OSX/libsecurity_filedb/lib/AtomicFile.h

   1 /*
   2  * Copyright (c) 2000-2001,2003,2011-2012,2014 Apple Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 //  AtomicFile.h - Description t.b.d.
  21 //
  22 #ifndef _SECURITY_ATOMICFILE_H_
  23 #define _SECURITY_ATOMICFILE_H_  1
  24
  25 #include <security_utilities/refcount.h>
  26 #include <Security/cssm.h>
  27 #include <string>
  28 #include <sys/stat.h>
  29
  30 namespace Security
  31 {
  32
  33 class AtomicBufferedFile;
  34 class AtomicLockedFile;
  35 class AtomicTempFile;
  36
  37 class AtomicFile
  38 {
  39 public:
  40         AtomicFile(const std::string &inPath);
  41         ~AtomicFile();
  42
  43     // Acquire the write lock and remove the file.
  44     void performDelete();
  45
  46     // Acquire the write lock and rename the file.
  47     void rename(const std::string &inNewPath);
  48
  49         // Lock the file for writing and return a newly created AtomicTempFile.
  50     RefPointer<AtomicTempFile> create(mode_t mode);
  51
  52     // Lock the file for writing and return a newly created AtomicTempFile.
  53         RefPointer<AtomicTempFile> write();
  54
  55         // Return a bufferedFile containing current version of the file for reading.
  56         RefPointer<AtomicBufferedFile> read();
  57
  58         const string& path() const { return mPath; }
  59         const string& dir() const { return mDir; }
  60         const string& file() const { return mFile; }
  61         const string& lockFileName() { return mLockFilePath; }
  62
  63         mode_t mode() const;
  64         bool isOnLocalFileSystem() {return mIsLocalFileSystem;}
  65
  66     enum OffsetType
  67         {
  68         FromStart,
  69                 FromEnd                 // only works with offset of 0
  70     };
  71
  72         static void pathSplit(const std::string &inFull, std::string &outDir, std::string &outFile);
  73         static void mkpath(const std::string &inDir, mode_t mode = 0777);
  74         static int ropen(const char *const name, int flags, mode_t mode);
  75         static int rclose(int fd);
  76
  77 private:
  78         bool mIsLocalFileSystem;
  79         string mPath;
  80         string mDir;
  81         string mFile;
  82         string mLockFilePath;
  83 };
  84
  85
  86 //
  87 // AtomicBufferedFile - This represents an instance of a file opened for reading.
  88 // The file is read into memory and closed after this is done.
  89 // The memory is released when this object is destroyed.
  90 //
  91 class AtomicBufferedFile : public RefCount
  92 {
  93 public:
  94         AtomicBufferedFile(const std::string &inPath, bool isLocalFileSystem);
  95         ~AtomicBufferedFile();
  96
  97         // Open the file and return it's size.
  98         off_t open();
  99
 100         // Read inLength bytes starting at inOffset.
 101         const uint8 *read(off_t inOffset, off_t inLength, off_t &outLength);
 102
 103         // Return the current mode bits of the file
 104         mode_t mode();
 105
 106         // Close the file (this doesn't release the buffer).
 107         void close();
 108
 109         // Return the length of the file.
 110         off_t length() const { return mLength; }
 111
 112 private:
 113         void loadBuffer();
 114         void unloadBuffer();
 115
 116 private:
 117         // Complete path to the file
 118         string mPath;
 119
 120         // File descriptor to the file or -1 if it's not currently open.
 121         int mFileRef;
 122
 123         // This is where the data from the file is read in to.
 124         uint8 *mBuffer;
 125
 126         // Length of file in bytes.
 127         off_t mLength;
 128 };
 129
 130
 131 //
 132 // AtomicTempFile - A temporary file to write changes to.
 133 //
 134 class AtomicTempFile : public RefCount
 135 {
 136 public:
 137         // Start a write for a new file.
 138         AtomicTempFile(AtomicFile &inFile, const RefPointer<AtomicLockedFile> &inLockedFile, mode_t mode);
 139
 140         // Start a write of an existing file.
 141         AtomicTempFile(AtomicFile &inFile, const RefPointer<AtomicLockedFile> &inLockedFile);
 142
 143         ~AtomicTempFile();
 144
 145     // Commit the current create or write and close the write file.
 146     void commit();
 147
 148     void write(AtomicFile::OffsetType inOffsetType, off_t inOffset, const uint32 *inData, uint32 inCount);
 149     void write(AtomicFile::OffsetType inOffsetType, off_t inOffset, const uint8 *inData, size_t inLength);
 150     void write(AtomicFile::OffsetType inOffsetType, off_t inOffset, const uint32 inData);
 151
 152 private:
 153         // Called by both constructors.
 154         void create(mode_t mode);
 155
 156         // Fsync the file
 157         void fsync();
 158
 159         // Close the file
 160         void close();
 161
 162     // Rollback the current create or write (happens automatically if commit() isn't called before the destructor is).
 163     void rollback() _NOEXCEPT;
 164
 165 private:
 166         // Our AtomicFile object.
 167         AtomicFile &mFile;
 168
 169         RefPointer<AtomicLockedFile> mLockedFile;
 170
 171         // Complete path to the file
 172         string mPath;
 173
 174         // File descriptor to the file or -1 if it's not currently open.
 175         int mFileRef;
 176
 177         // If this is true we unlink both mPath and mFile.path() when we rollback.
 178         bool mCreating;
 179 };
 180
 181
 182 class FileLocker
 183 {
 184 public:
 185         virtual ~FileLocker();
 186
 187         virtual void lock(mode_t mode) = 0;
 188         virtual void unlock() = 0;
 189 };
 190
 191
 192
 193 class LocalFileLocker : public FileLocker
 194 {
 195 public:
 196         LocalFileLocker(AtomicFile &inFile);
 197         virtual ~LocalFileLocker();
 198
 199         virtual void lock(mode_t mode);
 200         virtual void unlock();
 201
 202 private:
 203         int mLockFile;
 204         string mPath;
 205 };
 206
 207
 208
 209 class NetworkFileLocker : public FileLocker
 210 {
 211 public:
 212         NetworkFileLocker(AtomicFile &inFile);
 213         virtual ~NetworkFileLocker();
 214
 215         virtual void lock(mode_t mode);
 216         virtual void unlock();
 217
 218 private:
 219         std::string unique(mode_t mode);
 220         int rlink(const char *const old, const char *const newn, struct stat &sto);
 221         int myrename(const char *const old, const char *const newn);
 222         int xcreat(const char *const name, mode_t mode, time_t &tim);
 223
 224         // The directory in which we create the lock
 225         string mDir;
 226
 227         // Complete path to the file
 228         string mPath;
 229 };
 230
 231
 232
 233 // The current lock being held.
 234 class AtomicLockedFile : public RefCount
 235 {
 236 public:
 237         // Create a write lock for inFile.
 238         AtomicLockedFile(AtomicFile &inFile);
 239
 240         ~AtomicLockedFile();
 241
 242 private:
 243         void lock(mode_t mode = (S_IRUSR|S_IRGRP|S_IROTH) /* === 0444 */);
 244         void unlock() _NOEXCEPT;
 245
 246 private:
 247         FileLocker* mFileLocker;
 248 };
 249
 250
 251 } // end namespace Security
 252
 253
 254 #endif // _SECURITY_ATOMICFILE_H_