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 */
35static void
36inp_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 */
49static int
50inp_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 */
62static int
63inp_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 */
73void
74ud_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 */
84void
85ud_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 */
98void
99ud_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 */
111void
112ud_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 */
123int
124ud_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 */
143uint8_t
144ud_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/*
174vim: set ts=2 sw=2 expandtab
175*/
176