third_party/mach_override/libudis86/input.c

   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
  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
  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
  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
  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
  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
  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
 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
 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
 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 */