usr/src/lib/libc/stdio/refill.c

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * %sccs.include.redist.c%
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)refill.c    5.3 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include "local.h"

static
lflush(fp)
        FILE *fp;
{

        if ((fp->_flags & (__SLBF|__SWR)) == __SLBF|__SWR)
                return (__sflush(fp));
        return (0);
}

/*
 * Refill a stdio buffer.
 * Return EOF on eof or error, 0 otherwise.
 */
__srefill(fp)
        register FILE *fp;
{

        /* make sure stdio is set up */
        if (!__sdidinit)
                __sinit();

        fp->_r = 0;             /* largely a convenience for callers */

        /* SysV does not make this test; take it out for compatibility */
        if (fp->_flags & __SEOF)
                return (EOF);

        /* if not already reading, have to be reading and writing */
        if ((fp->_flags & __SRD) == 0) {
                if ((fp->_flags & __SRW) == 0) {
                        errno = EBADF;
                        return (EOF);
                }
                /* switch to reading */
                if (fp->_flags & __SWR) {
                        if (__sflush(fp))
                                return (EOF);
                        fp->_flags &= ~__SWR;
                        fp->_w = 0;
                        fp->_lbfsize = 0;
                }
                fp->_flags |= __SRD;
        } else {
                /*
                 * We were reading.  If there is an ungetc buffer,
                 * we must have been reading from that.  Drop it,
                 * restoring the previous buffer (if any).  If there
                 * is anything in that buffer, return.
                 */
                if (HASUB(fp)) {
                        FREEUB(fp);
                        if ((fp->_r = fp->_ur) != 0) {
                                fp->_p = fp->_up;
                                return (0);
                        }
                }
        }

        if (fp->_bf._base == NULL)
                __smakebuf(fp);

        /*
         * Before reading from a line buffered or unbuffered file,
         * flush all line buffered output files, per the ANSI C
         * standard.
         */
        if (fp->_flags & (__SLBF|__SNBF))
                (void) _fwalk(lflush);
        fp->_p = fp->_bf._base;
        fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
        fp->_flags &= ~__SMOD;  /* buffer contents are again pristine */
        if (fp->_r <= 0) {
                if (fp->_r == 0)
                        fp->_flags |= __SEOF;
                else {
                        fp->_r = 0;
                        fp->_flags |= __SERR;
                }
                return (EOF);
        }
        return (0);
}