#include "transfer.h"
#include <iostream>
using namespace std;
//Author: Kian Mirjalali
//K = 1+log(N+1)
typedef vector<int> VI;
static inline int rangeXorVec(const VI& v, int begin, int end) {
int s = 0;
for (int i = begin; i < end; i++)
s ^= v[i];
return s;
}
static inline int bitMaskXorVec(const VI& v, int N, int bitIndex) {
int s = 0;
for (int i = 0; i < N; i++)
if ((((i + 1) >> bitIndex) & 1) == 1)
s ^= v[i];
return s;
}
static inline int getL(int N) {
int L = 0;
for (int i=N; i>0; i/=2)
L++;
return L;
}
static inline int callLimit(int N) {
switch (N) {
case 63: return 20000;
case 255: return 200000;
}
cerr << "invalid value of N: " << N << endl;
exit(1);
}
VI get_attachment(VI source) {
const int N = source.size();
static int callCount = 0;
if (++callCount > callLimit(N)) {
cerr << "too many calls of get_attachment() : " << callCount << endl;
exit(1);
}
int L = getL(N);
VI attachment;
for (int l=0; l<L; l++)
attachment.push_back(bitMaskXorVec(source, N, l));
attachment.push_back(rangeXorVec(attachment, 0, L));
return attachment;
}
VI retrieve(VI data) {
int ds = data.size();
int N = ds/2;
while (N+getL(N)+1 < ds)
N++;
static int callCount = 0;
if (++callCount > callLimit(N)) {
cerr << "too many calls of retrieve() : " << callCount << endl;
exit(1);
}
VI result(data.begin(), data.begin()+N);
VI attachment(data.begin()+N, data.end());
int L = attachment.size()-1;
if (attachment.back() != rangeXorVec(attachment, 0, L))
return result;
int c = 0;
for (int l=0; l<L; l++)
if (attachment[l] != bitMaskXorVec(result, N, l))
c |= (1<<l);
c--;
if (c >= 0)
result[c] = 1-result[c];
return result;
}
