xref: /netbsd/src/external/public-domain/xz/dist/src/common/mythread.h

///////////////////////////////////////////////////////////////////////////////
//
/// \file       mythread.h
/// \brief      Some threading related helper macros and functions
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef MYTHREAD_H
#define MYTHREAD_H

#include "sysdefs.h"

// If any type of threading is enabled, #define MYTHREAD_ENABLED.
#if defined(MYTHREAD_POSIX) || defined(MYTHREAD_WIN95) \
                    || defined(MYTHREAD_VISTA)
#         define MYTHREAD_ENABLED 1
#endif


#ifdef MYTHREAD_ENABLED

////////////////////////////////////////
// Shared between all threading types //
////////////////////////////////////////

// Locks a mutex for a duration of a block.
//
// Perform mythread_mutex_lock(&mutex) in the beginning of a block
// and mythread_mutex_unlock(&mutex) at the end of the block. "break"
// may be used to unlock the mutex and jump out of the block.
// mythread_sync blocks may be nested.
//
// Example:
//
//     mythread_sync(mutex) {
//         foo();
//         if (some_error)
//             break; // Skips bar()
//         bar();
//     }
//
// At least GCC optimizes the loops completely away so it doesn't slow
// things down at all compared to plain mythread_mutex_lock(&mutex)
// and mythread_mutex_unlock(&mutex) calls.
//
#define mythread_sync(mutex) mythread_sync_helper1(mutex, __LINE__)
#define mythread_sync_helper1(mutex, line) mythread_sync_helper2(mutex, line)
#define mythread_sync_helper2(mutex, line) \
          for (unsigned int mythread_i_ ## line = 0; \
                              mythread_i_ ## line \
                                        ? (mythread_mutex_unlock(&(mutex)), 0) \
                                        : (mythread_mutex_lock(&(mutex)), 1); \
                              mythread_i_ ## line = 1) \
                    for (unsigned int mythread_j_ ## line = 0; \
                                        !mythread_j_ ## line; \
                                        mythread_j_ ## line = 1)
#endif


#if !defined(MYTHREAD_ENABLED)

//////////////////
// No threading //
//////////////////

// Calls the given function once. This isn't thread safe.
#define mythread_once(func) \
do { \
          static bool once_ = false; \
          if (!once_) { \
                    func(); \
                    once_ = true; \
          } \
} while (0)


#if !(defined(_WIN32) && !defined(__CYGWIN__))
// Use sigprocmask() to set the signal mask in single-threaded programs.
#include <signal.h>

static inline void
mythread_sigmask(int how, const sigset_t *restrict set,
                    sigset_t *restrict oset)
{
          int ret = sigprocmask(how, set, oset);
          assert(ret == 0);
          (void)ret;
}
#endif


#elif defined(MYTHREAD_POSIX)

////////////////////
// Using pthreads //
////////////////////

#include <sys/time.h>
#include <pthread.h>
#include <signal.h>
#include <time.h>
#include <errno.h>

#define MYTHREAD_RET_TYPE void *
#define MYTHREAD_RET_VALUE NULL

typedef pthread_t mythread;
typedef pthread_mutex_t mythread_mutex;

typedef struct {
          pthread_cond_t cond;
#ifdef HAVE_CLOCK_GETTIME
          // Clock ID (CLOCK_REALTIME or CLOCK_MONOTONIC) associated with
          // the condition variable.
          clockid_t clk_id;
#endif
} mythread_cond;

typedef struct timespec mythread_condtime;


// Calls the given function once in a thread-safe way.
#define mythread_once(func) \
          do { \
                    static pthread_once_t once_ = PTHREAD_ONCE_INIT; \
                    pthread_once(&once_, &func); \
          } while (0)


// Use pthread_sigmask() to set the signal mask in multi-threaded programs.
// Do nothing on OpenVMS since it lacks pthread_sigmask().
static inline void
mythread_sigmask(int how, const sigset_t *restrict set,
                    sigset_t *restrict oset)
{
#ifdef __VMS
          (void)how;
          (void)set;
          (void)oset;
#else
          int ret = pthread_sigmask(how, set, oset);
          assert(ret == 0);
          (void)ret;
#endif
}


// Creates a new thread with all signals blocked. Returns zero on success
// and non-zero on error.
static inline int
mythread_create(mythread *thread, void *(*func)(void *arg), void *arg)
{
          sigset_t old;
          sigset_t all;
          sigfillset(&all);

          mythread_sigmask(SIG_SETMASK, &all, &old);
          const int ret = pthread_create(thread, NULL, func, arg);
          mythread_sigmask(SIG_SETMASK, &old, NULL);

          return ret;
}

// Joins a thread. Returns zero on success and non-zero on error.
static inline int
mythread_join(mythread thread)
{
          return pthread_join(thread, NULL);
}


// Initiatlizes a mutex. Returns zero on success and non-zero on error.
static inline int
mythread_mutex_init(mythread_mutex *mutex)
{
          return pthread_mutex_init(mutex, NULL);
}

static inline void
mythread_mutex_destroy(mythread_mutex *mutex)
{
          int ret = pthread_mutex_destroy(mutex);
          assert(ret == 0);
          (void)ret;
}

static inline void
mythread_mutex_lock(mythread_mutex *mutex)
{
          int ret = pthread_mutex_lock(mutex);
          assert(ret == 0);
          (void)ret;
}

static inline void
mythread_mutex_unlock(mythread_mutex *mutex)
{
          int ret = pthread_mutex_unlock(mutex);
          assert(ret == 0);
          (void)ret;
}


// Initializes a condition variable.
//
// Using CLOCK_MONOTONIC instead of the default CLOCK_REALTIME makes the
// timeout in pthread_cond_timedwait() work correctly also if system time
// is suddenly changed. Unfortunately CLOCK_MONOTONIC isn't available
// everywhere while the default CLOCK_REALTIME is, so the default is
// used if CLOCK_MONOTONIC isn't available.
//
// If clock_gettime() isn't available at all, gettimeofday() will be used.
static inline int
mythread_cond_init(mythread_cond *mycond)
{
#ifdef HAVE_CLOCK_GETTIME
          // NOTE: HAVE_DECL_CLOCK_MONOTONIC is always defined to 0 or 1.
#         if defined(HAVE_PTHREAD_CONDATTR_SETCLOCK) && HAVE_DECL_CLOCK_MONOTONIC
          struct timespec ts;
          pthread_condattr_t condattr;

          // POSIX doesn't seem to *require* that pthread_condattr_setclock()
          // will fail if given an unsupported clock ID. Test that
          // CLOCK_MONOTONIC really is supported using clock_gettime().
          if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0
                              && pthread_condattr_init(&condattr) == 0) {
                    int ret = pthread_condattr_setclock(
                                        &condattr, CLOCK_MONOTONIC);
                    if (ret == 0)
                              ret = pthread_cond_init(&mycond->cond, &condattr);

                    pthread_condattr_destroy(&condattr);

                    if (ret == 0) {
                              mycond->clk_id = CLOCK_MONOTONIC;
                              return 0;
                    }
          }

          // If anything above fails, fall back to the default CLOCK_REALTIME.
          // POSIX requires that all implementations of clock_gettime() must
          // support at least CLOCK_REALTIME.
#         endif

          mycond->clk_id = CLOCK_REALTIME;
#endif

          return pthread_cond_init(&mycond->cond, NULL);
}

static inline void
mythread_cond_destroy(mythread_cond *cond)
{
          int ret = pthread_cond_destroy(&cond->cond);
          assert(ret == 0);
          (void)ret;
}

static inline void
mythread_cond_signal(mythread_cond *cond)
{
          int ret = pthread_cond_signal(&cond->cond);
          assert(ret == 0);
          (void)ret;
}

static inline void
mythread_cond_wait(mythread_cond *cond, mythread_mutex *mutex)
{
          int ret = pthread_cond_wait(&cond->cond, mutex);
          assert(ret == 0);
          (void)ret;
}

// Waits on a condition or until a timeout expires. If the timeout expires,
// non-zero is returned, otherwise zero is returned.
static inline int
mythread_cond_timedwait(mythread_cond *cond, mythread_mutex *mutex,
                    const mythread_condtime *condtime)
{
          int ret = pthread_cond_timedwait(&cond->cond, mutex, condtime);
          assert(ret == 0 || ret == ETIMEDOUT);
          return ret;
}

// Sets condtime to the absolute time that is timeout_ms milliseconds
// in the future. The type of the clock to use is taken from cond.
static inline void
mythread_condtime_set(mythread_condtime *condtime, const mythread_cond *cond,
                    uint32_t timeout_ms)
{
          condtime->tv_sec = timeout_ms / 1000;
          condtime->tv_nsec = (timeout_ms % 1000) * 1000000;

#ifdef HAVE_CLOCK_GETTIME
          struct timespec now;
          int ret = clock_gettime(cond->clk_id, &now);
          assert(ret == 0);
          (void)ret;

          condtime->tv_sec += now.tv_sec;
          condtime->tv_nsec += now.tv_nsec;
#else
          (void)cond;

          struct timeval now;
          gettimeofday(&now, NULL);

          condtime->tv_sec += now.tv_sec;
          condtime->tv_nsec += now.tv_usec * 1000L;
#endif

          // tv_nsec must stay in the range [0, 999_999_999].
          if (condtime->tv_nsec >= 1000000000L) {
                    condtime->tv_nsec -= 1000000000L;
                    ++condtime->tv_sec;
          }
}


#elif defined(MYTHREAD_WIN95) || defined(MYTHREAD_VISTA)

/////////////////////
// Windows threads //
/////////////////////

#define WIN32_LEAN_AND_MEAN
#ifdef MYTHREAD_VISTA
#         undef _WIN32_WINNT
#         define _WIN32_WINNT 0x0600
#endif
#include <windows.h>
#include <process.h>

#define MYTHREAD_RET_TYPE unsigned int __stdcall
#define MYTHREAD_RET_VALUE 0

typedef HANDLE mythread;
typedef CRITICAL_SECTION mythread_mutex;

#ifdef MYTHREAD_WIN95
typedef HANDLE mythread_cond;
#else
typedef CONDITION_VARIABLE mythread_cond;
#endif

typedef struct {
          // Tick count (milliseconds) in the beginning of the timeout.
          // NOTE: This is 32 bits so it wraps around after 49.7 days.
          // Multi-day timeouts may not work as expected.
          DWORD start;

          // Length of the timeout in milliseconds. The timeout expires
          // when the current tick count minus "start" is equal or greater
          // than "timeout".
          DWORD timeout;
} mythread_condtime;


// mythread_once() is only available with Vista threads.
#ifdef MYTHREAD_VISTA
#define mythread_once(func) \
          do { \
                    static INIT_ONCE once_ = INIT_ONCE_STATIC_INIT; \
                    BOOL pending_; \
                    if (!InitOnceBeginInitialize(&once_, 0, &pending_, NULL)) \
                              abort(); \
                    if (pending_) \
                              func(); \
                    if (!InitOnceComplete(&once, 0, NULL)) \
                              abort(); \
          } while (0)
#endif


// mythread_sigmask() isn't available on Windows. Even a dummy version would
// make no sense because the other POSIX signal functions are missing anyway.


static inline int
mythread_create(mythread *thread,
                    unsigned int (__stdcall *func)(void *arg), void *arg)
{
          uintptr_t ret = _beginthreadex(NULL, 0, func, arg, 0, NULL);
          if (ret == 0)
                    return -1;

          *thread = (HANDLE)ret;
          return 0;
}

static inline int
mythread_join(mythread thread)
{
          int ret = 0;

          if (WaitForSingleObject(thread, INFINITE) != WAIT_OBJECT_0)
                    ret = -1;

          if (!CloseHandle(thread))
                    ret = -1;

          return ret;
}


static inline int
mythread_mutex_init(mythread_mutex *mutex)
{
          InitializeCriticalSection(mutex);
          return 0;
}

static inline void
mythread_mutex_destroy(mythread_mutex *mutex)
{
          DeleteCriticalSection(mutex);
}

static inline void
mythread_mutex_lock(mythread_mutex *mutex)
{
          EnterCriticalSection(mutex);
}

static inline void
mythread_mutex_unlock(mythread_mutex *mutex)
{
          LeaveCriticalSection(mutex);
}


static inline int
mythread_cond_init(mythread_cond *cond)
{
#ifdef MYTHREAD_WIN95
          *cond = CreateEvent(NULL, FALSE, FALSE, NULL);
          return *cond == NULL ? -1 : 0;
#else
          InitializeConditionVariable(cond);
          return 0;
#endif
}

static inline void
mythread_cond_destroy(mythread_cond *cond)
{
#ifdef MYTHREAD_WIN95
          CloseHandle(*cond);
#else
          (void)cond;
#endif
}

static inline void
mythread_cond_signal(mythread_cond *cond)
{
#ifdef MYTHREAD_WIN95
          SetEvent(*cond);
#else
          WakeConditionVariable(cond);
#endif
}

static inline void
mythread_cond_wait(mythread_cond *cond, mythread_mutex *mutex)
{
#ifdef MYTHREAD_WIN95
          LeaveCriticalSection(mutex);
          WaitForSingleObject(*cond, INFINITE);
          EnterCriticalSection(mutex);
#else
          BOOL ret = SleepConditionVariableCS(cond, mutex, INFINITE);
          assert(ret);
          (void)ret;
#endif
}

static inline int
mythread_cond_timedwait(mythread_cond *cond, mythread_mutex *mutex,
                    const mythread_condtime *condtime)
{
#ifdef MYTHREAD_WIN95
          LeaveCriticalSection(mutex);
#endif

          DWORD elapsed = GetTickCount() - condtime->start;
          DWORD timeout = elapsed >= condtime->timeout
                              ? 0 : condtime->timeout - elapsed;

#ifdef MYTHREAD_WIN95
          DWORD ret = WaitForSingleObject(*cond, timeout);
          assert(ret == WAIT_OBJECT_0 || ret == WAIT_TIMEOUT);

          EnterCriticalSection(mutex);

          return ret == WAIT_TIMEOUT;
#else
          BOOL ret = SleepConditionVariableCS(cond, mutex, timeout);
          assert(ret || GetLastError() == ERROR_TIMEOUT);
          return !ret;
#endif
}

static inline void
mythread_condtime_set(mythread_condtime *condtime, const mythread_cond *cond,
                    uint32_t timeout)
{
          (void)cond;
          condtime->start = GetTickCount();
          condtime->timeout = timeout;
}

#endif

#endif