f78ceafdce
used new shared cache functionality (yay) --HG-- extra : convert_revision : svn%3A39bc706e-5318-0410-9160-8a85361fbb7c/trunk%401651
285 lines
11 KiB
C
285 lines
11 KiB
C
/*
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** 2001 September 16
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** This header file (together with is companion C source-code file
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** "os.c") attempt to abstract the underlying operating system so that
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** the SQLite library will work on both POSIX and windows systems.
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**
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** This header file is #include-ed by sqliteInt.h and thus ends up
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** being included by every source file.
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*/
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#ifndef _SQLITE_OS_H_
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#define _SQLITE_OS_H_
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/*
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** Figure out if we are dealing with Unix, Windows, or some other
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** operating system. After the following block of preprocess macros,
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** all of OS_UNIX, OS_WIN, OS_OS2, and OS_OTHER will defined to either
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** 1 or 0. One of the four will be 1. The other three will be 0.
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*/
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#if defined(OS_OTHER)
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# if OS_OTHER==1
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# undef OS_UNIX
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# define OS_UNIX 0
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# undef OS_WIN
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# define OS_WIN 0
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# undef OS_OS2
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# define OS_OS2 0
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# else
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# undef OS_OTHER
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# endif
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#endif
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#if !defined(OS_UNIX) && !defined(OS_OTHER)
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# define OS_OTHER 0
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# ifndef OS_WIN
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# if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__BORLANDC__)
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# define OS_WIN 1
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# define OS_UNIX 0
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# define OS_OS2 0
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# elif defined(__EMX__) || defined(_OS2) || defined(OS2) || defined(_OS2_) || defined(__OS2__)
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# define OS_WIN 0
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# define OS_UNIX 0
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# define OS_OS2 1
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# else
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# define OS_WIN 0
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# define OS_UNIX 1
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# define OS_OS2 0
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# endif
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# else
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# define OS_UNIX 0
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# define OS_OS2 0
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# endif
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#else
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# ifndef OS_WIN
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# define OS_WIN 0
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# endif
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#endif
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/*
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** Define the maximum size of a temporary filename
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*/
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#if OS_WIN
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# include <windows.h>
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# define SQLITE_TEMPNAME_SIZE (MAX_PATH+50)
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#elif OS_OS2
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# if (__GNUC__ > 3 || __GNUC__ == 3 && __GNUC_MINOR__ >= 3) && defined(OS2_HIGH_MEMORY)
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# include <os2safe.h> /* has to be included before os2.h for linking to work */
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# endif
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# define INCL_DOSDATETIME
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# define INCL_DOSFILEMGR
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# define INCL_DOSERRORS
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# define INCL_DOSMISC
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# define INCL_DOSPROCESS
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# define INCL_DOSMODULEMGR
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# include <os2.h>
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# define SQLITE_TEMPNAME_SIZE (CCHMAXPATHCOMP)
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#else
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# define SQLITE_TEMPNAME_SIZE 200
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#endif
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/* If the SET_FULLSYNC macro is not defined above, then make it
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** a no-op
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*/
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#ifndef SET_FULLSYNC
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# define SET_FULLSYNC(x,y)
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#endif
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/*
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** The default size of a disk sector
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*/
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#ifndef SQLITE_DEFAULT_SECTOR_SIZE
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# define SQLITE_DEFAULT_SECTOR_SIZE 512
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#endif
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/*
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** Temporary files are named starting with this prefix followed by 16 random
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** alphanumeric characters, and no file extension. They are stored in the
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** OS's standard temporary file directory, and are deleted prior to exit.
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** If sqlite is being embedded in another program, you may wish to change the
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** prefix to reflect your program's name, so that if your program exits
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** prematurely, old temporary files can be easily identified. This can be done
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** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
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**
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** 2006-10-31: The default prefix used to be "sqlite_". But then
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** Mcafee started using SQLite in their anti-virus product and it
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** started putting files with the "sqlite" name in the c:/temp folder.
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** This annoyed many windows users. Those users would then do a
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** Google search for "sqlite", find the telephone numbers of the
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** developers and call to wake them up at night and complain.
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** For this reason, the default name prefix is changed to be "sqlite"
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** spelled backwards. So the temp files are still identified, but
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** anybody smart enough to figure out the code is also likely smart
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** enough to know that calling the developer will not help get rid
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** of the file.
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*/
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#ifndef SQLITE_TEMP_FILE_PREFIX
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# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
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#endif
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/*
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** If using an alternative OS interface, then we must have an "os_other.h"
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** header file available for that interface. Presumably the "os_other.h"
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** header file contains #defines similar to those above.
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*/
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#if OS_OTHER
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# include "os_other.h"
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#endif
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/*
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** The following values may be passed as the second argument to
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** sqlite3OsLock(). The various locks exhibit the following semantics:
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**
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** SHARED: Any number of processes may hold a SHARED lock simultaneously.
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** RESERVED: A single process may hold a RESERVED lock on a file at
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** any time. Other processes may hold and obtain new SHARED locks.
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** PENDING: A single process may hold a PENDING lock on a file at
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** any one time. Existing SHARED locks may persist, but no new
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** SHARED locks may be obtained by other processes.
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** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.
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**
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** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a
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** process that requests an EXCLUSIVE lock may actually obtain a PENDING
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** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
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** sqlite3OsLock().
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*/
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#define NO_LOCK 0
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#define SHARED_LOCK 1
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#define RESERVED_LOCK 2
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#define PENDING_LOCK 3
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#define EXCLUSIVE_LOCK 4
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/*
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** File Locking Notes: (Mostly about windows but also some info for Unix)
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**
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** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
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** those functions are not available. So we use only LockFile() and
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** UnlockFile().
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**
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** LockFile() prevents not just writing but also reading by other processes.
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** A SHARED_LOCK is obtained by locking a single randomly-chosen
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** byte out of a specific range of bytes. The lock byte is obtained at
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** random so two separate readers can probably access the file at the
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** same time, unless they are unlucky and choose the same lock byte.
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** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
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** There can only be one writer. A RESERVED_LOCK is obtained by locking
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** a single byte of the file that is designated as the reserved lock byte.
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** A PENDING_LOCK is obtained by locking a designated byte different from
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** the RESERVED_LOCK byte.
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**
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** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
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** which means we can use reader/writer locks. When reader/writer locks
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** are used, the lock is placed on the same range of bytes that is used
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** for probabilistic locking in Win95/98/ME. Hence, the locking scheme
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** will support two or more Win95 readers or two or more WinNT readers.
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** But a single Win95 reader will lock out all WinNT readers and a single
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** WinNT reader will lock out all other Win95 readers.
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**
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** The following #defines specify the range of bytes used for locking.
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** SHARED_SIZE is the number of bytes available in the pool from which
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** a random byte is selected for a shared lock. The pool of bytes for
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** shared locks begins at SHARED_FIRST.
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**
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** These #defines are available in sqlite_aux.h so that adaptors for
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** connecting SQLite to other operating systems can use the same byte
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** ranges for locking. In particular, the same locking strategy and
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** byte ranges are used for Unix. This leaves open the possiblity of having
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** clients on win95, winNT, and unix all talking to the same shared file
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** and all locking correctly. To do so would require that samba (or whatever
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** tool is being used for file sharing) implements locks correctly between
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** windows and unix. I'm guessing that isn't likely to happen, but by
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** using the same locking range we are at least open to the possibility.
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**
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** Locking in windows is manditory. For this reason, we cannot store
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** actual data in the bytes used for locking. The pager never allocates
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** the pages involved in locking therefore. SHARED_SIZE is selected so
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** that all locks will fit on a single page even at the minimum page size.
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** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE
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** is set high so that we don't have to allocate an unused page except
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** for very large databases. But one should test the page skipping logic
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** by setting PENDING_BYTE low and running the entire regression suite.
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**
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** Changing the value of PENDING_BYTE results in a subtly incompatible
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** file format. Depending on how it is changed, you might not notice
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** the incompatibility right away, even running a full regression test.
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** The default location of PENDING_BYTE is the first byte past the
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** 1GB boundary.
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**
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*/
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#ifndef SQLITE_TEST
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#define PENDING_BYTE 0x40000000 /* First byte past the 1GB boundary */
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#else
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extern unsigned int sqlite3_pending_byte;
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#define PENDING_BYTE sqlite3_pending_byte
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#endif
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#define RESERVED_BYTE (PENDING_BYTE+1)
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#define SHARED_FIRST (PENDING_BYTE+2)
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#define SHARED_SIZE 510
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/*
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** Functions for accessing sqlite3_file methods
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*/
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int sqlite3OsClose(sqlite3_file*);
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int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
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int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
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int sqlite3OsTruncate(sqlite3_file*, i64 size);
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int sqlite3OsSync(sqlite3_file*, int);
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int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
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int sqlite3OsLock(sqlite3_file*, int);
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int sqlite3OsUnlock(sqlite3_file*, int);
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int sqlite3OsCheckReservedLock(sqlite3_file *id);
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int sqlite3OsFileControl(sqlite3_file*,int,void*);
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int sqlite3OsSectorSize(sqlite3_file *id);
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int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
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/*
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** Functions for accessing sqlite3_vfs methods
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*/
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int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
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int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
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int sqlite3OsAccess(sqlite3_vfs *, const char *, int);
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int sqlite3OsGetTempname(sqlite3_vfs *, int, char *);
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int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
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void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);
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void sqlite3OsDlError(sqlite3_vfs *, int, char *);
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void *sqlite3OsDlSym(sqlite3_vfs *, void *, const char *);
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void sqlite3OsDlClose(sqlite3_vfs *, void *);
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int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
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int sqlite3OsSleep(sqlite3_vfs *, int);
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int sqlite3OsCurrentTime(sqlite3_vfs *, double*);
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/*
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** Convenience functions for opening and closing files using
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** sqlite3_malloc() to obtain space for the file-handle structure.
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*/
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int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);
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int sqlite3OsCloseFree(sqlite3_file *);
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/*
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** Each OS-specific backend defines an instance of the following
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** structure for returning a pointer to its sqlite3_vfs. If OS_OTHER
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** is defined (meaning that the application-defined OS interface layer
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** is used) then there is no default VFS. The application must
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** register one or more VFS structures using sqlite3_vfs_register()
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** before attempting to use SQLite.
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*/
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#if OS_UNIX || OS_WIN || OS_OS2
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sqlite3_vfs *sqlite3OsDefaultVfs(void);
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#else
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# define sqlite3OsDefaultVfs(X) 0
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#endif
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#endif /* _SQLITE_OS_H_ */
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