//

// Java Does USB

// Copyright (c) 2022 Manuel Bleichenbacher

// Licensed under MIT License

// https://opensource.org/licenses/MIT

//

// Reference C++ code common for Linux / macOS / Windows

//

#include "prng.hpp"

prng::prng(uint32_t init) : state(init), nbytes(0), bits(0) {}

void prng::reset(uint32_t init)

{

state = init;

nbytes = 0;

bits = 0;

}

uint32_t prng::next()

{

uint32_t x = state;

x ^= x << 13;

x ^= x >> 17;

x ^= x << 5;

state = x;

return x;

}

void prng::fill(uint8_t *buf, int len)

{

for (int i = 0; i < len; i++)

{

if (nbytes == 0)

{

bits = next();

nbytes = 4;

}

buf[i] = bits;

bits >>= 8;

nbytes--;

}

}

void prng::fill(std::vector<uint8_t>& buf, int len)

{

if (len == -1 || len > buf.size())

len = static_cast<int>(buf.size());

fill(buf.data(), len);

}

int prng::verify(const uint8_t *buf, int len)

{

for (int i = 0; i < len; i++)

{

if (nbytes == 0)

{

bits = next();

nbytes = 4;

}

if (buf[i] != (uint8_t)bits)

return i;

bits >>= 8;

nbytes--;

}

return -1;

}

int prng::verify(const std::vector<uint8_t> &buf, int len)

{

if (len == -1 || len > buf.size())

len = static_cast<int>(buf.size());

return verify(buf.data(), len);

}