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