sffilbuf.c revision 34f9b3eef6fdadbda0a846aa4d68691ac40eace5
/***********************************************************************
* *
* 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"
/* Fill the buffer of a stream with data.
** If n < 0, sffilbuf() attempts to fill the buffer if it's empty.
** If n == 0, if the buffer is not empty, just return the first byte;
** otherwise fill the buffer and return the first byte.
** If n > 0, even if the buffer is not empty, try a read to get as
** close to n as possible. n is reset to -1 if stack pops.
**
** Written by Kiem-Phong Vo
*/
#if __STD_C
int _sffilbuf(Sfio_t* f, reg int n)
#else
int _sffilbuf(f,n)
Sfio_t* f; /* fill the read buffer of this stream */
reg int n; /* see above */
#endif
{
reg ssize_t r;
reg int first, local, rcrv, rc, justseek;
SFMTXDECL(f);
SFMTXENTER(f,-1);
GETLOCAL(f,local);
/* any peek data must be preserved across stacked streams */
rcrv = f->mode&(SF_RC|SF_RV|SF_LOCK);
rc = f->getr;
justseek = f->bits&SF_JUSTSEEK; f->bits &= ~SF_JUSTSEEK;
for(first = 1;; first = 0, (f->mode &= ~SF_LOCK) )
{ /* check mode */
if(SFMODE(f,local) != SF_READ && _sfmode(f,SF_READ,local) < 0)
SFMTXRETURN(f,-1);
SFLOCK(f,local);
/* current extent of available data */
if((r = f->endb-f->next) > 0)
{ /* on first iteration, n is amount beyond current buffer;
afterward, n is the exact amount requested */
if((first && n <= 0) || (!first && n <= r) ||
(f->flags&SF_STRING))
break;
/* try shifting left to make room for new data */
if(!(f->bits&SF_MMAP) && f->next > f->data &&
n > (f->size - (f->endb-f->data)) )
{ ssize_t s = r;
/* try to maintain block alignment */
if(f->blksz > 0 && (f->here%f->blksz) == 0 )
{ s = ((r + f->blksz-1)/f->blksz)*f->blksz;
if(s+n > f->size)
s = r;
}
memcpy(f->data, f->endb-s, s);
f->next = f->data + (s-r);
f->endb = f->data + s;
}
}
else if(!(f->flags&SF_STRING) && !(f->bits&SF_MMAP) )
f->next = f->endb = f->endr = f->data;
if(f->bits&SF_MMAP)
r = n > 0 ? n : f->size;
else if(!(f->flags&SF_STRING) )
{ r = f->size - (f->endb - f->data); /* available buffer */
if(n > 0)
{ if(r > n && f->extent < 0 && (f->flags&SF_SHARE) )
r = n; /* read only as much as requested */
else if(justseek && n <= f->iosz && f->iosz <= f->size)
r = f->iosz; /* limit buffer filling */
}
}
/* SFRD takes care of discipline read and stack popping */
f->mode |= rcrv;
f->getr = rc;
if((r = SFRD(f,f->endb,r,f->disc)) >= 0)
{ r = f->endb - f->next;
break;
}
}
SFOPEN(f,local);
rcrv = (n == 0) ? (r > 0 ? (int)(*f->next++) : EOF) : (int)r;
SFMTXRETURN(f,rcrv);
}