FlareOn Task10: solution to the part 2

solution10_p2.cpp

#include <iostream>

#ifdef _MSC_VER
#include <stdint.h>
#else
#include <inttypes.h>
#include <climits>
#endif

static inline uint32_t rotr32(uint32_t n, unsigned int c)
{
    const unsigned int mask = (CHAR_BIT * sizeof(n) - 1);
    c &= mask;
    return (n >> c) | (n << ((-c)&mask));
}

uint32_t encode_chunk(uint32_t pass_chunk, uint32_t t1, uint32_t t2, uint32_t t3)
{
    uint32_t v2 = pass_chunk + t1;
    uint32_t v3 = rotr32(v2, t2);
    uint32_t res = v3 ^ t3;
    return res;
}

void decode(uint32_t val[2])
{
    uint32_t t1[] = {
        0x4b695809, 0xe35b9b24, 0x71adcd92, 0x38d6e6c9,
        0x5a844444, 0x2d422222, 0x16a11111, 0xcdbfbfa8,
        0xe6dfdfd4, 0xf36fefea, 0x79b7f7f5, 0xfa34ccda,
        0x7d1a666d, 0xf8620416, 0x7c31020b, 0x78f7b625
    };

    uint32_t t2[] = {
        0xf, 0x11, 0x11, 0x11,
        0xc, 0xc, 0xc, 0x15,
        0x15, 0x15, 0x15, 0xf,
        0xf, 0xf, 0xf, 0x12
    };

    uint32_t t3[] = {
        0x674a1dea, 0xad92774c, 0x56c93ba6, 0x2b649dd3,
        0x8b853750, 0x45c29ba8, 0x22e14dd4, 0x8f47df53,
        0x47a3efa9, 0x23d1f7d4, 0x11e8fbea, 0x96c3044c,
        0x4b618226, 0xbb87b8aa, 0x5dc3dc55, 0xb0d69793
    };

    uint32_t part1 = val[1];
    uint32_t part2 = val[0];
    uint32_t prev = 0;
    for (int i = 15; i >= 0; i--) {
        uint32_t res = part2 ^ encode_chunk(part1, t1[i], t2[i], t3[i]);
        part2 = part1;
        part1 = res;
    }
    val[0] = part1;
    val[1] = part2;
}

void print_chunk(uint32_t chunk)
{
    char* ptr = (char*)&chunk;
    for (size_t i = 0; i < 4; i++)
    {
        std::cout << ptr[i];
    }
}

int main()
{

    /* Copied buffer:
    StartOffset(h): 0015C100, EndOffset(h): 0015C11F, Length(h): 00000020 */
    unsigned char rawData[32] = {
        0x64, 0xA0, 0x60, 0x02, //0
        0xEA, 0x8A, 0x87, 0x7D, //1
        0x6C, 0xE9, 0x7C, 0xE4,
        0x82, 0x3F, 0x2D, 0x0C, 
        0x8C, 0xB7, 0xB5, 0xEB,
        0xCF, 0x35, 0x4F, 0x42,
        0x4F, 0xAD, 0x2B, 0x49,
        0x20, 0x28, 0x7C, 0xE0
    };

    uint32_t *enc = (uint32_t*)rawData;
	
    for (int i = 0; i < 8; i += 2) {
        uint32_t val[2] = { enc[i], enc[i+1] };
        decode(val);
        print_chunk(val[0]);
        print_chunk(val[1]);
    }
    std::cout << std::endl;
    return 0;
}