source: vbox/trunk/src/libs/liblzma-5.8.1/simple/armthumb.c@ 108911

// 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