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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,
** will defined to either 1 or 0. One of the four will be 1. The other
** three will be 0.
#if defined(SQLITE_OS_OTHER)
# define SQLITE_OS_UNIX 0
# define SQLITE_OS_WIN 0
# undef SQLITE_OS_OS2
# define SQLITE_OS_OS2 0
# else
# endif
#if !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_OTHER)
# define SQLITE_OS_OTHER 0
# ifndef SQLITE_OS_WIN
# if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
# define SQLITE_OS_WIN 1
# define SQLITE_OS_UNIX 0
# define SQLITE_OS_OS2 0
# elif defined(__EMX__) || defined(_OS2) || defined(OS2) || defined(_OS2_) || defined(__OS2__)
# define SQLITE_OS_WIN 0
# define SQLITE_OS_UNIX 0
# define SQLITE_OS_OS2 1
# else
# define SQLITE_OS_WIN 0
# define SQLITE_OS_UNIX 1
# define SQLITE_OS_OS2 0
# endif
# else
# define SQLITE_OS_UNIX 0
# define SQLITE_OS_OS2 0
# endif
# ifndef SQLITE_OS_WIN
# define SQLITE_OS_WIN 0
# endif
** Determine if we are dealing with WindowsCE - which has a much
** reduced API.
#if defined(_WIN32_WCE)
# define SQLITE_OS_WINCE 1
# define SQLITE_OS_WINCE 0
** Define the maximum size of a temporary filename
# include <windows.h>
# 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
# include <os2.h>
# include <uconv.h>
/* If the SET_FULLSYNC macro is not defined above, then make it
** a no-op
# define SET_FULLSYNC(x,y)
** The default size of a disk sector
** 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.
# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
** 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 PENDING_LOCK 3
** 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.
** 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.
# define PENDING_BYTE (0x40000000)
# define PENDING_BYTE sqlite3PendingByte
#define SHARED_SIZE 510
** Wrapper around OS specific sqlite3_os_init() function.
int sqlite3OsInit(void);
** 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 *pResOut);
int sqlite3OsFileControl(sqlite3_file*,int,void*);
#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
int sqlite3OsSectorSize(sqlite3_file *id);
int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
void sqlite3OsShmBarrier(sqlite3_file *id);
int sqlite3OsShmUnmap(sqlite3_file *id, int);
** 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 *pResOut);
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);
void sqlite3OsDlClose(sqlite3_vfs *, void *);
int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
int sqlite3OsSleep(sqlite3_vfs *, int);
int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
** 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 *);
#endif /* _SQLITE_OS_H_ */