src/liblzma/simple/armthumb.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       armthumb.c
   6 /// \brief      Filter for ARM-Thumb binaries
   7 ///
   8 //  Authors:    Igor Pavlov
   9 //              Lasse Collin
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "simple_private.h"
  14
  15
  16 static size_t
  17 armthumb_code(void *simple lzma_attribute((__unused__)),
  18                 uint32_t now_pos, bool is_encoder,
  19                 uint8_t *buffer, size_t size)
  20 {
  21         size_t i;
  22         for (i = 0; i + 4 <= size; i += 2) {
  23                 if ((buffer[i + 1] & 0xF8) == 0xF0
  24                                 && (buffer[i + 3] & 0xF8) == 0xF8) {
  25                         uint32_t src = (((uint32_t)(buffer[i + 1]) & 7) << 19)
  26                                 | ((uint32_t)(buffer[i + 0]) << 11)
  27                                 | (((uint32_t)(buffer[i + 3]) & 7) << 8)
  28                                 | (uint32_t)(buffer[i + 2]);
  29
  30                         src <<= 1;
  31
  32                         uint32_t dest;
  33                         if (is_encoder)
  34                                 dest = now_pos + (uint32_t)(i) + 4 + src;
  35                         else
  36                                 dest = src - (now_pos + (uint32_t)(i) + 4);
  37
  38                         dest >>= 1;
  39                         buffer[i + 1] = 0xF0 | ((dest >> 19) & 0x7);
  40                         buffer[i + 0] = (dest >> 11);
  41                         buffer[i + 3] = 0xF8 | ((dest >> 8) & 0x7);
  42                         buffer[i + 2] = (dest);
  43                         i += 2;
  44                 }
  45         }
  46
  47         return i;
  48 }
  49
  50
  51 static lzma_ret
  52 armthumb_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
  53                 const lzma_filter_info *filters, bool is_encoder)
  54 {
  55         return lzma_simple_coder_init(next, allocator, filters,
  56                         &armthumb_code, 0, 4, 2, is_encoder);
  57 }
  58
  59
  60 #ifdef HAVE_ENCODER_ARMTHUMB
  61 extern lzma_ret
  62 lzma_simple_armthumb_encoder_init(lzma_next_coder *next,
  63                 const lzma_allocator *allocator,
  64                 const lzma_filter_info *filters)
  65 {
  66         return armthumb_coder_init(next, allocator, filters, true);
  67 }
  68 #endif
  69
  70
  71 #ifdef HAVE_DECODER_ARMTHUMB
  72 extern lzma_ret
  73 lzma_simple_armthumb_decoder_init(lzma_next_coder *next,
  74                 const lzma_allocator *allocator,
  75                 const lzma_filter_info *filters)
  76 {
  77         return armthumb_coder_init(next, allocator, filters, false);
  78 }
  79 #endif