//===-------------------------- random.cpp --------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "libc/stdio/rand.h"
#include "third_party/libcxx/__config"
#include "third_party/libcxx/random"
#include "third_party/libcxx/system_error"
#include "third_party/libcxx/errno.h"
#include "third_party/libcxx/stdio.h"
#include "third_party/libcxx/stdlib.h"

_LIBCPP_BEGIN_NAMESPACE_STD

#if defined(_LIBCPP_USING_GETENTROPY)

random_device::random_device(const string& __token) {
  if (__token != "/dev/urandom")
    __throw_system_error(ENOENT,
                         ("random device not supported " + __token).c_str());
}

random_device::~random_device() {}

unsigned random_device::operator()() {
  unsigned r;
  size_t n = sizeof(r);
  int err = getentropy(&r, n);
  if (err)
    __throw_system_error(errno, "random_device getentropy failed");
  return r;
}

#elif defined(_LIBCPP_USING_ARC4_RANDOM)

random_device::random_device(const string& __token) {
  if (__token != "/dev/urandom")
    __throw_system_error(ENOENT,
                         ("random device not supported " + __token).c_str());
}

random_device::~random_device() {}

unsigned random_device::operator()() { return arc4random(); }

#elif defined(_LIBCPP_USING_DEV_RANDOM)

random_device::random_device(const string& __token)
    : __f_(open(__token.c_str(), O_RDONLY)) {
  if (__f_ < 0)
    __throw_system_error(errno,
                         ("random_device failed to open " + __token).c_str());
}

random_device::~random_device() { close(__f_); }

unsigned random_device::operator()() {
  unsigned r;
  size_t n = sizeof(r);
  char* p = reinterpret_cast<char*>(&r);
  while (n > 0) {
    ssize_t s = read(__f_, p, n);
    if (s == 0)
      __throw_system_error(ENODATA, "random_device got EOF");
    if (s == -1) {
      if (errno != EINTR)
        __throw_system_error(errno, "random_device got an unexpected error");
      continue;
    }
    n -= static_cast<size_t>(s);
    p += static_cast<size_t>(s);
  }
  return r;
}

#elif defined(_LIBCPP_USING_NACL_RANDOM)

random_device::random_device(const string& __token) {
  if (__token != "/dev/urandom")
    __throw_system_error(ENOENT,
                         ("random device not supported " + __token).c_str());
  int error = nacl_secure_random_init();
  if (error)
    __throw_system_error(error,
                         ("random device failed to open " + __token).c_str());
}

random_device::~random_device() {}

unsigned random_device::operator()() {
  unsigned r;
  size_t n = sizeof(r);
  size_t bytes_written;
  int error = nacl_secure_random(&r, n, &bytes_written);
  if (error != 0)
    __throw_system_error(error, "random_device failed getting bytes");
  else if (bytes_written != n)
    __throw_runtime_error("random_device failed to obtain enough bytes");
  return r;
}

#elif defined(_LIBCPP_USING_WIN32_RANDOM)

random_device::random_device(const string& __token) {
  if (__token != "/dev/urandom")
    __throw_system_error(ENOENT,
                         ("random device not supported " + __token).c_str());
}

random_device::~random_device() {}

unsigned random_device::operator()() {
  unsigned r;
  errno_t err = rand_s(&r);
  if (err)
    __throw_system_error(err, "random_device rand_s failed.");
  return r;
}

#else
#error "Random device not implemented for this architecture"
#endif

double random_device::entropy() const _NOEXCEPT { return 0; }

_LIBCPP_END_NAMESPACE_STD