/* ** 2001 September 16 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ****************************************************************************** ** ** This header file (together with is companion C source-code file ** "os.c") attempt to abstract the underlying operating system so that ** the SQLite library will work on both POSIX and windows systems. */ #ifndef _SQLITE_OS_H_ #define _SQLITE_OS_H_ /* ** Figure out if we are dealing with Unix, Windows or MacOS. ** ** N.B. MacOS means Mac Classic (or Carbon). Treat Darwin (OS X) as Unix. ** The MacOS build is designed to use CodeWarrior (tested with v8) */ #if !defined(OS_UNIX) && !defined(OS_TEST) && !defined(OS_OTHER) # define OS_OTHER 0 # ifndef OS_WIN # if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) # define OS_WIN 1 # define OS_UNIX 0 # else # define OS_WIN 0 # define OS_UNIX 1 # endif # else # define OS_UNIX 0 # endif #else # ifndef OS_WIN # define OS_WIN 0 # endif #endif /* ** Invoke the appropriate operating-system specific header file. */ #if OS_TEST # include "os_test.h" #endif #if OS_UNIX # include "os_unix.h" #endif #if OS_WIN # include "os_win.h" #endif /* os_other.c and os_other.h are not delivered with SQLite. These files ** are place-holders that can be filled in by third-party developers to ** implement backends to their on proprietary operating systems. */ #if OS_OTHER # include "os_other.h" #endif /* If the SET_FULLSYNC macro is not defined above, then make it ** a no-op */ #ifndef SET_FULLSYNC # define SET_FULLSYNC(x,y) #endif /* ** Temporary files are named starting with this prefix followed by 16 random ** alphanumeric characters, and no file extension. They are stored in the ** OS's standard temporary file directory, and are deleted prior to exit. ** If sqlite is being embedded in another program, you may wish to change the ** prefix to reflect your program's name, so that if your program exits ** prematurely, old temporary files can be easily identified. This can be done ** using -DTEMP_FILE_PREFIX=myprefix_ on the compiler command line. */ #ifndef TEMP_FILE_PREFIX # define TEMP_FILE_PREFIX "sqlite_" #endif /* ** The following values may be passed as the second argument to ** sqlite3OsLock(). The various locks exhibit the following semantics: ** ** SHARED: Any number of processes may hold a SHARED lock simultaneously. ** RESERVED: A single process may hold a RESERVED lock on a file at ** any time. Other processes may hold and obtain new SHARED locks. ** PENDING: A single process may hold a PENDING lock on a file at ** any one time. Existing SHARED locks may persist, but no new ** SHARED locks may be obtained by other processes. ** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks. ** ** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a ** process that requests an EXCLUSIVE lock may actually obtain a PENDING ** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to ** sqlite3OsLock(). */ #define NO_LOCK 0 #define SHARED_LOCK 1 #define RESERVED_LOCK 2 #define PENDING_LOCK 3 #define EXCLUSIVE_LOCK 4 /* ** File Locking Notes: (Mostly about windows but also some info for Unix) ** ** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because ** those functions are not available. So we use only LockFile() and ** UnlockFile(). ** ** LockFile() prevents not just writing but also reading by other processes. ** A SHARED_LOCK is obtained by locking a single randomly-chosen ** byte out of a specific range of bytes. The lock byte is obtained at ** random so two separate readers can probably access the file at the ** same time, unless they are unlucky and choose the same lock byte. ** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range. ** There can only be one writer. A RESERVED_LOCK is obtained by locking ** a single byte of the file that is designated as the reserved lock byte. ** A PENDING_LOCK is obtained by locking a designated byte different from ** the RESERVED_LOCK byte. ** ** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available, ** which means we can use reader/writer locks. When reader/writer locks ** are used, the lock is placed on the same range of bytes that is used ** for probabilistic locking in Win95/98/ME. Hence, the locking scheme ** will support two or more Win95 readers or two or more WinNT readers. ** But a single Win95 reader will lock out all WinNT readers and a single ** WinNT reader will lock out all other Win95 readers. ** ** The following #defines specify the range of bytes used for locking. ** SHARED_SIZE is the number of bytes available in the pool from which ** a random byte is selected for a shared lock. The pool of bytes for ** shared locks begins at SHARED_FIRST. ** ** These #defines are available in os.h so that Unix can use the same ** byte ranges for locking. This leaves open the possiblity of having ** clients on win95, winNT, and unix all talking to the same shared file ** and all locking correctly. To do so would require that samba (or whatever ** tool is being used for file sharing) implements locks correctly between ** windows and unix. I'm guessing that isn't likely to happen, but by ** using the same locking range we are at least open to the possibility. ** ** Locking in windows is manditory. For this reason, we cannot store ** actual data in the bytes used for locking. The pager never allocates ** the pages involved in locking therefore. SHARED_SIZE is selected so ** that all locks will fit on a single page even at the minimum page size. ** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE ** is set high so that we don't have to allocate an unused page except ** for very large databases. But one should test the page skipping logic ** by setting PENDING_BYTE low and running the entire regression suite. ** ** Changing the value of PENDING_BYTE results in a subtly incompatible ** file format. Depending on how it is changed, you might not notice ** the incompatibility right away, even running a full regression test. ** The default location of PENDING_BYTE is the first byte past the ** 1GB boundary. ** */ #define PENDING_BYTE 0x40000000 /* First byte past the 1GB boundary */ /* #define PENDING_BYTE 0x5400 // Page 22 - for testing */ #define RESERVED_BYTE (PENDING_BYTE+1) #define SHARED_FIRST (PENDING_BYTE+2) #define SHARED_SIZE 510 int sqlite3OsDelete(const char*); int sqlite3OsFileExists(const char*); int sqlite3OsOpenReadWrite(const char*, OsFile*, int*); int sqlite3OsOpenExclusive(const char*, OsFile*, int); int sqlite3OsOpenReadOnly(const char*, OsFile*); int sqlite3OsOpenDirectory(const char*, OsFile*); int sqlite3OsSyncDirectory(const char*); int sqlite3OsTempFileName(char*); int sqlite3OsIsDirWritable(char*); int sqlite3OsClose(OsFile*); int sqlite3OsRead(OsFile*, void*, int amt); int sqlite3OsWrite(OsFile*, const void*, int amt); int sqlite3OsSeek(OsFile*, i64 offset); int sqlite3OsSync(OsFile*); int sqlite3OsTruncate(OsFile*, i64 size); int sqlite3OsFileSize(OsFile*, i64 *pSize); char *sqlite3OsFullPathname(const char*); int sqlite3OsLock(OsFile*, int); int sqlite3OsUnlock(OsFile*, int); int sqlite3OsCheckReservedLock(OsFile *id); /* The interface for file I/O is above. Other miscellaneous functions ** are below */ int sqlite3OsRandomSeed(char*); int sqlite3OsSleep(int ms); int sqlite3OsCurrentTime(double*); void sqlite3OsEnterMutex(void); void sqlite3OsLeaveMutex(void); #endif /* _SQLITE_OS_H_ */