gecko-dev/netwerk/base/nsFileStreams.h

/* -*- Mode: C++; tab-width: 4; 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/. */

#ifndef nsFileStreams_h__
#define nsFileStreams_h__

#include "mozilla/UniquePtr.h"
#include "nsIFileStreams.h"
#include "nsIFile.h"
#include "nsICloneableInputStream.h"
#include "nsIInputStream.h"
#include "nsIOutputStream.h"
#include "nsISafeOutputStream.h"
#include "nsISeekableStream.h"
#include "nsILineInputStream.h"
#include "nsCOMPtr.h"
#include "nsIIPCSerializableInputStream.h"
#include "nsReadLine.h"
#include <algorithm>

namespace mozilla {
namespace ipc {
class FileDescriptor;
}  // namespace ipc
}  // namespace mozilla

////////////////////////////////////////////////////////////////////////////////

class nsFileStreamBase : public nsISeekableStream, public nsIFileMetadata {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSISEEKABLESTREAM
  NS_DECL_NSITELLABLESTREAM
  NS_DECL_NSIFILEMETADATA

  nsFileStreamBase();

 protected:
  virtual ~nsFileStreamBase();

  nsresult Close();
  nsresult Available(uint64_t* _retval);
  nsresult Read(char* aBuf, uint32_t aCount, uint32_t* _retval);
  nsresult ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
                        uint32_t aCount, uint32_t* _retval);
  nsresult IsNonBlocking(bool* _retval);
  nsresult Flush();
  nsresult Write(const char* aBuf, uint32_t aCount, uint32_t* _retval);
  nsresult WriteFrom(nsIInputStream* aFromStream, uint32_t aCount,
                     uint32_t* _retval);
  nsresult WriteSegments(nsReadSegmentFun aReader, void* aClosure,
                         uint32_t aCount, uint32_t* _retval);

  PRFileDesc* mFD;

  /**
   * Flags describing our behavior.  See the IDL file for possible values.
   */
  int32_t mBehaviorFlags;

  enum {
    // This is the default value. It will be changed by Deserialize or Init.
    eUnitialized,
    // The opening has been deferred. See DEFER_OPEN.
    eDeferredOpen,
    // The file has been opened. mFD is not null.
    eOpened,
    // The file has been closed. mFD is null.
    eClosed,
    // Something bad happen in the Open() or in Deserialize(). The actual
    // error value is stored in mErrorValue.
    eError
  } mState;

  struct OpenParams {
    nsCOMPtr<nsIFile> localFile;
    int32_t ioFlags;
    int32_t perm;
  };

  /**
   * Data we need to do an open.
   */
  OpenParams mOpenParams;

  nsresult mErrorValue;

  /**
   * Prepares the data we need to open the file, and either does the open now
   * by calling DoOpen(), or leaves it to be opened later by a call to
   * DoPendingOpen().
   */
  nsresult MaybeOpen(nsIFile* aFile, int32_t aIoFlags, int32_t aPerm,
                     bool aDeferred);

  /**
   * Cleans up data prepared in MaybeOpen.
   */
  void CleanUpOpen();

  /**
   * Open the file. This is called either from MaybeOpen (during Init)
   * or from DoPendingOpen (if DEFER_OPEN is used when initializing this
   * stream). The default behavior of DoOpen is to open the file and save the
   * file descriptor.
   */
  virtual nsresult DoOpen();

  /**
   * Based on mState, this method does the opening, return an error, or do
   * nothing. If the return value is not NS_OK, please, return it back to the
   * callee.
   */
  inline nsresult DoPendingOpen();
};

////////////////////////////////////////////////////////////////////////////////

// nsFileInputStream is cloneable only on the parent process because only there
// it can open the same file multiple times.

class nsFileInputStream : public nsFileStreamBase,
                          public nsIFileInputStream,
                          public nsILineInputStream,
                          public nsIIPCSerializableInputStream,
                          public nsICloneableInputStream {
 public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIFILEINPUTSTREAM
  NS_DECL_NSILINEINPUTSTREAM
  NS_DECL_NSIIPCSERIALIZABLEINPUTSTREAM
  NS_DECL_NSICLONEABLEINPUTSTREAM

  NS_IMETHOD Close() override;
  NS_IMETHOD Tell(int64_t* aResult) override;
  NS_IMETHOD Available(uint64_t* _retval) override;
  NS_IMETHOD Read(char* aBuf, uint32_t aCount, uint32_t* _retval) override;
  NS_IMETHOD ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
                          uint32_t aCount, uint32_t* _retval) override {
    return nsFileStreamBase::ReadSegments(aWriter, aClosure, aCount, _retval);
  }
  NS_IMETHOD IsNonBlocking(bool* _retval) override {
    return nsFileStreamBase::IsNonBlocking(_retval);
  }

  // Overrided from nsFileStreamBase
  NS_IMETHOD Seek(int32_t aWhence, int64_t aOffset) override;

  nsFileInputStream()
      : mLineBuffer(nullptr), mIOFlags(0), mPerm(0), mCachedPosition(0) {}

  static nsresult Create(nsISupports* aOuter, REFNSIID aIID, void** aResult);

 protected:
  virtual ~nsFileInputStream() = default;

  void SerializeInternal(mozilla::ipc::InputStreamParams& aParams,
                         FileDescriptorArray& aFileDescriptors);

  nsresult SeekInternal(int32_t aWhence, int64_t aOffset,
                        bool aClearBuf = true);

  mozilla::UniquePtr<nsLineBuffer<char>> mLineBuffer;

  /**
   * The file being opened.
   */
  nsCOMPtr<nsIFile> mFile;
  /**
   * The IO flags passed to Init() for the file open.
   */
  int32_t mIOFlags;
  /**
   * The permissions passed to Init() for the file open.
   */
  int32_t mPerm;

  /**
   * Cached position for Tell for automatically reopening streams.
   */
  int64_t mCachedPosition;

 protected:
  /**
   * Internal, called to open a file.  Parameters are the same as their
   * Init() analogues.
   */
  nsresult Open(nsIFile* file, int32_t ioFlags, int32_t perm);

  bool IsCloneable() const;
};

////////////////////////////////////////////////////////////////////////////////

class nsFileOutputStream : public nsFileStreamBase, public nsIFileOutputStream {
 public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIFILEOUTPUTSTREAM
  NS_FORWARD_NSIOUTPUTSTREAM(nsFileStreamBase::)

  static nsresult Create(nsISupports* aOuter, REFNSIID aIID, void** aResult);
  nsresult InitWithFileDescriptor(const mozilla::ipc::FileDescriptor& aFd);

 protected:
  virtual ~nsFileOutputStream() = default;
};

////////////////////////////////////////////////////////////////////////////////

/**
 * A safe file output stream that overwrites the destination file only
 * once writing is complete. This protects against incomplete writes
 * due to the process or the thread being interrupted or crashed.
 */
class nsAtomicFileOutputStream : public nsFileOutputStream,
                                 public nsISafeOutputStream {
 public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSISAFEOUTPUTSTREAM

  nsAtomicFileOutputStream() : mTargetFileExists(true), mWriteResult(NS_OK) {}

  virtual nsresult DoOpen() override;

  NS_IMETHOD Close() override;
  NS_IMETHOD Write(const char* buf, uint32_t count, uint32_t* result) override;
  NS_IMETHOD Init(nsIFile* file, int32_t ioFlags, int32_t perm,
                  int32_t behaviorFlags) override;

 protected:
  virtual ~nsAtomicFileOutputStream() = default;

  nsCOMPtr<nsIFile> mTargetFile;
  nsCOMPtr<nsIFile> mTempFile;

  bool mTargetFileExists;
  nsresult mWriteResult;  // Internally set in Write()
};

////////////////////////////////////////////////////////////////////////////////

/**
 * A safe file output stream that overwrites the destination file only
 * once writing + flushing is complete. This protects against more
 * classes of software/hardware errors than nsAtomicFileOutputStream,
 * at the expense of being more costly to the disk, OS and battery.
 */
class nsSafeFileOutputStream : public nsAtomicFileOutputStream {
 public:
  NS_IMETHOD Finish() override;
};

////////////////////////////////////////////////////////////////////////////////

class nsFileStream : public nsFileStreamBase,
                     public nsIInputStream,
                     public nsIOutputStream,
                     public nsIFileStream {
 public:
  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIFILESTREAM
  NS_FORWARD_NSIINPUTSTREAM(nsFileStreamBase::)

  // Can't use NS_FORWARD_NSIOUTPUTSTREAM due to overlapping methods
  // Close() and IsNonBlocking()
  NS_IMETHOD Flush() override { return nsFileStreamBase::Flush(); }
  NS_IMETHOD Write(const char* aBuf, uint32_t aCount,
                   uint32_t* _retval) override {
    return nsFileStreamBase::Write(aBuf, aCount, _retval);
  }
  NS_IMETHOD WriteFrom(nsIInputStream* aFromStream, uint32_t aCount,
                       uint32_t* _retval) override {
    return nsFileStreamBase::WriteFrom(aFromStream, aCount, _retval);
  }
  NS_IMETHOD WriteSegments(nsReadSegmentFun aReader, void* aClosure,
                           uint32_t aCount, uint32_t* _retval) override {
    return nsFileStreamBase::WriteSegments(aReader, aClosure, aCount, _retval);
  }

 protected:
  virtual ~nsFileStream() = default;
};

////////////////////////////////////////////////////////////////////////////////

#endif  // nsFileStreams_h__