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/*
* Copyright (C) 2009 The Android Open Source Project
*
* 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 ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
#define ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
#include <fcntl.h>
#include <string>
#include "base/macros.h"
#include "random_access_file.h"
namespace unix_file {
// If true, check whether Flush and Close are called before destruction.
static constexpr bool kCheckSafeUsage = true;
// A RandomAccessFile implementation backed by a file descriptor.
//
// Not thread safe.
class FdFile : public RandomAccessFile {
public:
FdFile() = default;
// Creates an FdFile using the given file descriptor.
// Takes ownership of the file descriptor.
FdFile(int fd, bool check_usage);
FdFile(int fd, const std::string& path, bool check_usage);
FdFile(int fd, const std::string& path, bool check_usage, bool read_only_mode);
FdFile(const std::string& path, int flags, bool check_usage)
: FdFile(path, flags, 0640, check_usage) {}
FdFile(const std::string& path, int flags, mode_t mode, bool check_usage);
// Move constructor.
FdFile(FdFile&& other) noexcept;
// Move assignment operator.
FdFile& operator=(FdFile&& other) noexcept;
// Release the file descriptor. This will make further accesses to this FdFile invalid. Disables
// all further state checking.
int Release();
void Reset(int fd, bool check_usage);
// Destroys an FdFile, closing the file descriptor if Close hasn't already
// been called. (If you care about the return value of Close, call it
// yourself; this is meant to handle failure cases and read-only accesses.
// Note though that calling Close and checking its return value is still no
// guarantee that data actually made it to stable storage.)
virtual ~FdFile();
// RandomAccessFile API.
int Close() override WARN_UNUSED;
int64_t Read(char* buf, int64_t byte_count, int64_t offset) const override WARN_UNUSED;
int SetLength(int64_t new_length) override WARN_UNUSED;
int64_t GetLength() const override;
int64_t Write(const char* buf, int64_t byte_count, int64_t offset) override WARN_UNUSED;
int Flush() override WARN_UNUSED;
// Short for SetLength(0); Flush(); Close();
// If the file was opened with a path name and unlink = true, also calls Unlink() on the path.
// Note that it is the the caller's responsibility to avoid races.
bool Erase(bool unlink = false);
// Call unlink() if the file was opened with a path, and if open() with the name shows that
// the file descriptor of this file is still up-to-date. This is still racy, though, and it
// is up to the caller to ensure correctness in a multi-process setup.
bool Unlink();
// Try to Flush(), then try to Close(); If either fails, call Erase().
int FlushCloseOrErase() WARN_UNUSED;
// Try to Flush and Close(). Attempts both, but returns the first error.
int FlushClose() WARN_UNUSED;
// Bonus API.
int Fd() const;
bool ReadOnlyMode() const;
bool CheckUsage() const;
bool IsOpened() const;
const std::string& GetPath() const {
return file_path_;
}
bool ReadFully(void* buffer, size_t byte_count) WARN_UNUSED;
bool PreadFully(void* buffer, size_t byte_count, size_t offset) WARN_UNUSED;
bool WriteFully(const void* buffer, size_t byte_count) WARN_UNUSED;
bool PwriteFully(const void* buffer, size_t byte_count, size_t offset) WARN_UNUSED;
// Copy data from another file.
bool Copy(FdFile* input_file, int64_t offset, int64_t size);
// Clears the file content and resets the file offset to 0.
// Returns true upon success, false otherwise.
bool ClearContent();
// Resets the file offset to the beginning of the file.
bool ResetOffset();
// This enum is public so that we can define the << operator over it.
enum class GuardState {
kBase, // Base, file has not been flushed or closed.
kFlushed, // File has been flushed, but not closed.
kClosed, // File has been flushed and closed.
kNoCheck // Do not check for the current file instance.
};
// WARNING: Only use this when you know what you're doing!
void MarkUnchecked();
// Compare against another file. Returns 0 if the files are equivalent, otherwise returns -1 or 1
// depending on if the lenghts are different. If the lengths are the same, the function returns
// the difference of the first byte that differs.
int Compare(FdFile* other);
protected:
// If the guard state indicates checking (!=kNoCheck), go to the target state "target". Print the
// given warning if the current state is or exceeds warn_threshold.
void moveTo(GuardState target, GuardState warn_threshold, const char* warning);
// If the guard state indicates checking (<kNoCheck), and is below the target state "target", go
// to "target." If the current state is higher (excluding kNoCheck) than the trg state, print the
// warning.
void moveUp(GuardState target, const char* warning);
// Forcefully sets the state to the given one. This can overwrite kNoCheck.
void resetGuard(GuardState new_state) {
if (kCheckSafeUsage) {
guard_state_ = new_state;
}
}
GuardState guard_state_ = GuardState::kClosed;
// Opens file 'file_path' using 'flags' and 'mode'.
bool Open(const std::string& file_path, int flags);
bool Open(const std::string& file_path, int flags, mode_t mode);
private:
template <bool kUseOffset>
bool WriteFullyGeneric(const void* buffer, size_t byte_count, size_t offset);
void Destroy(); // For ~FdFile and operator=(&&).
int fd_ = -1;
std::string file_path_;
bool read_only_mode_ = false;
DISALLOW_COPY_AND_ASSIGN(FdFile);
};
std::ostream& operator<<(std::ostream& os, const FdFile::GuardState& kind);
} // namespace unix_file
#endif // ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
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