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Add experimental SQLITE_FCNTL_EXTERNAL_READER file control.

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FossilOrigin-Name: e16da5af822ef31d7e05992403cf9787fbb3d9abb0b5283aba55ea07e1830a72
This commit is contained in:
dan
2021-04-02 19:55:48 +00:00
parent ec435c40ed
commit aecc04d642
6 changed files with 176 additions and 10 deletions
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39
src/os_unix.c
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@@ -3951,6 +3951,7 @@ static void unixModeBit(unixFile *pFile, unsigned char mask, int *pArg){
/* Forward declaration */
static int unixGetTempname(int nBuf, char *zBuf);
static int unixFcntlExternalReader(unixFile*, int*);
/*
** Information and control of an open file handle.
@@ -4067,6 +4068,10 @@ static int unixFileControl(sqlite3_file *id, int op, void *pArg){
return proxyFileControl(id,op,pArg);
}
#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
case SQLITE_FCNTL_EXTERNAL_READER: {
return unixFcntlExternalReader((unixFile*)id, (int*)pArg);
}
}
return SQLITE_NOTFOUND;
}
@@ -4312,6 +4317,40 @@ struct unixShm {
#define UNIX_SHM_BASE ((22+SQLITE_SHM_NLOCK)*4) /* first lock byte */
#define UNIX_SHM_DMS (UNIX_SHM_BASE+SQLITE_SHM_NLOCK) /* deadman switch */
/*
** Use F_GETLK to check whether or not there are any readers with open
** wal-mode transactions in other processes on database file pFile. If
** no error occurs, return SQLITE_OK and set (*piOut) to 1 if there are
** such transactions, or 0 otherwise. If an error occurs, return an
** SQLite error code. The final value of *piOut is undefined in this
** case.
*/
static int unixFcntlExternalReader(unixFile *pFile, int *piOut){
int rc = SQLITE_OK;
*piOut = 0;
if( pFile->pShm){
unixShmNode *pShmNode = pFile->pShm->pShmNode;
struct flock f;
memset(&f, 0, sizeof(f));
f.l_type = F_WRLCK;
f.l_whence = SEEK_SET;
f.l_start = UNIX_SHM_BASE + 3;
f.l_len = SQLITE_SHM_NLOCK - 3;
sqlite3_mutex_enter(pShmNode->pShmMutex);
if( osFcntl(pShmNode->hShm, F_GETLK, &f)<0 ){
rc = SQLITE_IOERR_LOCK;
}else{
*piOut = (f.l_type!=F_UNLCK);
}
sqlite3_mutex_leave(pShmNode->pShmMutex);
}
return rc;
}
/*
** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
**