//decimate sound to SAMPLE_RATE, using averaging
void decimate(const u::bytes& s, u::bytes& d, size_t channels, size_t skip)
{
REQUIRE_FALSE(s.empty());
REQUIRE_EQUAL(s.size() % 2, 0);
//get sizes
auto dz = (s.size() / skip);
auto nz = d.size() + dz;
//add padding
if(nz % 2 == 1) nz += 1;
CHECK_EQUAL(nz % 2, 0);
//resize dest
const auto odz = d.size();
d.resize(nz);
//cast to short arrays
auto ss = reinterpret_cast<const short*>(s.data());
const auto sz = s.size() / 2;
auto sd = reinterpret_cast<short*>(d.data());
const auto sdz = nz / 2;
int accum = 0;
size_t c = 1;
size_t si = 0;
auto di = odz / 2;
for(;si < sz; si+=channels)
{
accum += static_cast<int>(ss[si]);
if(c == skip)
{
accum /= c;
sd[di] = accum;
di++;
accum = 0;
c = 1;
continue;
}
c++;
}
//repeat last value if we have padding
si = sz-1;
while(di < sdz)
{
sd[di] = ss[si];
di++;
}
CHECK_EQUAL(di, sdz);
}
void inflate(const u::bytes& s, u::bytes& d, size_t channels, size_t rep)
{
REQUIRE_EQUAL(s.size() % 2, 0);
rep*=channels;
d.resize(s.size() * rep);
auto ss = reinterpret_cast<const short*>(s.data());
auto sz = s.size() / 2;
auto sd = reinterpret_cast<short*>(d.data());
size_t di = 0;
for(size_t si = 0; si < sz; si++)
for(size_t p = 0; p < rep; p++, di++)
sd[di] = ss[si];
}
//simple low pass filter
void reduce_noise(u::bytes& s, size_t len)
{
REQUIRE_EQUAL(s.size() % 2, 0);
auto ss = reinterpret_cast<short*>(s.data());
len /= 2;
for(size_t i = 1; i < len; i++)
ss[i] = (0.333 * ss[i]) + ((1 - 0.333) * ss[i-1]) + 0.5;
}
u::bytes public_key::encrypt(const u::bytes& b) const
{
INVARIANT(_k);
INVARIANT_FALSE(_ks.empty());
u::mutex_scoped_lock l(BOTAN_MUTEX);
init_rng();
CHECK(RNG);
std::stringstream rs;
b::PK_Encryptor_EME e{*_k, EME_SCHEME};
size_t advance = 0;
while(advance < b.size())
{
size_t size = std::min(e.maximum_input_size(), b.size()-advance);
auto c = e.encrypt(reinterpret_cast<const unsigned char*>(b.data())+advance, size, *RNG);
u::bytes bs{std::begin(c), std::end(c)};
rs << bs;
advance+=size;
}
return u::to_bytes(rs.str());
}
u::bytes private_key::sign(const u::bytes& b) const
{
INVARIANT(_k);
u::mutex_scoped_lock l(BOTAN_MUTEX);
init_rng();
CHECK(RNG);
b::PK_Signer s{*_k, EMSA_SCHEME};
auto r = s.sign_message(reinterpret_cast<const unsigned char*>(b.data()), b.size(), *RNG);
ENSURE_EQUAL(r.size(), SIGNATURE_SIZE);
return u::bytes {std::begin(r), std::end(r)};
}