modernc.org/cc@v1.0.1/v2/testdata/_sqlite/src/os.h (about)

     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_ */