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Annotation of embedaddon/sqlite3/tool/getlock.c, revision 1.1

1.1     ! misho       1: /*
        !             2: ** This utility program looks at an SQLite database and determines whether
        !             3: ** or not it is locked, the kind of lock, and who is holding this lock.
        !             4: **
        !             5: ** This only works on unix when the posix advisory locking method is used
        !             6: ** (which is the default on unix) and when the PENDING_BYTE is in its
        !             7: ** usual place.
        !             8: */
        !             9: #include <sys/types.h>
        !            10: #include <sys/stat.h>
        !            11: #include <unistd.h>
        !            12: #include <fcntl.h>
        !            13: #include <string.h>
        !            14: #include <stdio.h>
        !            15: #include <stdlib.h>
        !            16: #include <errno.h>
        !            17: 
        !            18: static void usage(const char *argv0){
        !            19:   fprintf(stderr, "Usage: %s database\n", argv0);
        !            20:   exit(1);
        !            21: }
        !            22: 
        !            23: /* Check for a conflicting lock.  If one is found, print an this
        !            24: ** on standard output using the format string given and return 1.
        !            25: ** If there are no conflicting locks, return 0.
        !            26: */
        !            27: static int isLocked(
        !            28:   int h,                /* File descriptor to check */
        !            29:   int type,             /* F_RDLCK or F_WRLCK */
        !            30:   unsigned int iOfst,   /* First byte of the lock */
        !            31:   unsigned int iCnt,    /* Number of bytes in the lock range */
        !            32:   const char *zType     /* Type of lock */
        !            33: ){
        !            34:   struct flock lk;
        !            35: 
        !            36:   memset(&lk, 0, sizeof(lk));
        !            37:   lk.l_type = type;
        !            38:   lk.l_whence = SEEK_SET;
        !            39:   lk.l_start = iOfst;
        !            40:   lk.l_len = iCnt;
        !            41:   if( fcntl(h, F_GETLK, &lk)==(-1) ){
        !            42:     fprintf(stderr, "fcntl(%d) failed: errno=%d\n", h, errno);
        !            43:     exit(1);
        !            44:   }
        !            45:   if( lk.l_type==F_UNLCK ) return 0;
        !            46:   printf("%s lock held by %d\n", zType, (int)lk.l_pid);
        !            47:   return 1;
        !            48: }
        !            49: 
        !            50: /*
        !            51: ** Location of locking bytes in the database file
        !            52: */
        !            53: #define PENDING_BYTE      (0x40000000)
        !            54: #define RESERVED_BYTE     (PENDING_BYTE+1)
        !            55: #define SHARED_FIRST      (PENDING_BYTE+2)
        !            56: #define SHARED_SIZE       510
        !            57: 
        !            58: /*
        !            59: ** Lock locations for shared-memory locks used by WAL mode.
        !            60: */
        !            61: #define SHM_BASE          120
        !            62: #define SHM_WRITE         SHM_BASE
        !            63: #define SHM_CHECKPOINT    (SHM_BASE+1)
        !            64: #define SHM_RECOVER       (SHM_BASE+2)
        !            65: #define SHM_READ_FIRST    (SHM_BASE+3)
        !            66: #define SHM_READ_SIZE     5
        !            67: 
        !            68: 
        !            69: int main(int argc, char **argv){
        !            70:   int hDb;        /* File descriptor for the open database file */
        !            71:   int hShm;       /* File descriptor for WAL shared-memory file */
        !            72:   char *zShm;     /* Name of the shared-memory file for WAL mode */
        !            73:   ssize_t got;    /* Bytes read from header */
        !            74:   int isWal;                 /* True if in WAL mode */
        !            75:   int nName;                 /* Length of filename */
        !            76:   unsigned char aHdr[100];   /* Database header */
        !            77:   int nLock = 0;             /* Number of locks held */
        !            78:   int i;                     /* Loop counter */
        !            79: 
        !            80:   if( argc!=2 ) usage(argv[0]);
        !            81:   hDb = open(argv[1], O_RDONLY, 0);
        !            82:   if( hDb<0 ){
        !            83:     fprintf(stderr, "cannot open %s\n", argv[1]);
        !            84:     return 1;
        !            85:   }
        !            86: 
        !            87:   /* Make sure we are dealing with an database file */
        !            88:   got = read(hDb, aHdr, 100);
        !            89:   if( got!=100 || memcmp(aHdr, "SQLite format 3",16)!=0 ){
        !            90:     fprintf(stderr, "not an SQLite database: %s\n", argv[1]);
        !            91:     exit(1);
        !            92:   }
        !            93: 
        !            94:   /* First check for an exclusive lock */
        !            95:   if( isLocked(hDb, F_RDLCK, SHARED_FIRST, SHARED_SIZE, "EXCLUSIVE") ){
        !            96:     return 0;
        !            97:   }
        !            98:   isWal = aHdr[18]==2;
        !            99:   if( isWal==0 ){
        !           100:     /* Rollback mode */
        !           101:     if( isLocked(hDb, F_RDLCK, PENDING_BYTE, 1, "PENDING") ) return 0;
        !           102:     if( isLocked(hDb, F_RDLCK, RESERVED_BYTE, 1, "RESERVED") ) return 0;
        !           103:     if( isLocked(hDb, F_WRLCK, SHARED_FIRST, SHARED_SIZE, "SHARED") ){
        !           104:       return 0;
        !           105:     }
        !           106:   }else{
        !           107:     /* WAL mode */
        !           108:     nName = (int)strlen(argv[1]);
        !           109:     zShm = malloc( nName + 100 );
        !           110:     if( zShm==0 ){
        !           111:       fprintf(stderr, "out of memory\n");
        !           112:       exit(1);
        !           113:     }
        !           114:     memcpy(zShm, argv[1], nName);
        !           115:     memcpy(&zShm[nName], "-shm", 5);
        !           116:     hShm = open(zShm, O_RDONLY, 0);
        !           117:     if( hShm<0 ){
        !           118:       fprintf(stderr, "cannot open %s\n", zShm);
        !           119:       return 1;
        !           120:     }
        !           121:     if( isLocked(hShm, F_RDLCK, SHM_RECOVER, 1, "WAL-RECOVERY") ){
        !           122:       return 0;
        !           123:     }
        !           124:     nLock += isLocked(hShm, F_RDLCK, SHM_CHECKPOINT, 1, "WAL-CHECKPOINT");
        !           125:     nLock += isLocked(hShm, F_RDLCK, SHM_WRITE, 1, "WAL-WRITE");
        !           126:     for(i=0; i<SHM_READ_SIZE; i++){
        !           127:       nLock += isLocked(hShm, F_WRLCK, SHM_READ_FIRST+i, 1, "WAL-READ");
        !           128:     }
        !           129:   }
        !           130:   if( nLock==0 ){
        !           131:     printf("file is not locked\n");
        !           132:   }
        !           133:   return 0;
        !           134: }