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* Copyright 2015 Facebook, Inc.
* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#ifndef FOLLY_FILE_H_
#define FOLLY_FILE_H_
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string>
#include <folly/Portability.h>
#include <folly/Range.h>
namespace folly {
* A File represents an open file.
class File {
* Creates an empty File object, for late initialization.
* Create a File object from an existing file descriptor.
* Takes ownership of the file descriptor if ownsFd is true.
explicit File(int fd, bool ownsFd = false);
* Open and create a file object. Throws on error.
explicit File(const char* name, int flags = O_RDONLY, mode_t mode = 0666);
explicit File(
const std::string& name, int flags = O_RDONLY, mode_t mode = 0666);
explicit File(StringPiece name, int flags = O_RDONLY, mode_t mode = 0666);
* Create and return a temporary, owned file (uses tmpfile()).
static File temporary();
* Return the file descriptor, or -1 if the file was closed.
int fd() const { return fd_; }
* Returns 'true' iff the file was successfully opened.
explicit operator bool() const {
return fd_ != -1;
* Duplicate file descriptor and return File that owns it.
File dup() const;
* If we own the file descriptor, close the file and throw on error.
* Otherwise, do nothing.
void close();
* Closes the file (if owned). Returns true on success, false (and sets
* errno) on error.
bool closeNoThrow();
* Returns and releases the file descriptor; no longer owned by this File.
* Returns -1 if the File object didn't wrap a file.
int release() noexcept;
* Swap this File with another.
void swap(File& other);
// movable
File(File&&) noexcept;
File& operator=(File&&);
// NOTE THAT THESE LOCKS ARE flock() LOCKS. That is, they may only be used
// for inter-process synchronization -- an attempt to acquire a second lock
// on the same file descriptor from the same process may succeed. Attempting
// to acquire a second lock on a different file descriptor for the same file
// should fail, but some systems might implement flock() using fcntl() locks,
// in which case it will succeed.
void lock();
bool try_lock();
void unlock();
void lock_shared();
bool try_lock_shared();
void unlock_shared();
void doLock(int op);
bool doTryLock(int op);
// unique
File(const File&) = delete;
File& operator=(const File&) = delete;
int fd_;
bool ownsFd_;
void swap(File& a, File& b);
} // namespace folly
#endif /* FOLLY_FILE_H_ */