os.h.svn-base
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- /*
- ** 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.
- **
- ** This header file is #include-ed by sqliteInt.h and thus ends up
- ** being included by every source file.
- */
- #ifndef _SQLITE_OS_H_
- #define _SQLITE_OS_H_
- /*
- ** Figure out if we are dealing with Unix, Windows, or some other
- ** operating system. After the following block of preprocess macros,
- ** all of OS_UNIX, OS_WIN, OS_OS2, and OS_OTHER will defined to either
- ** 1 or 0. One of the four will be 1. The other three will be 0.
- */
- #if defined(OS_OTHER)
- # if OS_OTHER==1
- # undef OS_UNIX
- # define OS_UNIX 0
- # undef OS_WIN
- # define OS_WIN 0
- # undef OS_OS2
- # define OS_OS2 0
- # else
- # undef OS_OTHER
- # endif
- #endif
- #if !defined(OS_UNIX) && !defined(OS_OTHER)
- # define OS_OTHER 0
- # ifndef OS_WIN
- # if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
- # define OS_WIN 1
- # define OS_UNIX 0
- # define OS_OS2 0
- # elif defined(__EMX__) || defined(_OS2) || defined(OS2) || defined(_OS2_) || defined(__OS2__)
- # define OS_WIN 0
- # define OS_UNIX 0
- # define OS_OS2 1
- # else
- # define OS_WIN 0
- //# define OS_UNIX 1
- # define OS_OS20 1
- # define OS_OS2 0
- # endif
- # else
- # define OS_UNIX 0
- # define OS_OS2 0
- # endif
- #else
- # ifndef OS_WIN
- # define OS_WIN 0
- # endif
- #endif
- /*
- ** Define the maximum size of a temporary filename
- */
- #if OS_WIN
- # include <windows.h>
- # define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
- #elif OS_OS2
- # if (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 3) && defined(OS2_HIGH_MEMORY)
- # include <os2safe.h> /* has to be included before os2.h for linking to work */
- # endif
- # define INCL_DOSDATETIME
- # define INCL_DOSFILEMGR
- # define INCL_DOSERRORS
- # define INCL_DOSMISC
- # define INCL_DOSPROCESS
- # define INCL_DOSMODULEMGR
- # define INCL_DOSSEMAPHORES
- # include <os2.h>
- # include <uconv.h>
- # define SQLITE_TEMPNAME_SIZE (CCHMAXPATHCOMP)
- #else
- # define SQLITE_TEMPNAME_SIZE 200
- #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
- /*
- ** The default size of a disk sector
- */
- #ifndef SQLITE_DEFAULT_SECTOR_SIZE
- # define SQLITE_DEFAULT_SECTOR_SIZE 512
- #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 -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
- **
- ** 2006-10-31: The default prefix used to be "sqlite_". But then
- ** Mcafee started using SQLite in their anti-virus product and it
- ** started putting files with the "sqlite" name in the c:/temp folder.
- ** This annoyed many windows users. Those users would then do a
- ** Google search for "sqlite", find the telephone numbers of the
- ** developers and call to wake them up at night and complain.
- ** For this reason, the default name prefix is changed to be "sqlite"
- ** spelled backwards. So the temp files are still identified, but
- ** anybody smart enough to figure out the code is also likely smart
- ** enough to know that calling the developer will not help get rid
- ** of the file.
- */
- #ifndef SQLITE_TEMP_FILE_PREFIX
- # define SQLITE_TEMP_FILE_PREFIX "etilqs_"
- #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 sqlite_aux.h so that adaptors for
- ** connecting SQLite to other operating systems can use the same byte
- ** ranges for locking. In particular, the same locking strategy and
- ** byte ranges are used for Unix. 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.
- **
- */
- #ifndef SQLITE_TEST
- #define PENDING_BYTE 0x40000000 /* First byte past the 1GB boundary */
- #else
- extern unsigned int sqlite3_pending_byte;
- #define PENDING_BYTE sqlite3_pending_byte
- #endif
- #define RESERVED_BYTE (PENDING_BYTE+1)
- #define SHARED_FIRST (PENDING_BYTE+2)
- #define SHARED_SIZE 510
- /*
- ** Functions for accessing sqlite3_file methods
- */
- int sqlite3OsClose(sqlite3_file*);
- int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
- int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
- int sqlite3OsTruncate(sqlite3_file*, i64 size);
- int sqlite3OsSync(sqlite3_file*, int);
- int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
- int sqlite3OsLock(sqlite3_file*, int);
- int sqlite3OsUnlock(sqlite3_file*, int);
- int sqlite3OsCheckReservedLock(sqlite3_file *id);
- int sqlite3OsFileControl(sqlite3_file*,int,void*);
- int sqlite3OsSectorSize(sqlite3_file *id);
- int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
- /*
- ** Functions for accessing sqlite3_vfs methods
- */
- int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
- int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
- int sqlite3OsAccess(sqlite3_vfs *, const char *, int);
- int sqlite3OsGetTempname(sqlite3_vfs *, int, char *);
- int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
- void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);
- void sqlite3OsDlError(sqlite3_vfs *, int, char *);
- void *sqlite3OsDlSym(sqlite3_vfs *, void *, const char *);
- void sqlite3OsDlClose(sqlite3_vfs *, void *);
- int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
- int sqlite3OsSleep(sqlite3_vfs *, int);
- int sqlite3OsCurrentTime(sqlite3_vfs *, double*);
- /*
- ** Convenience functions for opening and closing files using
- ** sqlite3_malloc() to obtain space for the file-handle structure.
- */
- int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
- int sqlite3OsCloseFree(sqlite3_file *);
- /*
- ** Each OS-specific backend defines an instance of the following
- ** structure for returning a pointer to its sqlite3_vfs. If OS_OTHER
- ** is defined (meaning that the application-defined OS interface layer
- ** is used) then there is no default VFS. The application must
- ** register one or more VFS structures using sqlite3_vfs_register()
- ** before attempting to use SQLite.
- */
- sqlite3_vfs *sqlite3OsDefaultVfs(void);
- #endif /* _SQLITE_OS_H_ */