usr/src/lib/libast/common/sfio/sfungetc.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                   Phong Vo <kpv@research.att.com>                    *
  20 *                                                                      *
  21 ***********************************************************************/
  22 #include        "sfhdr.h"
  23
  24 /*      Push back one byte to a given SF_READ stream
  25 **
  26 **      Written by Kiem-Phong Vo.
  27 */
  28 #if __STD_C
  29 static int _uexcept(Sfio_t* f, int type, Void_t* val, Sfdisc_t* disc)
  30 #else
  31 static int _uexcept(f,type,val,disc)
  32 Sfio_t          *f;
  33 int             type;
  34 Void_t*         val;
  35 Sfdisc_t        *disc;
  36 #endif
  37 {
  38         NOTUSED(val);
  39
  40         /* hmm! This should never happen */
  41         if(disc != _Sfudisc)
  42                 return -1;
  43
  44         /* close the unget stream */
  45         if(type != SF_CLOSING)
  46                 (void)sfclose((*_Sfstack)(f,NIL(Sfio_t*)));
  47
  48         return 1;
  49 }
  50
  51 #if __STD_C
  52 int sfungetc(Sfio_t* f, int c)
  53 #else
  54 int sfungetc(f,c)
  55 Sfio_t*         f;      /* push back one byte to this stream */
  56 int             c;      /* the value to be pushed back */
  57 #endif
  58 {
  59         reg Sfio_t*     uf;
  60         SFMTXDECL(f);
  61
  62         SFMTXENTER(f, -1)
  63
  64         if(c < 0 || (f->mode != SF_READ && _sfmode(f,SF_READ,0) < 0))
  65                 SFMTXRETURN(f, -1);
  66         SFLOCK(f,0);
  67
  68         /* fast handling of the typical unget */
  69         if(f->next > f->data && f->next[-1] == (uchar)c)
  70         {       f->next -= 1;
  71                 goto done;
  72         }
  73
  74         /* make a string stream for unget characters */
  75         if(f->disc != _Sfudisc)
  76         {       if(!(uf = sfnew(NIL(Sfio_t*),NIL(char*),(size_t)SF_UNBOUND,
  77                                 -1,SF_STRING|SF_READ)))
  78                 {       c = -1;
  79                         goto done;
  80                 }
  81                 _Sfudisc->exceptf = _uexcept;
  82                 sfdisc(uf,_Sfudisc);
  83                 SFOPEN(f,0); (void)sfstack(f,uf); SFLOCK(f,0);
  84         }
  85
  86         /* space for data */
  87         if(f->next == f->data)
  88         {       reg uchar*      data;
  89                 if(f->size < 0)
  90                         f->size = 0;
  91                 if(!(data = (uchar*)malloc(f->size+16)))
  92                 {       c = -1;
  93                         goto done;
  94                 }
  95                 f->flags |= SF_MALLOC;
  96                 if(f->data)
  97                         memcpy((char*)(data+16),(char*)f->data,f->size);
  98                 f->size += 16;
  99                 f->data  = data;
 100                 f->next  = data+16;
 101                 f->endb  = data+f->size;
 102         }
 103
 104         *--f->next = (uchar)c;
 105 done:
 106         SFOPEN(f,0);
 107         SFMTXRETURN(f, c);
 108 }