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 #ifdef HAVE_WIN32_FILEMAP 26 #include <windows.h> 27 #endif 28 29 namespace android { 30 31 /* 32 * This represents a memory-mapped file. It might be the entire file or 33 * only part of it. This requires a little bookkeeping because the mapping 34 * needs to be aligned on page boundaries, and in some cases we'd like to 35 * have multiple references to the mapped area without creating additional 36 * maps. 37 * 38 * This always uses MAP_SHARED. 39 * 40 * TODO: we should be able to create a new FileMap that is a subset of 41 * an existing FileMap and shares the underlying mapped pages. Requires 42 * completing the refcounting stuff and possibly introducing the notion 43 * of a FileMap hierarchy. 44 */ 45 class FileMap { 46 public: 47 FileMap(void); 48 49 /* 50 * Create a new mapping on an open file. 51 * 52 * Closing the file descriptor does not unmap the pages, so we don't 53 * claim ownership of the fd. 54 * 55 * Returns "false" on failure. 56 */ 57 bool create(const char* origFileName, int fd, 58 off_t offset, size_t length, bool readOnly); 59 60 /* 61 * Return the name of the file this map came from, if known. 62 */ getFileName(void)63 const char* getFileName(void) const { return mFileName; } 64 65 /* 66 * Get a pointer to the piece of the file we requested. 67 */ getDataPtr(void)68 void* getDataPtr(void) const { return mDataPtr; } 69 70 /* 71 * Get the length we requested. 72 */ getDataLength(void)73 size_t getDataLength(void) const { return mDataLength; } 74 75 /* 76 * Get the data offset used to create this map. 77 */ getDataOffset(void)78 off_t getDataOffset(void) const { return mDataOffset; } 79 80 /* 81 * Get a "copy" of the object. 82 */ acquire(void)83 FileMap* acquire(void) { mRefCount++; return this; } 84 85 /* 86 * Call this when mapping is no longer needed. 87 */ release(void)88 void release(void) { 89 if (--mRefCount <= 0) 90 delete this; 91 } 92 93 /* 94 * This maps directly to madvise() values, but allows us to avoid 95 * including <sys/mman.h> everywhere. 96 */ 97 enum MapAdvice { 98 NORMAL, RANDOM, SEQUENTIAL, WILLNEED, DONTNEED 99 }; 100 101 /* 102 * Apply an madvise() call to the entire file. 103 * 104 * Returns 0 on success, -1 on failure. 105 */ 106 int advise(MapAdvice advice); 107 108 protected: 109 // don't delete objects; call release() 110 ~FileMap(void); 111 112 private: 113 // these are not implemented 114 FileMap(const FileMap& src); 115 const FileMap& operator=(const FileMap& src); 116 117 int mRefCount; // reference count 118 char* mFileName; // original file name, if known 119 void* mBasePtr; // base of mmap area; page aligned 120 size_t mBaseLength; // length, measured from "mBasePtr" 121 off_t mDataOffset; // offset used when map was created 122 void* mDataPtr; // start of requested data, offset from base 123 size_t mDataLength; // length, measured from "mDataPtr" 124 #ifdef HAVE_WIN32_FILEMAP 125 HANDLE mFileHandle; // Win32 file handle 126 HANDLE mFileMapping; // Win32 file mapping handle 127 #endif 128 129 static long mPageSize; 130 }; 131 132 }; // namespace android 133 134 #endif // __LIBS_FILE_MAP_H 135