1 /* 2 ** 2001 September 16 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ****************************************************************************** 12 ** 13 ** This header file (together with is companion C source-code file 14 ** "os.c") attempt to abstract the underlying operating system so that 15 ** the SQLite library will work on both POSIX and windows systems. 16 ** 17 ** This header file is #include-ed by sqliteInt.h and thus ends up 18 ** being included by every source file. 19 */ 20 #ifndef _SQLITE_OS_H_ 21 #define _SQLITE_OS_H_ 22 23 /* 24 ** Figure out if we are dealing with Unix, Windows, or some other 25 ** operating system. After the following block of preprocess macros, 26 ** all of SQLITE_OS_UNIX, SQLITE_OS_WIN, and SQLITE_OS_OTHER 27 ** will defined to either 1 or 0. One of the four will be 1. The other 28 ** three will be 0. 29 */ 30 #if defined(SQLITE_OS_OTHER) 31 # if SQLITE_OS_OTHER==1 32 # undef SQLITE_OS_UNIX 33 # define SQLITE_OS_UNIX 0 34 # undef SQLITE_OS_WIN 35 # define SQLITE_OS_WIN 0 36 # else 37 # undef SQLITE_OS_OTHER 38 # endif 39 #endif 40 #if !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_OTHER) 41 # define SQLITE_OS_OTHER 0 42 # ifndef SQLITE_OS_WIN 43 # if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__) 44 # define SQLITE_OS_WIN 1 45 # define SQLITE_OS_UNIX 0 46 # else 47 # define SQLITE_OS_WIN 0 48 # define SQLITE_OS_UNIX 1 49 # endif 50 # else 51 # define SQLITE_OS_UNIX 0 52 # endif 53 #else 54 # ifndef SQLITE_OS_WIN 55 # define SQLITE_OS_WIN 0 56 # endif 57 #endif 58 59 #if SQLITE_OS_WIN 60 # include <windows.h> 61 #endif 62 63 /* 64 ** Determine if we are dealing with Windows NT. 65 ** 66 ** We ought to be able to determine if we are compiling for win98 or winNT 67 ** using the _WIN32_WINNT macro as follows: 68 ** 69 ** #if defined(_WIN32_WINNT) 70 ** # define SQLITE_OS_WINNT 1 71 ** #else 72 ** # define SQLITE_OS_WINNT 0 73 ** #endif 74 ** 75 ** However, vs2005 does not set _WIN32_WINNT by default, as it ought to, 76 ** so the above test does not work. We'll just assume that everything is 77 ** winNT unless the programmer explicitly says otherwise by setting 78 ** SQLITE_OS_WINNT to 0. 79 */ 80 #if SQLITE_OS_WIN && !defined(SQLITE_OS_WINNT) 81 # define SQLITE_OS_WINNT 1 82 #endif 83 84 /* 85 ** Determine if we are dealing with WindowsCE - which has a much 86 ** reduced API. 87 */ 88 #if defined(_WIN32_WCE) 89 # define SQLITE_OS_WINCE 1 90 #else 91 # define SQLITE_OS_WINCE 0 92 #endif 93 94 /* 95 ** Determine if we are dealing with WinRT, which provides only a subset of 96 ** the full Win32 API. 97 */ 98 #if !defined(SQLITE_OS_WINRT) 99 # define SQLITE_OS_WINRT 0 100 #endif 101 102 /* If the SET_FULLSYNC macro is not defined above, then make it 103 ** a no-op 104 */ 105 #ifndef SET_FULLSYNC 106 # define SET_FULLSYNC(x,y) 107 #endif 108 109 /* 110 ** The default size of a disk sector 111 */ 112 #ifndef SQLITE_DEFAULT_SECTOR_SIZE 113 # define SQLITE_DEFAULT_SECTOR_SIZE 4096 114 #endif 115 116 /* 117 ** Temporary files are named starting with this prefix followed by 16 random 118 ** alphanumeric characters, and no file extension. They are stored in the 119 ** OS's standard temporary file directory, and are deleted prior to exit. 120 ** If sqlite is being embedded in another program, you may wish to change the 121 ** prefix to reflect your program's name, so that if your program exits 122 ** prematurely, old temporary files can be easily identified. This can be done 123 ** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line. 124 ** 125 ** 2006-10-31: The default prefix used to be "sqlite_". But then 126 ** Mcafee started using SQLite in their anti-virus product and it 127 ** started putting files with the "sqlite" name in the c:/temp folder. 128 ** This annoyed many windows users. Those users would then do a 129 ** Google search for "sqlite", find the telephone numbers of the 130 ** developers and call to wake them up at night and complain. 131 ** For this reason, the default name prefix is changed to be "sqlite" 132 ** spelled backwards. So the temp files are still identified, but 133 ** anybody smart enough to figure out the code is also likely smart 134 ** enough to know that calling the developer will not help get rid 135 ** of the file. 136 */ 137 #ifndef SQLITE_TEMP_FILE_PREFIX 138 # define SQLITE_TEMP_FILE_PREFIX "etilqs_" 139 #endif 140 141 /* 142 ** The following values may be passed as the second argument to 143 ** sqlite3OsLock(). The various locks exhibit the following semantics: 144 ** 145 ** SHARED: Any number of processes may hold a SHARED lock simultaneously. 146 ** RESERVED: A single process may hold a RESERVED lock on a file at 147 ** any time. Other processes may hold and obtain new SHARED locks. 148 ** PENDING: A single process may hold a PENDING lock on a file at 149 ** any one time. Existing SHARED locks may persist, but no new 150 ** SHARED locks may be obtained by other processes. 151 ** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks. 152 ** 153 ** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a 154 ** process that requests an EXCLUSIVE lock may actually obtain a PENDING 155 ** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to 156 ** sqlite3OsLock(). 157 */ 158 #define NO_LOCK 0 159 #define SHARED_LOCK 1 160 #define RESERVED_LOCK 2 161 #define PENDING_LOCK 3 162 #define EXCLUSIVE_LOCK 4 163 164 /* 165 ** File Locking Notes: (Mostly about windows but also some info for Unix) 166 ** 167 ** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because 168 ** those functions are not available. So we use only LockFile() and 169 ** UnlockFile(). 170 ** 171 ** LockFile() prevents not just writing but also reading by other processes. 172 ** A SHARED_LOCK is obtained by locking a single randomly-chosen 173 ** byte out of a specific range of bytes. The lock byte is obtained at 174 ** random so two separate readers can probably access the file at the 175 ** same time, unless they are unlucky and choose the same lock byte. 176 ** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range. 177 ** There can only be one writer. A RESERVED_LOCK is obtained by locking 178 ** a single byte of the file that is designated as the reserved lock byte. 179 ** A PENDING_LOCK is obtained by locking a designated byte different from 180 ** the RESERVED_LOCK byte. 181 ** 182 ** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available, 183 ** which means we can use reader/writer locks. When reader/writer locks 184 ** are used, the lock is placed on the same range of bytes that is used 185 ** for probabilistic locking in Win95/98/ME. Hence, the locking scheme 186 ** will support two or more Win95 readers or two or more WinNT readers. 187 ** But a single Win95 reader will lock out all WinNT readers and a single 188 ** WinNT reader will lock out all other Win95 readers. 189 ** 190 ** The following #defines specify the range of bytes used for locking. 191 ** SHARED_SIZE is the number of bytes available in the pool from which 192 ** a random byte is selected for a shared lock. The pool of bytes for 193 ** shared locks begins at SHARED_FIRST. 194 ** 195 ** The same locking strategy and 196 ** byte ranges are used for Unix. This leaves open the possiblity of having 197 ** clients on win95, winNT, and unix all talking to the same shared file 198 ** and all locking correctly. To do so would require that samba (or whatever 199 ** tool is being used for file sharing) implements locks correctly between 200 ** windows and unix. I'm guessing that isn't likely to happen, but by 201 ** using the same locking range we are at least open to the possibility. 202 ** 203 ** Locking in windows is manditory. For this reason, we cannot store 204 ** actual data in the bytes used for locking. The pager never allocates 205 ** the pages involved in locking therefore. SHARED_SIZE is selected so 206 ** that all locks will fit on a single page even at the minimum page size. 207 ** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE 208 ** is set high so that we don't have to allocate an unused page except 209 ** for very large databases. But one should test the page skipping logic 210 ** by setting PENDING_BYTE low and running the entire regression suite. 211 ** 212 ** Changing the value of PENDING_BYTE results in a subtly incompatible 213 ** file format. Depending on how it is changed, you might not notice 214 ** the incompatibility right away, even running a full regression test. 215 ** The default location of PENDING_BYTE is the first byte past the 216 ** 1GB boundary. 217 ** 218 */ 219 #ifdef SQLITE_OMIT_WSD 220 # define PENDING_BYTE (0x40000000) 221 #else 222 # define PENDING_BYTE sqlite3PendingByte 223 #endif 224 #define RESERVED_BYTE (PENDING_BYTE+1) 225 #define SHARED_FIRST (PENDING_BYTE+2) 226 #define SHARED_SIZE 510 227 228 /* 229 ** Wrapper around OS specific sqlite3_os_init() function. 230 */ 231 int sqlite3OsInit(void); 232 233 /* 234 ** Functions for accessing sqlite3_file methods 235 */ 236 int sqlite3OsClose(sqlite3_file*); 237 int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset); 238 int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset); 239 int sqlite3OsTruncate(sqlite3_file*, i64 size); 240 int sqlite3OsSync(sqlite3_file*, int); 241 int sqlite3OsFileSize(sqlite3_file*, i64 *pSize); 242 int sqlite3OsLock(sqlite3_file*, int); 243 int sqlite3OsUnlock(sqlite3_file*, int); 244 int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut); 245 int sqlite3OsFileControl(sqlite3_file*,int,void*); 246 void sqlite3OsFileControlHint(sqlite3_file*,int,void*); 247 #define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0 248 int sqlite3OsSectorSize(sqlite3_file *id); 249 int sqlite3OsDeviceCharacteristics(sqlite3_file *id); 250 int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **); 251 int sqlite3OsShmLock(sqlite3_file *id, int, int, int); 252 void sqlite3OsShmBarrier(sqlite3_file *id); 253 int sqlite3OsShmUnmap(sqlite3_file *id, int); 254 int sqlite3OsFetch(sqlite3_file *id, i64, int, void **); 255 int sqlite3OsUnfetch(sqlite3_file *, i64, void *); 256 257 258 /* 259 ** Functions for accessing sqlite3_vfs methods 260 */ 261 int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *); 262 int sqlite3OsDelete(sqlite3_vfs *, const char *, int); 263 int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut); 264 int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *); 265 #ifndef SQLITE_OMIT_LOAD_EXTENSION 266 void *sqlite3OsDlOpen(sqlite3_vfs *, const char *); 267 void sqlite3OsDlError(sqlite3_vfs *, int, char *); 268 void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void); 269 void sqlite3OsDlClose(sqlite3_vfs *, void *); 270 #endif /* SQLITE_OMIT_LOAD_EXTENSION */ 271 int sqlite3OsRandomness(sqlite3_vfs *, int, char *); 272 int sqlite3OsSleep(sqlite3_vfs *, int); 273 int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*); 274 275 /* 276 ** Convenience functions for opening and closing files using 277 ** sqlite3_malloc() to obtain space for the file-handle structure. 278 */ 279 int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*); 280 int sqlite3OsCloseFree(sqlite3_file *); 281 282 #endif /* _SQLITE_OS_H_ */ 283