FileReaderSync.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "FileReaderSync.h"

#include "js/ArrayBuffer.h"  // JS::NewArrayBufferWithContents
#include "js/RootingAPI.h"   // JS::{,Mutable}Handle
#include "js/Utility.h"  // js::ArrayBufferContentsArena, JS::FreePolicy, js_pod_arena_malloc
#include "mozilla/Unused.h"
#include "mozilla/Base64.h"
#include "mozilla/dom/File.h"
#include "mozilla/Encoding.h"
#include "mozilla/dom/FileReaderSyncBinding.h"
#include "nsCExternalHandlerService.h"
#include "nsComponentManagerUtils.h"
#include "nsCOMPtr.h"
#include "nsError.h"
#include "nsIConverterInputStream.h"
#include "nsIInputStream.h"
#include "nsIMultiplexInputStream.h"
#include "nsStreamUtils.h"
#include "nsStringStream.h"
#include "nsISupportsImpl.h"
#include "nsNetUtil.h"
#include "nsServiceManagerUtils.h"
#include "nsIAsyncInputStream.h"
#include "mozilla/dom/WorkerPrivate.h"
#include "mozilla/dom/WorkerRunnable.h"

using namespace mozilla;
using namespace mozilla::dom;
using mozilla::dom::GlobalObject;
using mozilla::dom::Optional;

// static
UniquePtr<FileReaderSync> FileReaderSync::Constructor(
    const GlobalObject& aGlobal) {
  return MakeUnique<FileReaderSync>();
}

bool FileReaderSync::WrapObject(JSContext* aCx,
                                JS::Handle<JSObject*> aGivenProto,
                                JS::MutableHandle<JSObject*> aReflector) {
  return FileReaderSync_Binding::Wrap(aCx, this, aGivenProto, aReflector);
}

void FileReaderSync::ReadAsArrayBuffer(JSContext* aCx,
                                       JS::Handle<JSObject*> aScopeObj,
                                       Blob& aBlob,
                                       JS::MutableHandle<JSObject*> aRetval,
                                       ErrorResult& aRv) {
  uint64_t blobSize = aBlob.GetSize(aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  UniquePtr<char[], JS::FreePolicy> bufferData(
      js_pod_arena_malloc<char>(js::ArrayBufferContentsArena, blobSize));
  if (!bufferData) {
    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
    return;
  }

  nsCOMPtr<nsIInputStream> stream;
  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  uint32_t numRead;
  aRv = SyncRead(stream, bufferData.get(), blobSize, &numRead);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  // The file is changed in the meantime?
  if (numRead != blobSize) {
    aRv.Throw(NS_ERROR_FAILURE);
    return;
  }

  JSObject* arrayBuffer =
      JS::NewArrayBufferWithContents(aCx, blobSize, std::move(bufferData));
  if (!arrayBuffer) {
    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
    return;
  }

  aRetval.set(arrayBuffer);
}

void FileReaderSync::ReadAsBinaryString(Blob& aBlob, nsAString& aResult,
                                        ErrorResult& aRv) {
  nsCOMPtr<nsIInputStream> stream;
  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  uint32_t numRead;
  do {
    char readBuf[4096];
    aRv = SyncRead(stream, readBuf, sizeof(readBuf), &numRead);
    if (NS_WARN_IF(aRv.Failed())) {
      return;
    }

    uint32_t oldLength = aResult.Length();
    AppendASCIItoUTF16(Substring(readBuf, readBuf + numRead), aResult);
    if (aResult.Length() - oldLength != numRead) {
      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
      return;
    }
  } while (numRead > 0);
}

void FileReaderSync::ReadAsText(Blob& aBlob,
                                const Optional<nsAString>& aEncoding,
                                nsAString& aResult, ErrorResult& aRv) {
  nsCOMPtr<nsIInputStream> stream;
  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  nsCString sniffBuf;
  if (!sniffBuf.SetLength(3, fallible)) {
    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
    return;
  }

  uint32_t numRead = 0;
  aRv = SyncRead(stream, sniffBuf.BeginWriting(), sniffBuf.Length(), &numRead);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  // No data, we don't need to continue.
  if (numRead == 0) {
    aResult.Truncate();
    return;
  }

  // Try the API argument.
  const Encoding* encoding =
      aEncoding.WasPassed() ? Encoding::ForLabel(aEncoding.Value()) : nullptr;
  if (!encoding) {
    // API argument failed. Try the type property of the blob.
    nsAutoString type16;
    aBlob.GetType(type16);
    NS_ConvertUTF16toUTF8 type(type16);
    nsAutoCString specifiedCharset;
    bool haveCharset;
    int32_t charsetStart, charsetEnd;
    NS_ExtractCharsetFromContentType(type, specifiedCharset, &haveCharset,
                                     &charsetStart, &charsetEnd);
    encoding = Encoding::ForLabel(specifiedCharset);
    if (!encoding) {
      // Type property failed. Use UTF-8.
      encoding = UTF_8_ENCODING;
    }
  }

  if (numRead < sniffBuf.Length()) {
    sniffBuf.Truncate(numRead);
  }

  // Let's recreate the full stream using a:
  // multiplexStream(syncStream + original stream)
  // In theory, we could try to see if the inputStream is a nsISeekableStream,
  // but this doesn't work correctly for nsPipe3 - See bug 1349570.

  nsCOMPtr<nsIMultiplexInputStream> multiplexStream =
      do_CreateInstance("@mozilla.org/io/multiplex-input-stream;1");
  if (NS_WARN_IF(!multiplexStream)) {
    aRv.Throw(NS_ERROR_FAILURE);
    return;
  }

  nsCOMPtr<nsIInputStream> sniffStringStream;
  aRv = NS_NewCStringInputStream(getter_AddRefs(sniffStringStream), sniffBuf);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  aRv = multiplexStream->AppendStream(sniffStringStream);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  uint64_t blobSize = aBlob.GetSize(aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  nsCOMPtr<nsIInputStream> syncStream;
  aRv = ConvertAsyncToSyncStream(blobSize - sniffBuf.Length(), stream.forget(),
                                 getter_AddRefs(syncStream));
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  // ConvertAsyncToSyncStream returns a null syncStream if the stream has been
  // already closed or there is nothing to read.
  if (syncStream) {
    aRv = multiplexStream->AppendStream(syncStream);
    if (NS_WARN_IF(aRv.Failed())) {
      return;
    }
  }

  nsAutoCString charset;
  encoding->Name(charset);

  nsCOMPtr<nsIInputStream> multiplex(do_QueryInterface(multiplexStream));
  aRv = ConvertStream(multiplex, charset.get(), aResult);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }
}

void FileReaderSync::ReadAsDataURL(Blob& aBlob, nsAString& aResult,
                                   ErrorResult& aRv) {
  nsAutoString scratchResult;
  scratchResult.AssignLiteral("data:");

  nsString contentType;
  aBlob.GetType(contentType);

  if (contentType.IsEmpty()) {
    scratchResult.AppendLiteral("application/octet-stream");
  } else {
    scratchResult.Append(contentType);
  }
  scratchResult.AppendLiteral(";base64,");

  nsCOMPtr<nsIInputStream> stream;
  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  uint64_t blobSize = aBlob.GetSize(aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  nsCOMPtr<nsIInputStream> syncStream;
  aRv = ConvertAsyncToSyncStream(blobSize, stream.forget(),
                                 getter_AddRefs(syncStream));
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  MOZ_ASSERT(syncStream);

  uint64_t size;
  aRv = syncStream->Available(&size);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  // The file is changed in the meantime?
  if (blobSize != size) {
    return;
  }

  nsAutoString encodedData;
  aRv = Base64EncodeInputStream(syncStream, encodedData, size);
  if (NS_WARN_IF(aRv.Failed())) {
    return;
  }

  scratchResult.Append(encodedData);

  aResult = scratchResult;
}

nsresult FileReaderSync::ConvertStream(nsIInputStream* aStream,
                                       const char* aCharset,
                                       nsAString& aResult) {
  nsCOMPtr<nsIConverterInputStream> converterStream =
      do_CreateInstance("@mozilla.org/intl/converter-input-stream;1");
  NS_ENSURE_TRUE(converterStream, NS_ERROR_FAILURE);

  nsresult rv = converterStream->Init(
      aStream, aCharset, 8192,
      nsIConverterInputStream::DEFAULT_REPLACEMENT_CHARACTER);
  NS_ENSURE_SUCCESS(rv, rv);

  nsCOMPtr<nsIUnicharInputStream> unicharStream = converterStream;
  NS_ENSURE_TRUE(unicharStream, NS_ERROR_FAILURE);

  uint32_t numChars;
  nsString result;
  while (NS_SUCCEEDED(unicharStream->ReadString(8192, result, &numChars)) &&
         numChars > 0) {
    uint32_t oldLength = aResult.Length();
    aResult.Append(result);
    if (aResult.Length() - oldLength != result.Length()) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
  }

  return rv;
}

namespace {

// This runnable is used to terminate the sync event loop.
class ReadReadyRunnable final : public WorkerSyncRunnable {
 public:
  explicit ReadReadyRunnable(nsIEventTarget* aSyncLoopTarget)
      : WorkerSyncRunnable(aSyncLoopTarget, "ReadReadyRunnable") {}

  bool WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override {
    aWorkerPrivate->AssertIsOnWorkerThread();
    MOZ_ASSERT(mSyncLoopTarget);

    nsCOMPtr<nsIEventTarget> syncLoopTarget;
    mSyncLoopTarget.swap(syncLoopTarget);

    aWorkerPrivate->StopSyncLoop(syncLoopTarget, NS_OK);
    return true;
  }

 private:
  ~ReadReadyRunnable() override = default;
};

// This class implements nsIInputStreamCallback and it will be called when the
// stream is ready to be read.
class ReadCallback final : public nsIInputStreamCallback {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  ReadCallback(WorkerPrivate* aWorkerPrivate, nsIEventTarget* aEventTarget)
      : mEventTarget(aEventTarget) {}

  NS_IMETHOD
  OnInputStreamReady(nsIAsyncInputStream* aStream) override {
    // I/O Thread. Now we need to block the sync event loop.
    RefPtr<ReadReadyRunnable> runnable = new ReadReadyRunnable(mEventTarget);
    return mEventTarget->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
  }

 private:
  ~ReadCallback() = default;

  nsCOMPtr<nsIEventTarget> mEventTarget;
};

NS_IMPL_ADDREF(ReadCallback);
NS_IMPL_RELEASE(ReadCallback);

NS_INTERFACE_MAP_BEGIN(ReadCallback)
  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIInputStreamCallback)
NS_INTERFACE_MAP_END

}  // namespace

nsresult FileReaderSync::SyncRead(nsIInputStream* aStream, char* aBuffer,
                                  uint32_t aBufferSize,
                                  uint32_t* aTotalBytesRead) {
  MOZ_ASSERT(aStream);
  MOZ_ASSERT(aBuffer);
  MOZ_ASSERT(aTotalBytesRead);

  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
  MOZ_ASSERT(workerPrivate);

  *aTotalBytesRead = 0;

  nsCOMPtr<nsIAsyncInputStream> asyncStream;
  nsCOMPtr<nsIEventTarget> target;

  while (*aTotalBytesRead < aBufferSize) {
    uint32_t currentBytesRead = 0;

    // Let's read something.
    nsresult rv =
        aStream->Read(aBuffer + *aTotalBytesRead,
                      aBufferSize - *aTotalBytesRead, &currentBytesRead);

    // Nothing else to read.
    if (rv == NS_BASE_STREAM_CLOSED ||
        (NS_SUCCEEDED(rv) && currentBytesRead == 0)) {
      return NS_OK;
    }

    // An error.
    if (NS_FAILED(rv) && rv != NS_BASE_STREAM_WOULD_BLOCK) {
      return rv;
    }

    // All good.
    if (NS_SUCCEEDED(rv)) {
      *aTotalBytesRead += currentBytesRead;
      continue;
    }

    // We need to proceed async.
    if (!asyncStream) {
      asyncStream = do_QueryInterface(aStream);
      if (!asyncStream) {
        return rv;
      }
    }

    AutoSyncLoopHolder syncLoop(workerPrivate, Canceling);

    nsCOMPtr<nsISerialEventTarget> syncLoopTarget =
        syncLoop.GetSerialEventTarget();
    if (!syncLoopTarget) {
      // SyncLoop creation can fail if the worker is shutting down.
      return NS_ERROR_DOM_INVALID_STATE_ERR;
    }

    RefPtr<ReadCallback> callback =
        new ReadCallback(workerPrivate, syncLoopTarget);

    if (!target) {
      target = do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
      MOZ_ASSERT(target);
    }

    rv = asyncStream->AsyncWait(callback, 0, aBufferSize - *aTotalBytesRead,
                                target);
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    if (NS_WARN_IF(NS_FAILED(syncLoop.Run()))) {
      return NS_ERROR_DOM_INVALID_STATE_ERR;
    }
  }

  return NS_OK;
}

nsresult FileReaderSync::ConvertAsyncToSyncStream(
    uint64_t aStreamSize, already_AddRefed<nsIInputStream> aAsyncStream,
    nsIInputStream** aSyncStream) {
  nsCOMPtr<nsIInputStream> asyncInputStream = std::move(aAsyncStream);

  // If the stream is not async, we just need it to be bufferable.
  nsCOMPtr<nsIAsyncInputStream> asyncStream =
      do_QueryInterface(asyncInputStream);
  if (!asyncStream) {
    return NS_NewBufferedInputStream(aSyncStream, asyncInputStream.forget(),
                                     4096);
  }

  nsAutoCString buffer;
  if (!buffer.SetLength(aStreamSize, fallible)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  uint32_t read;
  nsresult rv =
      SyncRead(asyncInputStream, buffer.BeginWriting(), aStreamSize, &read);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  if (read != aStreamSize) {
    return NS_ERROR_FAILURE;
  }

  rv = NS_NewCStringInputStream(aSyncStream, std::move(buffer));
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  return NS_OK;
}