Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kcc-4/lib/stdio/ungetc.c
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/*
* UNGETC - unget a character to stream
*
* Copyright (c) 1986 by Ian Macky, SRI International
*/
#include "stdio.h"
int ungetc(c, f)
char c;
register FILE *f;
{
if ((f->siocheck != _SIOF_OPEN) || !(f->sioflgs & _SIOF_READ) || c == EOF)
return EOF; /* validate FILE block */
if (f->sioflgs & _SIOF_PBC) {
if (f->siocnt >= _SIO_NPBC) /* room for another? */
return EOF; /* no, so punt */
f->siocnt++; /* yes, bump count */
return *f->siocp-- = c; /* and store new char in buf */
} else {
f->sio2cp = f->siocp; /* save old pointer */
f->sio2cnt = f->siocnt; /* save old count */
f->siocp = f->siopbc + _SIO_NPBC - 2; /* point to before EOB */
f->siocnt = 1; /* start with 1 char */
f->sioflgs |= _SIOF_PBC; /* flag that we're in unget */
return *(f->siocp + 1) = c; /* store and return the char */
}
}