// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       armthumb.c

/// \brief      Filter for ARM-Thumb binaries

///

//  Authors:    Igor Pavlov

//              Lasse Collin

//

///////////////////////////////////////////////////////////////////////////////

#include "simple_private.h"

static size_t

armthumb_code(void *simple lzma_attribute((__unused__)),

    uint32_t now_pos, bool is_encoder,

    uint8_t *buffer, size_t size)

{

  if (size < 4)

    return 0;

  size -= 4;

  size_t i;

  for (i = 0; i <= size; i += 2) {

    if ((buffer[i + 1] & 0xF8) == 0xF0

        && (buffer[i + 3] & 0xF8) == 0xF8) {

      uint32_t src = (((uint32_t)(buffer[i + 1]) & 7) << 19)

        | ((uint32_t)(buffer[i + 0]) << 11)

        | (((uint32_t)(buffer[i + 3]) & 7) << 8)

        | (uint32_t)(buffer[i + 2]);

      src <<= 1;

      uint32_t dest;

      if (is_encoder)

        dest = now_pos + (uint32_t)(i) + 4 + src;

      else

        dest = src - (now_pos + (uint32_t)(i) + 4);

      dest >>= 1;

      buffer[i + 1] = 0xF0 | ((dest >> 19) & 0x7);

      buffer[i + 0] = (dest >> 11);

      buffer[i + 3] = 0xF8 | ((dest >> 8) & 0x7);

      buffer[i + 2] = (dest);

      i += 2;

    }

  }

  return i;

}

static lzma_ret

armthumb_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,

    const lzma_filter_info *filters, bool is_encoder)

{

  return lzma_simple_coder_init(next, allocator, filters,

      &armthumb_code, 0, 4, 2, is_encoder);

}

#ifdef HAVE_ENCODER_ARMTHUMB

extern lzma_ret

lzma_simple_armthumb_encoder_init(lzma_next_coder *next,

    const lzma_allocator *allocator,

    const lzma_filter_info *filters)

{

  return armthumb_coder_init(next, allocator, filters, true);

}

#endif

#ifdef HAVE_DECODER_ARMTHUMB

extern lzma_ret

lzma_simple_armthumb_decoder_init(lzma_next_coder *next,

    const lzma_allocator *allocator,

    const lzma_filter_info *filters)

{

  return armthumb_coder_init(next, allocator, filters, false);

}

#endif