armthumb.c

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//
//  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(void *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 = (((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);
}
 
 
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);
}
 
 
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);
}