libast/sfio/sfpool.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"

/*  Management of pools of streams.
**  If pf is not nil, f is pooled with pf and f becomes current;
**  otherwise, f is isolated from its pool. flag can be one of
**  0 or SF_SHARE.
**
**  Written by Kiem-Phong Vo.
*/

/* Note that we do not free the space for a pool once it is allocated.
** This is to prevent memory faults in calls such as sfsync(NULL) that walk the pool
** link list and during such walks may free up streams&pools. Free pools will be
** reused in newpool().
*/
#if __STD_C
static int delpool(reg Sfpool_t* p)
#else
static int delpool(p)
reg Sfpool_t*   p;
#endif
{
    POOLMTXENTER(p);

    if(p->s_sf && p->sf != p->array)
        free((Void_t*)p->sf);
    p->mode = SF_AVAIL;

    POOLMTXRETURN(p,0);
}

#if __STD_C
static Sfpool_t* newpool(reg int mode)
#else
static Sfpool_t* newpool(mode)
reg int mode;
#endif
{
    reg Sfpool_t    *p, *last = &_Sfpool;

    /* look to see if there is a free pool */
    for(last = &_Sfpool, p = last->next; p; last = p, p = p->next)
    {   if(p->mode == SF_AVAIL )
        {   p->mode = 0;
            break;
        }
    }

    if(!p)
    {   POOLMTXLOCK(last);

        if(!(p = (Sfpool_t*) malloc(sizeof(Sfpool_t))) )
        {   POOLMTXUNLOCK(last);
            return NIL(Sfpool_t*);
        }

        (void)vtmtxopen(&p->mutex, VT_INIT); /* initialize mutex */

        p->mode = 0;
        p->n_sf = 0;
        p->next = NIL(Sfpool_t*);
        last->next = p;

        POOLMTXUNLOCK(last);
    }

    POOLMTXENTER(p);

    p->mode = mode&SF_SHARE;
    p->s_sf = sizeof(p->array)/sizeof(p->array[0]);
    p->sf = p->array;

    POOLMTXRETURN(p,p);
}

/* move a stream to head */
#if __STD_C
static int _sfphead(Sfpool_t* p, Sfio_t* f, int n)
#else
static int _sfphead(p, f, n)
Sfpool_t*   p;  /* the pool         */
Sfio_t*     f;  /* the stream           */
int     n;  /* current position in pool */
#endif
{
    reg Sfio_t* head;
    reg ssize_t k, w, v;
    reg int     rv;

    POOLMTXENTER(p);

    if(n == 0)
        POOLMTXRETURN(p,0);

    head = p->sf[0];
    if(SFFROZEN(head) )
        POOLMTXRETURN(p,-1);

    SFLOCK(head,0);
    rv = -1;

    if(!(p->mode&SF_SHARE) || (head->mode&SF_READ) || (f->mode&SF_READ) )
    {   if(SFSYNC(head) < 0)
            goto done;
    }
    else    /* shared pool of write-streams, data can be moved among streams */
    {   if(SFMODE(head,1) != SF_WRITE && _sfmode(head,SF_WRITE,1) < 0)
            goto done;
        /**/ASSERT(f->next == f->data);

        v = head->next - head->data;    /* pending data     */
        if((k = v - (f->endb-f->data)) <= 0)
            k = 0;
        else    /* try to write out amount exceeding f's capacity */
        {   if((w = SFWR(head,head->data,k,head->disc)) == k)
                v -= k;
            else    /* write failed, recover buffer then quit */
            {   if(w > 0)
                {   v -= w;
                    memcpy(head->data,(head->data+w),v);
                }
                head->next = head->data+v;
                goto done;
            }
        }

        /* move data from head to f */
        if((head->data+k) != f->data )
            memcpy(f->data,(head->data+k),v);
        f->next = f->data+v;
    }

    f->mode &= ~SF_POOL;
    head->mode |= SF_POOL;
    head->next = head->endr = head->endw = head->data; /* clear write buffer */

    p->sf[n] = head;
    p->sf[0] = f;
    rv = 0;

done:
    head->mode &= ~SF_LOCK; /* partially unlock because it's no longer head */

    POOLMTXRETURN(p,rv);
}

/* delete a stream from its pool */
#if __STD_C
static int _sfpdelete(Sfpool_t* p, Sfio_t* f, int n)
#else
static int _sfpdelete(p, f, n)
Sfpool_t*   p;  /* the pool     */
Sfio_t*     f;  /* the stream       */
int     n;  /* position in pool */
#endif
{
    POOLMTXENTER(p);

    p->n_sf -= 1;
    for(; n < p->n_sf; ++n)
        p->sf[n] = p->sf[n+1];

    f->pool = NIL(Sfpool_t*);
    f->mode &= ~SF_POOL;

    if(p->n_sf == 0 || p == &_Sfpool)
    {   if(p != &_Sfpool)
            delpool(p);
        goto done;
    }

    /* !_Sfpool, make sure head stream is an open stream */
    for(n = 0; n < p->n_sf; ++n)
        if(!SFFROZEN(p->sf[n]))
            break;
    if(n < p->n_sf && n > 0)
    {   f = p->sf[n];
        p->sf[n] = p->sf[0];
        p->sf[0] = f;
    }

    /* head stream has SF_POOL off */
    f = p->sf[0];
    f->mode &= ~SF_POOL;
    if(!SFFROZEN(f))
        _SFOPEN(f);

    /* if only one stream left, delete pool */
    if(p->n_sf == 1 )
    {   _sfpdelete(p,f,0);
        _sfsetpool(f);
    }

done:
    POOLMTXRETURN(p,0);
}

#if __STD_C
static int _sfpmove(reg Sfio_t* f, reg int type)
#else
static int _sfpmove(f,type)
reg Sfio_t* f;
reg int     type;   /* <0 : deleting, 0: move-to-front, >0: inserting */
#endif
{
    reg Sfpool_t*   p;
    reg int     n;

    if(type > 0)
        return _sfsetpool(f);
    else
    {   if(!(p = f->pool) )
            return -1;
        for(n = p->n_sf-1; n >= 0; --n)
            if(p->sf[n] == f)
                break;
        if(n < 0)
            return -1;

        return type == 0 ? _sfphead(p,f,n) : _sfpdelete(p,f,n);
    }
}

#if __STD_C
Sfio_t* sfpool(reg Sfio_t* f, reg Sfio_t* pf, reg int mode)
#else
Sfio_t* sfpool(f,pf,mode)
reg Sfio_t* f;
reg Sfio_t* pf;
reg int     mode;
#endif
{
    int     k;
    Sfpool_t*   p;
    Sfio_t*     rv;

    _Sfpmove = _sfpmove;

    if(!f)  /* return head of pool of pf regardless of lock states */
    {   if(!pf)
            return NIL(Sfio_t*);
        else if(!pf->pool || pf->pool == &_Sfpool)
            return pf;
        else    return pf->pool->sf[0];
    }

    if(f)   /* check for permissions */
    {   SFMTXLOCK(f);
        if((f->mode&SF_RDWR) != f->mode && _sfmode(f,0,0) < 0)
        {   SFMTXUNLOCK(f);
            return NIL(Sfio_t*);
        }
        if(f->disc == _Sfudisc)
            (void)sfclose((*_Sfstack)(f,NIL(Sfio_t*)));
    }
    if(pf)
    {   SFMTXLOCK(pf);
        if((pf->mode&SF_RDWR) != pf->mode && _sfmode(pf,0,0) < 0)
        {   if(f)
                SFMTXUNLOCK(f);
            SFMTXUNLOCK(pf);
            return NIL(Sfio_t*);
        }
        if(pf->disc == _Sfudisc)
            (void)sfclose((*_Sfstack)(pf,NIL(Sfio_t*)));
    }

    /* f already in the same pool with pf */
    if(f == pf || (pf && f->pool == pf->pool && f->pool != &_Sfpool) )
    {   if(f)
            SFMTXUNLOCK(f);
        if(pf)
            SFMTXUNLOCK(pf);
        return pf;
    }

    /* lock streams before internal manipulations */
    rv = NIL(Sfio_t*);
    SFLOCK(f,0);
    if(pf)
        SFLOCK(pf,0);

    if(!pf) /* deleting f from its current pool */
    {   if((p = f->pool) != NIL(Sfpool_t*) && p != &_Sfpool)
            for(k = 0; k < p->n_sf && pf == NIL(Sfio_t*); ++k)
                if(p->sf[k] != f) /* a stream != f represents the pool */
                    pf = p->sf[k];
        if(!pf) /* already isolated */
        {   rv = f; /* just return self */
            goto done;
        }

        if(_sfpmove(f,-1) < 0 || _sfsetpool(f) < 0)
            goto done; /* can't delete */

        if(!pf->pool || pf->pool == &_Sfpool || pf->pool->n_sf <= 0 )
            rv = pf;
        else    rv = pf->pool->sf[0];   /* return head of old pool */
        goto done;
    }

    if(pf->pool && pf->pool != &_Sfpool) /* always use current mode */
        mode = pf->pool->mode;

    if(mode&SF_SHARE) /* can only have write streams */
    {   if(SFMODE(f,1) != SF_WRITE && _sfmode(f,SF_WRITE,1) < 0)
            goto done;
        if(SFMODE(pf,1) != SF_WRITE && _sfmode(pf,SF_WRITE,1) < 0)
            goto done;
        if(f->next > f->data && SFSYNC(f) < 0) /* start f clean */
            goto done;
    }

    if(_sfpmove(f,-1) < 0)  /* isolate f from current pool */
        goto done;

    if(!(p = pf->pool) || p == &_Sfpool) /* making a new pool */
    {   if(!(p = newpool(mode)) )
            goto done;
        if(_sfpmove(pf,-1) < 0) /* isolate pf from its current pool */
            goto done;
        pf->pool = p;
        p->sf[0] = pf;
        p->n_sf += 1;
    }

    f->pool = p;    /* add f to pf's pool */
    if(_sfsetpool(f) < 0)
        goto done;

    /**/ASSERT(p->sf[0] == pf && p->sf[p->n_sf-1] == f);
    SFOPEN(pf,0);
    SFOPEN(f,0);
    if(_sfpmove(f,0) < 0) /* make f head of pool */
        goto done;
    rv = pf;

done:
    if(f)
    {   SFOPEN(f,0);
        SFMTXUNLOCK(f);
    }
    if(pf)
    {   SFOPEN(pf,0);
        SFMTXUNLOCK(pf);
    }
    return rv;
}