da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin/***********************************************************************
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* This software is part of the ast package *
3e14f97f673e8a630f076077de35afdd43dc1587Roger A. Faulkner* Copyright (c) 1985-2010 AT&T Intellectual Property *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* and is licensed under the *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* Common Public License, Version 1.0 *
7c2fbfb345896881c631598ee3852ce9ce33fb07April Chin* by AT&T Intellectual Property *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* A copy of the License is available at *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9) *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* Information and Software Systems Research *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* AT&T Research *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* Florham Park NJ *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* Glenn Fowler <gsf@research.att.com> *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* David Korn <dgk@research.att.com> *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin* Phong Vo <kpv@research.att.com> *
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin***********************************************************************/
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin/* Set the IO pointer to a specific location in the stream
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin** Written by Kiem-Phong Vo.
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chinstatic void newpos(f, p)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin f->endb = (f->mode&SF_WRITE) ? f->data+f->size : f->data;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if((f->here = p) < 0)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* set and initialize the stream to a definite mode */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(hardseek&SF_PUBLIC) /* seek ptr must follow file descriptor */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* Xopen-compliant */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if((type &= (SEEK_SET|SEEK_CUR|SEEK_END)) != SEEK_SET &&
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { /* let system call set errno */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* throw away ungetc data */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* lock the stream for internal manipulations */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* clear error and eof bits */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin r = p + f->extent;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin else r = p;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(r >= 0 && r <= f->size)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin memclear((char*)(f->data+f->extent),(int)(p-f->extent));
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* check exception handler, note that this may pop stream */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { /* see if we can avoid flushing buffer */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(!hardseek && type < SEEK_END && !(f->flags&SF_APPENDWR) )
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(r == s)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin p = (hardseek || r != f->here) ? SFSK(f,r,SEEK_SET,f->disc) : r;
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(p >= 0)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* if get here, must be a read stream */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(r <= f->here && r >= (f->here - (f->endb-f->data)) )
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { if((s = SFSK(f, (Sfoff_t)0, SEEK_CUR, f->disc)) == f->here ||
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin (s = SFSK(f, f->here, SEEK_SET, f->disc)) == f->here) )
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin else if(s < 0)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* desired position */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { /* if mmap is not great, stop mmaping if moving around too much */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { /* for mmap, f->here can be virtual except for hardseek */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { /* reduce wastage in future buffer fillings */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* buffer is now considered empty */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* small backseeks often come in bunches, so seek back as far as possible */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(p < f->lpos && f->size > f->blksz && (p + f->blksz) > s)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { if((r = s - f->size) < 0)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* try to align buffer to block boundary to enhance I/O speed */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin r = p - (p%f->blksz);
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin /* seeking around and wasting data, be conservative */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(f->iosz > 0 && (p > f->lpos || p < f->lpos-f->size) )
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if((hardseek || r != f->here) && (f->here = SFSK(f,r,SEEK_SET,f->disc)) != r)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin { if(r < p) /* now try to just get to p */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(f->here != p)
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(r < p) /* read to cover p */
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin if(p <= f->here && p >= (f->here - (f->endb - f->data)) )
da2e3ebdc1edfbc5028edf1354e7dd2fa69a7968chin else /* recover from read failure by just seeking to p */