xref: /onnv-gate/usr/src/lib/libast/common/sfio/sfread.c (revision 12068:08a39a083754)
14887Schin /***********************************************************************
24887Schin *                                                                      *
34887Schin *               This software is part of the ast package               *
4*12068SRoger.Faulkner@Oracle.COM *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
54887Schin *                      and is licensed under the                       *
64887Schin *                  Common Public License, Version 1.0                  *
78462SApril.Chin@Sun.COM *                    by AT&T Intellectual Property                     *
84887Schin *                                                                      *
94887Schin *                A copy of the License is available at                 *
104887Schin *            http://www.opensource.org/licenses/cpl1.0.txt             *
114887Schin *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
124887Schin *                                                                      *
134887Schin *              Information and Software Systems Research               *
144887Schin *                            AT&T Research                             *
154887Schin *                           Florham Park NJ                            *
164887Schin *                                                                      *
174887Schin *                 Glenn Fowler <gsf@research.att.com>                  *
184887Schin *                  David Korn <dgk@research.att.com>                   *
194887Schin *                   Phong Vo <kpv@research.att.com>                    *
204887Schin *                                                                      *
214887Schin ***********************************************************************/
224887Schin #include	"sfhdr.h"
234887Schin 
244887Schin /*	Read n bytes from a stream into a buffer
254887Schin **
264887Schin **	Written by Kiem-Phong Vo.
274887Schin */
284887Schin 
294887Schin #if __STD_C
sfread(Sfio_t * f,Void_t * buf,size_t n)308462SApril.Chin@Sun.COM ssize_t sfread(Sfio_t* f, Void_t* buf, size_t n)
314887Schin #else
324887Schin ssize_t sfread(f,buf,n)
338462SApril.Chin@Sun.COM Sfio_t*		f;	/* read from this stream. 	*/
344887Schin Void_t*		buf;	/* buffer to read into		*/
358462SApril.Chin@Sun.COM size_t		n;	/* number of bytes to be read. 	*/
364887Schin #endif
374887Schin {
384887Schin 	reg uchar	*s, *begs;
394887Schin 	reg ssize_t	r;
404887Schin 	reg int		local, justseek;
418462SApril.Chin@Sun.COM 	SFMTXDECL(f);
424887Schin 
438462SApril.Chin@Sun.COM 	SFMTXENTER(f, (ssize_t)(-1));
444887Schin 
454887Schin 	GETLOCAL(f,local);
464887Schin 	justseek = f->bits&SF_JUSTSEEK; f->bits &= ~SF_JUSTSEEK;
474887Schin 
484887Schin 	if(!buf)
494887Schin 		SFMTXRETURN(f, (ssize_t)(n == 0 ? 0 : -1) );
504887Schin 
514887Schin 	/* release peek lock */
524887Schin 	if(f->mode&SF_PEEK)
534887Schin 	{	if(!(f->mode&SF_READ) )
544887Schin 			SFMTXRETURN(f, (ssize_t)(-1));
554887Schin 
564887Schin 		if(f->mode&SF_GETR)
574887Schin 		{	if(((uchar*)buf + f->val) != f->next &&
584887Schin 			   (!f->rsrv || f->rsrv->data != (uchar*)buf) )
594887Schin 				SFMTXRETURN(f, (ssize_t)(-1));
604887Schin 			f->mode &= ~SF_PEEK;
614887Schin 			SFMTXRETURN(f, 0);
624887Schin 		}
634887Schin 		else
644887Schin 		{	if((uchar*)buf != f->next)
654887Schin 				SFMTXRETURN(f, (ssize_t)(-1));
664887Schin 			f->mode &= ~SF_PEEK;
674887Schin 			if(f->mode&SF_PKRD)
684887Schin 			{	/* actually read the data now */
694887Schin 				f->mode &= ~SF_PKRD;
704887Schin 				if(n > 0)
714887Schin 					n = (r = sysreadf(f->file,f->data,n)) < 0 ? 0 : r;
724887Schin 				f->endb = f->data+n;
734887Schin 				f->here += n;
744887Schin 			}
754887Schin 			f->next += n;
764887Schin 			f->endr = f->endb;
774887Schin 			SFMTXRETURN(f, n);
784887Schin 		}
794887Schin 	}
804887Schin 
814887Schin 	s = begs = (uchar*)buf;
824887Schin 	for(;; f->mode &= ~SF_LOCK)
834887Schin 	{	/* check stream mode */
844887Schin 		if(SFMODE(f,local) != SF_READ && _sfmode(f,SF_READ,local) < 0)
854887Schin 		{	n = s > begs ? s-begs : (size_t)(-1);
864887Schin 			SFMTXRETURN(f, (ssize_t)n);
874887Schin 		}
884887Schin 
894887Schin 		SFLOCK(f,local);
904887Schin 
914887Schin 		if((r = f->endb - f->next) > 0) /* has buffered data */
924887Schin 		{	if(r > (ssize_t)n)
934887Schin 				r = (ssize_t)n;
944887Schin 			if(s != f->next)
954887Schin 				memcpy(s, f->next, r);
964887Schin 			f->next += r;
974887Schin 			s += r;
984887Schin 			n -= r;
994887Schin 		}
1004887Schin 
1014887Schin 		if(n <= 0)	/* all done */
1024887Schin 			break;
1034887Schin 
1044887Schin 		if(!(f->flags&SF_STRING) && !(f->bits&SF_MMAP) )
1054887Schin 		{	f->next = f->endb = f->data;
1064887Schin 
1074887Schin 			/* exact IO is desirable for these cases */
1084887Schin 			if(SFDIRECT(f,n) ||
1094887Schin 			   ((f->flags&SF_SHARE) && f->extent < 0) )
1104887Schin 				r = (ssize_t)n;
1114887Schin 			else if(justseek && n <= f->iosz && f->iosz <= f->size)
1124887Schin 				r = f->iosz;	/* limit buffering */
1134887Schin 			else	r = f->size;	/* full buffering */
1144887Schin 
1154887Schin 			/* if read almost full size, then just do it direct */
1164887Schin 			if(r > (ssize_t)n && (r - r/8) <= (ssize_t)n)
1174887Schin 				r = (ssize_t)n;
1184887Schin 
1194887Schin 			/* read directly to user's buffer */
1204887Schin 			if(r == (ssize_t)n && (r = SFRD(f,s,r,f->disc)) >= 0)
1214887Schin 			{	s += r;
1224887Schin 				n -= r;
1234887Schin 				if(r == 0 || n == 0) /* eof or eob */
1244887Schin 					break;
1254887Schin 			}
1264887Schin 			else	goto do_filbuf;
1274887Schin 		}
1284887Schin 		else
1294887Schin 		{ do_filbuf:
1304887Schin 			if(justseek)
1314887Schin 				f->bits |= SF_JUSTSEEK;
1324887Schin 			if(SFFILBUF(f,-1) <= 0)
1334887Schin 				break;
1344887Schin 		}
1354887Schin 	}
1364887Schin 
1374887Schin 	SFOPEN(f,local);
1384887Schin 	r = s-begs;
1394887Schin 	SFMTXRETURN(f, r);
1404887Schin }
141