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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 make an unseekable read stream seekable
**
** sfraise(f,SFSK_DISCARD,0) discards previous seek data
** but seeks from current offset on still allowed
**
** Written by Kiem-Phong Vo, kpv@research.att.com, 03/18/1998.
*/
typedef struct _skable_s
{ Sfdisc_t disc; /* sfio discipline */
Sfio_t* shadow; /* to shadow data */
Sfoff_t discard;/* sfseek(f,-1,SEEK_SET) discarded data */
Sfoff_t extent; /* shadow extent */
int eof; /* if eof has been reached */
} Seek_t;
#if __STD_C
static ssize_t skwrite(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t skwrite(f, buf, n, disc)
Sfio_t* f; /* stream involved */
Void_t* buf; /* buffer to read into */
size_t n; /* number of bytes to read */
Sfdisc_t* disc; /* discipline */
#endif
{
return (ssize_t)(-1);
}
#if __STD_C
static ssize_t skread(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc)
#else
static ssize_t skread(f, buf, n, disc)
Sfio_t* f; /* stream involved */
Void_t* buf; /* buffer to read into */
size_t n; /* number of bytes to read */
Sfdisc_t* disc; /* discipline */
#endif
{
Seek_t* sk;
Sfio_t* sf;
Sfoff_t addr;
ssize_t r, w, p;
sk = (Seek_t*)disc;
sf = sk->shadow;
if(sk->eof)
return sfread(sf,buf,n);
addr = sfseek(sf,(Sfoff_t)0,SEEK_CUR);
if(addr+n <= sk->extent)
return sfread(sf,buf,n);
if((r = (ssize_t)(sk->extent-addr)) > 0)
{ if((w = sfread(sf,buf,r)) != r)
return w;
buf = (char*)buf + r;
n -= r;
}
/* do a raw read */
if((w = sfrd(f,buf,n,disc)) <= 0)
{ sk->eof = 1;
w = 0;
}
else
{
if((p = sfwrite(sf,buf,w)) != w)
sk->eof = 1;
if(p > 0)
sk->extent += p;
}
return r+w;
}
#if __STD_C
static Sfoff_t skseek(Sfio_t* f, Sfoff_t addr, int type, Sfdisc_t* disc)
#else
static Sfoff_t skseek(f, addr, type, disc)
Sfio_t* f;
Sfoff_t addr;
int type;
Sfdisc_t* disc;
#endif
{
Seek_t* sk;
Sfio_t* sf;
char buf[SF_BUFSIZE];
ssize_t r, w;
sk = (Seek_t*)disc;
sf = sk->shadow;
switch (type)
{
case SEEK_SET:
addr -= sk->discard;
break;
case SEEK_CUR:
addr += sftell(sf);
break;
case SEEK_END:
addr += sk->extent;
break;
default:
return -1;
}
if(addr < 0)
return (Sfoff_t)(-1);
else if(addr > sk->extent)
{ if(sk->eof)
return (Sfoff_t)(-1);
/* read enough to reach the seek point */
while(addr > sk->extent)
{ if(addr > sk->extent+sizeof(buf) )
w = sizeof(buf);
else w = (int)(addr-sk->extent);
if((r = sfrd(f,buf,w,disc)) <= 0)
w = r-1;
else if((w = sfwrite(sf,buf,r)) > 0)
sk->extent += w;
if(w != r)
{ sk->eof = 1;
break;
}
}
if(addr > sk->extent)
return (Sfoff_t)(-1);
}
return sfseek(sf,addr,SEEK_SET) + sk->discard;
}
/* on close, remove the discipline */
#if __STD_C
static int skexcept(Sfio_t* f, int type, Void_t* data, Sfdisc_t* disc)
#else
static int skexcept(f,type,data,disc)
Sfio_t* f;
int type;
Void_t* data;
Sfdisc_t* disc;
#endif
{
Seek_t* sk;
sk = (Seek_t*)disc;
switch (type)
{
case SF_FINAL:
case SF_DPOP:
sfclose(sk->shadow);
free(disc);
break;
case SFSK_DISCARD:
sk->eof = 0;
sk->discard += sk->extent;
sk->extent = 0;
sfseek(sk->shadow,(Sfoff_t)0,SEEK_SET);
break;
}
return 0;
}
#if __STD_C
int sfdcseekable(Sfio_t* f)
#else
int sfdcseekable(f)
Sfio_t* f;
#endif
{
reg Seek_t* sk;
/* see if already seekable */
if(sfseek(f,(Sfoff_t)0,SEEK_CUR) >= 0)
return 0;
if(!(sk = (Seek_t*)malloc(sizeof(Seek_t))) )
return -1;
memset(sk, 0, sizeof(*sk));
sk->disc.readf = skread;
sk->disc.writef = skwrite;
sk->disc.seekf = skseek;
sk->disc.exceptf = skexcept;
sk->shadow = sftmp(SF_BUFSIZE);
sk->discard = 0;
sk->extent = 0;
sk->eof = 0;
if(sfdisc(f, (Sfdisc_t*)sk) != (Sfdisc_t*)sk)
{ sfclose(sk->shadow);
free(sk);
return -1;
}
return 0;
}
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