The Android Open Source Project | 54b6cfa | 2008-10-21 07:00:00 -0700 | [diff] [blame^] | 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 | */ |
| 63 | const char* getFileName(void) const { return mFileName; } |
| 64 | |
| 65 | /* |
| 66 | * Get a pointer to the piece of the file we requested. |
| 67 | */ |
| 68 | void* getDataPtr(void) const { return mDataPtr; } |
| 69 | |
| 70 | /* |
| 71 | * Get the length we requested. |
| 72 | */ |
| 73 | size_t getDataLength(void) const { return mDataLength; } |
| 74 | |
| 75 | /* |
| 76 | * Get the data offset used to create this map. |
| 77 | */ |
| 78 | off_t getDataOffset(void) const { return mDataOffset; } |
| 79 | |
| 80 | /* |
| 81 | * Get a "copy" of the object. |
| 82 | */ |
| 83 | FileMap* acquire(void) { mRefCount++; return this; } |
| 84 | |
| 85 | /* |
| 86 | * Call this when mapping is no longer needed. |
| 87 | */ |
| 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 |