The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       armthumb.c
/// \brief      Filter for ARM-Thumb binaries
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "simple_private.h"


static size_t
armthumb_code(lzma_simple *simple lzma_attribute((__unused__)),
        uint32_t now_pos, bool is_encoder,
        uint8_t *buffer, size_t size)
{
    size_t i;
    for (i = 0; i + 4 <= size; i += 2) {
        if ((buffer[i + 1] & 0xF8) == 0xF0
                && (buffer[i + 3] & 0xF8) == 0xF8) {
            uint32_t src = ((buffer[i + 1] & 0x7) << 19)
                    | (buffer[i + 0] << 11)
                    | ((buffer[i + 3] & 0x7) << 8)
                    | (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, 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);
}


extern lzma_ret
lzma_simple_armthumb_encoder_init(lzma_next_coder *next,
        lzma_allocator *allocator, const lzma_filter_info *filters)
{
    return armthumb_coder_init(next, allocator, filters, true);
}


extern lzma_ret
lzma_simple_armthumb_decoder_init(lzma_next_coder *next,
        lzma_allocator *allocator, const lzma_filter_info *filters)
{
    return armthumb_coder_init(next, allocator, filters, false);
}