/*

** 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_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

# include <os2.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

/*

** If using an alternative OS interface, then we must have an "os_other.h"

** header file available for that interface.  Presumably the "os_other.h"

** header file contains #defines similar to those above.

*/

#if OS_OTHER

# include "os_other.h"

#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.

*/

#if OS_UNIX || OS_WIN || OS_OS2

sqlite3_vfs *sqlite3OsDefaultVfs(void);

#else

# define sqlite3OsDefaultVfs(X) 0

#endif

#endif /* _SQLITE_OS_H_ */