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/***********************************************************************
* *
* This software is part of the ast package *
* Copyright (c) 1985-2009 AT&T Intellectual Property *
* and is licensed under the *
* Common Public License, Version 1.0 *
* by AT&T Intellectual Property *
* *
* A copy of the License is available at *
* http://www.opensource.org/licenses/cpl1.0.txt *
* (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9) *
* *
* 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"
/* Reserve a segment of data or buffer.
**
** Written by Kiem-Phong Vo.
*/
#if __STD_C
Void_t* sfreserve(Sfio_t* f, ssize_t size, int type)
#else
Void_t* sfreserve(f,size,type)
Sfio_t* f; /* file to peek */
ssize_t size; /* size of peek */
int type; /* LOCKR: lock stream, LASTR: last record */
#endif
{
reg ssize_t n, now, sz, iosz;
reg Sfrsrv_t* rsrv;
reg Void_t* data;
reg int mode, local;
SFMTXDECL(f);
SFMTXENTER(f,NIL(Void_t*));
sz = size < 0 ? -size : size;
/* see if we need to bias toward SF_WRITE instead of the default SF_READ */
if(type < 0)
mode = 0;
else if((mode = type&SF_WRITE) )
type &= ~SF_WRITE;
/* return the last record */
if(type == SF_LASTR )
{ if((n = f->endb - f->next) > 0 && n == f->val )
{ data = (Void_t*)f->next;
f->next += n;
}
else if((rsrv = f->rsrv) && (n = -rsrv->slen) > 0)
{ rsrv->slen = 0;
_Sfi = f->val = n;
data = (Void_t*)rsrv->data;
}
else
{ _Sfi = f->val = -1;
data = NIL(Void_t*);
}
SFMTXRETURN(f, data);
}
if(type > 0)
{ if(type == 1 ) /* upward compatibility mode */
type = SF_LOCKR;
else if(type != SF_LOCKR)
SFMTXRETURN(f, NIL(Void_t*));
}
if(size == 0 && (type < 0 || type == SF_LOCKR) )
{ if((f->mode&SF_RDWR) != f->mode && _sfmode(f,0,0) < 0)
SFMTXRETURN(f, NIL(Void_t*));
SFLOCK(f,0);
if((n = f->endb - f->next) < 0)
n = 0;
goto done;
}
/* iterate until get to a stream that has data or buffer space */
for(local = 0;; local = SF_LOCAL)
{ _Sfi = f->val = -1;
if(!mode && !(mode = f->flags&SF_READ) )
mode = SF_WRITE;
if((int)f->mode != mode && _sfmode(f,mode,local) < 0)
{ SFOPEN(f,0);
SFMTXRETURN(f, NIL(Void_t*));
}
SFLOCK(f,local);
if((n = now = f->endb - f->next) < 0)
n = 0;
if(n > 0 && n >= sz) /* all done */
break;
/* set amount to perform IO */
if(size == 0 || (f->mode&SF_WRITE))
iosz = -1;
else if(size < 0 && n == 0 && f->push) /* maybe stack-pop */
{ if((iosz = f->push->endb - f->push->next) == 0)
iosz = f->push->size;
if(iosz < sz)
iosz = sz; /* so only get what is asked for */
}
else
{ iosz = sz - n; /* get enough to fulfill requirement */
if(size < 0 && iosz < (f->size - n) )
iosz = f->size - n; /* get as much as possible */
if(iosz <= 0) /* nothing to do */
break;
}
/* do a buffer refill or flush */
now = n;
if(f->mode&SF_WRITE)
(void)SFFLSBUF(f, iosz);
else if(type == SF_LOCKR && f->extent < 0 && (f->flags&SF_SHARE) )
{ if(n == 0) /* peek-read only if there is no buffered data */
{ f->mode |= SF_RV;
(void)SFFILBUF(f, iosz );
}
if((n = f->endb - f->next) < sz)
{ if(f->mode&SF_PKRD)
{ f->endb = f->endr = f->next;
f->mode &= ~SF_PKRD;
}
break;
}
}
else
{ /* sfreserve(f,0,0) == sfread(f, sfreserve(f,-1,SF_LOCKR), 0) */
if(size == 0 && type == 0)
f->mode |= SF_RV;
(void)SFFILBUF(f, iosz );
}
if((n = f->endb - f->next) <= 0)
n = 0;
if(n >= sz) /* got it */
break;
if(n == now || sferror(f) || sfeof(f)) /* no progress */
break;
/* request was only to assess data availability */
if(type == SF_LOCKR && size > 0 && n > 0 )
break;
}
done: /* compute the buffer to be returned */
data = NIL(Void_t*);
if(size == 0 || n == 0)
{ if(n > 0) /* got data */
data = (Void_t*)f->next;
else if(type == SF_LOCKR && size == 0 && (rsrv = _sfrsrv(f,0)) )
data = (Void_t*)rsrv->data;
}
else if(n >= sz) /* got data */
data = (Void_t*)f->next;
else if(f->flags&SF_STRING) /* try extending string buffer */
{ if((f->mode&SF_WRITE) && (f->flags&SF_MALLOC) )
{ (void)SFWR(f,f->next,sz,f->disc);
if((n = f->endb - f->next) >= sz )
data = (Void_t*)f->next;
}
}
else if(f->mode&SF_WRITE) /* allocate side buffer */
{ if(type == SF_LOCKR && (rsrv = _sfrsrv(f, sz)) )
data = (Void_t*)rsrv->data;
}
else if(type != SF_LOCKR && sz > f->size && (rsrv = _sfrsrv(f,sz)) )
{ if((n = SFREAD(f,(Void_t*)rsrv->data,sz)) >= sz) /* read side buffer */
data = (Void_t*)rsrv->data;
else rsrv->slen = -n;
}
SFOPEN(f,0);
if(data)
{ if(type == SF_LOCKR)
{ f->mode |= SF_PEEK;
if((f->mode & SF_READ) && size == 0 && data != f->next)
f->mode |= SF_GETR; /* so sfread() will unlock */
f->endr = f->endw = f->data;
}
else
{ if(data == (Void_t*)f->next)
f->next += (size >= 0 ? size : n);
}
}
_Sfi = f->val = n; /* return true buffer size */
SFMTXRETURN(f, data);
}
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