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// 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/files/file_path.h"
#include "base/macros.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);
#if defined(OS_LINUX)
//! \brief Wraps LoggingOpenMemoryFileForWrite().
//!
//! \return `true` if the operation succeeded, `false` if it failed, with an
//! error message logged.
//!
//! \note After a successful call, this method or Open() cannot be called
// again until after Close().
bool OpenMemfd(const base::FilePath& path);
//! \brief Returns the underlying file descriptor.
//!
//! \note This is used when this writes to a Memfd.
int fd();
#endif
//! \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_