1/***********************************************************************
2*                                                                      *
3*               This software is part of the ast package               *
4*          Copyright (c) 1985-2011 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
29static int _uexcept(Sfio_t* f, int type, Void_t* val, Sfdisc_t* disc)
30#else
31static int _uexcept(f,type,val,disc)
32Sfio_t		*f;
33int		type;
34Void_t*		val;
35Sfdisc_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
52int sfungetc(Sfio_t* f, int c)
53#else
54int sfungetc(f,c)
55Sfio_t*		f;	/* push back one byte to this stream */
56int		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;
105done:
106	SFOPEN(f,0);
107	SFMTXRETURN(f, c);
108}
109