1 /* udis86 - libudis86/input.c
2 *
3 * Copyright (c) 2002-2009 Vivek Thampi
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without modification,
7 * are permitted provided that the following conditions are met:
8 *
9 * * Redistributions of source code must retain the above copyright notice,
10 * this list of conditions and the following disclaimer.
11 * * Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
19 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
20 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
21 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
22 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
24 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26 #include "extern.h"
27 #include "types.h"
28 #include "input.h"
29 #include "udint.h"
30
31 /*
32 * inp_init
33 * Initializes the input system.
34 */
35 static void
inp_init(struct ud * u)36 inp_init(struct ud *u)
37 {
38 u->inp_curr = 0;
39 u->inp_fill = 0;
40 u->inp_ctr = 0;
41 u->inp_end = 0;
42 }
43
44
45 /* -----------------------------------------------------------------------------
46 * inp_buff_hook() - Hook for buffered inputs.
47 * -----------------------------------------------------------------------------
48 */
49 static int
inp_buff_hook(struct ud * u)50 inp_buff_hook(struct ud* u)
51 {
52 if (u->inp_buff < u->inp_buff_end)
53 return *u->inp_buff++;
54 else return -1;
55 }
56
57 #ifndef __UD_STANDALONE__
58 /* -----------------------------------------------------------------------------
59 * inp_file_hook() - Hook for FILE inputs.
60 * -----------------------------------------------------------------------------
61 */
62 static int
inp_file_hook(struct ud * u)63 inp_file_hook(struct ud* u)
64 {
65 return fgetc(u->inp_file);
66 }
67 #endif /* __UD_STANDALONE__*/
68
69 /* =============================================================================
70 * ud_inp_set_hook() - Sets input hook.
71 * =============================================================================
72 */
73 void
ud_set_input_hook(register struct ud * u,int (* hook)(struct ud *))74 ud_set_input_hook(register struct ud* u, int (*hook)(struct ud*))
75 {
76 u->inp_hook = hook;
77 inp_init(u);
78 }
79
80 /* =============================================================================
81 * ud_inp_set_buffer() - Set buffer as input.
82 * =============================================================================
83 */
84 void
ud_set_input_buffer(register struct ud * u,const uint8_t * buf,size_t len)85 ud_set_input_buffer(register struct ud* u, const uint8_t* buf, size_t len)
86 {
87 u->inp_hook = inp_buff_hook;
88 u->inp_buff = buf;
89 u->inp_buff_end = buf + len;
90 inp_init(u);
91 }
92
93 #ifndef __UD_STANDALONE__
94 /* =============================================================================
95 * ud_input_set_file() - Set buffer as input.
96 * =============================================================================
97 */
98 void
ud_set_input_file(register struct ud * u,FILE * f)99 ud_set_input_file(register struct ud* u, FILE* f)
100 {
101 u->inp_hook = inp_file_hook;
102 u->inp_file = f;
103 inp_init(u);
104 }
105 #endif /* __UD_STANDALONE__ */
106
107 /* =============================================================================
108 * ud_input_skip() - Skip n input bytes.
109 * =============================================================================
110 */
111 void
ud_input_skip(struct ud * u,size_t n)112 ud_input_skip(struct ud* u, size_t n)
113 {
114 while (n--) {
115 u->inp_hook(u);
116 }
117 }
118
119 /* =============================================================================
120 * ud_input_end() - Test for end of input.
121 * =============================================================================
122 */
123 int
ud_input_end(const struct ud * u)124 ud_input_end(const struct ud* u)
125 {
126 return (u->inp_curr == u->inp_fill) && u->inp_end;
127 }
128
129
130 /*
131 * ud_inp_next
132 * Loads and returns the next byte from input.
133 *
134 * inp_curr and inp_fill are pointers to the cache. The program is
135 * written based on the property that they are 8-bits in size, and
136 * will eventually wrap around forming a circular buffer. So, the
137 * size of the cache is 256 in size, kind of unnecessary yet
138 * optimal.
139 *
140 * A buffer inp_sess stores the bytes disassembled for a single
141 * session.
142 */
143 uint8_t
ud_inp_next(struct ud * u)144 ud_inp_next(struct ud* u)
145 {
146 int c = -1;
147 /* if current pointer is not upto the fill point in the
148 * input cache.
149 */
150 if (u->inp_curr != u->inp_fill) {
151 c = u->inp_cache[ ++u->inp_curr ];
152 /* if !end-of-input, call the input hook and get a byte */
153 } else if (u->inp_end || (c = u->inp_hook(u)) == -1) {
154 /* end-of-input, mark it as an error, since the decoder,
155 * expected a byte more.
156 */
157 UDERR(u, "byte expected, eoi received");
158 /* flag end of input */
159 u->inp_end = 1;
160 return 0;
161 } else {
162 /* increment pointers, we have a new byte. */
163 u->inp_curr = ++u->inp_fill;
164 /* add the byte to the cache */
165 u->inp_cache[u->inp_fill] = c;
166 }
167 /* record bytes input per decode-session. */
168 u->inp_sess[u->inp_ctr++] = c;
169 /* return byte */
170 return (uint8_t) c;
171 }
172
173 /*
174 vim: set ts=2 sw=2 expandtab
175 */
176