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third_party/crashpad/crashpad/util/file/file_writer.h

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_FILE_FILE_WRITER_H_
+#define CRASHPAD_UTIL_FILE_FILE_WRITER_H_
+
+#include <sys/types.h>
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/files/file_path.h"
+#include "util/file/file_io.h"
+#include "util/file/file_seeker.h"
+
+namespace crashpad {
+
+//! \brief A version of `iovec` with a `const` #iov_base field.
+//!
+//! This structure is intended to be used for write operations.
+//
+// Type compatibility with iovec is tested with static assertions in the
+// implementation file.
+struct WritableIoVec {
+  //! \brief The base address of a memory region for output.
+  const void* iov_base;
+
+  //! \brief The size of the memory pointed to by #iov_base.
+  size_t iov_len;
+};
+
+//! \brief An interface to write to files and other file-like objects with
+//!     semantics matching the underlying platform (POSIX or Windows).
+class FileWriterInterface : public virtual FileSeekerInterface {
+ public:
+  virtual ~FileWriterInterface() {}
+
+  //! \brief Wraps LoggingWriteFile(), or provides an implementation with
+  //!     identical semantics.
+  //!
+  //! \return `true` if the operation succeeded, `false` if it failed, with an
+  //!     error message logged.
+  virtual bool Write(const void* data, size_t size) = 0;
+
+  //! \brief Wraps `writev()` on POSIX or provides an alternate implementation
+  //!     with identical semantics. This method will write entire buffers,
+  //!     continuing after a short write or after being interrupted. On
+  //!     non-POSIX this is a simple wrapper around Write().
+  //!
+  //! \return `true` if the operation succeeded, `false` if it failed, with an
+  //!     error message logged.
+  //!
+  //! \note The contents of \a iovecs are undefined when this method returns.
+  virtual bool WriteIoVec(std::vector<WritableIoVec>* iovecs) = 0;
+};
+
+//! \brief A file writer backed by a FileHandle.
+//!
+//! FileWriter requires users to provide a FilePath to open, but this class
+//! accepts an already-open FileHandle instead. Like FileWriter, this class may
+//! write to a filesystem-based file, but unlike FileWriter, this class is not
+//! responsible for creating or closing the file. Users of this class must
+//! ensure that the file handle is closed appropriately elsewhere. Objects of
+//! this class may be used to write to file handles not associated with
+//! filesystem-based files, although special attention should be paid to the
+//! Seek() method, which may not function on file handles that do not refer to
+//! disk-based files.
+//!
+//! This class is expected to be used when other code is responsible for
+//! creating files and already provides file handles.
+class WeakFileHandleFileWriter : public FileWriterInterface {
+ public:
+  explicit WeakFileHandleFileWriter(FileHandle file_handle);
+  ~WeakFileHandleFileWriter() override;
+
+  // FileWriterInterface:
+  bool Write(const void* data, size_t size) override;
+  bool WriteIoVec(std::vector<WritableIoVec>* iovecs) override;
+
+  // FileSeekerInterface:
+
+  //! \copydoc FileWriterInterface::Seek()
+  //!
+  //! \note This method is only guaranteed to function on file handles referring
+  //!     to disk-based files.
+  FileOffset Seek(FileOffset offset, int whence) override;
+
+ private:
+  void set_file_handle(FileHandle file_handle) { file_handle_ = file_handle; }
+
+  FileHandle file_handle_;  // weak
+
+  // FileWriter uses this class as its internal implementation, and it needs to
+  // be able to call set_file_handle(). FileWriter cannot initialize a
+  // WeakFileHandleFileWriter with a correct file descriptor at the time of
+  // construction because no file descriptor will be available until
+  // FileWriter::Open() is called.
+  friend class FileWriter;
+
+  DISALLOW_COPY_AND_ASSIGN(WeakFileHandleFileWriter);
+};
+
+//! \brief A file writer implementation that wraps traditional system file
+//!     operations on files accessed through the filesystem.
+class FileWriter : public FileWriterInterface {
+ public:
+  FileWriter();
+  ~FileWriter() override;
+
+  // FileWriterInterface:
+
+  //! \brief Wraps LoggingOpenFileForWrite().
+  //!
+  //! \return `true` if the operation succeeded, `false` if it failed, with an
+  //!     error message logged.
+  //!
+  //! \note After a successful call, this method cannot be called again until
+  //!     after Close().
+  bool Open(const base::FilePath& path,
+            FileWriteMode write_mode,
+            FilePermissions permissions);
+
+  //! \brief Wraps CheckedCloseHandle().
+  //!
+  //! \note It is only valid to call this method on an object that has had a
+  //!     successful Open() that has not yet been matched by a subsequent call
+  //!     to this method.
+  void Close();
+
+  // FileWriterInterface:
+
+  //! \copydoc FileWriterInterface::Write()
+  //!
+  //! \note It is only valid to call this method between a successful Open() and
+  //!     a Close().
+  bool Write(const void* data, size_t size) override;
+
+  //! \copydoc FileWriterInterface::WriteIoVec()
+  //!
+  //! \note It is only valid to call this method between a successful Open() and
+  //!     a Close().
+  bool WriteIoVec(std::vector<WritableIoVec>* iovecs) override;
+
+  // FileSeekerInterface:
+
+  //! \copydoc FileWriterInterface::Seek()
+  //!
+  //! \note It is only valid to call this method between a successful Open() and
+  //!     a Close().
+  FileOffset Seek(FileOffset offset, int whence) override;
+
+ private:
+  ScopedFileHandle file_;
+  WeakFileHandleFileWriter weak_file_handle_file_writer_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileWriter);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_FILE_FILE_WRITER_H_