fix curls detection of ssl on AROS. Adjust the used link libraries (linking ssl twice...

[AROS-Contrib.git] / sqlite3 / os_aros.c

/*
** 2004 May 22
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains code that is specific to Unix systems.
*/
#include "sqliteInt.h"
#include "os.h"
#if OS_AROS              /* This file is used on unix only */


#include <time.h>
#include <errno.h>
#include <unistd.h>

#ifdef SQLITE_DEBUG
const char *arosErrLoc = NULL;
const char const *__arossql__NULL = NULL;
#endif

/*
** Do not include any of the File I/O interface procedures if the
** SQLITE_OMIT_DISKIO macro is defined (indicating that there database
** will be in-memory only)
*/
#ifndef SQLITE_OMIT_DISKIO


/*
** Define various macros that are missing from some systems.
*/
#ifndef O_LARGEFILE
#       define O_LARGEFILE 0
#endif
#ifdef SQLITE_DISABLE_LFS
#       undef O_LARGEFILE
#       define O_LARGEFILE 0
#endif
#ifndef O_NOFOLLOW
#       define O_NOFOLLOW 0
#endif
#ifndef O_BINARY
#       define O_BINARY 0
#endif

/* Include code that is common to all os_*.c files */
#include "os_common.h"


/*
 * An instance of the following structure serves as the key used to locate
 * a particular lockInfo structure given its inode.
 * */
struct lockKey {
        dev_t dev;       /* Device number */
        ino_t ino;       /* Inode number */
};
#define openKey lockKey


/*
 * An instance of the following structure is allocated for each open inode on
 * each thread with a different process ID. (Threads have different process IDs
 * on linux, but not on most other unixes.)
 *
 * A single inode can have multiple file descriptors, so each OsFile structure
 * contains a pointer to an instance of this object and this object keeps
 * a count of the number of OsFiles pointing to it.
 * */
struct lockInfo {
        struct lockKey key;  /* The lookup key */
        int cnt;             /* Number of SHARED locks held */
        int locktype;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
        int nRef;            /* Number of pointers to this structure */
};


/*
 * An instance of the following structure is allocated for each open inode.
 * This structure keeps track of the number of locks on that inode. If a close
 * is attempted against an inode that is holding locks, the close is deferred
 * until all locks clear by adding the file descriptor to be closed to the
 * pending list.
 * */
struct openCnt {
        struct openKey key;   /* The lookup key */
        int nRef;             /* Number of pointers to this structure */
        int nLock;            /* Number of outstanding locks */
        int nPending;         /* Number of pending close() operations */
        int *aPending;        /* Malloced space holding fd's awaiting a close() */
};


/* 
 * These hash table maps inodes and process IDs into lockInfo and openCnt
 * structures. Access to these hash tables must be protected by a mutex.
 * */
static Hash lockHash = { SQLITE_HASH_BINARY, 0, 0, 0, 0, 0 };
static Hash openHash = { SQLITE_HASH_BINARY, 0, 0, 0, 0, 0 };


/*
 * Release a lockInfo structure previously allocated by findLockInfo().
 * */
static void releaseLockInfo(struct lockInfo *pLock)
{
        pLock->nRef--;
        if( pLock->nRef==0 )
        {
                sqlite3HashInsert(&lockHash, &pLock->key, sizeof(pLock->key), 0);
                sqliteFree(pLock);
        }
}


/*
 * Release a openCnt structure previously allocated by findLockInfo().
 * */
static void releaseOpenCnt(struct openCnt *pOpen)
{
        pOpen->nRef--;
        if( pOpen->nRef==0 )
        {
                sqlite3HashInsert(&openHash, &pOpen->key, sizeof(pOpen->key), 0);
                sqliteFree(pOpen->aPending);
                sqliteFree(pOpen);
        }
}


/*
 * Given a file descriptor, locate lockInfo and openCnt structures that
 * describes that file descriptor. Create a new ones if necessary. The return
 * values might be unset if an error occurs.
 * 
 * Return the number of errors.
 * */
static int findLockInfo(
                int fd,                      /* The file descriptor used in the key */
                struct lockInfo **ppLock,    /* Return the lockInfo structure here */
                struct openCnt **ppOpen      /* Return the openCnt structure here */
                )
{
        int rc;
        struct lockKey key1;
        struct openKey key2;
        struct stat statbuf;
        struct lockInfo *pLock;
        struct openCnt *pOpen;
        rc = fstat(fd, &statbuf);
        if( rc!=0 ) return 1;
        memset(&key1, 0, sizeof(key1));
        key1.dev = statbuf.st_dev;
        key1.ino = statbuf.st_ino;
        memset(&key2, 0, sizeof(key2));
        key2.dev = statbuf.st_dev;
        key2.ino = statbuf.st_ino;
        pLock = (struct lockInfo*)sqlite3HashFind(&lockHash, &key1, sizeof(key1));
        if( !pLock )
        {
                struct lockInfo *pOld;
                pLock = sqliteMallocRaw( sizeof(*pLock) );
                if( !pLock ) return 1;
                pLock->key = key1;
                pLock->nRef = 1;
                pLock->cnt = 0;
                pLock->locktype = 0;
                pOld = sqlite3HashInsert(&lockHash, &pLock->key, sizeof(key1), pLock);
                if( pOld )
                {
                        assert( pOld==pLock );
                        sqliteFree(pLock);
                        return 1;
                }
        }
        else pLock->nRef++;
        
        *ppLock = pLock;
        pOpen = (struct openCnt*)sqlite3HashFind(&openHash, &key2, sizeof(key2));
        if( !pOpen )
        {
                struct openCnt *pOld;
                pOpen = sqliteMallocRaw( sizeof(*pOpen) );
                if( !pOpen )
                {
                        releaseLockInfo(pLock);
                        return 1;
                }
                pOpen->key = key2;
                pOpen->nRef = 1;
                pOpen->nLock = 0;
                pOpen->nPending = 0;
                pOpen->aPending = NULL;
                pOld = sqlite3HashInsert(&openHash, &pOpen->key, sizeof(key2), pOpen);
                if( pOld )
                {
                        assert( pOld==pOpen );
                        sqliteFree(pOpen);
                        releaseLockInfo(pLock);
                        return 1;
                }
        }
        else pOpen->nRef++;
        
        *ppOpen = pOpen;
        return 0;
}


/*
 * Delete the named file.
 * */
err_t sqlite3OsDelete( CONST_STRPTR zFilename )
{
        unlink(zFilename);
        return SQLITE_OK;
}


/*
 * Return TRUE if the named file exists.
 * */
BOOL sqlite3OsFileExists( CONST_STRPTR zFilename )
{
        return access(zFilename, F_OK)==0;
}


/*
 * Attempt to open a file for both reading and writing. If that fails, try
 * opening it read-only. If the file does not exist, try to create it.
 * 
 * On success, a handle for the open file is written to *id and *pReadonly is
 * set to 0 if the file was opened for reading and writing or 1 if the file was
 * opened read-only. The function returns SQLITE_OK.
 *
 * On failure, the function returns SQLITE_CANTOPEN and leaves *id and
 * *pReadonly unchanged.
 * */
err_t sqlite3OsOpenReadWrite(
                CONST_STRPTR zFilename,
                OsFile *id,
                int *pReadonly
                )
{
        int rc;
        assert( !id->isOpen );
        id->dirfd = -1;
        id->h = open(zFilename, O_RDWR|O_CREAT|O_LARGEFILE|O_BINARY,
                        SQLITE_DEFAULT_FILE_PERMISSIONS);
        if( id->h < 0 )
        {
#ifdef EISDIR
                if( errno==EISDIR ) return SQLITE_CANTOPEN;
#endif
                id->h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY);
                if( id->h < 0 ) return SQLITE_CANTOPEN;
                *pReadonly = TRUE;
        }
        else *pReadonly = FALSE;
        
        sqlite3OsEnterMutex();
        rc = findLockInfo(id->h, &id->pLock, &id->pOpen);
        sqlite3OsLeaveMutex();
        if( rc )
        {
                close(id->h);
                return SQLITE_NOMEM;
        }
        id->locktype = 0;
        id->isOpen = 1;
        TRACE("OPEN    %-3d %s\n", id->h, zFilename);
        OpenCounter(+1);
        return SQLITE_OK;
}


/*
 * Attempt to open a new file for exclusive access by this process. The file
 * will be opened for both reading and writing. To avoid a potential security
 * problem, we do not allow the file to have previously existed. Nor do we
 * allow the file to be a symbolic link.
 *
 * If delFlag is true, then make arrangements to automatically delete the file
 * when it is closed.
 *
 * On success, write the file handle into *id and return SQLITE_OK.
 *
 * On failure, return SQLITE_CANTOPEN.
 * */
err_t sqlite3OsOpenExclusive(CONST_STRPTR zFilename, OsFile *id, BOOL delFlag)
{
        int rc;
        
        assert( !id->isOpen );
        if( access(zFilename, F_OK)==0 )
                return SQLITE_CANTOPEN;

        id->dirfd = -1;
        if( 0 > (id->h = open(zFilename,
                                        O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW|O_LARGEFILE|O_BINARY,
                                        0600)))
                return SQLITE_CANTOPEN;
        
        sqlite3OsEnterMutex();
        rc = findLockInfo(id->h, &id->pLock, &id->pOpen);
        sqlite3OsLeaveMutex();
        if( rc )
        {
                close(id->h);
                unlink(zFilename);
                return SQLITE_NOMEM;
        }
        id->locktype = 0;
        id->isOpen = TRUE;
        if( delFlag )
                unlink(zFilename);
        TRACE("OPEN-EX %-3d %s\n", id->h, zFilename);
        OpenCounter(+1);
        return SQLITE_OK;
}


/*
 * Attempt to open a new file for read-only access.
 *
 * On success, write the file handle into *id and return SQLITE_OK.
 * On failure, return SQLITE_CANTOPEN.
 * */
err_t sqlite3OsOpenReadOnly( CONST_STRPTR zFilename, OsFile *id )
{
        int rc;
        assert( !id->isOpen );
        id->dirfd = -1;
        if( 0 > (id->h = open(zFilename, O_RDONLY|O_LARGEFILE|O_BINARY)))
                return SQLITE_CANTOPEN;
        sqlite3OsEnterMutex();
        rc = findLockInfo(id->h, &id->pLock, &id->pOpen);
        sqlite3OsLeaveMutex();
        if( rc )
        {
                close(id->h);
                return SQLITE_NOMEM;
        }
        id->locktype = 0;
        id->isOpen = TRUE;
        TRACE("OPEN-RO %-3d %s\n", id->h, zFilename);
        OpenCounter(+1);
        return SQLITE_OK;
}


/*
 * Attempt to open a file descriptor for the directory that contains a file.
 * This file descriptor can be used to fsync() the directory in order to make
 * sure the creation of a new file is actually written to disk.
 *
 * This routine is only meaningful for Unix. It is a no-op under windows since
 * windows does not support hard links.
 *
 * On success, a handle for a previously open file is at *id is updated with
 * the new directory file descriptor and SQLITE_OK is returned.
 *
 * On failure, the function returns SQLITE_CANTOPEN and leaves *id unchanged.
 * */
err_t sqlite3OsOpenDirectory( CONST_STRPTR zDirname, OsFile *id )
{
        if( !id->isOpen )
        {
                /* 
                 * Do not open the directory if the corresponding file is not already
                 * open.
                 * */
                return SQLITE_CANTOPEN;
        }
        assert( id->dirfd<0 );
        if( 0 > (id->dirfd = open(zDirname, O_RDONLY|O_BINARY, 0)))
                return SQLITE_CANTOPEN;
        TRACE("OPENDIR %-3d %s\n", id->dirfd, zDirname);
        return SQLITE_OK;
}


/*
 * If the following global variable points to a string which is the name of
 * a directory, then that directory will be used to store temporary files.
 * */
STRPTR sqlite3_temp_directory = NULL;


/*
 * Create a temporary file name in zBuf. zBuf must be big enough to hold at
 * least SQLITE_TEMPNAME_SIZE characters.
 * */
err_t sqlite3OsTempFileName(char *zBuf)
{
        static CONST_STRPTR azDirs[] = {
                0,
                "T:",
                "RAM:",
        };
        static const unsigned char zChars[] =
                "abcdefghijklmnopqrstuvwxyz"
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                "0123456789";
        int i, j;
        struct stat buf;
        CONST_STRPTR zDir = ".";
        
        azDirs[0] = sqlite3_temp_directory;

        for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++)
        {
                if( !azDirs[i] ) continue;
                if( stat(azDirs[i], &buf) ) continue;
                if( !S_ISDIR(buf.st_mode) ) continue;
                if( access(azDirs[i], F_OK) ) continue;
                zDir = azDirs[i];
                break;
        }
        do {
                sprintf(zBuf, "%s/"TEMP_FILE_PREFIX, zDir);
                j = strlen(zBuf);
                sqlite3Randomness(15, &zBuf[j]);
                for(i=0; i<15; i++, j++)
                        zBuf[j] = (char)zChars[((unsigned char)zBuf[j])%(sizeof(zChars)-1)];
                zBuf[j] = '\0';
        }while( access(zBuf,F_OK)==0 );
        return SQLITE_OK;
}


#ifndef SQLITE_OMIT_PAGER_PRAGMAS
/*
 * Check that a given pathname is a directory and is writable.
 * */
BOOL sqlite3OsIsDirWritable( CONST_STRPTR zBuf )
{
        struct stat buf;
        if( !zBuf ) return FALSE;
        if( zBuf[0]=='\0' ) return FALSE;
        if( stat(zBuf, &buf) ) return FALSE;
        if( !S_ISDIR(buf.st_mode) ) return FALSE;
        if( access(zBuf, R_OK|W_OK|X_OK) ) return FALSE;
        return TRUE;
}
#endif /* SQLITE_OMIT_PAGER_PRAGMAS */


/*
 * Read data from a file into a buffer. Return SQLITE_OK if all bytes were read
 * successfully and SQLITE_IOERR if anything goes wrong.
 * */
err_t sqlite3OsRead(OsFile *id, void *pBuf, int amt)
{
        int got;
        assert( id->isOpen );
        SimulateIOError(SQLITE_IOERR);
        TIMER_START;
        got = read(id->h, pBuf, amt);
        TIMER_END;
        TRACE("READ    %-3d %5d %7d %d\n", id->h, got, last_page, TIMER_ELAPSED);
        SEEK(0);
        /* if( got<0 ) got = 0; */
        if( got==amt ) return SQLITE_OK;
        return SQLITE_IOERR;
}


/*
 * Write data from a buffer into a file. Return SQLITE_OK on success or some
 * other error code on failure.
 * */
err_t sqlite3OsWrite(OsFile *id, const void *pBuf, int amt)
{
        int wrote = 0;
        assert( id->isOpen );
        assert( amt>0 );
        SimulateIOError(SQLITE_IOERR);
        SimulateDiskfullError;
        TIMER_START;
        while( amt>0 && (wrote = write(id->h, pBuf, amt))>0 )
        {
                amt -= wrote;
                pBuf = &((char*)pBuf)[wrote];
        }
        TIMER_END;
        TRACE("WRITE   %-3d %5d %7d %d\n", id->h, wrote, last_page, TIMER_ELAPSED);
        SEEK(0);
        if( amt>0 ) return SQLITE_FULL;
        return SQLITE_OK;
}


/*
 * Move the read/write pointer in a file.
 * */
err_t sqlite3OsSeek(OsFile *id, i64 offset)
{
        assert( id->isOpen );
        SEEK(offset/1024 + 1);
        lseek(id->h, offset, SEEK_SET);
        return SQLITE_OK;
}


#ifdef SQLITE_TEST
/*
 * Count the number of fullsyncs and normal syncs. This is used to test that
 * syncs and fullsyncs are occuring at the right times.
 * */
int sqlite3_sync_count = 0;
int sqlite3_fullsync_count = 0;
#endif


/*
 * The fsync() system call does not work as advertised on many unix systems.
 * The following procedure is an attempt to make it work better.
 * 
 * The SQLITE_NO_SYNC macro disables all fsync()s. This is useful for testing
 * when we want to run through the test suite quickly. You are strongly
 * advised *not* to deploy with SQLITE_NO_SYNC enabled, however, since with
 * SQLITE_NO_SYNC enabled, an OS crash or power failure will likely corrupt
 * the database file.
 * */
static int full_fsync(int fd, int fullSync)
{
        int rc;
        
        /*
         * Record the number of times that we do a normal fsync() and FULLSYNC.
         * This is used during testing to verify that this procedure gets called
         * with the correct arguments.
         * */
#ifdef SQLITE_TEST
        if( fullSync ) sqlite3_fullsync_count++;
        sqlite3_sync_count++;
#endif

        /*
         * If we compiled with the SQLITE_NO_SYNC flag, then syncing is a no-op
         * */
#ifdef SQLITE_NO_SYNC
        rc = SQLITE_OK;
#else

#ifdef F_FULLFSYNC
        if( fullSync )
                rc = fcntl(fd, F_FULLFSYNC, 0);
        else rc = 1;
        
        /* If the FULLSYNC failed, try to do a normal fsync() */
        if( rc ) rc = fsync(fd);
#else
        rc = fsync(fd);
#endif /* defined(F_FULLFSYNC) */
#endif /* defined(SQLITE_NO_SYNC) */

        return rc;
}


/*
 * Make sure all writes to a particular file are committed to disk.
 *
 * Under Unix, also make sure that the directory entry for the file has been
 * created by fsync-ing the directory that contains the file. If we do not do
 * this and we encounter a power failure, the directory entry for the journal
 * might not exist after we reboot. The next SQLite to access the file will not
 * know that the journal exists (because the directory entry for the journal
 * was never created) and the transaction will not roll back - possibly leading
 * to database corruption.
 * */
err_t sqlite3OsSync(OsFile *id)
{
        assert( id->isOpen );
        SimulateIOError(SQLITE_IOERR);
        TRACE("SYNC    %-3d\n", id->h);
        if( full_fsync(id->h, id->fullSync) )
                return SQLITE_IOERR;
        if( id->dirfd>=0 )
        {
                TRACE("DIRSYNC %-3d\n", id->dirfd);
                full_fsync(id->dirfd, id->fullSync);
                close(id->dirfd);  /* Only need to sync once, so close the directory */
                id->dirfd = -1;    /* when we are done. */
        }
        return SQLITE_OK;
}


/*
 * Sync the directory zDirname. This is a no-op on operating systems other
 * than UNIX.
 * 
 * This is used to make sure the master journal file has truely been deleted
 * before making changes to individual journals on a multi-database commit.
 * The F_FULLFSYNC option is not needed here.
 * */
err_t sqlite3OsSyncDirectory( CONST_STRPTR zDirname )
{
        int fd;
        int r;
        SimulateIOError(SQLITE_IOERR);
        fd = open(zDirname, O_RDONLY|O_BINARY, 0);
        TRACE("DIRSYNC %-3d (%s)\n", fd, zDirname);
        if( fd<0 ) return SQLITE_CANTOPEN;

        r = fsync(fd);
        close(fd);
        return ((r==0)?SQLITE_OK:SQLITE_IOERR);
}


/*
 * Truncate an open file to a specified size.
 * */
err_t sqlite3OsTruncate(OsFile *id, i64 nByte)
{
        assert( id->isOpen );
        SimulateIOError(SQLITE_IOERR);
        return ftruncate(id->h, nByte)==0 ? SQLITE_OK : SQLITE_IOERR;
}


/*
 * Determine the current size of a file in bytes.
 * */
err_t sqlite3OsFileSize(OsFile *id, i64 *pSize)
{
        struct stat buf;
        assert( id->isOpen );
        SimulateIOError(SQLITE_IOERR);
        if( fstat(id->h, &buf)!=0 )
                return SQLITE_IOERR;
        *pSize = buf.st_size;
        return SQLITE_OK;
}


/*
 * This routine checks if there is a RESERVED lock held on the specified file
 * by this or any other process. If such a lock is held, return non-zero. If
 * the file is unlocked or holds only SHARED locks, then return zero.
 * */
BOOL sqlite3OsCheckReservedLock(OsFile *id)
{
        BOOL r = FALSE;

        assert( id->isOpen );
        sqlite3OsEnterMutex(); /* Needed because id->pLock is shared across
                                                          threads */
        /* Check if a thread in this process holds such a lock */
        if( id->pLock->locktype > SHARED_LOCK )
                r = TRUE;

        /* Otherwise see if some other process holds it. */
#if !OS_AROS
        if( !r )
        {
                struct flock lock;
                lock.l_whence = SEEK_SET;
                lock.l_start = RESERVED_BYTE;
                lock.l_len = 1;
                lock.l_type = F_WRLCK;
                fcntl(id->h, F_GETLK, &lock);
                if( lock.l_type != F_UNLCK )
                        r = TRUE;
        }
#endif
        
        sqlite3OsLeaveMutex();
        TRACE("TEST WR-LOCK %d %d\n", id->h, r);
        
        return r;
}


#ifdef SQLITE_DEBUG
/*
 * Helper function for printing out trace information from debugging binaries.
 * This returns the string represetation of the supplied integer lock-type.
 * */
static const char * locktypeName(int locktype)
{
        switch( locktype )
        {
                case NO_LOCK: return "NONE";
                case SHARED_LOCK: return "SHARED";
                case RESERVED_LOCK: return "RESERVED";
                case PENDING_LOCK: return "PENDING";
                case EXCLUSIVE_LOCK: return "EXCLUSIVE";
        }
        return "ERROR";
}
#endif


/*
 * Lock the file with the lock specified by parameter locktype - one of the
 * following:
 *     (1) SHARED_LOCK
 *     (2) RESERVED_LOCK
 *     (3) PENDING_LOCK
 *     (4) EXCLUSIVE_LOCK
 * 
 * Sometimes when requesting one lock state, additional lock states are
 * inserted in between. The locking might fail on one of the later transitions
 * leaving the lock state different from what it started but still short of its
 * goal. The following chart shows the allowed transitions and the inserted
 * intermediate states:
 *
 *    UNLOCKED -> SHARED
 *    SHARED -> RESERVED
 *    SHARED -> (PENDING) -> EXCLUSIVE
 *    RESERVED -> (PENDING) -> EXCLUSIVE
 *    PENDING -> EXCLUSIVE
 *
 * This routine will only increase a lock. Use the sqlite3OsUnlock() routine to
 * lower a locking level.
 * */
err_t sqlite3OsLock(OsFile *id, int locktype)
{
        /*
         * The following describes the implementation of the various locks and lock
         * transitions in terms of the POSIX advisory shared and exclusive lock
         * primitives (called read-locks and write-locks below, to avoid confusion
         * with SQLite lock names). The algorithms are complicated slightly in
         * order to be compatible with windows systems simultaneously accessing the
         * same database file, in case that is ever required.
         *
         * Symbols defined in os.h indentify the 'pending byte' and the 'reserved
         * byte', each single bytes at well known offsets, and the 'shared byte
         * range', a range of 510 bytes at a well known offset.
         *
         * To obtain a SHARED lock, a read-lock is obtained on the 'pending byte'.
         * If this is successful, a random byte from the 'shared byte range' is
         * read-locked and the lock on the 'pending byte' released. A process may
         * only obtain a RESERVED lock after it has a SHARED lock. A RESERVED lock
         * is implemented by grabbing a write-lock on the 'reserved byte'.
         *
         * A process may only obtain a PENDING lock after it has obtained a SHARED
         * lock. A PENDING lock is implemented by obtaining a write-lock on the
         * 'pending byte'. This ensures that no new SHARED locks can be obtained,
         * but existing SHARED locks are allowed to persist. A process does not
         * have to obtain a RESERVED lock on the way to a PENDING lock. This
         * property is used by the algorithm for rolling back a journal file after
         * a crash.
         *
         * An EXCLUSIVE lock, obtained after a PENDING lock is held, is implemented
         * by obtaining a write-lock on the entire 'shared byte range'. Since all
         * other locks require a read-lock on one of the bytes within this range,
         * this ensures that no other locks are held on the database.
         *
         * The reason a single byte cannot be used instead of the 'shared byte
         * range' is that some versions of windows do not support read-locks. By
         * locking a random byte from a range, concurrent SHARED locks may exist
         * even if the locking primitive used is always a write-lock.
         * */
        int rc = SQLITE_OK;
        struct lockInfo *pLock = id->pLock;
        struct flock lock;
        int s;
        SETFNC( "sqlite3OsLock" );

        assert( id->isOpen );
        TRACE("LOCK    %d %s was %s(%s,%d) pid=%d\n", id->h,
                        locktypeName(locktype),
                        locktypeName(id->locktype),
                        locktypeName(pLock->locktype),
                        pLock->cnt, getpid() );
        
        /*
         * If there is already a lock of this type or more restrictive on the
         * OsFile, do nothing. Don't use the end_lock: exit path, as
         * sqlite3OsEnterMutex() hasn't been called yet.
         * */
        if( id->locktype >= locktype )
        {
                TRACE("LOCK    %d %s ok (already held)\n", id->h,
                                locktypeName(locktype));
                return SQLITE_OK;
        }

        /* Make sure the locking sequence is correct */
        assert( id->locktype != NO_LOCK || locktype == SHARED_LOCK );
        assert( locktype != PENDING_LOCK );
        assert( locktype != RESERVED_LOCK || id->locktype == SHARED_LOCK );

        /* This mutex is needed because id->pLock is shared across threads */
        sqlite3OsEnterMutex();

        /*
         * If some thread using this PID has a lock via a different OsFile* handle
         * that precludes the requested lock, return BUSY.
         * */
        if( (id->locktype != pLock->locktype
                                && (pLock->locktype >= PENDING_LOCK
                                        || locktype > SHARED_LOCK)))
        {
                rc = SQLITE_BUSY;
                goto end_lock;
        }
        
        /*
         * If a SHARED lock is requested, and some thread using this PID already
         * has a SHARED or RESERVED lock, then increment reference counts and
         * return SQLITE_OK.
         * */
        if( locktype == SHARED_LOCK
                        && (pLock->locktype == SHARED_LOCK
                                || pLock->locktype == RESERVED_LOCK))
        {
                assert( locktype == SHARED_LOCK );
                assert( id->locktype == NO_LOCK );
                assert( pLock->cnt > 0 );
                id->locktype = SHARED_LOCK;
                pLock->cnt++;
                id->pOpen->nLock++;
                goto end_lock;
        }

        lock.l_len = 1L;
        lock.l_whence = SEEK_SET;

        /*
         * A PENDING lock is needed before acquiring a SHARED lock and before
         * acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will be
         * released.
         * */
        if( locktype == SHARED_LOCK
                        || (locktype == EXCLUSIVE_LOCK
                                && id->locktype < PENDING_LOCK))
        {
                lock.l_type = (locktype == SHARED_LOCK ? F_RDLCK : F_WRLCK);
                lock.l_start = PENDING_BYTE;
                s = fcntl(id->h, F_SETLK, &lock);
#if !OS_AROS
                if( s )
                {
                        rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
                        ERRLOC( funcn );
                        goto end_lock;
                }
#endif
        }
        
        /*
         * If control gets to this point, then actually go ahead and make OS calls
         * for the specified lock.
         * */
        if( locktype == SHARED_LOCK )
        {
                assert( !pLock->cnt );
                assert( !pLock->locktype );
                
                /* Now get the read-lock */
                lock.l_start = SHARED_FIRST;
                lock.l_len = SHARED_SIZE;
                s = fcntl(id->h, F_SETLK, &lock);

                /* Drop the temporary PENDING lock */
                lock.l_start = PENDING_BYTE;
                lock.l_len = 1L;
                lock.l_type = F_UNLCK;
#if !OS_AROS
                fcntl(id->h, F_SETLK, &lock);
                if( s )
                {
                        rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
                        ERRLOC( funcn );
                }
                else
#endif
                {
                        id->locktype = SHARED_LOCK;
                        id->pOpen->nLock++;
                        pLock->cnt = 1;
                }
        }
        else if( locktype == EXCLUSIVE_LOCK && pLock->cnt > 1 )
        {
                /*
                 * We are trying for an exclusive lock but another thread in this same
                 * process is still holding a shared lock.
                 * */
                rc = SQLITE_BUSY;
        }
        else
        {
                /*
                 * The request was for a RESERVED or EXCLUSIVE lock. It is assumed that
                 * there is a SHARED or greater lock on the file already.
                 * */
                assert( id->locktype );
                lock.l_type = F_WRLCK;
                switch( locktype )
                {
                        case RESERVED_LOCK:
                                lock.l_start = RESERVED_BYTE;
                                break;
                        case EXCLUSIVE_LOCK:
                                lock.l_start = SHARED_FIRST;
                                lock.l_len = SHARED_SIZE;
                                break;
                        default:
                                assert(0);
                }
                s = fcntl(id->h, F_SETLK, &lock);
#if !OS_AROS
                if( s )
                {
                        rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
                        ERRLOC( funcn );
                }
#endif
        }
        
        if( rc == SQLITE_OK )
        {
                id->locktype = locktype;
                pLock->locktype = locktype;
        }
        else if( locktype == EXCLUSIVE_LOCK )
        {
                id->locktype = PENDING_LOCK;
                pLock->locktype = PENDING_LOCK;
        }

end_lock:
        sqlite3OsLeaveMutex();
        TRACE("LOCK    %d %s %s\n", id->h, locktypeName(locktype),
                        rc==SQLITE_OK ? "ok" : "failed");
        return rc;
}


/*
 * Lower the locking level on file descriptor id to locktype. locktype must be
 * either NO_LOCK or SHARED_LOCK.
 *
 * If the locking level of the file descriptor is already at or below the
 * requested locking level, this routine is a no-op.
 *
 * It is not possible for this routine to fail if the second argument is
 * NO_LOCK. If the second argument is SHARED_LOCK, this routine might return
 * SQLITE_IOERR instead of SQLITE_OK.
 * */
err_t sqlite3OsUnlock(OsFile *id, int locktype)
{
        struct lockInfo *pLock;
        struct flock lock;
        int rc = SQLITE_OK;

        assert( id->isOpen );
        TRACE("UNLOCK  %d %d was %d(%d,%d) pid=%d\n", id->h, locktype,
                        id->locktype, id->pLock->locktype, id->pLock->cnt, getpid());
        
        assert( locktype <= SHARED_LOCK );
        if( id->locktype <= locktype )
                return SQLITE_OK;
        
        sqlite3OsEnterMutex();
        pLock = id->pLock;
        assert( pLock->cnt );
        if( id->locktype > SHARED_LOCK )
        {
                assert( pLock->locktype == id->locktype );
                if( locktype == SHARED_LOCK )
                {
                        lock.l_type = F_RDLCK;
                        lock.l_whence = SEEK_SET;
                        lock.l_start = SHARED_FIRST;
                        lock.l_len = SHARED_SIZE;
#if !OS_AROS
                        if( fcntl(id->h, F_SETLK, &lock)!=0 )
                        {
                                /* This should never happen */
                                rc = SQLITE_IOERR;
                        }
#endif
                }
                lock.l_type = F_UNLCK;
                lock.l_whence = SEEK_SET;
                lock.l_start = PENDING_BYTE;
                lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
#if !OS_AROS
                fcntl(id->h, F_SETLK, &lock);
#endif
                pLock->locktype = SHARED_LOCK;
        }
        
        if( locktype == NO_LOCK )
        {
                struct openCnt *pOpen;
                
                /*
                 * Decrement the shared lock counter. Release the lock using an OS call
                 * only when all threads in this same process have released the lock.
                 * */
                pLock->cnt--;
                if( !pLock->cnt )
                {
                        lock.l_type = F_UNLCK;
                        lock.l_whence = SEEK_SET;
                        lock.l_start = lock.l_len = 0L;
#if !OS_AROS
                        fcntl(id->h, F_SETLK, &lock);
#endif
                        pLock->locktype = NO_LOCK;
                }

                /*
                 * Decrement the count of locks against this same file. When the count
                 * reaches zero, close any other file descriptors whose close was
                 * deferred because of outstanding locks.
                 * */
                pOpen = id->pOpen;
                pOpen->nLock--;
                assert( pOpen->nLock >= 0 );
                if( pOpen->nLock==0 && pOpen->nPending>0 )
                {
                        int i;
                        for(i=0; i<pOpen->nPending; i++)
                                close(pOpen->aPending[i]);
                        sqliteFree(pOpen->aPending);
                        pOpen->nPending = 0;
                        pOpen->aPending = 0;
                }
        }
        sqlite3OsLeaveMutex();
        id->locktype = locktype;
        return rc;
}


/*
 * Close a file.
 * */
err_t sqlite3OsClose(OsFile *id)
{
        if( !id->isOpen ) return SQLITE_OK;
        sqlite3OsUnlock(id, NO_LOCK);
        if( id->dirfd>=0 ) close(id->dirfd);
        id->dirfd = -1;
        sqlite3OsEnterMutex();
        if( id->pOpen->nLock )
        {
                /*
                 * If there are outstanding locks, do not actually close the file just
                 * yet because that would clear those locks. Instead, add the file
                 * descriptor to pOpen->aPending. It will be automatically closed when
                 * the last lock is cleared.
                 * */
                int *aNew;
                struct openCnt *pOpen = id->pOpen;
                pOpen->nPending++;
                aNew = sqliteRealloc( pOpen->aPending, pOpen->nPending*sizeof(int) );
                if( !aNew )
                        ;       /* If a malloc fails, just leak the file descriptor */
                else
                {
                        pOpen->aPending = aNew;
                        pOpen->aPending[pOpen->nPending-1] = id->h;
                }
        }
        else
        {
                /* There are no outstanding locks so we can close the file
                 * immediately.
                 * */
                close(id->h);
        }
        releaseLockInfo(id->pLock);
        releaseOpenCnt(id->pOpen);
        sqlite3OsLeaveMutex();
        id->isOpen = FALSE;
        TRACE("CLOSE   %-3d\n", id->h);
        OpenCounter(-1);
        return SQLITE_OK;
}


/*
 * Turn a relative pathname into a full pathname. Return a pointer to the full
 * pathname stored in space obtained from sqliteMalloc(). The calling function
 * is responsible for freeing this space once it is no longer needed.
 * */
char *sqlite3OsFullPathname(CONST_STRPTR zRelative)
{
        STRPTR zFull = NULL;
#if !OS_AROS
        if( zRelative[0]=='/' )
        {
                sqlite3SetString(&zFull, zRelative, NULL);
        }
        else
#endif
        {
                char zBuf[5000];
                zBuf[0] = 0;
                sqlite3SetString( &zFull, getcwd(zBuf, sizeof(zBuf)), "/", zRelative,
                                NULL);
        }
        return zFull;
}
#endif /* SQLITE_OMIT_DISKIO */


/*
 * Everything above deals with file I/O. Everything that follows deals with
 * other miscellanous aspects of the operating system interface.
 *
 * */


/*
 * Get information to seed the random number generator. The seed is written
 * into the buffer zBuf[256]. The calling function must supply a sufficiently
 * large buffer.
 * */
int sqlite3OsRandomSeed(char *zBuf)
{
        /*
         * When testing, initializing zBuf[] to zero is all we do. That means that
         * we always use the same random number sequence.* This makes the tests
         * repeatable.
         * */
        memset(zBuf, 0, 256);
#if !defined(SQLITE_TEST)
        {
                int pid, fd;
                /* See if we can use /dev/urandom for random numbers... */
                fd = open("/dev/urandom", O_RDONLY);
                if( fd < 0 )
                {
                        time((time_t*)zBuf);
                        pid = getpid();
                        memcpy(&zBuf[sizeof(time_t)], &pid, sizeof(pid));
                }
                else
                {
                        read(fd, zBuf, 256);
                        close(fd);
                }
        }
#endif
        return SQLITE_OK;
}


/*
 * Sleep for a little while. Return the amount of time slept.
 * */
int sqlite3OsSleep(int ms)
{
#if defined(HAVE_USLEEP) && HAVE_USLEEP
        usleep(ms*1000);
        return ms;
#else
        sleep((ms+999)/1000);
        return 1000*((ms+999)/1000);
#endif
}


/*
 * Static variables used for thread synchronization.
 * */
static BOOL inMutex = FALSE;


/*
 * The following pair of routine implement mutual exclusion for multi-threaded
 * processes. Only a single thread is allowed to executed code that is
 * surrounded by EnterMutex() and LeaveMutex().
 *
 * SQLite uses only a single Mutex. There is not much critical code and what
 * little there is executes quickly and without blocking.
 * */
void sqlite3OsEnterMutex()
{
        assert( !inMutex );
        inMutex = TRUE;
}
void sqlite3OsLeaveMutex()
{
        assert( inMutex );
        inMutex = FALSE;
}


/*
 * The following variable, if set to a non-zero value, becomes the result
 * returned from sqlite3OsCurrentTime(). This is used for testing.
 * */
#ifdef SQLITE_TEST
int sqlite3_current_time = 0;
#endif


/*
 * Find the current time (in Universal Coordinated Time). Write the current
 * time and date as a Julian Day number into *prNow and return FALSE. Return
 * TRUE if the time and date cannot be found.
 * */
BOOL sqlite3OsCurrentTime(double *prNow)
{
        time_t t;
        time(&t);
        *prNow = t/86400.0 + 2440587.5;
#ifdef SQLITE_TEST
        if( sqlite3_current_time )
                *prNow = sqlite3_current_time/86400.0 + 2440587.5;
#endif
        return FALSE;
}

#endif /* OS_AROS */