111 lines
5.5 KiB
C++
111 lines
5.5 KiB
C++
/*
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* IAsyncFile.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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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 FLOW_IASYNCFILE_H
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#define FLOW_IASYNCFILE_H
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#pragma once
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#include "flow/flow.h"
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// All outstanding operations must be cancelled before the destructor of IAsyncFile is called.
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// The desirability of the above semantic is disputed. Some classes (AsyncFileBlobStore,
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// AsyncFileCached) maintain references, while others (AsyncFileNonDurable) don't, and the comment
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// is unapplicable to some others as well (AsyncFileKAIO). It's safest to assume that all operations
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// must complete or cancel, but you should probably look at the file implementations you'll be using.
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class IAsyncFile {
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public:
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virtual ~IAsyncFile();
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// Pass these to g_network->open to get an IAsyncFile
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enum {
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// Implementation relies on the low bits being the same as the SQLite flags (this is validated by a static_assert there)
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OPEN_READONLY = 0x1,
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OPEN_READWRITE = 0x2,
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OPEN_CREATE = 0x4,
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OPEN_EXCLUSIVE = 0x10,
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// Further flag values are arbitrary bits
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OPEN_UNBUFFERED = 0x10000,
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OPEN_UNCACHED = 0x20000,
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OPEN_LOCK = 0x40000,
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OPEN_ATOMIC_WRITE_AND_CREATE = 0x80000, // A temporary file is opened, and on the first call to sync() it is atomically renamed to the given filename
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OPEN_LARGE_PAGES = 0x100000,
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OPEN_NO_AIO = 0x200000, // Don't use AsyncFileKAIO or similar implementations that rely on filesystem support for AIO
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OPEN_CACHED_READ_ONLY = 0x400000 // AsyncFileCached opens files read/write even if you specify read only
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};
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virtual void addref() = 0;
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virtual void delref() = 0;
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// For read() and write(), the data buffer must remain valid until the future is ready
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virtual Future<int> read( void* data, int length, int64_t offset ) = 0; // Returns number of bytes actually read (from [0,length])
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virtual Future<Void> write( void const* data, int length, int64_t offset ) = 0;
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// The zeroed data is not guaranteed to be durable after `zeroRange` returns. A call to sync() would be required.
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// This operation holds a reference to the AsyncFile, and does not need to be cancelled before a reference is dropped.
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virtual Future<Void> zeroRange( int64_t offset, int64_t length );
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virtual Future<Void> truncate( int64_t size ) = 0;
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virtual Future<Void> sync() = 0;
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virtual Future<Void> flush() { return Void(); } // Sends previous writes to the OS if they have been buffered in memory, but does not make them power safe
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virtual Future<int64_t> size() = 0;
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virtual std::string getFilename() = 0;
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// Attempt to read the *length bytes at offset without copying. If successful, a pointer to the
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// requested bytes is written to *data, and the number of bytes successfully read is
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// written to *length. If unsuccessful, *data and *length are undefined.
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// readZeroCopy may fail (returning io_error) at any time, even if the requested bytes are readable.
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// For example, an implementation of IAsyncFile may not implement readZeroCopy or may implement it
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// only in certain cases (e.g. when the requested range does not cross a page boundary). So callers
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// should always retry a failed readZeroCopy as a read().
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// Once readZeroCopy succeeds, the returned bytes will be pinned in memory until releaseZeroCopy is
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// called, so the caller must always ensure that a matching call to releaseZeroCopy takes place.
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// Between readZeroCopy and releaseZeroCopy, it is illegal (undefined behavior) to concurrently write
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// to an overlapping range of bytes, whether or not using the same IAsyncFile handle.
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virtual Future<Void> readZeroCopy( void** data, int* length, int64_t offset ) { return io_error(); }
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virtual void releaseZeroCopy( void* data, int length, int64_t offset ) {}
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virtual int64_t debugFD() = 0;
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};
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typedef void (*runCycleFuncPtr)();
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class IAsyncFileSystem {
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public:
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// Opens a file for asynchronous I/O
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virtual Future< Reference<class IAsyncFile> > open( std::string filename, int64_t flags, int64_t mode ) = 0;
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// Deletes the given file. If mustBeDurable, returns only when the file is guaranteed to be deleted even after a power failure.
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virtual Future< Void > deleteFile( std::string filename, bool mustBeDurable ) = 0;
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// Unlinks a file and then deletes it slowly by truncating the file repeatedly.
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// If mustBeDurable, returns only when the file is guaranteed to be deleted even after a power failure.
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virtual Future<Void> incrementalDeleteFile( std::string filename, bool mustBeDurable );
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static IAsyncFileSystem* filesystem() { return filesystem(g_network); }
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static runCycleFuncPtr runCycleFunc() { return reinterpret_cast<runCycleFuncPtr>(reinterpret_cast<flowGlobalType>(g_network->global(INetwork::enRunCycleFunc))); }
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static IAsyncFileSystem* filesystem(INetwork* networkPtr) { return static_cast<IAsyncFileSystem*>(networkPtr->global(INetwork::enFileSystem)); }
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protected:
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IAsyncFileSystem() {}
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virtual ~IAsyncFileSystem() {} // Please don't try to delete through this interface!
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};
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#endif
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