Quelle IOUtils.cpp Sprache: C

/* -*- 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 "IOUtils.h"

#include <cstdint>

#include "ErrorList.h"
#include "TypedArray.h"
#include "js/ArrayBuffer.h"
#include "js/ColumnNumber.h"  // JS::ColumnNumberOneOrigin
#include "js/JSON.h"
#include "js/Utility.h"
#include "js/experimental/TypedData.h"
#include "jsfriendapi.h"
#include "mozilla/Assertions.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/Compression.h"
#include "mozilla/Encoding.h"
#include "mozilla/EndianUtils.h"
#include "mozilla/ErrorNames.h"
#include "mozilla/FileUtils.h"
#include "mozilla/Maybe.h"
#include "mozilla/ResultExtensions.h"
#include "mozilla/Services.h"
#include "mozilla/Span.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/TextUtils.h"
#include "mozilla/Try.h"
#include "mozilla/Unused.h"
#include "mozilla/Utf8.h"
#include "mozilla/dom/BindingUtils.h"
#include "mozilla/dom/IOUtilsBinding.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/WorkerCommon.h"
#include "mozilla/dom/WorkerRef.h"
#include "mozilla/ipc/LaunchError.h"
#include "PathUtils.h"
#include "nsCOMPtr.h"
#include "nsError.h"
#include "nsFileStreams.h"
#include "nsIDirectoryEnumerator.h"
#include "nsIFile.h"
#include "nsIGlobalObject.h"
#include "nsIInputStream.h"
#include "nsISupports.h"
#include "nsLocalFile.h"
#include "nsNetUtil.h"
#include "nsNSSComponent.h"
#include "nsPrintfCString.h"
#include "nsReadableUtils.h"
#include "nsString.h"
#include "nsStringFwd.h"
#include "nsTArray.h"
#include "nsThreadManager.h"
#include "nsXULAppAPI.h"
#include "prerror.h"
#include "prio.h"
#include "prtime.h"
#include "prtypes.h"
#include "ScopedNSSTypes.h"
#include "secoidt.h"

#if defined(XP_UNIX) && !defined(ANDROID)
#  include "nsSystemInfo.h"
#endif

#if defined(XP_WIN)
#  include "nsILocalFileWin.h"
#elif defined(XP_MACOSX)
#  include "nsILocalFileMac.h"
#endif

#ifdef XP_UNIX
#  include "base/process_util.h"
#endif

#define REJECT_IF_INIT_PATH_FAILED(_file, _path, _promise, _msg, ...) \
  do {                                                                \
    if (nsresult _rv = PathUtils::InitFileWithPath((_file), (_path)); \
        NS_FAILED(_rv)) {                                             \
      (_promise)->MaybeRejectWithOperationError(FormatErrorMessage(   \
          _rv, _msg ": could not parse path", ##__VA_ARGS__));        \
      return;                                                         \
    }                                                                 \
  } while (0)

#define IOUTILS_TRY_WITH_CONTEXT(_expr, _fmt, ...)            \
  do {                                                        \
    if (nsresult _rv = (_expr); NS_FAILED(_rv)) {             \
      return Err(IOUtils::IOError(_rv, _fmt, ##__VA_ARGS__)); \
    }                                                         \
  } while (0)

static constexpr auto SHUTDOWN_ERROR =
    "IOUtils: Shutting down and refusing additional I/O tasks"_ns;

namespace mozilla::dom {

// static helper functions

/**
* Platform-specific (e.g. Windows, Unix) implementations of XPCOM APIs may
* report I/O errors inconsistently. For convenience, this function will attempt
* to match a |nsresult| against known results which imply a file cannot be
* found.
*
* @see nsLocalFileWin.cpp
* @see nsLocalFileUnix.cpp
*/
static bool IsFileNotFound(nsresult aResult) {
  return aResult == NS_ERROR_FILE_NOT_FOUND;
}
/**
* Like |IsFileNotFound|, but checks for known results that suggest a file
* is not a directory.
*/
static bool IsNotDirectory(nsresult aResult) {
  return aResult == NS_ERROR_FILE_DESTINATION_NOT_DIR ||
         aResult == NS_ERROR_FILE_NOT_DIRECTORY;
}

/**
* Formats an error message and appends the error name to the end.
*/
static nsCString MOZ_FORMAT_PRINTF(2, 3)
    FormatErrorMessage(nsresult aError, const char* const aFmt, ...) {
  nsAutoCString errorName;
  GetErrorName(aError, errorName);

  nsCString msg;

  va_list ap;
  va_start(ap, aFmt);
  msg.AppendVprintf(aFmt, ap);
  va_end(ap);

  msg.AppendPrintf(" (%s)", errorName.get());

  return msg;
}

static nsCString FormatErrorMessage(nsresult aError,
                                    const nsCString& aMessage) {
  nsAutoCString errorName;
  GetErrorName(aError, errorName);

  nsCString msg(aMessage);
  msg.AppendPrintf(" (%s)", errorName.get());

  return msg;
}

[[nodiscard]] inline bool ToJSValue(
    JSContext* aCx, const IOUtils::InternalFileInfo& aInternalFileInfo,
    JS::MutableHandle<JS::Value> aValue) {
  FileInfo info;
  info.mPath.Construct(aInternalFileInfo.mPath);
  info.mType.Construct(aInternalFileInfo.mType);
  info.mSize.Construct(aInternalFileInfo.mSize);

  if (aInternalFileInfo.mCreationTime.isSome()) {
    info.mCreationTime.Construct(aInternalFileInfo.mCreationTime.ref());
  }
  info.mLastAccessed.Construct(aInternalFileInfo.mLastAccessed);
  info.mLastModified.Construct(aInternalFileInfo.mLastModified);

  info.mPermissions.Construct(aInternalFileInfo.mPermissions);

  return ToJSValue(aCx, info, aValue);
}

template <typename T>
static void ResolveJSPromise(Promise* aPromise, T&& aValue) {
  if constexpr (std::is_same_v<T, Ok>) {
    aPromise->MaybeResolveWithUndefined();
  } else if constexpr (std::is_same_v<T, nsTArray<uint8_t>>) {
    TypedArrayCreator<Uint8Array> array(aValue);
    aPromise->MaybeResolve(array);
  } else {
    aPromise->MaybeResolve(std::forward<T>(aValue));
  }
}

static void RejectJSPromise(Promise* aPromise, const IOUtils::IOError& aError) {
  const auto errMsg = FormatErrorMessage(aError.Code(), aError.Message());

  switch (aError.Code()) {
    case NS_ERROR_FILE_UNRESOLVABLE_SYMLINK:
      [[fallthrough]];
    case NS_ERROR_FILE_NOT_FOUND:
      [[fallthrough]];
    case NS_ERROR_FILE_INVALID_PATH:
      [[fallthrough]];
    case NS_ERROR_NOT_AVAILABLE:
      aPromise->MaybeRejectWithNotFoundError(errMsg);
      break;

    case NS_ERROR_FILE_IS_LOCKED:
      [[fallthrough]];
    case NS_ERROR_FILE_ACCESS_DENIED:
      aPromise->MaybeRejectWithNotAllowedError(errMsg);
      break;

    case NS_ERROR_FILE_TOO_BIG:
      [[fallthrough]];
    case NS_ERROR_FILE_NO_DEVICE_SPACE:
      [[fallthrough]];
    case NS_ERROR_FILE_DEVICE_FAILURE:
      [[fallthrough]];
    case NS_ERROR_FILE_FS_CORRUPTED:
      [[fallthrough]];
    case NS_ERROR_FILE_CORRUPTED:
      aPromise->MaybeRejectWithNotReadableError(errMsg);
      break;

    case NS_ERROR_FILE_ALREADY_EXISTS:
      aPromise->MaybeRejectWithNoModificationAllowedError(errMsg);
      break;

    case NS_ERROR_FILE_COPY_OR_MOVE_FAILED:
      [[fallthrough]];
    case NS_ERROR_FILE_NAME_TOO_LONG:
      [[fallthrough]];
    case NS_ERROR_FILE_UNRECOGNIZED_PATH:
      [[fallthrough]];
    case NS_ERROR_FILE_DIR_NOT_EMPTY:
      aPromise->MaybeRejectWithOperationError(errMsg);
      break;

    case NS_ERROR_FILE_READ_ONLY:
      aPromise->MaybeRejectWithReadOnlyError(errMsg);
      break;

    case NS_ERROR_FILE_NOT_DIRECTORY:
      [[fallthrough]];
    case NS_ERROR_FILE_DESTINATION_NOT_DIR:
      [[fallthrough]];
    case NS_ERROR_FILE_IS_DIRECTORY:
      [[fallthrough]];
    case NS_ERROR_FILE_UNKNOWN_TYPE:
      aPromise->MaybeRejectWithInvalidAccessError(errMsg);
      break;

    case NS_ERROR_ILLEGAL_INPUT:
      [[fallthrough]];
    case NS_ERROR_ILLEGAL_VALUE:
      aPromise->MaybeRejectWithDataError(errMsg);
      break;

    case NS_ERROR_ABORT:
      aPromise->MaybeRejectWithAbortError(errMsg);
      break;

    default:
      aPromise->MaybeRejectWithUnknownError(errMsg);
  }
}

static void RejectShuttingDown(Promise* aPromise) {
  RejectJSPromise(aPromise, IOUtils::IOError(NS_ERROR_ABORT, SHUTDOWN_ERROR));
}

static bool AssertParentProcessWithCallerLocationImpl(GlobalObject& aGlobal,
                                                      nsCString& reason) {
  if (MOZ_LIKELY(XRE_IsParentProcess())) {
    return true;
  }

  AutoJSAPI jsapi;
  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
  MOZ_ALWAYS_TRUE(global);
  MOZ_ALWAYS_TRUE(jsapi.Init(global));

  JSContext* cx = jsapi.cx();

  JS::AutoFilename scriptFilename;
  uint32_t lineNo = 0;
  JS::ColumnNumberOneOrigin colNo;

  NS_ENSURE_TRUE(
      JS::DescribeScriptedCaller(&scriptFilename, cx, &lineNo, &colNo), false);

  NS_ENSURE_TRUE(scriptFilename.get(), false);

  reason.AppendPrintf(" Called from %s:%d:%d.", scriptFilename.get(), lineNo,
                      colNo.oneOriginValue());
  return false;
}

static void AssertParentProcessWithCallerLocation(GlobalObject& aGlobal) {
  nsCString reason = "IOUtils can only be used in the parent process."_ns;
  if (!AssertParentProcessWithCallerLocationImpl(aGlobal, reason)) {
    MOZ_CRASH_UNSAFE_PRINTF("%s", reason.get());
  }
}

// IOUtils implementation
/* static */
MOZ_RUNINIT IOUtils::StateMutex IOUtils::sState{"IOUtils::sState"};

/* static */
template <typename Fn>
already_AddRefed<Promise> IOUtils::WithPromiseAndState(GlobalObject& aGlobal,
                                                       ErrorResult& aError,
                                                       Fn aFn) {
  AssertParentProcessWithCallerLocation(aGlobal);

  RefPtr<Promise> promise = CreateJSPromise(aGlobal, aError);
  if (!promise) {
    return nullptr;
  }

  if (auto state = GetState()) {
    aFn(promise, state.ref());
  } else {
    RejectShuttingDown(promise);
  }
  return promise.forget();
}

/* static */
template <typename OkT, typename Fn>
void IOUtils::DispatchAndResolve(IOUtils::EventQueue* aQueue, Promise* aPromise,
                                 Fn aFunc) {
  RefPtr<StrongWorkerRef> workerRef;
  if (!NS_IsMainThread()) {
    // We need to manually keep the worker alive until the promise returned by
    // Dispatch() resolves or rejects.
    workerRef = StrongWorkerRef::CreateForcibly(GetCurrentThreadWorkerPrivate(),
                                                __func__);
  }

  if (RefPtr<IOPromise<OkT>> p = aQueue->Dispatch<OkT, Fn>(std::move(aFunc))) {
    p->Then(
        GetCurrentSerialEventTarget(), __func__,
        [workerRef, promise = RefPtr(aPromise)](OkT&& ok) {
          ResolveJSPromise(promise, std::forward<OkT>(ok));
        },
        [workerRef, promise = RefPtr(aPromise)](const IOError& err) {
          RejectJSPromise(promise, err);
        });
  }
}

/* static */
already_AddRefed<Promise> IOUtils::Read(GlobalObject& aGlobal,
                                        const nsAString& aPath,
                                        const ReadOptions& aOptions,
                                        ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise, "Could not read `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        Maybe<uint32_t> toRead = Nothing();
        if (!aOptions.mMaxBytes.IsNull()) {
          if (aOptions.mDecompress) {
            RejectJSPromise(
                promise, IOError(NS_ERROR_ILLEGAL_INPUT,
                                 "Could not read `%s': the `maxBytes' and "
                                 "`decompress' options are mutually exclusive",
                                 file->HumanReadablePath().get()));
            return;
          }

          if (aOptions.mMaxBytes.Value() == 0) {
            // Resolve with an empty buffer.
            nsTArray<uint8_t> arr(0);
            promise->MaybeResolve(TypedArrayCreator<Uint8Array>(arr));
            return;
          }
          toRead.emplace(aOptions.mMaxBytes.Value());
        }

        DispatchAndResolve<JsBuffer>(
            state->mEventQueue, promise,
            [file = std::move(file), offset = aOptions.mOffset, toRead,
             decompress = aOptions.mDecompress]() {
              return ReadSync(file, offset, toRead, decompress,
                              BufferKind::Uint8Array);
            });
      });
}

/* static */
RefPtr<SyncReadFile> IOUtils::OpenFileForSyncReading(GlobalObject& aGlobal,
                                                     const nsAString& aPath,
                                                     ErrorResult& aRv) {
  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());

  // This API is only exposed to workers, so we should not be on the main
  // thread here.
  MOZ_RELEASE_ASSERT(!NS_IsMainThread());

  nsCOMPtr<nsIFile> file = new nsLocalFile();
  if (nsresult rv = PathUtils::InitFileWithPath(file, aPath); NS_FAILED(rv)) {
    aRv.ThrowOperationError(FormatErrorMessage(
        rv, "Could not parse path (%s)", NS_ConvertUTF16toUTF8(aPath).get()));
    return nullptr;
  }

  RefPtr<nsFileRandomAccessStream> stream = new nsFileRandomAccessStream();
  if (nsresult rv =
          stream->Init(file, PR_RDONLY | nsIFile::OS_READAHEAD, 0666, 0);
      NS_FAILED(rv)) {
    aRv.ThrowOperationError(
        FormatErrorMessage(rv, "Could not open the file at %s",
                           NS_ConvertUTF16toUTF8(aPath).get()));
    return nullptr;
  }

  int64_t size = 0;
  if (nsresult rv = stream->GetSize(&size); NS_FAILED(rv)) {
    aRv.ThrowOperationError(FormatErrorMessage(
        rv, "Could not get the stream size for the file at %s",
        NS_ConvertUTF16toUTF8(aPath).get()));
    return nullptr;
  }

  return new SyncReadFile(aGlobal.GetAsSupports(), std::move(stream), size);
}

/* static */
already_AddRefed<Promise> IOUtils::ReadUTF8(GlobalObject& aGlobal,
                                            const nsAString& aPath,
                                            const ReadUTF8Options& aOptions,
                                            ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise, "Could not read `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<JsBuffer>(
            state->mEventQueue, promise,
            [file = std::move(file), decompress = aOptions.mDecompress]() {
              return ReadUTF8Sync(file, decompress);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::ReadJSON(GlobalObject& aGlobal,
                                            const nsAString& aPath,
                                            const ReadUTF8Options& aOptions,
                                            ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise, "Could not read `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        RefPtr<StrongWorkerRef> workerRef;
        if (!NS_IsMainThread()) {
          // We need to manually keep the worker alive until the promise
          // returned by Dispatch() resolves or rejects.
          workerRef = StrongWorkerRef::CreateForcibly(
              GetCurrentThreadWorkerPrivate(), __func__);
        }

        state->mEventQueue
            ->template Dispatch<JsBuffer>(
                [file, decompress = aOptions.mDecompress]() {
                  return ReadUTF8Sync(file, decompress);
                })
            ->Then(
                GetCurrentSerialEventTarget(), __func__,
                [workerRef, promise = RefPtr{promise},
                 file](JsBuffer&& aBuffer) {
                  AutoJSAPI jsapi;
                  if (NS_WARN_IF(!jsapi.Init(promise->GetGlobalObject()))) {
                    RejectJSPromise(
                        promise,
                        IOError(
                            NS_ERROR_DOM_UNKNOWN_ERR,
                            "Could not read `%s': could not initialize JS API",
                            file->HumanReadablePath().get()));
                    return;
                  }
                  JSContext* cx = jsapi.cx();

                  JS::Rooted<JSString*> jsonStr(
                      cx,
                      IOUtils::JsBuffer::IntoString(cx, std::move(aBuffer)));
                  if (!jsonStr) {
                    RejectJSPromise(
                        promise,
                        IOError(
                            NS_ERROR_OUT_OF_MEMORY,
                            "Could not read `%s': failed to allocate buffer",
                            file->HumanReadablePath().get()));
                    return;
                  }

                  JS::Rooted<JS::Value> val(cx);
                  if (!JS_ParseJSON(cx, jsonStr, &val)) {
                    JS::Rooted<JS::Value> exn(cx);
                    if (JS_GetPendingException(cx, &exn)) {
                      JS_ClearPendingException(cx);
                      promise->MaybeReject(exn);
                    } else {
                      RejectJSPromise(promise,
                                      IOError(NS_ERROR_DOM_UNKNOWN_ERR,
                                              "Could not read `%s': ParseJSON "
                                              "threw an uncatchable exception",
                                              file->HumanReadablePath().get()));
                    }

                    return;
                  }

                  promise->MaybeResolve(val);
                },
                [workerRef, promise = RefPtr{promise}](const IOError& aErr) {
                  RejectJSPromise(promise, aErr);
                });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::Write(GlobalObject& aGlobal,
                                         const nsAString& aPath,
                                         const Uint8Array& aData,
                                         const WriteOptions& aOptions,
                                         ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not write to `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        Maybe<Buffer<uint8_t>> buf = aData.CreateFromData<Buffer<uint8_t>>();
        if (buf.isNothing()) {
          promise->MaybeRejectWithOperationError(nsPrintfCString(
              "Could not write to `%s': could not allocate buffer",
              file->HumanReadablePath().get()));
          return;
        }

        auto result = InternalWriteOpts::FromBinding(aOptions);
        if (result.isErr()) {
          RejectJSPromise(
              promise,
              IOError::WithCause(result.unwrapErr(), "Could not write to `%s'",
                                 file->HumanReadablePath().get()));
          return;
        }

        DispatchAndResolve<uint32_t>(
            state->mEventQueue, promise,
            [file = std::move(file), buf = buf.extract(),
             opts = result.unwrap()]() { return WriteSync(file, buf, opts); });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::WriteUTF8(GlobalObject& aGlobal,
                                             const nsAString& aPath,
                                             const nsACString& aString,
                                             const WriteOptions& aOptions,
                                             ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not write to `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        auto result = InternalWriteOpts::FromBinding(aOptions);
        if (result.isErr()) {
          RejectJSPromise(
              promise,
              IOError::WithCause(result.unwrapErr(), "Could not write to `%s'",
                                 file->HumanReadablePath().get()));
          return;
        }

        DispatchAndResolve<uint32_t>(
            state->mEventQueue, promise,
            [file = std::move(file), str = nsCString(aString),
             opts = result.unwrap()]() {
              return WriteSync(file, AsBytes(Span(str)), opts);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::WriteJSON(GlobalObject& aGlobal,
                                             const nsAString& aPath,
                                             JS::Handle<JS::Value> aValue,
                                             const WriteOptions& aOptions,
                                             ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not write to `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        auto result = InternalWriteOpts::FromBinding(aOptions);
        if (result.isErr()) {
          RejectJSPromise(
              promise,
              IOError::WithCause(result.unwrapErr(), "Could not write to `%s'",
                                 file->HumanReadablePath().get()));
          return;
        }

        auto opts = result.unwrap();

        if (opts.mMode == WriteMode::Append ||
            opts.mMode == WriteMode::AppendOrCreate) {
          promise->MaybeRejectWithNotSupportedError(
              nsPrintfCString("Could not write to `%s': IOUtils.writeJSON does "
                              "not support appending to files.",
                              file->HumanReadablePath().get()));
          return;
        }

        JSContext* cx = aGlobal.Context();
        JS::Rooted<JS::Value> rootedValue(cx, aValue);
        nsString string;
        if (!nsContentUtils::StringifyJSON(cx, aValue, string,
                                           UndefinedIsNullStringLiteral)) {
          JS::Rooted<JS::Value> exn(cx, JS::UndefinedValue());
          if (JS_GetPendingException(cx, &exn)) {
            JS_ClearPendingException(cx);
            promise->MaybeReject(exn);
          } else {
            RejectJSPromise(promise,
                            IOError(NS_ERROR_DOM_UNKNOWN_ERR,
                                    "Could not serialize object to JSON"_ns));
          }
          return;
        }

        DispatchAndResolve<uint32_t>(
            state->mEventQueue, promise,
            [file = std::move(file), string = std::move(string),
             opts = std::move(opts)]() -> Result<uint32_t, IOError> {
              nsAutoCString utf8Str;
              if (!CopyUTF16toUTF8(string, utf8Str, fallible)) {
                return Err(IOError(
                    NS_ERROR_OUT_OF_MEMORY,
                    "Failed to write to `%s': could not allocate buffer",
                    file->HumanReadablePath().get()));
              }
              return WriteSync(file, AsBytes(Span(utf8Str)), opts);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::Move(GlobalObject& aGlobal,
                                        const nsAString& aSourcePath,
                                        const nsAString& aDestPath,
                                        const MoveOptions& aOptions,
                                        ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> sourceFile = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(sourceFile, aSourcePath, promise,
                                   "Could not move `%s' to `%s'",
                                   NS_ConvertUTF16toUTF8(aSourcePath).get(),
                                   NS_ConvertUTF16toUTF8(aDestPath).get());

        nsCOMPtr<nsIFile> destFile = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(destFile, aDestPath, promise,
                                   "Could not move `%s' to `%s'",
                                   NS_ConvertUTF16toUTF8(aSourcePath).get(),
                                   NS_ConvertUTF16toUTF8(aDestPath).get());

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [sourceFile = std::move(sourceFile), destFile = std::move(destFile),
             noOverwrite = aOptions.mNoOverwrite]() {
              return MoveSync(sourceFile, destFile, noOverwrite);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::Remove(GlobalObject& aGlobal,
                                          const nsAString& aPath,
                                          const RemoveOptions& aOptions,
                                          ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not remove `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [file = std::move(file), ignoreAbsent = aOptions.mIgnoreAbsent,
             recursive = aOptions.mRecursive,
             retryReadonly = aOptions.mRetryReadonly]() {
              return RemoveSync(file, ignoreAbsent, recursive, retryReadonly);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::MakeDirectory(
    GlobalObject& aGlobal, const nsAString& aPath,
    const MakeDirectoryOptions& aOptions, ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not make directory `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<Ok>(state->mEventQueue, promise,
                               [file = std::move(file),
                                createAncestors = aOptions.mCreateAncestors,
                                ignoreExisting = aOptions.mIgnoreExisting,
                                permissions = aOptions.mPermissions]() {
                                 return MakeDirectorySync(file, createAncestors,
                                                          ignoreExisting,
                                                          permissions);
                               });
      });
}

already_AddRefed<Promise> IOUtils::Stat(GlobalObject& aGlobal,
                                        const nsAString& aPath,
                                        ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise, "Could not stat `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<InternalFileInfo>(
            state->mEventQueue, promise,
            [file = std::move(file)]() { return StatSync(file); });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::Copy(GlobalObject& aGlobal,
                                        const nsAString& aSourcePath,
                                        const nsAString& aDestPath,
                                        const CopyOptions& aOptions,
                                        ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> sourceFile = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(sourceFile, aSourcePath, promise,
                                   "Could not copy `%s' to `%s'",
                                   NS_ConvertUTF16toUTF8(aSourcePath).get(),
                                   NS_ConvertUTF16toUTF8(aDestPath).get());

        nsCOMPtr<nsIFile> destFile = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(destFile, aDestPath, promise,
                                   "Could not copy `%s' to `%s'",
                                   NS_ConvertUTF16toUTF8(aSourcePath).get(),
                                   NS_ConvertUTF16toUTF8(aDestPath).get());

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [sourceFile = std::move(sourceFile), destFile = std::move(destFile),
             noOverwrite = aOptions.mNoOverwrite,
             recursive = aOptions.mRecursive]() {
              return CopySync(sourceFile, destFile, noOverwrite, recursive);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::SetAccessTime(
    GlobalObject& aGlobal, const nsAString& aPath,
    const Optional<int64_t>& aAccess, ErrorResult& aError) {
  return SetTime(aGlobal, aPath, aAccess, &nsIFile::SetLastAccessedTime,
                 "access", aError);
}

/* static */
already_AddRefed<Promise> IOUtils::SetModificationTime(
    GlobalObject& aGlobal, const nsAString& aPath,
    const Optional<int64_t>& aModification, ErrorResult& aError) {
  return SetTime(aGlobal, aPath, aModification, &nsIFile::SetLastModifiedTime,
                 "modification", aError);
}

/* static */
already_AddRefed<Promise> IOUtils::SetTime(GlobalObject& aGlobal,
                                           const nsAString& aPath,
                                           const Optional<int64_t>& aNewTime,
                                           IOUtils::SetTimeFn aSetTimeFn,
                                           const char* const aTimeKind,
                                           ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not set %s time on `%s'", aTimeKind,
                                   NS_ConvertUTF16toUTF8(aPath).get());

        int64_t newTime = aNewTime.WasPassed() ? aNewTime.Value()
                                               : PR_Now() / PR_USEC_PER_MSEC;
        DispatchAndResolve<int64_t>(
            state->mEventQueue, promise,
            [file = std::move(file), aSetTimeFn, newTime]() {
              return SetTimeSync(file, aSetTimeFn, newTime);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::HasChildren(
    GlobalObject& aGlobal, const nsAString& aPath,
    const HasChildrenOptions& aOptions, ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not check children of `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<bool>(
            state->mEventQueue, promise,
            [file = std::move(file), ignoreAbsent = aOptions.mIgnoreAbsent]() {
              return HasChildrenSync(file, ignoreAbsent);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::GetChildren(
    GlobalObject& aGlobal, const nsAString& aPath,
    const GetChildrenOptions& aOptions, ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not get children of `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<nsTArray<nsString>>(
            state->mEventQueue, promise,
            [file = std::move(file), ignoreAbsent = aOptions.mIgnoreAbsent]() {
              return GetChildrenSync(file, ignoreAbsent);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::SetPermissions(GlobalObject& aGlobal,
                                                  const nsAString& aPath,
                                                  uint32_t aPermissions,
                                                  const bool aHonorUmask,
                                                  ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
#if defined(XP_UNIX) && !defined(ANDROID)
        if (aHonorUmask) {
          aPermissions &= ~nsSystemInfo::gUserUmask;
        }
#endif

        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not set permissions on `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [file = std::move(file), permissions = aPermissions]() {
              return SetPermissionsSync(file, permissions);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::Exists(GlobalObject& aGlobal,
                                          const nsAString& aPath,
                                          ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not determine if `%s' exists",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<bool>(
            state->mEventQueue, promise,
            [file = std::move(file)]() { return ExistsSync(file); });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::CreateUniqueFile(GlobalObject& aGlobal,
                                                    const nsAString& aParent,
                                                    const nsAString& aPrefix,
                                                    const uint32_t aPermissions,
                                                    ErrorResult& aError) {
  return CreateUnique(aGlobal, aParent, aPrefix, nsIFile::NORMAL_FILE_TYPE,
                      aPermissions, aError);
}

/* static */
already_AddRefed<Promise> IOUtils::CreateUniqueDirectory(
    GlobalObject& aGlobal, const nsAString& aParent, const nsAString& aPrefix,
    const uint32_t aPermissions, ErrorResult& aError) {
  return CreateUnique(aGlobal, aParent, aPrefix, nsIFile::DIRECTORY_TYPE,
                      aPermissions, aError);
}

/* static */
already_AddRefed<Promise> IOUtils::CreateUnique(GlobalObject& aGlobal,
                                                const nsAString& aParent,
                                                const nsAString& aPrefix,
                                                const uint32_t aFileType,
                                                const uint32_t aPermissions,
                                                ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aParent, promise, "Could not create unique %s in `%s'",
            aFileType == nsIFile::NORMAL_FILE_TYPE ? "file" : "directory",
            NS_ConvertUTF16toUTF8(aParent).get());

        if (nsresult rv = file->Append(aPrefix); NS_FAILED(rv)) {
          RejectJSPromise(
              promise,
              IOError(
                  rv,
                  "Could not create unique %s: could not append prefix `%s' to "
                  "parent `%s'",
                  aFileType == nsIFile::NORMAL_FILE_TYPE ? "file" : "directory",
                  NS_ConvertUTF16toUTF8(aPrefix).get(),
                  file->HumanReadablePath().get()));
          return;
        }

        DispatchAndResolve<nsString>(
            state->mEventQueue, promise,
            [file = std::move(file), aPermissions, aFileType]() {
              return CreateUniqueSync(file, aFileType, aPermissions);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::ComputeHexDigest(
    GlobalObject& aGlobal, const nsAString& aPath,
    const HashAlgorithm aAlgorithm, ErrorResult& aError) {
  const bool nssInitialized = EnsureNSSInitializedChromeOrContent();

  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        if (!nssInitialized) {
          RejectJSPromise(promise, IOError(NS_ERROR_UNEXPECTED,
                                           "Could not initialize NSS"_ns));
          return;
        }

        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise, "Could not hash `%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<nsCString>(state->mEventQueue, promise,
                                      [file = std::move(file), aAlgorithm]() {
                                        return ComputeHexDigestSync(file,
                                                                    aAlgorithm);
                                      });
      });
}

#if defined(XP_WIN)

/* static */
already_AddRefed<Promise> IOUtils::GetWindowsAttributes(GlobalObject& aGlobal,
                                                        const nsAString& aPath,
                                                        ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(file, aPath, promise,
                                   "Could not get Windows file attributes of "
                                   "`%s'",
                                   NS_ConvertUTF16toUTF8(aPath).get());

        RefPtr<StrongWorkerRef> workerRef;
        if (!NS_IsMainThread()) {
          // We need to manually keep the worker alive until the promise
          // returned by Dispatch() resolves or rejects.
          workerRef = StrongWorkerRef::CreateForcibly(
              GetCurrentThreadWorkerPrivate(), __func__);
        }

        state->mEventQueue
            ->template Dispatch<uint32_t>([file = std::move(file)]() {
              return GetWindowsAttributesSync(file);
            })
            ->Then(
                GetCurrentSerialEventTarget(), __func__,
                [workerRef, promise = RefPtr{promise}](const uint32_t aAttrs) {
                  WindowsFileAttributes attrs;

                  attrs.mReadOnly.Construct(aAttrs & FILE_ATTRIBUTE_READONLY);
                  attrs.mHidden.Construct(aAttrs & FILE_ATTRIBUTE_HIDDEN);
                  attrs.mSystem.Construct(aAttrs & FILE_ATTRIBUTE_SYSTEM);

                  promise->MaybeResolve(attrs);
                },
                [workerRef, promise = RefPtr{promise}](const IOError& aErr) {
                  RejectJSPromise(promise, aErr);
                });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::SetWindowsAttributes(
    GlobalObject& aGlobal, const nsAString& aPath,
    const WindowsFileAttributes& aAttrs, ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aPath, promise,
            "Could not set Windows file attributes on `%s'",
            NS_ConvertUTF16toUTF8(aPath).get());

        uint32_t setAttrs = 0;
        uint32_t clearAttrs = 0;

        if (aAttrs.mReadOnly.WasPassed()) {
          if (aAttrs.mReadOnly.Value()) {
            setAttrs |= FILE_ATTRIBUTE_READONLY;
          } else {
            clearAttrs |= FILE_ATTRIBUTE_READONLY;
          }
        }

        if (aAttrs.mHidden.WasPassed()) {
          if (aAttrs.mHidden.Value()) {
            setAttrs |= FILE_ATTRIBUTE_HIDDEN;
          } else {
            clearAttrs |= FILE_ATTRIBUTE_HIDDEN;
          }
        }

        if (aAttrs.mSystem.WasPassed()) {
          if (aAttrs.mSystem.Value()) {
            setAttrs |= FILE_ATTRIBUTE_SYSTEM;
          } else {
            clearAttrs |= FILE_ATTRIBUTE_SYSTEM;
          }
        }

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [file = std::move(file), setAttrs, clearAttrs]() {
              return SetWindowsAttributesSync(file, setAttrs, clearAttrs);
            });
      });
}

#elif defined(XP_MACOSX)

/* static */
already_AddRefed<Promise> IOUtils::HasMacXAttr(GlobalObject& aGlobal,
                                               const nsAString& aPath,
                                               const nsACString& aAttr,
                                               ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aPath, promise,
            "Could not read the extended attribute `%s' from `%s'",
            PromiseFlatCString(aAttr).get(),
            NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<bool>(
            state->mEventQueue, promise,
            [file = std::move(file), attr = nsCString(aAttr)]() {
              return HasMacXAttrSync(file, attr);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::GetMacXAttr(GlobalObject& aGlobal,
                                               const nsAString& aPath,
                                               const nsACString& aAttr,
                                               ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aPath, promise,
            "Could not read extended attribute `%s' from `%s'",
            PromiseFlatCString(aAttr).get(),
            NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<nsTArray<uint8_t>>(
            state->mEventQueue, promise,
            [file = std::move(file), attr = nsCString(aAttr)]() {
              return GetMacXAttrSync(file, attr);
            });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::SetMacXAttr(GlobalObject& aGlobal,
                                               const nsAString& aPath,
                                               const nsACString& aAttr,
                                               const Uint8Array& aValue,
                                               ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aPath, promise,
            "Could not set the extended attribute `%s' on `%s'",
            PromiseFlatCString(aAttr).get(),
            NS_ConvertUTF16toUTF8(aPath).get());

        nsTArray<uint8_t> value;

        if (!aValue.AppendDataTo(value)) {
          RejectJSPromise(
              promise, IOError(NS_ERROR_OUT_OF_MEMORY,
                               "Could not set extended attribute `%s' on `%s': "
                               "could not allocate buffer",
                               PromiseFlatCString(aAttr).get(),
                               file->HumanReadablePath().get()));
          return;
        }

        DispatchAndResolve<Ok>(state->mEventQueue, promise,
                               [file = std::move(file), attr = nsCString(aAttr),
                                value = std::move(value)] {
                                 return SetMacXAttrSync(file, attr, value);
                               });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::DelMacXAttr(GlobalObject& aGlobal,
                                               const nsAString& aPath,
                                               const nsACString& aAttr,
                                               ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        nsCOMPtr<nsIFile> file = new nsLocalFile();
        REJECT_IF_INIT_PATH_FAILED(
            file, aPath, promise,
            "Could not delete extended attribute `%s' on `%s'",
            PromiseFlatCString(aAttr).get(),
            NS_ConvertUTF16toUTF8(aPath).get());

        DispatchAndResolve<Ok>(
            state->mEventQueue, promise,
            [file = std::move(file), attr = nsCString(aAttr)] {
              return DelMacXAttrSync(file, attr);
            });
      });
}

#endif

/* static */
already_AddRefed<Promise> IOUtils::GetFile(
    GlobalObject& aGlobal, const Sequence<nsString>& aComponents,
    ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        ErrorResult joinErr;
        nsCOMPtr<nsIFile> file = PathUtils::Join(aComponents, joinErr);
        if (joinErr.Failed()) {
          promise->MaybeReject(std::move(joinErr));
          return;
        }

        nsCOMPtr<nsIFile> parent;
        if (nsresult rv = file->GetParent(getter_AddRefs(parent));
            NS_FAILED(rv)) {
          RejectJSPromise(promise, IOError(rv,
                                           "Could not get nsIFile for `%s': "
                                           "could not get parent directory",
                                           file->HumanReadablePath().get()));
          return;
        }

        state->mEventQueue
            ->template Dispatch<Ok>([parent = std::move(parent)]() {
              return MakeDirectorySync(parent, /* aCreateAncestors = */ true,
                                       /* aIgnoreExisting = */ true, 0755);
            })
            ->Then(
                GetCurrentSerialEventTarget(), __func__,
                [file = std::move(file), promise = RefPtr(promise)](const Ok&) {
                  promise->MaybeResolve(file);
                },
                [promise = RefPtr(promise)](const IOError& err) {
                  RejectJSPromise(promise, err);
                });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::GetDirectory(
    GlobalObject& aGlobal, const Sequence<nsString>& aComponents,
    ErrorResult& aError) {
  return WithPromiseAndState(
      aGlobal, aError, [&](Promise* promise, auto& state) {
        ErrorResult joinErr;
        nsCOMPtr<nsIFile> dir = PathUtils::Join(aComponents, joinErr);
        if (joinErr.Failed()) {
          promise->MaybeReject(std::move(joinErr));
          return;
        }

        state->mEventQueue
            ->template Dispatch<Ok>([dir]() {
              return MakeDirectorySync(dir, /* aCreateAncestors = */ true,
                                       /* aIgnoreExisting = */ true, 0755);
            })
            ->Then(
                GetCurrentSerialEventTarget(), __func__,
                [dir, promise = RefPtr(promise)](const Ok&) {
                  promise->MaybeResolve(dir);
                },
                [promise = RefPtr(promise)](const IOError& err) {
                  RejectJSPromise(promise, err);
                });
      });
}

/* static */
already_AddRefed<Promise> IOUtils::CreateJSPromise(GlobalObject& aGlobal,
                                                   ErrorResult& aError) {
  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
  RefPtr<Promise> promise = Promise::Create(global, aError);
  if (aError.Failed()) {
    return nullptr;
  }
  MOZ_ASSERT(promise);
  return do_AddRef(promise);
}

/* static */
Result<IOUtils::JsBuffer, IOUtils::IOError> IOUtils::ReadSync(
    nsIFile* aFile, const uint64_t aOffset, const Maybe<uint32_t> aMaxBytes,
    const bool aDecompress, IOUtils::BufferKind aBufferKind) {
  MOZ_ASSERT(!NS_IsMainThread());
  // This is checked in IOUtils::Read.
  MOZ_ASSERT(aMaxBytes.isNothing() || !aDecompress,
             "maxBytes and decompress are mutually exclusive");

  if (aOffset > static_cast<uint64_t>(INT64_MAX)) {
    return Err(
        IOError(NS_ERROR_ILLEGAL_INPUT,
                "Could not read `%s': requested offset is too large (%" PRIu64
                " > %" PRId64 ")",
                aFile->HumanReadablePath().get(), aOffset, INT64_MAX));
  }

  const int64_t offset = static_cast<int64_t>(aOffset);

  RefPtr<nsFileRandomAccessStream> stream = new nsFileRandomAccessStream();
  if (nsresult rv =
          stream->Init(aFile, PR_RDONLY | nsIFile::OS_READAHEAD, 0666, 0);
      NS_FAILED(rv)) {
    if (IsFileNotFound(rv)) {
      return Err(IOError(rv, "Could not open `%s': file does not exist",
                         aFile->HumanReadablePath().get()));
    }
    return Err(
        IOError(rv, "Could not open `%s'", aFile->HumanReadablePath().get()));
  }

  uint32_t bufSize = 0;

  if (aMaxBytes.isNothing()) {
    // Limitation: We cannot read more than the maximum size of a TypedArray
    //            (UINT32_MAX bytes). Reject if we have been requested to
    //            perform too large of a read.

    int64_t rawStreamSize = -1;
    if (nsresult rv = stream->GetSize(&rawStreamSize); NS_FAILED(rv)) {
      return Err(
          IOError(NS_ERROR_FILE_ACCESS_DENIED,
                  "Could not open `%s': could not stat file or directory",
                  aFile->HumanReadablePath().get()));
    }
    MOZ_RELEASE_ASSERT(rawStreamSize >= 0);

    uint64_t streamSize = static_cast<uint64_t>(rawStreamSize);
    if (aOffset >= streamSize) {
      bufSize = 0;
    } else {
      if (streamSize - offset > static_cast<int64_t>(UINT32_MAX)) {
        return Err(IOError(NS_ERROR_FILE_TOO_BIG,
                           "Could not read `%s' with offset %" PRIu64
                           ": file is too large (%" PRIu64 " bytes)",
                           aFile->HumanReadablePath().get(), offset,
                           streamSize));
      }

      bufSize = static_cast<uint32_t>(streamSize - offset);
    }
  } else {
    bufSize = aMaxBytes.value();
  }

  if (offset > 0) {
    if (nsresult rv = stream->Seek(PR_SEEK_SET, offset); NS_FAILED(rv)) {
      return Err(IOError(
          rv, "Could not read `%s': could not seek to position %" PRId64,
          aFile->HumanReadablePath().get(), offset));
    }
  }

  JsBuffer buffer = JsBuffer::CreateEmpty(aBufferKind);

  if (bufSize > 0) {
    auto result = JsBuffer::Create(aBufferKind, bufSize);
    if (result.isErr()) {
      return Err(IOError::WithCause(result.unwrapErr(), "Could not read `%s'",
                                    aFile->HumanReadablePath().get()));
    }
    buffer = result.unwrap();
    Span<char> toRead = buffer.BeginWriting();

    // Read the file from disk.
    uint32_t totalRead = 0;
    while (totalRead != bufSize) {
      // Read no more than INT32_MAX on each call to stream->Read, otherwise it
      // returns an error.
      uint32_t bytesToReadThisChunk =
          std::min<uint32_t>(bufSize - totalRead, INT32_MAX);
      uint32_t bytesRead = 0;
      if (nsresult rv =
              stream->Read(toRead.Elements(), bytesToReadThisChunk, &bytesRead);
          NS_FAILED(rv)) {
        return Err(
            IOError(rv, "Could not read `%s': encountered an unexpected error",
                    aFile->HumanReadablePath().get()));
      }
      if (bytesRead == 0) {
        break;
      }
      totalRead += bytesRead;
      toRead = toRead.From(bytesRead);
    }

    buffer.SetLength(totalRead);
  }

  // Decompress the file contents, if required.
  if (aDecompress) {
    auto result =
        MozLZ4::Decompress(AsBytes(buffer.BeginReading()), aBufferKind);
    if (result.isErr()) {
      return Err(IOError::WithCause(result.unwrapErr(), "Could not read `%s'",
                                    aFile->HumanReadablePath().get()));
    }
    return result;
  }

  return std::move(buffer);
}

/* static */
Result<IOUtils::JsBuffer, IOUtils::IOError> IOUtils::ReadUTF8Sync(
    nsIFile* aFile, bool aDecompress) {
  auto result = ReadSync(aFile, 0, Nothing{}, aDecompress, BufferKind::String);
  if (result.isErr()) {
    return result.propagateErr();
  }

  JsBuffer buffer = result.unwrap();
  if (!IsUtf8(buffer.BeginReading())) {
    return Err(IOError(NS_ERROR_FILE_CORRUPTED,
                       "Could not read `%s': file is not UTF-8 encoded",
                       aFile->HumanReadablePath().get()));
  }

  return buffer;
}

/* static */
Result<uint32_t, IOUtils::IOError> IOUtils::WriteSync(
    nsIFile* aFile, const Span<const uint8_t>& aByteArray,
    const IOUtils::InternalWriteOpts& aOptions) {
  MOZ_ASSERT(!NS_IsMainThread());

  nsIFile* backupFile = aOptions.mBackupFile;
  nsIFile* tempFile = aOptions.mTmpFile;

  bool exists = false;
  IOUTILS_TRY_WITH_CONTEXT(
      aFile->Exists(&exists),
      "Could not write to `%s': could not stat file or directory",
      aFile->HumanReadablePath().get());

  if (exists && aOptions.mMode == WriteMode::Create) {
    return Err(IOError(NS_ERROR_FILE_ALREADY_EXISTS,
                       "Could not write to `%s': refusing to overwrite file, "
                       "`mode' is not \"overwrite\"",
                       aFile->HumanReadablePath().get()));
  }

  // If backupFile was specified, perform the backup as a move.
  if (exists && backupFile) {
    // We copy `destFile` here to a new `nsIFile` because
    // `nsIFile::MoveToFollowingLinks` will update the path of the file. If we
    // did not do this, we would end up having `destFile` point to the same
    // location as `backupFile`. Then, when we went to write to `destFile`, we
    // would end up overwriting `backupFile` and never actually write to the
    // file we were supposed to.
    nsCOMPtr<nsIFile> toMove;
    MOZ_ALWAYS_SUCCEEDS(aFile->Clone(getter_AddRefs(toMove)));

    bool noOverwrite = aOptions.mMode == WriteMode::Create;

    if (auto result = MoveSync(toMove, backupFile, noOverwrite);
        result.isErr()) {
      return Err(IOError::WithCause(
          result.unwrapErr(),
          "Could not write to `%s': failed to back up source file",
          aFile->HumanReadablePath().get()));
    }
  }

  // If tempFile was specified, we will write to there first, then perform a
  // move to ensure the file ends up at the final requested destination.
  nsIFile* writeFile;

  if (tempFile) {
    writeFile = tempFile;
  } else {
    writeFile = aFile;
  }

  int32_t flags = PR_WRONLY;

  switch (aOptions.mMode) {
    case WriteMode::Overwrite:
      flags |= PR_TRUNCATE | PR_CREATE_FILE;
      break;

    case WriteMode::Append:
      flags |= PR_APPEND;
      break;

    case WriteMode::AppendOrCreate:
      flags |= PR_APPEND | PR_CREATE_FILE;
      break;

    case WriteMode::Create:
      flags |= PR_CREATE_FILE | PR_EXCL;
      break;

    default:
      MOZ_CRASH("IOUtils: unknown write mode");
  }

  if (aOptions.mFlush) {
    flags |= PR_SYNC;
  }

  // Try to perform the write and ensure that the file is closed before
  // continuing.
  uint32_t totalWritten = 0;
  {
    // Compress the byte array if required.
    nsTArray<uint8_t> compressed;
    Span<const char> bytes;
    if (aOptions.mCompress) {
      auto result = MozLZ4::Compress(aByteArray);
      if (result.isErr()) {
        return Err(IOError::WithCause(result.unwrapErr(),
                                      "Could not write to `%s'",
                                      writeFile->HumanReadablePath().get()));
      }
      compressed = result.unwrap();
      bytes = Span(reinterpret_cast<const char*>(compressed.Elements()),
                   compressed.Length());
    } else {
      bytes = Span(reinterpret_cast<const char*>(aByteArray.Elements()),
                   aByteArray.Length());
    }

    RefPtr<nsFileOutputStream> stream = new nsFileOutputStream();
    if (nsresult rv = stream->Init(writeFile, flags, 0666, 0); NS_FAILED(rv)) {
      // Normalize platform-specific errors for opening a directory to an access
      // denied error.
      if (rv == nsresult::NS_ERROR_FILE_IS_DIRECTORY) {
        rv = NS_ERROR_FILE_ACCESS_DENIED;
      }
      return Err(IOError(
          rv, "Could not write to `%s': failed to open file for writing",
          writeFile->HumanReadablePath().get()));
    }

    // nsFileRandomAccessStream::Write uses PR_Write under the hood, which
    // accepts a *int32_t* for the chunk size.
    uint32_t chunkSize = INT32_MAX;
    Span<const char> pendingBytes = bytes;

    while (pendingBytes.Length() > 0) {
      if (pendingBytes.Length() < chunkSize) {
        chunkSize = pendingBytes.Length();
      }

      uint32_t bytesWritten = 0;
      if (nsresult rv =
              stream->Write(pendingBytes.Elements(), chunkSize, &bytesWritten);
          NS_FAILED(rv)) {
        return Err(IOError(rv,
                           "Could not write to `%s': failed to write chunk; "
                           "the file may be corrupt",
                           writeFile->HumanReadablePath().get()));
      }
      pendingBytes = pendingBytes.From(bytesWritten);
      totalWritten += bytesWritten;
    }
  }

  // If tempFile was passed, check destFile against writeFile and, if they
  // differ, the operation is finished by performing a move.
  if (tempFile) {
    nsAutoStringN<256> destPath;
    nsAutoStringN<256> writePath;

    MOZ_ALWAYS_SUCCEEDS(aFile->GetPath(destPath));
    MOZ_ALWAYS_SUCCEEDS(writeFile->GetPath(writePath));

    // nsIFile::MoveToFollowingLinks will only update the path of the file if
    // the move succeeds.
    if (destPath != writePath) {
      if (aOptions.mTmpFile) {
        bool isDir = false;
        if (nsresult rv = aFile->IsDirectory(&isDir);
            NS_FAILED(rv) && !IsFileNotFound(rv)) {
          return Err(IOError(
              rv, "Could not write to `%s': could not stat file or directory",
              aFile->HumanReadablePath().get()));
        }

        // If we attempt to write to a directory *without* a temp file, we get a
        // permission error.
        //
        // However, if we are writing to a temp file first, when we copy the
        // temp file over the destination file, we actually end up copying it
        // inside the directory, which is not what we want. In this case, we are
        // just going to bail out early.
        if (isDir) {
          return Err(IOError(NS_ERROR_FILE_ACCESS_DENIED,
                             "Could not write to `%s': file is a directory",
                             aFile->HumanReadablePath().get()));
        }
      }

      if (auto result = MoveSync(writeFile, aFile, /* aNoOverwrite = */ false);
          result.isErr()) {
        return Err(IOError::WithCause(
            result.unwrapErr(),
            "Could not write to `%s': could not move overwite with temporary "
            "file",
            aFile->HumanReadablePath().get()));
      }
    }
  }
  return totalWritten;
}

/* static */
Result<Ok, IOUtils::IOError> IOUtils::MoveSync(nsIFile* aSourceFile,
                                               nsIFile* aDestFile,
                                               bool aNoOverwrite) {
  MOZ_ASSERT(!NS_IsMainThread());

  // Ensure the source file exists before continuing. If it doesn't exist,
  // subsequent operations can fail in different ways on different platforms.
  bool srcExists = false;
  IOUTILS_TRY_WITH_CONTEXT(
      aSourceFile->Exists(&srcExists),
      "Could not move `%s' to `%s': could not stat source file or directory",
      aSourceFile->HumanReadablePath().get(),
      aDestFile->HumanReadablePath().get());

  if (!srcExists) {
    return Err(
        IOError(NS_ERROR_FILE_NOT_FOUND,
                "Could not move `%s' to `%s': source file does not exist",
                aSourceFile->HumanReadablePath().get(),
                aDestFile->HumanReadablePath().get()));
  }

  return CopyOrMoveSync(&nsIFile::MoveToFollowingLinks, "move", aSourceFile,
                        aDestFile, aNoOverwrite);
}

/* static */
Result<Ok, IOUtils::IOError> IOUtils::CopySync(nsIFile* aSourceFile,
                                               nsIFile* aDestFile,
                                               bool aNoOverwrite,
                                               bool aRecursive) {
  MOZ_ASSERT(!NS_IsMainThread());

  // Ensure the source file exists before continuing. If it doesn't exist,
  // subsequent operations can fail in different ways on different platforms.
  bool srcExists;
  IOUTILS_TRY_WITH_CONTEXT(
      aSourceFile->Exists(&srcExists),
      "Could not copy `%s' to `%s': could not stat source file or directory",
      aSourceFile->HumanReadablePath().get(),
      aDestFile->HumanReadablePath().get());

  if (!srcExists) {
    return Err(
        IOError(NS_ERROR_FILE_NOT_FOUND,
                "Could not copy `%s' to `%s': source file does not exist",
                aSourceFile->HumanReadablePath().get(),
                aDestFile->HumanReadablePath().get()));
  }

  // If source is a directory, fail immediately unless the recursive option is
  // true.
  bool srcIsDir = false;
  IOUTILS_TRY_WITH_CONTEXT(
      aSourceFile->IsDirectory(&srcIsDir),
      "Could not copy `%s' to `%s': could not stat source file or directory",
      aSourceFile->HumanReadablePath().get(),
      aDestFile->HumanReadablePath().get());

  if (srcIsDir && !aRecursive) {
    return Err(IOError(NS_ERROR_FILE_COPY_OR_MOVE_FAILED,
                       "Refused to copy directory `%s' to `%s': `recursive' is "
                       "false\n",
                       aSourceFile->HumanReadablePath().get(),
                       aDestFile->HumanReadablePath().get()));
  }

  return CopyOrMoveSync(&nsIFile::CopyToFollowingLinks, "copy", aSourceFile,
                        aDestFile, aNoOverwrite);
}

/* static */
template <typename CopyOrMoveFn>
Result<Ok, IOUtils::IOError> IOUtils::CopyOrMoveSync(CopyOrMoveFn aMethod,
                                                     const char* aMethodName,
                                                     nsIFile* aSource,
                                                     nsIFile* aDest,
                                                     bool aNoOverwrite) {
  MOZ_ASSERT(!NS_IsMainThread());

  // Case 1: Destination is an existing directory. Copy/move source into dest.
  bool destIsDir = false;
  bool destExists = true;

  nsresult rv = aDest->IsDirectory(&destIsDir);
  if (NS_SUCCEEDED(rv) && destIsDir) {
    rv = (aSource->*aMethod)(aDest, u""_ns);
    if (NS_FAILED(rv)) {
      return Err(IOError(rv, "Could not %s `%s' to `%s'", aMethodName,
                         aSource->HumanReadablePath().get(),
                         aDest->HumanReadablePath().get()));
    }
    return Ok();
  }

  if (NS_FAILED(rv)) {
    if (!IsFileNotFound(rv)) {
      // It's ok if the dest file doesn't exist. Case 2 handles this below.
      // Bail out early for any other kind of error though.
      return Err(IOError(rv, "Could not %s `%s' to `%s'", aMethodName,
                         aSource->HumanReadablePath().get(),
                         aDest->HumanReadablePath().get()));
    }
    destExists = false;
  }

  // Case 2: Destination is a file which may or may not exist.
  //         Try to copy or rename the source to the destination.
  //         If the destination exists and the source is not a regular file,
  //         then this may fail.
  if (aNoOverwrite && destExists) {
    return Err(IOError(NS_ERROR_FILE_ALREADY_EXISTS,
                       "Could not %s `%s' to `%s': destination file exists and "
                       "`noOverwrite' is true",
                       aMethodName, aSource->HumanReadablePath().get(),
                       aDest->HumanReadablePath().get()));
  }
  if (destExists && !destIsDir) {
    // If the source file is a directory, but the target is a file, abort early.
    // Different implementations of |CopyTo| and |MoveTo| seem to handle this
    // error case differently (or not at all), so we explicitly handle it here.
    bool srcIsDir = false;
    IOUTILS_TRY_WITH_CONTEXT(
        aSource->IsDirectory(&srcIsDir),
        "Could not %s `%s' to `%s': could not stat source file or directory",
        aMethodName, aSource->HumanReadablePath().get(),
        aDest->HumanReadablePath().get());
    if (srcIsDir) {
      return Err(IOError(
          NS_ERROR_FILE_DESTINATION_NOT_DIR,
          "Could not %s directory `%s' to `%s': destination is not a directory",
          aMethodName, aSource->HumanReadablePath().get(),
          aDest->HumanReadablePath().get()));
    }
  }

  // We would have already thrown if the path was zero-length.
  nsAutoString destName;
  MOZ_ALWAYS_SUCCEEDS(aDest->GetLeafName(destName));

--> --------------------

--> maximum size reached

--> --------------------

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