135 lines
3.7 KiB
C++
135 lines
3.7 KiB
C++
/*
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* Copyright (C) 2006 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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//
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// Encapsulate a shared file mapping.
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//
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#ifndef __LIBS_FILE_MAP_H
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#define __LIBS_FILE_MAP_H
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#include <sys/types.h>
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#ifdef HAVE_WIN32_FILEMAP
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#include <windows.h>
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#endif
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namespace android {
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/*
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* This represents a memory-mapped file. It might be the entire file or
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* only part of it. This requires a little bookkeeping because the mapping
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* needs to be aligned on page boundaries, and in some cases we'd like to
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* have multiple references to the mapped area without creating additional
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* maps.
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*
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* This always uses MAP_SHARED.
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*
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* TODO: we should be able to create a new FileMap that is a subset of
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* an existing FileMap and shares the underlying mapped pages. Requires
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* completing the refcounting stuff and possibly introducing the notion
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* of a FileMap hierarchy.
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*/
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class FileMap {
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public:
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FileMap(void);
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/*
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* Create a new mapping on an open file.
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*
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* Closing the file descriptor does not unmap the pages, so we don't
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* claim ownership of the fd.
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*
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* Returns "false" on failure.
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*/
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bool create(const char* origFileName, int fd,
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off_t offset, size_t length, bool readOnly);
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/*
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* Return the name of the file this map came from, if known.
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*/
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const char* getFileName(void) const { return mFileName; }
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/*
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* Get a pointer to the piece of the file we requested.
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*/
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void* getDataPtr(void) const { return mDataPtr; }
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/*
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* Get the length we requested.
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*/
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size_t getDataLength(void) const { return mDataLength; }
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/*
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* Get the data offset used to create this map.
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*/
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off_t getDataOffset(void) const { return mDataOffset; }
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/*
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* Get a "copy" of the object.
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*/
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FileMap* acquire(void) { mRefCount++; return this; }
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/*
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* Call this when mapping is no longer needed.
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*/
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void release(void) {
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if (--mRefCount <= 0)
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delete this;
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}
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/*
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* This maps directly to madvise() values, but allows us to avoid
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* including <sys/mman.h> everywhere.
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*/
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enum MapAdvice {
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NORMAL, RANDOM, SEQUENTIAL, WILLNEED, DONTNEED
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};
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/*
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* Apply an madvise() call to the entire file.
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*
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* Returns 0 on success, -1 on failure.
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*/
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int advise(MapAdvice advice);
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protected:
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// don't delete objects; call release()
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~FileMap(void);
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private:
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// these are not implemented
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FileMap(const FileMap& src);
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const FileMap& operator=(const FileMap& src);
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int mRefCount; // reference count
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char* mFileName; // original file name, if known
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void* mBasePtr; // base of mmap area; page aligned
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size_t mBaseLength; // length, measured from "mBasePtr"
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off_t mDataOffset; // offset used when map was created
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void* mDataPtr; // start of requested data, offset from base
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size_t mDataLength; // length, measured from "mDataPtr"
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#ifdef HAVE_WIN32_FILEMAP
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HANDLE mFileHandle; // Win32 file handle
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HANDLE mFileMapping; // Win32 file mapping handle
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#endif
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static long mPageSize;
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};
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}; // namespace android
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#endif // __LIBS_FILE_MAP_H
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