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 /* 37 ** The default size of a disk sector 38 */ 39 #ifndef SQLITE_DEFAULT_SECTOR_SIZE 40 # define SQLITE_DEFAULT_SECTOR_SIZE 4096 41 #endif 42 43 /* 44 ** Temporary files are named starting with this prefix followed by 16 random 45 ** alphanumeric characters, and no file extension. They are stored in the 46 ** OS's standard temporary file directory, and are deleted prior to exit. 47 ** If sqlite is being embedded in another program, you may wish to change the 48 ** prefix to reflect your program's name, so that if your program exits 49 ** prematurely, old temporary files can be easily identified. This can be done 50 ** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line. 51 ** 52 ** 2006-10-31: The default prefix used to be "sqlite_". But then 53 ** Mcafee started using SQLite in their anti-virus product and it 54 ** started putting files with the "sqlite" name in the c:/temp folder. 55 ** This annoyed many windows users. Those users would then do a 56 ** Google search for "sqlite", find the telephone numbers of the 57 ** developers and call to wake them up at night and complain. 58 ** For this reason, the default name prefix is changed to be "sqlite" 59 ** spelled backwards. So the temp files are still identified, but 60 ** anybody smart enough to figure out the code is also likely smart 61 ** enough to know that calling the developer will not help get rid 62 ** of the file. 63 */ 64 #ifndef SQLITE_TEMP_FILE_PREFIX 65 # define SQLITE_TEMP_FILE_PREFIX "etilqs_" 66 #endif 67 68 /* 69 ** The following values may be passed as the second argument to 70 ** sqlite3OsLock(). The various locks exhibit the following semantics: 71 ** 72 ** SHARED: Any number of processes may hold a SHARED lock simultaneously. 73 ** RESERVED: A single process may hold a RESERVED lock on a file at 74 ** any time. Other processes may hold and obtain new SHARED locks. 75 ** PENDING: A single process may hold a PENDING lock on a file at 76 ** any one time. Existing SHARED locks may persist, but no new 77 ** SHARED locks may be obtained by other processes. 78 ** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks. 79 ** 80 ** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a 81 ** process that requests an EXCLUSIVE lock may actually obtain a PENDING 82 ** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to 83 ** sqlite3OsLock(). 84 */ 85 #define NO_LOCK 0 86 #define SHARED_LOCK 1 87 #define RESERVED_LOCK 2 88 #define PENDING_LOCK 3 89 #define EXCLUSIVE_LOCK 4 90 91 /* 92 ** File Locking Notes: (Mostly about windows but also some info for Unix) 93 ** 94 ** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because 95 ** those functions are not available. So we use only LockFile() and 96 ** UnlockFile(). 97 ** 98 ** LockFile() prevents not just writing but also reading by other processes. 99 ** A SHARED_LOCK is obtained by locking a single randomly-chosen 100 ** byte out of a specific range of bytes. The lock byte is obtained at 101 ** random so two separate readers can probably access the file at the 102 ** same time, unless they are unlucky and choose the same lock byte. 103 ** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range. 104 ** There can only be one writer. A RESERVED_LOCK is obtained by locking 105 ** a single byte of the file that is designated as the reserved lock byte. 106 ** A PENDING_LOCK is obtained by locking a designated byte different from 107 ** the RESERVED_LOCK byte. 108 ** 109 ** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available, 110 ** which means we can use reader/writer locks. When reader/writer locks 111 ** are used, the lock is placed on the same range of bytes that is used 112 ** for probabilistic locking in Win95/98/ME. Hence, the locking scheme 113 ** will support two or more Win95 readers or two or more WinNT readers. 114 ** But a single Win95 reader will lock out all WinNT readers and a single 115 ** WinNT reader will lock out all other Win95 readers. 116 ** 117 ** The following #defines specify the range of bytes used for locking. 118 ** SHARED_SIZE is the number of bytes available in the pool from which 119 ** a random byte is selected for a shared lock. The pool of bytes for 120 ** shared locks begins at SHARED_FIRST. 121 ** 122 ** The same locking strategy and 123 ** byte ranges are used for Unix. This leaves open the possibility of having 124 ** clients on win95, winNT, and unix all talking to the same shared file 125 ** and all locking correctly. To do so would require that samba (or whatever 126 ** tool is being used for file sharing) implements locks correctly between 127 ** windows and unix. I'm guessing that isn't likely to happen, but by 128 ** using the same locking range we are at least open to the possibility. 129 ** 130 ** Locking in windows is manditory. For this reason, we cannot store 131 ** actual data in the bytes used for locking. The pager never allocates 132 ** the pages involved in locking therefore. SHARED_SIZE is selected so 133 ** that all locks will fit on a single page even at the minimum page size. 134 ** PENDING_BYTE defines the beginning of the locks. By default PENDING_BYTE 135 ** is set high so that we don't have to allocate an unused page except 136 ** for very large databases. But one should test the page skipping logic 137 ** by setting PENDING_BYTE low and running the entire regression suite. 138 ** 139 ** Changing the value of PENDING_BYTE results in a subtly incompatible 140 ** file format. Depending on how it is changed, you might not notice 141 ** the incompatibility right away, even running a full regression test. 142 ** The default location of PENDING_BYTE is the first byte past the 143 ** 1GB boundary. 144 ** 145 */ 146 #ifdef SQLITE_OMIT_WSD 147 # define PENDING_BYTE (0x40000000) 148 #else 149 # define PENDING_BYTE sqlite3PendingByte 150 #endif 151 #define RESERVED_BYTE (PENDING_BYTE+1) 152 #define SHARED_FIRST (PENDING_BYTE+2) 153 #define SHARED_SIZE 510 154 155 /* 156 ** Wrapper around OS specific sqlite3_os_init() function. 157 */ 158 int sqlite3OsInit(void); 159 160 /* 161 ** Functions for accessing sqlite3_file methods 162 */ 163 void sqlite3OsClose(sqlite3_file*); 164 int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset); 165 int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset); 166 int sqlite3OsTruncate(sqlite3_file*, i64 size); 167 int sqlite3OsSync(sqlite3_file*, int); 168 int sqlite3OsFileSize(sqlite3_file*, i64 *pSize); 169 int sqlite3OsLock(sqlite3_file*, int); 170 int sqlite3OsUnlock(sqlite3_file*, int); 171 int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut); 172 int sqlite3OsFileControl(sqlite3_file*,int,void*); 173 void sqlite3OsFileControlHint(sqlite3_file*,int,void*); 174 #define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0 175 int sqlite3OsSectorSize(sqlite3_file *id); 176 int sqlite3OsDeviceCharacteristics(sqlite3_file *id); 177 #ifndef SQLITE_OMIT_WAL 178 int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **); 179 int sqlite3OsShmLock(sqlite3_file *id, int, int, int); 180 void sqlite3OsShmBarrier(sqlite3_file *id); 181 int sqlite3OsShmUnmap(sqlite3_file *id, int); 182 #endif /* SQLITE_OMIT_WAL */ 183 int sqlite3OsFetch(sqlite3_file *id, i64, int, void **); 184 int sqlite3OsUnfetch(sqlite3_file *, i64, void *); 185 186 187 /* 188 ** Functions for accessing sqlite3_vfs methods 189 */ 190 int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *); 191 int sqlite3OsDelete(sqlite3_vfs *, const char *, int); 192 int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut); 193 int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *); 194 #ifndef SQLITE_OMIT_LOAD_EXTENSION 195 void *sqlite3OsDlOpen(sqlite3_vfs *, const char *); 196 void sqlite3OsDlError(sqlite3_vfs *, int, char *); 197 void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void); 198 void sqlite3OsDlClose(sqlite3_vfs *, void *); 199 #endif /* SQLITE_OMIT_LOAD_EXTENSION */ 200 int sqlite3OsRandomness(sqlite3_vfs *, int, char *); 201 int sqlite3OsSleep(sqlite3_vfs *, int); 202 int sqlite3OsGetLastError(sqlite3_vfs*); 203 int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*); 204 205 /* 206 ** Convenience functions for opening and closing files using 207 ** sqlite3_malloc() to obtain space for the file-handle structure. 208 */ 209 int sqlite3OsOpenMalloc(sqlite3_vfs *, const char *, sqlite3_file **, int,int*); 210 void sqlite3OsCloseFree(sqlite3_file *); 211 212 #endif /* _SQLITE_OS_H_ */ 213