hash.h

// Header guards
#ifndef HASH_H
#define HASH_H

#ifndef STRING_H
#define STRING_H
#include <string.h>
#endif

#ifndef STDBOOL_H
#define STDBOOL_H
#include <stdbool.h>
#endif

#include "coin.h"
#include "bytes.h"

buffer hash(buffer input);
static bool mine(buffer seed, buffer gold, bool echo);

// Calcular a hash de um buffer
buffer hash(buffer input) {
    const static unsigned char randomBytes[] = { 0x78, 0x16, 0xc3, 0xb3, 0x52, 0xf9, 0xe4, 0xad };
    const static unsigned short int randomBytesLength = sizeof(randomBytes);

    buffer digest = new_buffer(HASH_LENGTH);
    zero_buffer(digest);
    
    int result = 0;
    int i, j;
    for(i = 0; i < input.length; i++) {
        for(j = 0; j < HASH_LENGTH; j++) {
            digest.bytes[i % digest.length] = input.bytes[i] + i
                ^ randomBytes[(input.bytes[i] + i) % randomBytesLength];  
        }
        result ^= input.bytes[i] + i;
    }
    for(i = 0; i < digest.length; i++) {
        digest.bytes[i] ^= result + i;
    }
    return digest;
}

// Verifica se um buffer "gold" é uma hash de
// mineração válida para um buffer "seed"
static bool mine(buffer seed, buffer gold, bool echo) {    
    buffer input = new_buffer(seed.length + gold.length);
        
    concat_buffer(&input, seed);
    concat_buffer(&input, gold);

    buffer output = hash(input);

    if(echo) {
        print_buffer(output);
        printf(" = ");
        print_buffer(gold);
        printf("\n");
    }

    int i = 0, j = 1 << (8 - 1);
    while(!(output.bytes[i/8] & (j >> (i % 8))) && i <= DIFFICULTY) i++;
    return i >= DIFFICULTY;
}
#endif