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