159 lines
3.9 KiB
C++
159 lines
3.9 KiB
C++
/*
|
|
* Copyright 2013-present 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
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <fcntl.h>
|
|
#include <sys/stat.h>
|
|
#include <sys/types.h>
|
|
|
|
#include <string>
|
|
#include <system_error>
|
|
|
|
#include <folly/ExceptionWrapper.h>
|
|
#include <folly/Expected.h>
|
|
#include <folly/Portability.h>
|
|
#include <folly/Range.h>
|
|
#include <folly/portability/Unistd.h>
|
|
|
|
namespace folly {
|
|
|
|
/**
|
|
* A File represents an open file.
|
|
*/
|
|
class File {
|
|
public:
|
|
/**
|
|
* Creates an empty File object, for late initialization.
|
|
*/
|
|
File() noexcept;
|
|
|
|
/**
|
|
* 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) noexcept;
|
|
|
|
/**
|
|
* Open and create a file object. Throws on error.
|
|
* Owns the file descriptor implicitly.
|
|
*/
|
|
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);
|
|
|
|
/**
|
|
* All the constructors that are not noexcept can throw std::system_error.
|
|
* This is a helper method to use folly::Expected to chain a file open event
|
|
* to something else you want to do with the open fd.
|
|
*/
|
|
template <typename... Args>
|
|
static Expected<File, exception_wrapper> makeFile(Args&&... args) noexcept {
|
|
try {
|
|
return File(std::forward<Args>(args)...);
|
|
} catch (const std::system_error& se) {
|
|
return makeUnexpected(exception_wrapper(std::current_exception(), se));
|
|
}
|
|
}
|
|
|
|
~File();
|
|
|
|
/**
|
|
* 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) noexcept;
|
|
|
|
// movable
|
|
File(File&&) noexcept;
|
|
File& operator=(File&&);
|
|
|
|
// FLOCK (INTERPROCESS) LOCKS
|
|
//
|
|
// 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();
|
|
|
|
private:
|
|
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) noexcept;
|
|
|
|
} // namespace folly
|