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      1 /*
      2  * Copyright (C) 2006 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 //
     18 // Encapsulate a shared file mapping.
     19 //
     20 #ifndef __LIBS_FILE_MAP_H
     21 #define __LIBS_FILE_MAP_H
     22 
     23 #include <sys/types.h>
     24 
     25 #include <utils/Compat.h>
     26 
     27 #if defined(__MINGW32__)
     28 // Ensure that we always pull in winsock2.h before windows.h
     29 #ifdef HAVE_WINSOCK
     30 #include <winsock2.h>
     31 #endif
     32 #include <windows.h>
     33 #endif
     34 
     35 namespace android {
     36 
     37 /*
     38  * This represents a memory-mapped file.  It might be the entire file or
     39  * only part of it.  This requires a little bookkeeping because the mapping
     40  * needs to be aligned on page boundaries, and in some cases we'd like to
     41  * have multiple references to the mapped area without creating additional
     42  * maps.
     43  *
     44  * This always uses MAP_SHARED.
     45  *
     46  * TODO: we should be able to create a new FileMap that is a subset of
     47  * an existing FileMap and shares the underlying mapped pages.  Requires
     48  * completing the refcounting stuff and possibly introducing the notion
     49  * of a FileMap hierarchy.
     50  */
     51 class FileMap {
     52 public:
     53     FileMap(void);
     54 
     55     /*
     56      * Create a new mapping on an open file.
     57      *
     58      * Closing the file descriptor does not unmap the pages, so we don't
     59      * claim ownership of the fd.
     60      *
     61      * Returns "false" on failure.
     62      */
     63     bool create(const char* origFileName, int fd,
     64                 off64_t offset, size_t length, bool readOnly);
     65 
     66     ~FileMap(void);
     67 
     68     /*
     69      * Return the name of the file this map came from, if known.
     70      */
     71     const char* getFileName(void) const { return mFileName; }
     72 
     73     /*
     74      * Get a pointer to the piece of the file we requested.
     75      */
     76     void* getDataPtr(void) const { return mDataPtr; }
     77 
     78     /*
     79      * Get the length we requested.
     80      */
     81     size_t getDataLength(void) const { return mDataLength; }
     82 
     83     /*
     84      * Get the data offset used to create this map.
     85      */
     86     off64_t getDataOffset(void) const { return mDataOffset; }
     87 
     88     /*
     89      * This maps directly to madvise() values, but allows us to avoid
     90      * including <sys/mman.h> everywhere.
     91      */
     92     enum MapAdvice {
     93         NORMAL, RANDOM, SEQUENTIAL, WILLNEED, DONTNEED
     94     };
     95 
     96     /*
     97      * Apply an madvise() call to the entire file.
     98      *
     99      * Returns 0 on success, -1 on failure.
    100      */
    101     int advise(MapAdvice advice);
    102 
    103 protected:
    104 
    105 private:
    106     // these are not implemented
    107     FileMap(const FileMap& src);
    108     const FileMap& operator=(const FileMap& src);
    109 
    110     char*       mFileName;      // original file name, if known
    111     void*       mBasePtr;       // base of mmap area; page aligned
    112     size_t      mBaseLength;    // length, measured from "mBasePtr"
    113     off64_t     mDataOffset;    // offset used when map was created
    114     void*       mDataPtr;       // start of requested data, offset from base
    115     size_t      mDataLength;    // length, measured from "mDataPtr"
    116 #if defined(__MINGW32__)
    117     HANDLE      mFileHandle;    // Win32 file handle
    118     HANDLE      mFileMapping;   // Win32 file mapping handle
    119 #endif
    120 
    121     static long mPageSize;
    122 };
    123 
    124 }; // namespace android
    125 
    126 #endif // __LIBS_FILE_MAP_H
    127