1/*
2** 2001 September 16
3**
4** The author disclaims copyright to this source code. In place of
5** 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 file
14** "os.c") attempt to abstract the underlying operating system so that
15** 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 up
18** 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 the
25** 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 it
30** a no-op
31*/
32#ifndef SET_FULLSYNC
33# define SET_FULLSYNC(x,y)
34#endif
35
36/* Maximum pathname length. Note: FILENAME_MAX defined by stdio.h
37*/
38#ifndef SQLITE_MAX_PATHLEN
39# define SQLITE_MAX_PATHLEN FILENAME_MAX
40#endif
41
42/* Maximum number of symlinks that will be resolved while trying to
43** expand a filename in xFullPathname() in the VFS.
44*/
45#ifndef SQLITE_MAX_SYMLINK
46# define SQLITE_MAX_SYMLINK 200
47#endif
48
49/*
50** The default size of a disk sector
51*/
52#ifndef SQLITE_DEFAULT_SECTOR_SIZE
53# define SQLITE_DEFAULT_SECTOR_SIZE 4096
54#endif
55
56/*
57** Temporary files are named starting with this prefix followed by 16 random
58** alphanumeric characters, and no file extension. They are stored in the
59** 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 the
61** prefix to reflect your program's name, so that if your program exits
62** prematurely, old temporary files can be easily identified. This can be done
63** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
64**
65** 2006-10-31: The default prefix used to be "sqlite_". But then
66** Mcafee started using SQLite in their anti-virus product and it
67** 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 the
70** 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, but
73** anybody smart enough to figure out the code is also likely smart
74** enough to know that calling the developer will not help get rid
75** of the file.
76*/
77#ifndef SQLITE_TEMP_FILE_PREFIX
78# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
79#endif
80
81/*
82** The following values may be passed as the second argument to
83** 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 at
87** any time. Other processes may hold and obtain new SHARED locks.
88** PENDING: A single process may hold a PENDING lock on a file at
89** any one time. Existing SHARED locks may persist, but no new
90** 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, a
94** process that requests an EXCLUSIVE lock may actually obtain a PENDING
95** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
96** sqlite3OsLock().
97*/
98#define NO_LOCK 0
99#define SHARED_LOCK 1
100#define RESERVED_LOCK 2
101#define PENDING_LOCK 3
102#define EXCLUSIVE_LOCK 4
103
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 because
108** those functions are not available. So we use only LockFile() and
109** 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 locking
118** 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 from
120** 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 locks
124** are used, the lock is placed on the same range of bytes that is used
125** for probabilistic locking in Win95/98/ME. Hence, the locking scheme
126** 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 single
128** 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 which
132** a random byte is selected for a shared lock. The pool of bytes for
133** shared locks begins at SHARED_FIRST.
134**
135** The same locking strategy and
136** byte ranges are used for Unix. This leaves open the possibility of having
137** clients on win95, winNT, and unix all talking to the same shared file
138** and all locking correctly. To do so would require that samba (or whatever
139** tool is being used for file sharing) implements locks correctly between
140** windows and unix. I'm guessing that isn't likely to happen, but by
141** 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 store
144** actual data in the bytes used for locking. The pager never allocates
145** the pages involved in locking therefore. SHARED_SIZE is selected so
146** 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_BYTE
148** is set high so that we don't have to allocate an unused page except
149** 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 incompatible
153** file format. Depending on how it is changed, you might not notice
154** the incompatibility right away, even running a full regression test.
155** The default location of PENDING_BYTE is the first byte past the
156** 1GB boundary.
157**
158*/
159#ifdef SQLITE_OMIT_WSD
160# define PENDING_BYTE (0x40000000)
161#else
162# define PENDING_BYTE sqlite3PendingByte
163#endif
164#define RESERVED_BYTE (PENDING_BYTE+1)
165#define SHARED_FIRST (PENDING_BYTE+2)
166#define SHARED_SIZE 510
167
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 0xca093fa0
188int sqlite3OsSectorSize(sqlite3_file *id);
189int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
190#ifndef SQLITE_OMIT_WAL
191int 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_EXTENSION
208void *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