mythread.h

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// SPDX-License-Identifier: 0BSD
 
//
//
//  Author:     Lasse Collin
//
 
#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__)) && !defined(__wasm__)
// 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 <pthread.h>
#include <signal.h>
#include <time.h>
#include <errno.h>
 
// If clock_gettime() isn't available, use gettimeofday() from <sys/time.h>
// as a fallback. gettimeofday() is in SUSv2 and thus is supported on all
// relevant POSIX systems.
#ifndef HAVE_CLOCK_GETTIME
#   include <sys/time.h>
#endif
 
// MinGW-w64 with winpthreads:
//
// NOTE: Typical builds with MinGW-w64 don't use this code (MYTHREAD_POSIX).
// Instead, native Windows threading APIs are used (MYTHREAD_VISTA or
// MYTHREAD_WIN95).
//
// MinGW-w64 has _sigset_t (an integer type) in <sys/types.h>.
// If _POSIX was #defined, the header would add the alias sigset_t too.
// Let's keep this working even without _POSIX.
//
// There are no functions that actually do something with sigset_t
// because signals barely exist on Windows. The sigfillset macro below
// is just to silence warnings. There is no sigfillset() in MinGW-w64.
#ifdef __MINGW32__
#   include <sys/types.h>
#   define sigset_t _sigset_t
#   define sigfillset(set_ptr) do { *(set_ptr) = 0; } while (0)
#endif
 
#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().
// Do nothing on MinGW-w64 too to silence warnings (its pthread_sigmask()
// is #defined to 0 so it's a no-op).
static inline void
mythread_sigmask(int how, const sigset_t *restrict set,
        sigset_t *restrict oset)
{
#if defined(__VMS) || defined(__MINGW32__)
    (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);
}
 
 
// Initializes 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
#   if defined(HAVE_PTHREAD_CONDATTR_SETCLOCK) && \
        defined(HAVE_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 = (time_t)(timeout_ms / 1000);
    condtime->tv_nsec = (long)((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