#include "transfer.h"
using namespace std;
#define sz(x) int(x.size())
#define all(x) begin(x), end(x)
vector<int> parity(vector<int> source) {
int log = sz(source) == 63 ? 6 : 8;
vector<int> par(log, 0);
for (int i = 0; i < sz(source); i++) {
for (int j = 0; j < log; j++) {
if ((i + 1) >> j & 1) par[j] ^= source[i];
}
}
return par;
}
vector<int> get_attachment(vector<int> source) {
vector<int> par = parity(source);
int x = 0;
for (int i = 0; i < sz(par); i++) {
x ^= par[i];
}
par.push_back(x);
return par;
}
vector<int> retrieve(vector<int> data) {
int cut = sz(data) == 70 ? 63 : 255;
vector<int> source(begin(data), begin(data) + cut);
vector<int> code(begin(data) + cut, end(data));
vector<int> par = parity(source);
int x = 0;
int p = 0;
for (int i = 0; i < sz(code) - 1; i++) {
if (code[i] != par[i]) x ^= 1 << i;
p ^= code[i];
}
if (code.back() != p) return source;
if (x != 0) source[x - 1] ^= 1;
return source;
}
