4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
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.
11 ******************************************************************************
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.
17 ** This header file is #include-ed by sqliteInt.h and thus ends up
18 ** being included by every source file.
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, SQLITE_OS_OS2, and SQLITE_OS_OTHER
27 ** will defined to either 1 or 0. One of the four will be 1. The other
30 #if defined(SQLITE_OS_OTHER)
31 # if SQLITE_OS_OTHER==1
32 # undef SQLITE_OS_UNIX
33 # define SQLITE_OS_UNIX 0
35 # define SQLITE_OS_WIN 0
37 # define SQLITE_OS_OS2 0
39 # undef SQLITE_OS_OTHER
42 #if !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_OTHER)
43 # define SQLITE_OS_OTHER 0
44 # ifndef SQLITE_OS_WIN
45 # if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
46 # define SQLITE_OS_WIN 1
47 # define SQLITE_OS_UNIX 0
48 # define SQLITE_OS_OS2 0
49 # elif defined(__EMX__) || defined(_OS2) || defined(OS2) || defined(_OS2_) || defined(__OS2__)
50 # define SQLITE_OS_WIN 0
51 # define SQLITE_OS_UNIX 0
52 # define SQLITE_OS_OS2 1
54 # define SQLITE_OS_WIN 0
55 # define SQLITE_OS_UNIX 1
56 # define SQLITE_OS_OS2 0
59 # define SQLITE_OS_UNIX 0
60 # define SQLITE_OS_OS2 0
63 # ifndef SQLITE_OS_WIN
64 # define SQLITE_OS_WIN 0
69 ** Determine if we are dealing with WindowsCE - which has a much
72 #if defined(_WIN32_WCE)
73 # define SQLITE_OS_WINCE 1
75 # define SQLITE_OS_WINCE 0
80 ** Define the maximum size of a temporary filename
84 # define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
86 # if (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 3) && defined(OS2_HIGH_MEMORY)
87 # include <os2safe.h> /* has to be included before os2.h for linking to work */
89 # define INCL_DOSDATETIME
90 # define INCL_DOSFILEMGR
91 # define INCL_DOSERRORS
93 # define INCL_DOSPROCESS
94 # define INCL_DOSMODULEMGR
95 # define INCL_DOSSEMAPHORES
98 # define SQLITE_TEMPNAME_SIZE (CCHMAXPATHCOMP)
100 # define SQLITE_TEMPNAME_SIZE 200
103 /* If the SET_FULLSYNC macro is not defined above, then make it
107 # define SET_FULLSYNC(x,y)
111 ** The default size of a disk sector
113 #ifndef SQLITE_DEFAULT_SECTOR_SIZE
114 # define SQLITE_DEFAULT_SECTOR_SIZE 512
118 ** Temporary files are named starting with this prefix followed by 16 random
119 ** alphanumeric characters, and no file extension. They are stored in the
120 ** OS's standard temporary file directory, and are deleted prior to exit.
121 ** If sqlite is being embedded in another program, you may wish to change the
122 ** prefix to reflect your program's name, so that if your program exits
123 ** prematurely, old temporary files can be easily identified. This can be done
124 ** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
126 ** 2006-10-31: The default prefix used to be "sqlite_". But then
127 ** Mcafee started using SQLite in their anti-virus product and it
128 ** started putting files with the "sqlite" name in the c:/temp folder.
129 ** This annoyed many windows users. Those users would then do a
130 ** Google search for "sqlite", find the telephone numbers of the
131 ** developers and call to wake them up at night and complain.
132 ** For this reason, the default name prefix is changed to be "sqlite"
133 ** spelled backwards. So the temp files are still identified, but
134 ** anybody smart enough to figure out the code is also likely smart
135 ** enough to know that calling the developer will not help get rid
138 #ifndef SQLITE_TEMP_FILE_PREFIX
139 # define SQLITE_TEMP_FILE_PREFIX "etilqs_"
143 ** The following values may be passed as the second argument to
144 ** sqlite3OsLock(). The various locks exhibit the following semantics:
146 ** SHARED: Any number of processes may hold a SHARED lock simultaneously.
147 ** RESERVED: A single process may hold a RESERVED lock on a file at
148 ** any time. Other processes may hold and obtain new SHARED locks.
149 ** PENDING: A single process may hold a PENDING lock on a file at
150 ** any one time. Existing SHARED locks may persist, but no new
151 ** SHARED locks may be obtained by other processes.
152 ** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.
154 ** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a
155 ** process that requests an EXCLUSIVE lock may actually obtain a PENDING
156 ** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
160 #define SHARED_LOCK 1
161 #define RESERVED_LOCK 2
162 #define PENDING_LOCK 3
163 #define EXCLUSIVE_LOCK 4
166 ** File Locking Notes: (Mostly about windows but also some info for Unix)
168 ** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
169 ** those functions are not available. So we use only LockFile() and
172 ** LockFile() prevents not just writing but also reading by other processes.
173 ** A SHARED_LOCK is obtained by locking a single randomly-chosen
174 ** byte out of a specific range of bytes. The lock byte is obtained at
175 ** random so two separate readers can probably access the file at the
176 ** same time, unless they are unlucky and choose the same lock byte.
177 ** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
178 ** There can only be one writer. A RESERVED_LOCK is obtained by locking
179 ** a single byte of the file that is designated as the reserved lock byte.
180 ** A PENDING_LOCK is obtained by locking a designated byte different from
181 ** the RESERVED_LOCK byte.
183 ** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
184 ** which means we can use reader/writer locks. When reader/writer locks
185 ** are used, the lock is placed on the same range of bytes that is used
186 ** for probabilistic locking in Win95/98/ME. Hence, the locking scheme
187 ** will support two or more Win95 readers or two or more WinNT readers.
188 ** But a single Win95 reader will lock out all WinNT readers and a single
189 ** WinNT reader will lock out all other Win95 readers.
191 ** The following #defines specify the range of bytes used for locking.
192 ** SHARED_SIZE is the number of bytes available in the pool from which
193 ** a random byte is selected for a shared lock. The pool of bytes for
194 ** shared locks begins at SHARED_FIRST.
196 ** The same locking strategy and
197 ** byte ranges are used for Unix. This leaves open the possiblity of having
198 ** clients on win95, winNT, and unix all talking to the same shared file
199 ** and all locking correctly. To do so would require that samba (or whatever
200 ** tool is being used for file sharing) implements locks correctly between
201 ** windows and unix. I'm guessing that isn't likely to happen, but by
202 ** using the same locking range we are at least open to the possibility.
204 ** Locking in windows is manditory. For this reason, we cannot store
205 ** actual data in the bytes used for locking. The pager never allocates
206 ** the pages involved in locking therefore. SHARED_SIZE is selected so
207 ** that all locks will fit on a single page even at the minimum page size.
208 ** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE
209 ** is set high so that we don't have to allocate an unused page except
210 ** for very large databases. But one should test the page skipping logic
211 ** by setting PENDING_BYTE low and running the entire regression suite.
213 ** Changing the value of PENDING_BYTE results in a subtly incompatible
214 ** file format. Depending on how it is changed, you might not notice
215 ** the incompatibility right away, even running a full regression test.
216 ** The default location of PENDING_BYTE is the first byte past the
220 #ifdef SQLITE_OMIT_WSD
221 # define PENDING_BYTE (0x40000000)
223 # define PENDING_BYTE sqlite3PendingByte
225 #define RESERVED_BYTE (PENDING_BYTE+1)
226 #define SHARED_FIRST (PENDING_BYTE+2)
227 #define SHARED_SIZE 510
230 ** Wrapper around OS specific sqlite3_os_init() function.
232 int sqlite3OsInit(void);
235 ** Functions for accessing sqlite3_file methods
237 int sqlite3OsClose(sqlite3_file*);
238 int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
239 int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
240 int sqlite3OsTruncate(sqlite3_file*, i64 size);
241 int sqlite3OsSync(sqlite3_file*, int);
242 int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
243 int sqlite3OsLock(sqlite3_file*, int);
244 int sqlite3OsUnlock(sqlite3_file*, int);
245 int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut);
246 int sqlite3OsFileControl(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);
256 ** Functions for accessing sqlite3_vfs methods
258 int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
259 int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
260 int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);
261 int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
262 #ifndef SQLITE_OMIT_LOAD_EXTENSION
263 void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);
264 void sqlite3OsDlError(sqlite3_vfs *, int, char *);
265 void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void);
266 void sqlite3OsDlClose(sqlite3_vfs *, void *);
267 #endif /* SQLITE_OMIT_LOAD_EXTENSION */
268 int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
269 int sqlite3OsSleep(sqlite3_vfs *, int);
270 int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
273 ** Convenience functions for opening and closing files using
274 ** sqlite3_malloc() to obtain space for the file-handle structure.
276 int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
277 int sqlite3OsCloseFree(sqlite3_file *);
279 #endif /* _SQLITE_OS_H_ */