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/***********************************************************************
* *
* 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 "sfdchdr.h"
/* Discipline to treat a contiguous segment of a stream as a stream
** in its own right. The hard part in all this is to allow multiple
** segments of the stream to be used as substreams at the same time.
**
** Written by David G. Korn and Kiem-Phong Vo (03/18/1998)
*/
typedef struct _subfile_s
{
Sfdisc_t disc; /* sfio discipline */
Sfio_t* parent; /* parent stream */
Sfoff_t offset; /* starting offset */
Sfoff_t extent; /* size wanted */
Sfoff_t here; /* current seek location */
} Subfile_t;
#if __STD_C
static ssize_t streamio(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc, int type)
#else
static ssize_t streamio(f, buf, n, disc, type)
Sfio_t* f;
Void_t* buf;
size_t n;
Sfdisc_t* disc;
int type;
#endif
{
reg Subfile_t *su;
reg Sfoff_t here, parent;
reg ssize_t io;
su = (Subfile_t*)disc;
/* read just what we need */
if(su->extent >= 0 && (ssize_t)n > (io = (ssize_t)(su->extent - su->here)) )
n = io;
if(n <= 0)
return n;
/* save current location in parent stream */
parent = sfsk(f,(Sfoff_t)0,SEEK_CUR,disc);
/* read data */
here = su->here + su->offset;
if(sfsk(f,here,SEEK_SET,disc) != here)
io = 0;
else
{ if(type == SF_WRITE)
io = sfwr(f,buf,n,disc);
else io = sfrd(f,buf,n,disc);
if(io > 0)
su->here += io;
}
/* restore parent current position */
sfsk(f,parent,SEEK_SET,disc);
return io;
}
#if __STD_C
static ssize_t streamwrite(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t streamwrite(f, buf, n, disc)
Sfio_t* f;
Void_t* buf;
size_t n;
Sfdisc_t* disc;
#endif
{
return streamio(f,(Void_t*)buf,n,disc,SF_WRITE);
}
#if __STD_C
static ssize_t streamread(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t streamread(f, buf, n, disc)
Sfio_t* f;
Void_t* buf;
size_t n;
Sfdisc_t* disc;
#endif
{
return streamio(f,buf,n,disc,SF_READ);
}
#if __STD_C
static Sfoff_t streamseek(Sfio_t* f, Sfoff_t pos, int type, Sfdisc_t* disc)
#else
static Sfoff_t streamseek(f, pos, type, disc)
Sfio_t* f;
Sfoff_t pos;
int type;
Sfdisc_t* disc;
#endif
{
reg Subfile_t* su;
reg Sfoff_t here, parent;
su = (Subfile_t*)disc;
switch(type)
{
case SEEK_SET:
here = 0;
break;
case SEEK_CUR:
here = su->here;
break;
case SEEK_END:
if(su->extent >= 0)
here = su->extent;
else
{ parent = sfsk(f,(Sfoff_t)0,SEEK_CUR,disc);
if((here = sfsk(f,(Sfoff_t)0,SEEK_END,disc)) < 0)
return -1;
else here -= su->offset;
sfsk(f,parent,SEEK_SET,disc);
}
break;
default:
return -1;
}
pos += here;
if(pos < 0 || (su->extent >= 0 && pos >= su->extent))
return -1;
return (su->here = pos);
}
#if __STD_C
static int streamexcept(Sfio_t* f, int type, Void_t* data, Sfdisc_t* disc)
#else
static int streamexcept(f, type, data, disc)
Sfio_t* f;
int type;
Void_t* data;
Sfdisc_t* disc;
#endif
{
if(type == SF_FINAL || type == SF_DPOP)
free(disc);
return 0;
}
#if __STD_C
Sfio_t* sfdcsubstream(Sfio_t* f, Sfio_t* parent, Sfoff_t offset, Sfoff_t extent)
#else
Sfio_t* sfdcsubstream(f, parent, offset, extent)
Sfio_t* f; /* stream */
Sfio_t* parent; /* parent stream */
Sfoff_t offset; /* offset in f */
Sfoff_t extent; /* desired size */
#endif
{
reg Sfio_t* sp;
reg Subfile_t* su;
reg Sfoff_t here;
/* establish that we can seek to offset */
if((here = sfseek(parent,(Sfoff_t)0,SEEK_CUR)) < 0 || sfseek(parent,offset,SEEK_SET) < 0)
return 0;
else sfseek(parent,here,SEEK_SET);
sfpurge(parent);
if (!(sp = f) && !(sp = sfnew(NIL(Sfio_t*), NIL(Void_t*), (size_t)SF_UNBOUND, dup(sffileno(parent)), parent->flags)))
return 0;
if(!(su = (Subfile_t*)malloc(sizeof(Subfile_t))))
{ if(sp != f)
sfclose(sp);
return 0;
}
memset(su, 0, sizeof(*su));
su->disc.readf = streamread;
su->disc.writef = streamwrite;
su->disc.seekf = streamseek;
su->disc.exceptf = streamexcept;
su->parent = parent;
su->offset = offset;
su->extent = extent;
if(sfdisc(sp, (Sfdisc_t*)su) != (Sfdisc_t*)su)
{ free(su);
if(sp != f)
sfclose(sp);
return 0;
}
return sp;
}
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