/*
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* Copyright (C) 2011 The Android Open Source Project
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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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*/
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#ifndef ART_LIBARTBASE_BASE_SCOPED_FLOCK_H_
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#define ART_LIBARTBASE_BASE_SCOPED_FLOCK_H_
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#include <memory>
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#include <string>
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#include <android-base/unique_fd.h>
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#include "macros.h"
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#include "os.h"
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#include "unix_file/fd_file.h"
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namespace art {
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class LockedFile;
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class LockedFileCloseNoFlush;
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// A scoped File object that calls Close without flushing.
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typedef std::unique_ptr<LockedFile, LockedFileCloseNoFlush> ScopedFlock;
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class LockedFile : public unix_file::FdFile {
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public:
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// Attempts to acquire an exclusive file lock (see flock(2)) on the file
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// at filename, and blocks until it can do so.
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//
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// It is an error if its inode changed (usually due to a new file being
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// created at the same path) between attempts to lock it. In blocking mode,
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// locking will be retried if the file changed. In non-blocking mode, false
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// is returned and no attempt is made to re-acquire the lock.
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//
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// The file is opened with the provided flags.
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static ScopedFlock Open(const char* filename, int flags, bool block,
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std::string* error_msg);
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// Calls Open(filename, O_CREAT | O_RDWR, true, errror_msg)
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static ScopedFlock Open(const char* filename, std::string* error_msg);
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// Attempt to acquire an exclusive file lock (see flock(2)) on 'file'.
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// Returns true if the lock could be acquired or false if an error
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// occured.
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static ScopedFlock DupOf(const int fd, const std::string& path,
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const bool read_only_mode, std::string* error_message);
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// Release a lock held on this file, if any.
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void ReleaseLock();
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private:
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// Constructors should not be invoked directly, use one of the factory
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// methods instead.
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explicit LockedFile(FdFile&& other) : FdFile(std::move(other)) {
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}
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// Constructors should not be invoked directly, use one of the factory
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// methods instead.
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LockedFile(int fd, const std::string& path, bool check_usage, bool read_only_mode)
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: FdFile(fd, path, check_usage, read_only_mode) {
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}
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};
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class LockedFileCloseNoFlush {
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public:
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void operator()(LockedFile* ptr) {
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ptr->ReleaseLock();
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UNUSED(ptr->Close());
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delete ptr;
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}
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};
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} // namespace art
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#endif // ART_LIBARTBASE_BASE_SCOPED_FLOCK_H_
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