// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <randomenv.h>

#include <crypto/sha512.h>
#include <support/cleanse.h>
#include <util/time.h> // for GetTime()
#ifdef WIN32
#include <compat.h> // for Windows API
#endif

#include <algorithm>
#include <vector>

#include <stdint.h>

namespace {

void RandAddSeedPerfmon(CSHA512& hasher)
{
#ifdef WIN32
    // Don't need this on Linux, OpenSSL automatically uses /dev/urandom
    // Seed with the entire set of perfmon data

    // This can take up to 2 seconds, so only do it every 10 minutes
    static int64_t nLastPerfmon;
    if (GetTime() < nLastPerfmon + 10 * 60)
        return;
    nLastPerfmon = GetTime();

    std::vector<unsigned char> vData(250000, 0);
    long ret = 0;
    unsigned long nSize = 0;
    const size_t nMaxSize = 10000000; // Bail out at more than 10MB of performance data
    while (true) {
        nSize = vData.size();
        ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", nullptr, nullptr, vData.data(), &nSize);
        if (ret != ERROR_MORE_DATA || vData.size() >= nMaxSize)
            break;
        vData.resize(std::max((vData.size() * 3) / 2, nMaxSize)); // Grow size of buffer exponentially
    }
    RegCloseKey(HKEY_PERFORMANCE_DATA);
    if (ret == ERROR_SUCCESS) {
        hasher.Write(vData.data(), nSize);
        memory_cleanse(vData.data(), nSize);
    } else {
        // Performance data is only a best-effort attempt at improving the
        // situation when the OS randomness (and other sources) aren't
        // adequate. As a result, failure to read it is isn't considered critical,
        // so we don't call RandFailure().
        // TODO: Add logging when the logger is made functional before global
        // constructors have been invoked.
    }
#endif
}

} // namespace

void RandAddDynamicEnv(CSHA512& hasher)
{
    RandAddSeedPerfmon(hasher);
}

void RandAddStaticEnv(CSHA512& hasher)
{
}