// Copyright 2017 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include "absl/base/internal/sysinfo.h"

#include "absl/base/attributes.h"

#ifdef _WIN32

#include <windows.h>

#else

#include <fcntl.h>

#include <pthread.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#endif

#ifdef __linux__

#include <sys/syscall.h>

#endif

#if defined(__APPLE__) || defined(__FreeBSD__)

#include <sys/sysctl.h>

#endif

#ifdef __FreeBSD__

#include <pthread_np.h>

#endif

#ifdef __NetBSD__

#include <lwp.h>

#endif

#if defined(__myriad2__)

#include <rtems.h>

#endif

#include <string.h>

#include <cassert>

#include <cerrno>

#include <cstdint>

#include <cstdio>

#include <cstdlib>

#include <ctime>

#include <limits>

#include <thread>  // NOLINT(build/c++11)

#include <utility>

#include <vector>

#include "absl/base/call_once.h"

#include "absl/base/config.h"

#include "absl/base/internal/raw_logging.h"

#include "absl/base/internal/spinlock.h"

#include "absl/base/internal/unscaledcycleclock.h"

#include "absl/base/thread_annotations.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace base_internal {

namespace {

#if defined(_WIN32)

// Returns number of bits set in `bitMask`

DWORD Win32CountSetBits(ULONG_PTR bitMask) {

  for (DWORD bitSetCount = 0; ; ++bitSetCount) {

    if (bitMask == 0) return bitSetCount;

    bitMask &= bitMask - 1;

  }

}

// Returns the number of logical CPUs using GetLogicalProcessorInformation(), or

// 0 if the number of processors is not available or can not be computed.

// https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getlogicalprocessorinformation

int Win32NumCPUs() {

#pragma comment(lib, "kernel32.lib")

  using Info = SYSTEM_LOGICAL_PROCESSOR_INFORMATION;

  DWORD info_size = sizeof(Info);

  Info* info(static_cast<Info*>(malloc(info_size)));

  if (info == nullptr) return 0;

  bool success = GetLogicalProcessorInformation(info, &info_size);

  if (!success && GetLastError() == ERROR_INSUFFICIENT_BUFFER) {

    free(info);

    info = static_cast<Info*>(malloc(info_size));

    if (info == nullptr) return 0;

    success = GetLogicalProcessorInformation(info, &info_size);

  }

  DWORD logicalProcessorCount = 0;

  if (success) {

    Info* ptr = info;

    DWORD byteOffset = 0;

    while (byteOffset + sizeof(Info) <= info_size) {

      switch (ptr->Relationship) {

        case RelationProcessorCore:

          logicalProcessorCount += Win32CountSetBits(ptr->ProcessorMask);

          break;

        case RelationNumaNode:

        case RelationCache:

        case RelationProcessorPackage:

          // Ignore other entries

          break;

        default:

          // Ignore unknown entries

          break;

      }

      byteOffset += sizeof(Info);

      ptr++;

    }

  }

  free(info);

  return static_cast<int>(logicalProcessorCount);

}

#endif

}  // namespace

static int GetNumCPUs() {

#if defined(__myriad2__)

  return 1;

#elif defined(_WIN32)

  const int hardware_concurrency = Win32NumCPUs();

  return hardware_concurrency ? hardware_concurrency : 1;

#elif defined(_AIX)

  return sysconf(_SC_NPROCESSORS_ONLN);

#else

  // Other possibilities:

  //  - Read /sys/devices/system/cpu/online and use cpumask_parse()

  //  - sysconf(_SC_NPROCESSORS_ONLN)

  return static_cast<int>(std::thread::hardware_concurrency());

#endif

}

#if defined(_WIN32)

static double GetNominalCPUFrequency() {

#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP) && \

    !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)

  // UWP apps don't have access to the registry and currently don't provide an

  // API informing about CPU nominal frequency.

  return 1.0;

#else

#pragma comment(lib, "advapi32.lib")  // For Reg* functions.

  HKEY key;

  // Use the Reg* functions rather than the SH functions because shlwapi.dll

  // pulls in gdi32.dll which makes process destruction much more costly.

  if (RegOpenKeyExA(HKEY_LOCAL_MACHINE,

                    "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0", 0,

                    KEY_READ, &key) == ERROR_SUCCESS) {

    DWORD type = 0;

    DWORD data = 0;

    DWORD data_size = sizeof(data);

    auto result = RegQueryValueExA(key, "~MHz", nullptr, &type,

                                   reinterpret_cast<LPBYTE>(&data), &data_size);

    RegCloseKey(key);

    if (result == ERROR_SUCCESS && type == REG_DWORD &&

        data_size == sizeof(data)) {

      return data * 1e6;  // Value is MHz.

    }

  }

  return 1.0;

#endif  // WINAPI_PARTITION_APP && !WINAPI_PARTITION_DESKTOP

}

#elif defined(CTL_HW) && defined(HW_CPU_FREQ)

static double GetNominalCPUFrequency() {

  unsigned freq;

  size_t size = sizeof(freq);

  int mib[2] = {CTL_HW, HW_CPU_FREQ};

  if (sysctl(mib, 2, &freq, &size, nullptr, 0) == 0) {

    return static_cast<double>(freq);

  }

  return 1.0;

}

#else

// Helper function for reading a long from a file. Returns true if successful

// and the memory location pointed to by value is set to the value read.

static bool ReadLongFromFile(const char *file, long *value) {

  bool ret = false;

#if defined(_POSIX_C_SOURCE)

  const int file_mode = (O_RDONLY | O_CLOEXEC);

#else

  const int file_mode = O_RDONLY;

#endif

  int fd = open(file, file_mode);

  if (fd != -1) {

    char line[1024];

    char *err;

    memset(line, '\0', sizeof(line));

    ssize_t len;

    do {

      len = read(fd, line, sizeof(line) - 1);

    } while (len < 0 && errno == EINTR);

    if (len <= 0) {

      ret = false;

    } else {

      const long temp_value = strtol(line, &err, 10);

      if (line[0] != '\0' && (*err == '\n' || *err == '\0')) {

        *value = temp_value;

        ret = true;

      }

    }

    close(fd);

  }

  return ret;

}

#if defined(ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY)

// Reads a monotonic time source and returns a value in

// nanoseconds. The returned value uses an arbitrary epoch, not the

// Unix epoch.

static int64_t ReadMonotonicClockNanos() {

  struct timespec t;

#ifdef CLOCK_MONOTONIC_RAW

  int rc = clock_gettime(CLOCK_MONOTONIC_RAW, &t);

#else

  int rc = clock_gettime(CLOCK_MONOTONIC, &t);

#endif

  if (rc != 0) {

    ABSL_INTERNAL_LOG(

        FATAL, "clock_gettime() failed: (" + std::to_string(errno) + ")");

  }

  return int64_t{t.tv_sec} * 1000000000 + t.tv_nsec;

}

class UnscaledCycleClockWrapperForInitializeFrequency {

 public:

  static int64_t Now() { return base_internal::UnscaledCycleClock::Now(); }

};

struct TimeTscPair {

  int64_t time;  // From ReadMonotonicClockNanos().

  int64_t tsc;   // From UnscaledCycleClock::Now().

};

// Returns a pair of values (monotonic kernel time, TSC ticks) that

// approximately correspond to each other.  This is accomplished by

// doing several reads and picking the reading with the lowest

// latency.  This approach is used to minimize the probability that

// our thread was preempted between clock reads.

static TimeTscPair GetTimeTscPair() {

  int64_t best_latency = std::numeric_limits<int64_t>::max();

  TimeTscPair best;

  for (int i = 0; i < 10; ++i) {

    int64_t t0 = ReadMonotonicClockNanos();

    int64_t tsc = UnscaledCycleClockWrapperForInitializeFrequency::Now();

    int64_t t1 = ReadMonotonicClockNanos();

    int64_t latency = t1 - t0;

    if (latency < best_latency) {

      best_latency = latency;

      best.time = t0;

      best.tsc = tsc;

    }

  }

  return best;

}

// Measures and returns the TSC frequency by taking a pair of

// measurements approximately `sleep_nanoseconds` apart.

static double MeasureTscFrequencyWithSleep(int sleep_nanoseconds) {

  auto t0 = GetTimeTscPair();

  struct timespec ts;

  ts.tv_sec = 0;

  ts.tv_nsec = sleep_nanoseconds;

  while (nanosleep(&ts, &ts) != 0 && errno == EINTR) {}

  auto t1 = GetTimeTscPair();

  double elapsed_ticks = t1.tsc - t0.tsc;

  double elapsed_time = (t1.time - t0.time) * 1e-9;

  return elapsed_ticks / elapsed_time;

}

// Measures and returns the TSC frequency by calling

// MeasureTscFrequencyWithSleep(), doubling the sleep interval until the

// frequency measurement stabilizes.

static double MeasureTscFrequency() {

  double last_measurement = -1.0;

  int sleep_nanoseconds = 1000000;  // 1 millisecond.

  for (int i = 0; i < 8; ++i) {

    double measurement = MeasureTscFrequencyWithSleep(sleep_nanoseconds);

    if (measurement * 0.99 < last_measurement &&

        last_measurement < measurement * 1.01) {

      // Use the current measurement if it is within 1% of the

      // previous measurement.

      return measurement;

    }

    last_measurement = measurement;

    sleep_nanoseconds *= 2;

  }

  return last_measurement;

}

#endif  // ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY

static double GetNominalCPUFrequency() {

  long freq = 0;

  // Google's production kernel has a patch to export the TSC

  // frequency through sysfs. If the kernel is exporting the TSC

  // frequency use that. There are issues where cpuinfo_max_freq

  // cannot be relied on because the BIOS may be exporting an invalid

  // p-state (on x86) or p-states may be used to put the processor in

  // a new mode (turbo mode). Essentially, those frequencies cannot

  // always be relied upon. The same reasons apply to /proc/cpuinfo as

  // well.

  if (ReadLongFromFile("/sys/devices/system/cpu/cpu0/tsc_freq_khz", &freq)) {

    return freq * 1e3;  // Value is kHz.

  }

#if defined(ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY)

  // On these platforms, the TSC frequency is the nominal CPU

  // frequency.  But without having the kernel export it directly

  // though /sys/devices/system/cpu/cpu0/tsc_freq_khz, there is no

  // other way to reliably get the TSC frequency, so we have to

  // measure it ourselves.  Some CPUs abuse cpuinfo_max_freq by

  // exporting "fake" frequencies for implementing new features. For

  // example, Intel's turbo mode is enabled by exposing a p-state

  // value with a higher frequency than that of the real TSC

  // rate. Because of this, we prefer to measure the TSC rate

  // ourselves on i386 and x86-64.

  return MeasureTscFrequency();

#else

  // If CPU scaling is in effect, we want to use the *maximum*

  // frequency, not whatever CPU speed some random processor happens

  // to be using now.

  if (ReadLongFromFile("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",

                       &freq)) {

    return freq * 1e3;  // Value is kHz.

  }

  return 1.0;

#endif  // !ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY

}

#endif

ABSL_CONST_INIT static once_flag init_num_cpus_once;

ABSL_CONST_INIT static int num_cpus = 0;

// NumCPUs() may be called before main() and before malloc is properly

// initialized, therefore this must not allocate memory.

int NumCPUs() {

  base_internal::LowLevelCallOnce(

      &init_num_cpus_once, []() { num_cpus = GetNumCPUs(); });

  return num_cpus;

}

// A default frequency of 0.0 might be dangerous if it is used in division.

ABSL_CONST_INIT static once_flag init_nominal_cpu_frequency_once;

ABSL_CONST_INIT static double nominal_cpu_frequency = 1.0;

// NominalCPUFrequency() may be called before main() and before malloc is

// properly initialized, therefore this must not allocate memory.

double NominalCPUFrequency() {

  base_internal::LowLevelCallOnce(

      &init_nominal_cpu_frequency_once,

      []() { nominal_cpu_frequency = GetNominalCPUFrequency(); });

  return nominal_cpu_frequency;

}

#if defined(_WIN32)

pid_t GetTID() {

  return pid_t{GetCurrentThreadId()};

}

#elif defined(__linux__)

#ifndef SYS_gettid

#define SYS_gettid __NR_gettid

#endif

pid_t GetTID() {

  return static_cast<pid_t>(syscall(SYS_gettid));

}

#elif defined(__akaros__)

pid_t GetTID() {

  // Akaros has a concept of "vcore context", which is the state the program

  // is forced into when we need to make a user-level scheduling decision, or

  // run a signal handler.  This is analogous to the interrupt context that a

  // CPU might enter if it encounters some kind of exception.

  //

  // There is no current thread context in vcore context, but we need to give

  // a reasonable answer if asked for a thread ID (e.g., in a signal handler).

  // Thread 0 always exists, so if we are in vcore context, we return that.

  //

  // Otherwise, we know (since we are using pthreads) that the uthread struct

  // current_uthread is pointing to is the first element of a

  // struct pthread_tcb, so we extract and return the thread ID from that.

  //

  // TODO(dcross): Akaros anticipates moving the thread ID to the uthread

  // structure at some point. We should modify this code to remove the cast

  // when that happens.

  if (in_vcore_context())

    return 0;

  return reinterpret_cast<struct pthread_tcb *>(current_uthread)->id;

}

#elif defined(__myriad2__)

pid_t GetTID() {

  uint32_t tid;

  rtems_task_ident(RTEMS_SELF, 0, &tid);

  return tid;

}

#elif defined(__APPLE__)

pid_t GetTID() {

  uint64_t tid;

  // `nullptr` here implies this thread.  This only fails if the specified

  // thread is invalid or the pointer-to-tid is null, so we needn't worry about

  // it.

  pthread_threadid_np(nullptr, &tid);

  return static_cast<pid_t>(tid);

}

#elif defined(__FreeBSD__)

pid_t GetTID() { return static_cast<pid_t>(pthread_getthreadid_np()); }

#elif defined(__OpenBSD__)

pid_t GetTID() { return getthrid(); }

#elif defined(__NetBSD__)

pid_t GetTID() { return static_cast<pid_t>(_lwp_self()); }

#elif defined(__native_client__)

pid_t GetTID() {

  auto* thread = pthread_self();

  static_assert(sizeof(pid_t) == sizeof(thread),

                "In NaCL int expected to be the same size as a pointer");

  return reinterpret_cast<pid_t>(thread);

}

#else

// Fallback implementation of `GetTID` using `pthread_self`.

pid_t GetTID() {

  // `pthread_t` need not be arithmetic per POSIX; platforms where it isn't

  // should be handled above.

  return static_cast<pid_t>(pthread_self());

}

#endif

// GetCachedTID() caches the thread ID in thread-local storage (which is a

// userspace construct) to avoid unnecessary system calls. Without this caching,

// it can take roughly 98ns, while it takes roughly 1ns with this caching.

pid_t GetCachedTID() {

#ifdef ABSL_HAVE_THREAD_LOCAL

  static thread_local pid_t thread_id = GetTID();

  return thread_id;

#else

  return GetTID();

#endif  // ABSL_HAVE_THREAD_LOCAL

}

}  // namespace base_internal

ABSL_NAMESPACE_END

}  // namespace absl