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cde/src/lib/libast/sfio/sfpool.c

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/***********************************************************************
* *
* This software is part of the ast package *
* Copyright (c) 1985-2011 AT&T Intellectual Property *
* Copyright (c) 2020-2021 Contributors to ksh 93u+m *
* 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;
memmove(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 )
memmove(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;
}
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