/*

** 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_

/*

** Attempt to automatically detect the operating system and setup the

** necessary pre-processor macros for it.

*/

#include "os_setup.h"

/* 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 4096

#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.

**

** The same locking strategy and

** byte ranges are used for Unix. This leaves open the possibility 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.

**

*/

#ifdef SQLITE_OMIT_WSD

# define PENDING_BYTE (0x40000000)

#else

# define PENDING_BYTE sqlite3PendingByte

#endif

#define RESERVED_BYTE (PENDING_BYTE+1)

#define SHARED_FIRST (PENDING_BYTE+2)

#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*);

void sqlite3OsFileControlHint(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);

int sqlite3OsFetch(sqlite3_file *id, i64, int, void **);

int sqlite3OsUnfetch(sqlite3_file *, i64, void *);

/*

** 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 *);

#ifndef SQLITE_OMIT_LOAD_EXTENSION

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 *);

#endif /* SQLITE_OMIT_LOAD_EXTENSION */

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_ */