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