AryaWu/sqlite
0
1/*2** 2001 September 163**4** The author disclaims copyright to this source code. In place of5** a legal notice, here is a blessing:6**7** May you do good and not evil.8** May you find forgiveness for yourself and forgive others.9** May you share freely, never taking more than you give.10**11******************************************************************************12**13** This header file (together with is companion C source-code file14** "os.c") attempt to abstract the underlying operating system so that15** the SQLite library will work on both POSIX and windows systems.16**17** This header file is #include-ed by sqliteInt.h and thus ends up18** being included by every source file.19*/20#ifndef _SQLITE_OS_H_21#define _SQLITE_OS_H_22 23/*24** Attempt to automatically detect the operating system and setup the25** necessary pre-processor macros for it.26*/27#include "os_setup.h"28 29/* If the SET_FULLSYNC macro is not defined above, then make it30** a no-op31*/32#ifndef SET_FULLSYNC33# define SET_FULLSYNC(x,y)34#endif35 36/* Maximum pathname length. Note: FILENAME_MAX defined by stdio.h37*/38#ifndef SQLITE_MAX_PATHLEN39# define SQLITE_MAX_PATHLEN FILENAME_MAX40#endif41 42/* Maximum number of symlinks that will be resolved while trying to43** expand a filename in xFullPathname() in the VFS.44*/45#ifndef SQLITE_MAX_SYMLINK46# define SQLITE_MAX_SYMLINK 20047#endif48 49/*50** The default size of a disk sector51*/52#ifndef SQLITE_DEFAULT_SECTOR_SIZE53# define SQLITE_DEFAULT_SECTOR_SIZE 409654#endif55 56/*57** Temporary files are named starting with this prefix followed by 16 random58** alphanumeric characters, and no file extension. They are stored in the59** OS's standard temporary file directory, and are deleted prior to exit.60** If sqlite is being embedded in another program, you may wish to change the61** prefix to reflect your program's name, so that if your program exits62** prematurely, old temporary files can be easily identified. This can be done63** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.64**65** 2006-10-31: The default prefix used to be "sqlite_". But then66** Mcafee started using SQLite in their anti-virus product and it67** started putting files with the "sqlite" name in the c:/temp folder.68** This annoyed many windows users. Those users would then do a 69** Google search for "sqlite", find the telephone numbers of the70** developers and call to wake them up at night and complain.71** For this reason, the default name prefix is changed to be "sqlite" 72** spelled backwards. So the temp files are still identified, but73** anybody smart enough to figure out the code is also likely smart74** enough to know that calling the developer will not help get rid75** of the file.76*/77#ifndef SQLITE_TEMP_FILE_PREFIX78# define SQLITE_TEMP_FILE_PREFIX "etilqs_"79#endif80 81/*82** The following values may be passed as the second argument to83** sqlite3OsLock(). The various locks exhibit the following semantics:84**85** SHARED: Any number of processes may hold a SHARED lock simultaneously.86** RESERVED: A single process may hold a RESERVED lock on a file at87** any time. Other processes may hold and obtain new SHARED locks.88** PENDING: A single process may hold a PENDING lock on a file at89** any one time. Existing SHARED locks may persist, but no new90** SHARED locks may be obtained by other processes.91** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.92**93** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a94** process that requests an EXCLUSIVE lock may actually obtain a PENDING95** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to96** sqlite3OsLock().97*/98#define NO_LOCK 099#define SHARED_LOCK 1100#define RESERVED_LOCK 2101#define PENDING_LOCK 3102#define EXCLUSIVE_LOCK 4103 104/*105** File Locking Notes: (Mostly about windows but also some info for Unix)106**107** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because108** those functions are not available. So we use only LockFile() and109** UnlockFile().110**111** LockFile() prevents not just writing but also reading by other processes.112** A SHARED_LOCK is obtained by locking a single randomly-chosen 113** byte out of a specific range of bytes. The lock byte is obtained at 114** random so two separate readers can probably access the file at the 115** same time, unless they are unlucky and choose the same lock byte.116** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.117** There can only be one writer. A RESERVED_LOCK is obtained by locking118** a single byte of the file that is designated as the reserved lock byte.119** A PENDING_LOCK is obtained by locking a designated byte different from120** the RESERVED_LOCK byte.121**122** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,123** which means we can use reader/writer locks. When reader/writer locks124** are used, the lock is placed on the same range of bytes that is used125** for probabilistic locking in Win95/98/ME. Hence, the locking scheme126** will support two or more Win95 readers or two or more WinNT readers.127** But a single Win95 reader will lock out all WinNT readers and a single128** WinNT reader will lock out all other Win95 readers.129**130** The following #defines specify the range of bytes used for locking.131** SHARED_SIZE is the number of bytes available in the pool from which132** a random byte is selected for a shared lock. The pool of bytes for133** shared locks begins at SHARED_FIRST. 134**135** The same locking strategy and136** byte ranges are used for Unix. This leaves open the possibility of having137** clients on win95, winNT, and unix all talking to the same shared file138** and all locking correctly. To do so would require that samba (or whatever139** tool is being used for file sharing) implements locks correctly between140** windows and unix. I'm guessing that isn't likely to happen, but by141** using the same locking range we are at least open to the possibility.142**143** Locking in windows is manditory. For this reason, we cannot store144** actual data in the bytes used for locking. The pager never allocates145** the pages involved in locking therefore. SHARED_SIZE is selected so146** that all locks will fit on a single page even at the minimum page size.147** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE148** is set high so that we don't have to allocate an unused page except149** for very large databases. But one should test the page skipping logic 150** by setting PENDING_BYTE low and running the entire regression suite.151**152** Changing the value of PENDING_BYTE results in a subtly incompatible153** file format. Depending on how it is changed, you might not notice154** the incompatibility right away, even running a full regression test.155** The default location of PENDING_BYTE is the first byte past the156** 1GB boundary.157**158*/159#ifdef SQLITE_OMIT_WSD160# define PENDING_BYTE (0x40000000)161#else162# define PENDING_BYTE sqlite3PendingByte163#endif164#define RESERVED_BYTE (PENDING_BYTE+1)165#define SHARED_FIRST (PENDING_BYTE+2)166#define SHARED_SIZE 510167 168/*169** Wrapper around OS specific sqlite3_os_init() function.170*/171int sqlite3OsInit(void);172 173/* 174** Functions for accessing sqlite3_file methods 175*/176void sqlite3OsClose(sqlite3_file*);177int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);178int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);179int sqlite3OsTruncate(sqlite3_file*, i64 size);180int sqlite3OsSync(sqlite3_file*, int);181int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);182int sqlite3OsLock(sqlite3_file*, int);183int sqlite3OsUnlock(sqlite3_file*, int);184int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut);185int sqlite3OsFileControl(sqlite3_file*,int,void*);186void sqlite3OsFileControlHint(sqlite3_file*,int,void*);187#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0188int sqlite3OsSectorSize(sqlite3_file *id);189int sqlite3OsDeviceCharacteristics(sqlite3_file *id);190#ifndef SQLITE_OMIT_WAL191int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);192int sqlite3OsShmLock(sqlite3_file *id, int, int, int);193void sqlite3OsShmBarrier(sqlite3_file *id);194int sqlite3OsShmUnmap(sqlite3_file *id, int);195#endif /* SQLITE_OMIT_WAL */196int sqlite3OsFetch(sqlite3_file *id, i64, int, void **);197int sqlite3OsUnfetch(sqlite3_file *, i64, void *);198 199 200/* 201** Functions for accessing sqlite3_vfs methods 202*/203int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);204int sqlite3OsDelete(sqlite3_vfs *, const char *, int);205int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);206int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);207#ifndef SQLITE_OMIT_LOAD_EXTENSION208void *sqlite3OsDlOpen(sqlite3_vfs *, const char *);209void sqlite3OsDlError(sqlite3_vfs *, int, char *);210void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void);211void sqlite3OsDlClose(sqlite3_vfs *, void *);212#endif /* SQLITE_OMIT_LOAD_EXTENSION */213int sqlite3OsRandomness(sqlite3_vfs *, int, char *);214int sqlite3OsSleep(sqlite3_vfs *, int);215int sqlite3OsGetLastError(sqlite3_vfs*);216int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);217 218/*219** Convenience functions for opening and closing files using 220** sqlite3_malloc() to obtain space for the file-handle structure.221*/222int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*);223void sqlite3OsCloseFree(sqlite3_file *);224 225#endif /* _SQLITE_OS_H_ */226