libast/sfio/sfsync.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2011 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                 Eclipse Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*          http://www.eclipse.org/org/documents/epl-v10.html           *
*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#include    "sfhdr.h"

/*  Synchronize data in buffers with the file system.
**  If f is nil, all streams are sync-ed
**
**  Written by Kiem-Phong Vo.
*/

#if __STD_C
static int _sfall(void)
#else
static int _sfall()
#endif
{
    reg Sfpool_t    *p, *next;
    reg Sfio_t* f;
    reg int     n, rv;
    reg int     nsync, count, loop;
#define MAXLOOP 3

    for(loop = 0; loop < MAXLOOP; ++loop)
    {   rv = nsync = count = 0;
        for(p = &_Sfpool; p; p = next)
        {   /* find the next legitimate pool */
            for(next = p->next; next; next = next->next)
                if(next->n_sf > 0)
                    break;

            /* walk the streams for _Sfpool only */
            for(n = 0; n < ((p == &_Sfpool) ? p->n_sf : 1); ++n)
            {   count += 1;
                f = p->sf[n];

                if(f->flags&SF_STRING )
                    goto did_sync;
                if(SFFROZEN(f))
                    continue;
                if((f->mode&SF_READ) && (f->mode&SF_SYNCED) )
                    goto did_sync;
                if((f->mode&SF_READ) && !(f->bits&SF_MMAP) &&
                   f->next == f->endb)
                    goto did_sync;
                if((f->mode&SF_WRITE) && !(f->bits&SF_HOLE) &&
                   f->next == f->data)
                    goto did_sync;

                if(sfsync(f) < 0)
                    rv = -1;

            did_sync:
                nsync += 1;
            }
        }

        if(nsync == count)
            break;
    }
    return rv;
}

#if __STD_C
int sfsync(reg Sfio_t* f)
#else
int sfsync(f)
reg Sfio_t* f;  /* stream to be synchronized */
#endif
{
    int local, rv, mode, lock;
    Sfio_t* origf;
    SFMTXDECL(f);

    if(!(origf = f) )
        return _sfall();

    SFMTXENTER(origf,-1);

    GETLOCAL(origf,local);

    if(origf->disc == _Sfudisc) /* throw away ungetc */
        (void)sfclose((*_Sfstack)(origf,NIL(Sfio_t*)));

    rv = 0;

    lock = origf->mode&SF_LOCK;
    if(origf->mode == (SF_SYNCED|SF_READ) ) /* already synced */
        goto done;

    if((origf->mode&SF_RDWR) != SFMODE(origf,local) && _sfmode(origf,0,local) < 0)
    {   rv = -1;
        goto done;
    }

    for(; f; f = f->push)
    {
        if((f->flags&SF_IOCHECK) && f->disc && f->disc->exceptf)
            (void)(*f->disc->exceptf)(f,SF_SYNC,(Void_t*)((int)1),f->disc);

        SFLOCK(f,local);

        /* pretend that this stream is not on a stack */
        mode = f->mode&SF_PUSH;
        f->mode &= ~SF_PUSH;

        /* these streams do not need synchronization */
        if((f->flags&SF_STRING) || (f->mode&SF_SYNCED))
            goto next;

        if((f->mode&SF_WRITE) && (f->next > f->data || (f->bits&SF_HOLE)) )
        {   /* sync the buffer, make sure pool don't move */
            reg int pool = f->mode&SF_POOL;
            f->mode &= ~SF_POOL;
            if(f->next > f->data && (SFWRALL(f), SFFLSBUF(f,-1)) < 0)
                rv = -1;
            if(!SFISNULL(f) && (f->bits&SF_HOLE) )
            {   /* realize a previously created hole of 0's */
                if(SFSK(f,(Sfoff_t)(-1),SEEK_CUR,f->disc) >= 0)
                    (void)SFWR(f,"",1,f->disc);
                f->bits &= ~SF_HOLE;
            }
            f->mode |= pool;
        }

        if((f->mode&SF_READ) && f->extent >= 0 &&
           ((f->bits&SF_MMAP) || f->next < f->endb) )
        {   /* make sure the file pointer is at the right place */
            f->here -= (f->endb-f->next);
            f->endr = f->endw = f->data;
            f->mode = SF_READ|SF_SYNCED|lock;
            (void)SFSK(f,f->here,SEEK_SET,f->disc);

            if((f->flags&SF_SHARE) && !(f->flags&SF_PUBLIC) &&
               !(f->bits&SF_MMAP) )
            {   f->endb = f->next = f->data;
                f->mode &= ~SF_SYNCED;
            }
        }

    next:
        f->mode |= mode;
        SFOPEN(f,local);

        if((f->flags&SF_IOCHECK) && f->disc && f->disc->exceptf)
            (void)(*f->disc->exceptf)(f,SF_SYNC,(Void_t*)((int)0),f->disc);
    }

done:
    if(!local && f && (f->mode&SF_POOL) && f->pool && f != f->pool->sf[0])
        SFSYNC(f->pool->sf[0]);

    SFMTXRETURN(origf, rv);
}