, result.mContentType, aURI,
        /* aIsMultipart = */ false, aInnerWindowId);
  }

  MOZ_ASSERT(result.mImage);
  if (!result.mImage->HasError() || aIsMultipart) {
    // We allow multipart images to fail to initialize (which generally
    // indicates a bad content type) without cancelling the load, because
    // subsequent parts might be fine.
    result.mSucceeded = true;
  }

  return result;
}

class FinishPreparingForNewPartRunnable final : public Runnable {
 public:
  FinishPreparingForNewPartRunnable(imgRequest* aImgRequest,
                                    NewPartResult&& aResult)
      : Runnable("FinishPreparingForNewPartRunnable"),
        mImgRequest(aImgRequest),
        mResult(aResult) {
    MOZ_ASSERT(aImgRequest);
  }

  NS_IMETHOD Run() override {
    mImgRequest->FinishPreparingForNewPart(mResult);
    return NS_OK;
  }

 private:
  RefPtr<imgRequest> mImgRequest;
  NewPartResult mResult;
};

void imgRequest::FinishPreparingForNewPart(const NewPartResult& aResult) {
  MOZ_ASSERT(NS_IsMainThread());

  mContentType = aResult.mContentType;

  SetProperties(aResult.mContentType, aResult.mContentDisposition);

  if (aResult.mIsFirstPart) {
    // Notify listeners that we have an image.
    mImageAvailable = true;
    RefPtr<ProgressTracker> progressTracker = GetProgressTracker();
    progressTracker->OnImageAvailable();
    MOZ_ASSERT(progressTracker->HasImage());
  }

  if (aResult.mShouldResetCacheEntry) {
    ResetCacheEntry();
  }

  if (IsDecodeRequested()) {
    aResult.mImage->StartDecoding(imgIContainer::FLAG_NONE);
  }
}

bool imgRequest::ImageAvailable() const { return mImageAvailable; }

NS_IMETHODIMP
imgRequest::OnDataAvailable(nsIRequest* aRequest, nsIInputStream* aInStr,
                            uint64_t aOffset, uint32_t aCount) {
  LOG_SCOPE_WITH_PARAM(gImgLog, "imgRequest::OnDataAvailable", "count", aCount);

  NS_ASSERTION(aRequest, "imgRequest::OnDataAvailable -- no request!");

  RefPtr<Image> image;
  RefPtr<ProgressTracker> progressTracker;
  bool isMultipart = false;
  bool newPartPending = false;

  // Retrieve and update our state.
  {
    MutexAutoLock lock(mMutex);
    image = mImage;
    progressTracker = mProgressTracker;
    isMultipart = mIsMultiPartChannel;
    newPartPending = mNewPartPending;
    mNewPartPending = false;
  }

  // If this is a new part, we need to sniff its content type and create an
  // appropriate image.
  if (newPartPending) {
    NewPartResult result =
        PrepareForNewPart(aRequest, aInStr, aCount, mURI, isMultipart, image,
                          progressTracker, mInnerWindowId);
    bool succeeded = result.mSucceeded;

    if (result.mImage) {
      image = result.mImage;
      nsCOMPtr<nsIEventTarget> eventTarget;

      // Update our state to reflect this new part.
      {
        MutexAutoLock lock(mMutex);
        mImage = image;

        // We only get an event target if we are not on the main thread, because
        // we have to dispatch in that case. If we are on the main thread, but
        // on a different scheduler group than ProgressTracker would give us,
        // that is okay because nothing in imagelib requires that, just our
        // listeners (which have their own checks).
        if (!NS_IsMainThread()) {
          eventTarget = mProgressTracker->GetEventTarget();
          MOZ_ASSERT(eventTarget);
        }

        mProgressTracker = nullptr;
      }

      // Some property objects are not threadsafe, and we need to send
      // OnImageAvailable on the main thread, so finish on the main thread.
      if (!eventTarget) {
        MOZ_ASSERT(NS_IsMainThread());
        FinishPreparingForNewPart(result);
      } else {
        nsCOMPtr<nsIRunnable> runnable =
            new FinishPreparingForNewPartRunnable(this, std::move(result));
        eventTarget->Dispatch(CreateMediumHighRunnable(runnable.forget()),
                              NS_DISPATCH_NORMAL);
      }
    }

    if (!succeeded) {
      // Something went wrong; probably a content type issue.
      Cancel(NS_IMAGELIB_ERROR_FAILURE);
      return NS_BINDING_ABORTED;
    }
  }

  // Notify the image that it has new data.
  if (aInStr) {
    nsresult rv =
        image->OnImageDataAvailable(aRequest, nullptr, aInStr, aOffset, aCount);

    if (NS_FAILED(rv)) {
      MOZ_LOG(gImgLog, LogLevel::Warning,
              ("[this=%p] imgRequest::OnDataAvailable -- "
               "copy to RasterImage failed\n",
               this));
      Cancel(NS_IMAGELIB_ERROR_FAILURE);
      return NS_BINDING_ABORTED;
    }
  }

  return NS_OK;
}

void imgRequest::SetProperties(const nsACString& aContentType,
                               const nsACString& aContentDisposition) {
  /* set our mimetype as a property */
  nsCOMPtr<nsISupportsCString> contentType =
      do_CreateInstance("@mozilla.org/supports-cstring;1");
  if (contentType) {
    contentType->SetData(aContentType);
    mProperties->Set("type", contentType);
  }

  /* set our content disposition as a property */
  if (!aContentDisposition.IsEmpty()) {
    nsCOMPtr<nsISupportsCString> contentDisposition =
        do_CreateInstance("@mozilla.org/supports-cstring;1");
    if (contentDisposition) {
      contentDisposition->SetData(aContentDisposition);
      mProperties->Set("content-disposition", contentDisposition);
    }
  }
}

static nsresult sniff_mimetype_callback(nsIInputStream* in, void* data,
                                        const char* fromRawSegment,
                                        uint32_t toOffset, uint32_t count,
                                        uint32_t* writeCount) {
  mimetype_closure* closure = static_cast<mimetype_closure*>(data);

  NS_ASSERTION(closure, "closure is null!");

  if (count > 0) {
    imgLoader::GetMimeTypeFromContent(fromRawSegment, count, *closure->newType);
  }

  *writeCount = 0;
  return NS_ERROR_FAILURE;
}

/** nsIInterfaceRequestor methods **/

NS_IMETHODIMP
imgRequest::GetInterface(const nsIID& aIID, void** aResult) {
  if (!mPrevChannelSink || aIID.Equals(NS_GET_IID(nsIChannelEventSink))) {
    return QueryInterface(aIID, aResult);
  }

  NS_ASSERTION(
      mPrevChannelSink != this,
      "Infinite recursion - don't keep track of channel sinks that are us!");
  return mPrevChannelSink->GetInterface(aIID, aResult);
}

/** nsIChannelEventSink methods **/
NS_IMETHODIMP
imgRequest::AsyncOnChannelRedirect(nsIChannel* oldChannel,
                                   nsIChannel* newChannel, uint32_t flags,
                                   nsIAsyncVerifyRedirectCallback* callback) {
  NS_ASSERTION(mRequest && mChannel,
               "Got a channel redirect after we nulled out mRequest!");
  NS_ASSERTION(mChannel == oldChannel,
               "Got a channel redirect for an unknown channel!");
  NS_ASSERTION(newChannel, "Got a redirect to a NULL channel!");

  SetCacheValidation(mCacheEntry, oldChannel);

  // Prepare for callback
  mRedirectCallback = callback;
  mNewRedirectChannel = newChannel;

  nsCOMPtr<nsIChannelEventSink> sink(do_GetInterface(mPrevChannelSink));
  if (sink) {
    nsresult rv =
        sink->AsyncOnChannelRedirect(oldChannel, newChannel, flags, this);
    if (NS_FAILED(rv)) {
      mRedirectCallback = nullptr;
      mNewRedirectChannel = nullptr;
    }
    return rv;
  }

  (void)OnRedirectVerifyCallback(NS_OK);
  return NS_OK;
}

NS_IMETHODIMP
imgRequest::OnRedirectVerifyCallback(nsresult result) {
  NS_ASSERTION(mRedirectCallback, "mRedirectCallback not set in callback");
  NS_ASSERTION(mNewRedirectChannel, "mNewRedirectChannel not set in callback");

  if (NS_FAILED(result)) {
    mRedirectCallback->OnRedirectVerifyCallback(result);
    mRedirectCallback = nullptr;
    mNewRedirectChannel = nullptr;
    return NS_OK;
  }

  mChannel = mNewRedirectChannel;
  mTimedChannel = do_QueryInterface(mChannel);
  mNewRedirectChannel = nullptr;

  if (LOG_TEST(LogLevel::Debug)) {
    LOG_MSG_WITH_PARAM(gImgLog, "imgRequest::OnChannelRedirect", "old",
                       mFinalURI ? mFinalURI->GetSpecOrDefault().get() : "");
  }

  // If the previous URI is a non-HTTPS URI, record that fact for later use by
  // security code, which needs to know whether there is an insecure load at any
  // point in the redirect chain.
  bool schemeLocal = false;
  if (NS_FAILED(NS_URIChainHasFlags(mFinalURI,
                                    nsIProtocolHandler::URI_IS_LOCAL_RESOURCE,
                                    &schemeLocal)) ||
      (!mFinalURI->SchemeIs("https") && !mFinalURI->SchemeIs("chrome") &&
       !schemeLocal)) {
    MutexAutoLock lock(mMutex);

    // The csp directive upgrade-insecure-requests performs an internal redirect
    // to upgrade all requests from http to https before any data is fetched
    // from the network. Do not pollute mHadInsecureRedirect in case of such an
    // internal redirect.
    nsCOMPtr<nsILoadInfo> loadInfo = mChannel->LoadInfo();
    bool upgradeInsecureRequests =
        loadInfo ? loadInfo->GetUpgradeInsecureRequests() ||
                       loadInfo->GetBrowserUpgradeInsecureRequests()
                 : false;
    if (!upgradeInsecureRequests) {
      mHadInsecureRedirect = true;
    }
  }

  // Update the final URI.
  mChannel->GetURI(getter_AddRefs(mFinalURI));

  if (LOG_TEST(LogLevel::Debug)) {
    LOG_MSG_WITH_PARAM(gImgLog, "imgRequest::OnChannelRedirect", "new",
                       mFinalURI ? mFinalURI->GetSpecOrDefault().get() : "");
  }

  // Make sure we have a protocol that returns data rather than opens an
  // external application, e.g. 'mailto:'.
  bool doesNotReturnData = false;
  nsresult rv = NS_URIChainHasFlags(
      mFinalURI, nsIProtocolHandler::URI_DOES_NOT_RETURN_DATA,
      &doesNotReturnData);

  if (NS_SUCCEEDED(rv) && doesNotReturnData) {
    rv = NS_ERROR_ABORT;
  }

  if (NS_FAILED(rv)) {
    mRedirectCallback->OnRedirectVerifyCallback(rv);
    mRedirectCallback = nullptr;
    return NS_OK;
  }

  mRedirectCallback->OnRedirectVerifyCallback(NS_OK);
  mRedirectCallback = nullptr;
  return NS_OK;
}