thread.h

/*
------------------------------------------------------------------------------
          Licensing information can be found at the end of the file.
------------------------------------------------------------------------------

thread.h - v0.3 - Cross platform threading functions for C/C++.

Do this:
    #define THREAD_IMPLEMENTATION
before you include this file in *one* C/C++ file to create the implementation.
*/

#ifndef thread_h
#define thread_h

#ifndef THREAD_U64
    #define THREAD_U64 unsigned long long
#endif

#define THREAD_STACK_SIZE_DEFAULT ( 0 )
#define THREAD_SIGNAL_WAIT_INFINITE ( -1 )
#define THREAD_QUEUE_WAIT_INFINITE ( -1 )

typedef void* thread_id_t;
thread_id_t thread_current_thread_id( void );
void thread_yield( void );
void thread_set_high_priority( void );
void thread_exit( int return_code );

typedef void* thread_ptr_t;
thread_ptr_t thread_create( int (*thread_proc)( void* ), void* user_data, int stack_size );
void thread_destroy( thread_ptr_t thread );
int thread_join( thread_ptr_t thread );
int thread_detach( thread_ptr_t thread );

typedef union thread_mutex_t thread_mutex_t;
void thread_mutex_init( thread_mutex_t* mutex );
void thread_mutex_term( thread_mutex_t* mutex );
void thread_mutex_lock( thread_mutex_t* mutex );
void thread_mutex_unlock( thread_mutex_t* mutex );

typedef union thread_signal_t thread_signal_t;
void thread_signal_init( thread_signal_t* signal );
void thread_signal_term( thread_signal_t* signal );
void thread_signal_raise( thread_signal_t* signal );
int thread_signal_wait( thread_signal_t* signal, int timeout_ms );

typedef union thread_atomic_int_t thread_atomic_int_t;
int thread_atomic_int_load( thread_atomic_int_t* atomic );
void thread_atomic_int_store( thread_atomic_int_t* atomic, int desired );
int thread_atomic_int_inc( thread_atomic_int_t* atomic );
int thread_atomic_int_dec( thread_atomic_int_t* atomic );
int thread_atomic_int_add( thread_atomic_int_t* atomic, int value );
int thread_atomic_int_sub( thread_atomic_int_t* atomic, int value );
int thread_atomic_int_swap( thread_atomic_int_t* atomic, int desired );
int thread_atomic_int_compare_and_swap( thread_atomic_int_t* atomic, int expected, int desired );

typedef union thread_atomic_ptr_t thread_atomic_ptr_t;
void* thread_atomic_ptr_load( thread_atomic_ptr_t* atomic );
void thread_atomic_ptr_store( thread_atomic_ptr_t* atomic, void* desired );
void* thread_atomic_ptr_swap( thread_atomic_ptr_t* atomic, void* desired );
void* thread_atomic_ptr_compare_and_swap( thread_atomic_ptr_t* atomic, void* expected, void* desired );

typedef union thread_timer_t thread_timer_t;
void thread_timer_init( thread_timer_t* timer );
void thread_timer_term( thread_timer_t* timer );
void thread_timer_wait( thread_timer_t* timer, THREAD_U64 nanoseconds );

typedef void* thread_tls_t;
thread_tls_t thread_tls_create( void );
void thread_tls_destroy( thread_tls_t tls );
void thread_tls_set( thread_tls_t tls, void* value );
void* thread_tls_get( thread_tls_t tls );

typedef struct thread_queue_t thread_queue_t;
void thread_queue_init( thread_queue_t* queue, int size, void** values, int count );
void thread_queue_term( thread_queue_t* queue );
int thread_queue_produce( thread_queue_t* queue, void* value, int timeout_ms );
void* thread_queue_consume( thread_queue_t* queue, int timeout_ms );
int thread_queue_count( thread_queue_t* queue );

#endif /* thread_h */


/**

thread.h 
========

Cross platform threading functions for C/C++.

Example
-------

Here's a basic sample program which starts a second thread which just waits and prints a message.

    #define  THREAD_IMPLEMENTATION
    #include "thread.h"

    #include <stdio.h> // for printf
    
    int thread_proc( void* user_data) {
        thread_timer_t timer;
        thread_timer_init( &timer );

        int count = 0;
        thread_atomic_int_t* exit_flag = (thread_atomic_int_t*) user_data;
        while( thread_atomic_int_load( exit_flag ) == 0 ) {
            printf( "Thread... " );
            thread_timer_wait( &timer, 1000000000 ); // sleep for a second
            ++count;
        }

        thread_timer_term( &timer );
        printf( "Done\n" );
        return count;
    }

    int main( int argc, char** argv ) {        
        thread_atomic_int_t exit_flag;
        thread_atomic_int_store( &exit_flag, 0 );

        thread_ptr_t thread = thread_create( thread_proc, &exit_flag, "Example thread", THREAD_STACK_SIZE_DEFAULT );

        thread_timer_t timer;
        thread_timer_init( &timer );
        for( int i = 0; i < 5; ++i ) {
            printf( "Main... " );
            thread_timer_wait( &timer, 2000000000 ); // sleep for two seconds
        }
        thread_timer_term( &timer );
        
        thread_atomic_int_store( &exit_flag, 1 ); // signal thread to exit
        int retval = thread_join( thread );

        printf( "Count: %d\n", retval );

        thread_destroy( thread );
        return retval;
    }


API Documentation
-----------------

thread.h is a single-header library, and does not need any .lib files or other binaries, or any build scripts. To use it,
you just include thread.h to get the API declarations. To get the definitions, you must include thread.h from *one* 
single C or C++ file, and #define the symbol `THREAD_IMPLEMENTATION` before you do. 


### Customization

thread.h allows for specifying the exact type of 64-bit unsigned integer to be used in its API. By default, it is 
defined as `unsigned long long`, but as this is not a standard type on all compilers, you can redefine it by #defining 
THREAD_U64 before including thread.h. This is useful if you, for example, use the types from `<stdint.h>` in the rest of 
your program, and you want thread.h to use compatible types. In this case, you would include thread.h using the 
following code:

    #define THREAD_U64 uint64_t
    #include "thread.h"

Note that when customizing this data type, you need to use the same definition in every place where you include 
thread.h, as it affect the declarations as well as the definitions.


thread_current_thread_id
------------------------

    thread_id_t thread_current_thread_id( void )

Returns a unique identifier for the calling thread. After the thread terminates, the id might be reused for new threads.


thread_yield
------------

    void thread_yield( void )

Makes the calling thread yield execution to another thread. The operating system controls which thread is switched to.


thread_set_high_priority
------------------------

    void thread_set_high_priority( void )

When created, threads are set to run at normal priority. In some rare cases, such as a sound buffer update loop, it can
be necessary to have one thread of your application run on a higher priority than the rest. Calling 
`thread_set_high_priority` will raise the priority of the calling thread, giving it a chance to be run more often.
Do not increase the priority of a thread unless you absolutely have to, as it can negatively affect performance if used
without care.


thread_exit
-----------

    void thread_exit( int return_code )

Exits the calling thread, as if you had done `return return_code;` from the main body of the thread function.


thread_create
-------------

    thread_ptr_t thread_create( int (*thread_proc)( void* ), void* user_data, int stack_size )

Creates a new thread running the `thread_proc` function, passing the `user_data` through to it. The thread will have 
the stack size specified in the `stack_size` parameter. To get the operating system default stack size, use the 
defined constant `THREAD_STACK_SIZE_DEFAULT`. When returning from the thread_proc function, the value you return can 
be received in another thread by calling thread_join. `thread_create` returns a pointer to the thread instance, which 
can be used as a parameter to the functions `thread_destroy` and `thread_join`.


thread_destroy
--------------

    void thread_destroy( thread_ptr_t thread )

Destroys a thread that was created by calling `thread_create`. Make sure the thread has exited before you attempt to 
destroy it. This can be accomplished by calling `thread_join`. It is not possible for force termination of a thread by
calling `thread_destroy`.


thread_join
-----------

    int thread_join( thread_ptr_t thread )

Waits for the specified thread to exit. Returns the value which the thread returned when exiting.


thread_detach
-------------

    int thread_detach( thread_ptr_t thread )

Marks the thread as detached. When a detached thread terminates, its resources are automatically released back to the
system without the need for another thread to join with the terminated thread.
    
    
thread_mutex_init
-----------------
    
    void thread_mutex_init( thread_mutex_t* mutex )

Initializes the specified mutex instance, preparing it for use. A mutex can be used to lock sections of code, such that
it can only be run by one thread at a time.


thread_mutex_term
-----------------

    void thread_mutex_term( thread_mutex_t* mutex )

Terminates the specified mutex instance, releasing any system resources held by it.


thread_mutex_lock
-----------------

    void thread_mutex_lock( thread_mutex_t* mutex )

Takes an exclusive lock on a mutex. If the lock is already taken by another thread, `thread_mutex_lock` will yield the
calling thread and wait for the lock to become available before returning. The mutex must be initialized by calling
`thread_mutex_init` before it can be locked.


thread_mutex_unlock
-------------------

    void thread_mutex_unlock( thread_mutex_t* mutex )

Releases a lock taken by calling `thread_mutex_lock`. 


thread_signal_init
------------------

    void thread_signal_init( thread_signal_t* signal )

Initializes the specified signal instance, preparing it for use. A signal works like a flag, which can be waited on by
one thread, until it is raised from another thread. 


thread_signal_term
------------------

    void thread_signal_term( thread_signal_t* signal )

Terminates the specified signal instance, releasing any system resources held by it.


thread_signal_raise
-------------------

    void thread_signal_raise( thread_signal_t* signal )

Raise the specified signal. Other threads waiting for the signal will proceed.  


thread_signal_wait
------------------

    int thread_signal_wait( thread_signal_t* signal, int timeout_ms )

Waits for a signal to be raised, or until `timeout_ms` milliseconds have passed. If the wait timed out, a value of 0 is
returned, otherwise a non-zero value is returned. If the `timeout_ms` parameter is THREAD_SIGNAL_WAIT_INFINITE, 
`thread_signal_wait` waits indefinitely.


thread_atomic_int_load
----------------------

    int thread_atomic_int_load( thread_atomic_int_t* atomic )

Returns the value of `atomic` as an atomic operation.


thread_atomic_int_store
-----------------------

    void thread_atomic_int_store( thread_atomic_int_t* atomic, int desired )

Sets the value of `atomic` as an atomic operation.


thread_atomic_int_inc
---------------------

    int thread_atomic_int_inc( thread_atomic_int_t* atomic )

Increments the value of `atomic` by one, as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_int_dec
---------------------

    int thread_atomic_int_dec( thread_atomic_int_t* atomic )

Decrements the value of `atomic` by one, as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_int_add
---------------------

    int thread_atomic_int_add( thread_atomic_int_t* atomic, int value )

Adds the specified value to `atomic`, as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_int_sub
---------------------

    int thread_atomic_int_sub( thread_atomic_int_t* atomic, int value )

Subtracts the specified value to `atomic`, as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_int_swap
----------------------

    int thread_atomic_int_swap( thread_atomic_int_t* atomic, int desired )

Sets the value of `atomic` as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_int_compare_and_swap
----------------------------------

    int thread_atomic_int_compare_and_swap( thread_atomic_int_t* atomic, int expected, int desired )

Compares the value of `atomic` to the value of `expected`, and if they match, sets the vale of `atomic` to `desired`,
all as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_ptr_load
----------------------

    void* thread_atomic_ptr_load( thread_atomic_ptr_t* atomic )

Returns the value of `atomic` as an atomic operation.


thread_atomic_ptr_store
-----------------------

    void thread_atomic_ptr_store( thread_atomic_ptr_t* atomic, void* desired )

Sets the value of `atomic` as an atomic operation.


thread_atomic_ptr_swap
----------------------

    void* thread_atomic_ptr_swap( thread_atomic_ptr_t* atomic, void* desired )

Sets the value of `atomic` as an atomic operation. Returns the value `atomic` had before the operation.


thread_atomic_ptr_compare_and_swap
----------------------------------

    void* thread_atomic_ptr_compare_and_swap( thread_atomic_ptr_t* atomic, void* expected, void* desired )

Compares the value of `atomic` to the value of `expected`, and if they match, sets the vale of `atomic` to `desired`,
all as an atomic operation. Returns the value `atomic` had before the operation.


thread_timer_init
-----------------
    
    void thread_timer_init( thread_timer_t* timer )

Initializes the specified timer instance, preparing it for use. A timer can be used to sleep a thread for a high 
precision duration.


thread_timer_term
-----------------

    void thread_timer_term( thread_timer_t* timer )

Terminates the specified timer instance, releasing any system resources held by it.


thread_timer_wait
-----------------

    void thread_timer_wait( thread_timer_t* timer, THREAD_U64 nanoseconds )

Waits until `nanoseconds` amount of time have passed, before returning.


thread_tls_create
-----------------
    
    thread_tls_t thread_tls_create( void )

Creates  a thread local storage (TLS) index. Once created, each thread has its own value for that TLS index, which can
be set or retrieved individually.


thread_tls_destroy
------------------
    
    void thread_tls_destroy( thread_tls_t tls )

Destroys the specified TLS index. No further calls to `thread_tls_set` or `thread_tls_get` are valid after this.


thread_tls_set
--------------

    void thread_tls_set( thread_tls_t tls, void* value )

Stores a value in the calling thread's slot for the specified TLS index. Each thread has its own value for each TLS 
index.


thread_tls_get
--------------

    void* thread_tls_get( thread_tls_t tls )

Retrieves the value from the calling thread's slot for the specified TLS index. Each thread has its own value for each 
TLS index.


thread_queue_init
-----------------

    void thread_queue_init( thread_queue_t* queue, int size, void** values, int count )

Initializes the specified queue instance, preparing it for use. The queue is a lock-free (but not wait-free)
single-producer/single-consumer queue - it will not acquire any locks as long as there is space for adding or items to
be consume, but will lock and wait when there is not. The `size` parameter specifies the number of elements in the 
queue. The `values` parameter is an array of queue slots (`size` elements in length), each being of type `void*`. If
the queue is initially empty, the `count` parameter should be 0, otherwise it indicates the number of entires, from the
start of the `values` array, that the queue is initialized with. The `values` array is not copied, and must remain valid
until `thread_queue_term` is called.


thread_queue_term
-----------------

    void thread_queue_term( thread_queue_t* queue )

Terminates the specified queue instance, releasing any system resources held by it.


thread_queue_produce
--------------------

    int thread_queue_produce( thread_queue_t* queue, void* value, int timeout_ms )

Adds an element to a single-producer/single-consumer queue. If there is space in the queue to add another element, no
lock will be taken. If the queue is full, calling thread will sleep until an element is consumed from another thread, 
before adding the element, or until `timeout_ms` milliseconds have passed. If the wait timed out, a value of 0 is 
returned, otherwise a non-zero value is returned. If the `timeout_ms` parameter is THREAD_QUEUE_WAIT_INFINITE,  
`thread_queue_produce` waits indefinitely.


thread_queue_consume
--------------------

    void* thread_queue_consume( thread_queue_t* queue, int timeout_ms )

Removes an element from a single-producer/single-consumer queue. If the queue contains at least one element, no lock 
will be taken. If the queue is empty, the calling thread will sleep until an element is added from another thread, or 
until `timeout_ms` milliseconds have passed. If the wait timed out, a value of NULL is returned, otherwise 
`thread_queue_consume` returns the value that was removed from the queue. If the `timeout_ms` parameter is 
THREAD_QUEUE_WAIT_INFINITE, `thread_queue_consume` waits indefinitely.


thread_queue_count
------------------

    int thread_queue_count( thread_queue_t* queue )

Returns the number of elements currently held in a single-producer/single-consumer queue. Be aware that by the time you
get the count, it might have changed by another thread calling consume or produce, so use with care.

*/


/*
----------------------
    IMPLEMENTATION
----------------------
*/

#ifndef thread_impl
#define thread_impl

union thread_mutex_t 
    { 
    void* align; 
    char data[ 64 ];
    };

union thread_signal_t 
    { 
    void* align; 
    char data[ 116 ];
    };

union thread_atomic_int_t 
    {
    void* align;
    long i;
    };

union thread_atomic_ptr_t 
    {
    void* ptr;
    };

union thread_timer_t 
    { 
    void* data; 
    char d[ 8 ]; 
    };

struct thread_queue_t
    {
    thread_signal_t data_ready;
    thread_signal_t space_open;
    thread_atomic_int_t count;
    thread_atomic_int_t head;
    thread_atomic_int_t tail;
    void** values;
    int size;
    #ifndef NDEBUG
        thread_atomic_int_t id_produce_is_set;
        thread_id_t id_produce;
        thread_atomic_int_t id_consume_is_set;
        thread_id_t id_consume;
    #endif
    };

#endif /* thread_impl */



#ifdef THREAD_IMPLEMENTATION
#undef THREAD_IMPLEMENTATION

#ifndef THREAD_ASSERT
    #undef _CRT_NONSTDC_NO_DEPRECATE 
    #define _CRT_NONSTDC_NO_DEPRECATE 
    #undef _CRT_SECURE_NO_WARNINGS
    #define _CRT_SECURE_NO_WARNINGS
    #include <assert.h>
    #define THREAD_ASSERT( expression, message ) assert( ( expression ) && ( message ) )
#endif


#if defined( _WIN32 )

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

    #define _CRT_NONSTDC_NO_DEPRECATE 
    #define _CRT_SECURE_NO_WARNINGS

    #if !defined( _WIN32_WINNT ) || _WIN32_WINNT < 0x0501 
        #undef _WIN32_WINNT
        #define _WIN32_WINNT 0x501// requires Windows XP minimum
    #endif

    #define _WINSOCKAPI_
    #pragma warning( push )
    #pragma warning( disable: 4619 ) 
    #pragma warning( disable: 4668 ) // 'symbol' is not defined as a preprocessor macro, replacing with '0' for 'directives'
    #pragma warning( disable: 4768 ) // __declspec attributes before linkage specification are ignored	
    #pragma warning( disable: 4255 ) // 'function' : no function prototype given: converting '()' to '(void)'
    #include <windows.h>
    #pragma warning( pop )

   
#elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

    #include <pthread.h>
    #include <errno.h>
    #include <string.h>
    #include <sys/time.h>
    #include <stdint.h>

#else 
    #error Unknown platform.
#endif



thread_id_t thread_current_thread_id( void )
    {
    #if defined( _WIN32 )

        return (void*) (uintptr_t)GetCurrentThreadId();

    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )
    
        return (void*) pthread_self();

    #else 
        #error Unknown platform.
    #endif
    }


void thread_yield( void )
    {
    #if defined( _WIN32 )

        SwitchToThread();
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )
    
        sched_yield();
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_exit( int return_code )
    {
    #if defined( _WIN32 )

        ExitThread( (DWORD) return_code );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )
    
        pthread_exit( (void*)(uintptr_t) return_code );
    
    #else 
        #error Unknown platform.
    #endif
    }


thread_ptr_t thread_create( int (*thread_proc)( void* ), void* user_data, int stack_size )
    {
    #if defined( _WIN32 )

        DWORD thread_id;
        HANDLE handle = CreateThread( NULL, stack_size > 0 ? (size_t)stack_size : 0U, 
            (LPTHREAD_START_ROUTINE)(uintptr_t) thread_proc, user_data, 0, &thread_id );
        if( !handle ) return NULL;

        return (thread_ptr_t) handle;
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_t thread;
        if( 0 != pthread_create( &thread, NULL, ( void* (*)( void * ) ) thread_proc, user_data ) )
            return NULL;

        return (thread_ptr_t) thread;
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_destroy( thread_ptr_t thread )
    {
    #if defined( _WIN32 )

        WaitForSingleObject( (HANDLE) thread, INFINITE );
        CloseHandle( (HANDLE) thread );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_join( (pthread_t) thread, NULL );

    #else 
        #error Unknown platform.
    #endif
    }


int thread_join( thread_ptr_t thread )
    {
    #if defined( _WIN32 )

        WaitForSingleObject( (HANDLE) thread, INFINITE );
        DWORD retval;
        GetExitCodeThread( (HANDLE) thread, &retval );
        return (int) retval;
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        void* retval;
        pthread_join( (pthread_t) thread, &retval );
        return (int)(uintptr_t) retval;

    #else 
        #error Unknown platform.
    #endif
    }


int thread_detach( thread_ptr_t thread )
    {
    #if defined( _WIN32 )

        return CloseHandle( (HANDLE) thread ) != 0;

    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return pthread_detach( (pthread_t) thread ) == 0;

    #else 
        #error Unknown platform.
    #endif
    }

    
void thread_set_high_priority( void )
    {
    #if defined( _WIN32 )

        SetThreadPriority( GetCurrentThread(), THREAD_PRIORITY_HIGHEST );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        struct sched_param sp;
        memset( &sp, 0, sizeof( sp ) );
        sp.sched_priority = sched_get_priority_min( SCHED_RR );
        pthread_setschedparam( pthread_self(), SCHED_RR, &sp);

    #else 
        #error Unknown platform.
    #endif
    }


void thread_mutex_init( thread_mutex_t* mutex )
    {
    #if defined( _WIN32 )

        // Compile-time size check
        #pragma warning( push )
        #pragma warning( disable: 4214 ) // nonstandard extension used: bit field types other than int
        struct x { char thread_mutex_type_too_small : ( sizeof( thread_mutex_t ) < sizeof( CRITICAL_SECTION ) ? 0 : 1 ); }; 
        #pragma warning( pop )

        InitializeCriticalSectionAndSpinCount( (CRITICAL_SECTION*) mutex, 32 );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        // Compile-time size check
        struct x { char thread_mutex_type_too_small : ( sizeof( thread_mutex_t ) < sizeof( pthread_mutex_t ) ? 0 : 1 ); };

        pthread_mutex_init( (pthread_mutex_t*) mutex, NULL );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_mutex_term( thread_mutex_t* mutex )
    {
    #if defined( _WIN32 )
        
        DeleteCriticalSection( (CRITICAL_SECTION*) mutex );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_destroy( (pthread_mutex_t*) mutex );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_mutex_lock( thread_mutex_t* mutex )
    {
    #if defined( _WIN32 )

        EnterCriticalSection( (CRITICAL_SECTION*) mutex );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_lock( (pthread_mutex_t*) mutex );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_mutex_unlock( thread_mutex_t* mutex )
    {
    #if defined( _WIN32 )

        LeaveCriticalSection( (CRITICAL_SECTION*) mutex );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_unlock( (pthread_mutex_t*) mutex );
    
    #else 
        #error Unknown platform.
    #endif
    }


struct thread_internal_signal_t
    {
    #if defined( _WIN32 )

        #if _WIN32_WINNT >= 0x0600
            CRITICAL_SECTION mutex;
            CONDITION_VARIABLE condition;
            int value;
        #else 
            #pragma message( "Warning: _WIN32_WINNT < 0x0600 - condition variables not available" )
            HANDLE event;
        #endif 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_t mutex;
        pthread_cond_t condition;
        int value;

    #else 
        #error Unknown platform.
    #endif
    };


void thread_signal_init( thread_signal_t* signal )
    {
    // Compile-time size check
    #pragma warning( push )
    #pragma warning( disable: 4214 ) // nonstandard extension used: bit field types other than int
    struct x { char thread_signal_type_too_small : ( sizeof( thread_signal_t ) < sizeof( struct thread_internal_signal_t ) ? 0 : 1 ); };
    #pragma warning( pop )
    
    struct thread_internal_signal_t* internal = (struct thread_internal_signal_t*) signal;
        
    #if defined( _WIN32 )

        #if _WIN32_WINNT >= 0x0600
            InitializeCriticalSectionAndSpinCount( &internal->mutex, 32 );
            InitializeConditionVariable( &internal->condition );
            internal->value = 0;
        #else 
            internal->event = CreateEvent( NULL, FALSE, FALSE, NULL );
        #endif 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_init( &internal->mutex, NULL );
        pthread_cond_init( &internal->condition, NULL );
        internal->value = 0;
    
    #else 
        #error Unknown platform.
    #endif
    }


 void thread_signal_term( thread_signal_t* signal )
    {
    struct thread_internal_signal_t* internal = (struct thread_internal_signal_t*) signal;

    #if defined( _WIN32 )

        #if _WIN32_WINNT >= 0x0600
            DeleteCriticalSection( &internal->mutex );
        #else 
            CloseHandle( internal->event );
        #endif 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_destroy( &internal->mutex );
        pthread_cond_destroy( &internal->condition );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_signal_raise( thread_signal_t* signal )
    {
    struct thread_internal_signal_t* internal = (struct thread_internal_signal_t*) signal;

    #if defined( _WIN32 )

        #if _WIN32_WINNT >= 0x0600
            EnterCriticalSection( &internal->mutex );
            internal->value = 1;
            LeaveCriticalSection( &internal->mutex );       
            WakeConditionVariable( &internal->condition );
        #else 
            SetEvent( internal->event );
        #endif 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_mutex_lock( &internal->mutex );
        internal->value = 1;
        pthread_mutex_unlock( &internal->mutex );
        pthread_cond_signal( &internal->condition );
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_signal_wait( thread_signal_t* signal, int timeout_ms )
    {
    struct thread_internal_signal_t* internal = (struct thread_internal_signal_t*) signal;

    #if defined( _WIN32 )

        #if _WIN32_WINNT >= 0x0600
            int timed_out = 0;
            EnterCriticalSection( &internal->mutex );
            while( internal->value == 0 )
                {
                BOOL res = SleepConditionVariableCS( &internal->condition, &internal->mutex, timeout_ms < 0 ? INFINITE : timeout_ms );
                if( !res && GetLastError() == ERROR_TIMEOUT ) { timed_out = 1; break; }
                }
            internal->value = 0;
            LeaveCriticalSection( &internal->mutex );       
            return !timed_out;
        #else 
            int failed = WAIT_OBJECT_0 != WaitForSingleObject( internal->event, timeout_ms < 0 ? INFINITE : timeout_ms );
            return !failed;
        #endif 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        struct timespec ts;
        if( timeout_ms >= 0 )
            {
            struct timeval tv;
            gettimeofday( &tv, NULL );
            ts.tv_sec = time( NULL ) + timeout_ms / 1000;
            ts.tv_nsec = tv.tv_usec * 1000 + 1000 * 1000 * ( timeout_ms % 1000 );
            ts.tv_sec += ts.tv_nsec / ( 1000 * 1000 * 1000 );
            ts.tv_nsec %= ( 1000 * 1000 * 1000 );
            }

        int timed_out = 0;
        pthread_mutex_lock( &internal->mutex );
        while( internal->value == 0 )
            {
            if( timeout_ms < 0 ) 
                pthread_cond_wait( &internal->condition, &internal->mutex );
            else if( pthread_cond_timedwait( &internal->condition, &internal->mutex, &ts ) == ETIMEDOUT )
                {
                timed_out = 1;
                break;
                }

            }           
        if( !timed_out ) internal->value = 0;
        pthread_mutex_unlock( &internal->mutex );
        return !timed_out;
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_load( thread_atomic_int_t* atomic )
    {
    #if defined( _WIN32 )

        return InterlockedCompareExchange( &atomic->i, 0, 0 );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_fetch_and_add( &atomic->i, 0 );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_atomic_int_store( thread_atomic_int_t* atomic, int desired )
    {
    #if defined( _WIN32 )
    
        InterlockedExchange( &atomic->i, desired );

    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        __sync_fetch_and_and( &atomic->i, 0 );
        __sync_fetch_and_or( &atomic->i, desired );
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_inc( thread_atomic_int_t* atomic )
    {
    #if defined( _WIN32 )
    
        return InterlockedIncrement( &atomic->i ) - 1;
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_fetch_and_add( &atomic->i, 1 );
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_dec( thread_atomic_int_t* atomic )
    {
    #if defined( _WIN32 )
    
        return InterlockedDecrement( &atomic->i ) + 1;
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_fetch_and_sub( &atomic->i, 1 );

    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_add( thread_atomic_int_t* atomic, int value )
    {
    #if defined( _WIN32 )
    
        return InterlockedExchangeAdd ( &atomic->i, value );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_fetch_and_add( &atomic->i, value );
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_sub( thread_atomic_int_t* atomic, int value )
    {
    #if defined( _WIN32 )
    
        return InterlockedExchangeAdd( &atomic->i, -value );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_fetch_and_sub( &atomic->i, value );

    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_swap( thread_atomic_int_t* atomic, int desired )
    {
    #if defined( _WIN32 )
    
        return InterlockedExchange( &atomic->i, desired );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        int old = (int)__sync_lock_test_and_set( &atomic->i, desired );
        __sync_lock_release( &atomic->i );
        return old;
    
    #else 
        #error Unknown platform.
    #endif
    }


int thread_atomic_int_compare_and_swap( thread_atomic_int_t* atomic, int expected, int desired )
    {
    #if defined( _WIN32 )
    
        return InterlockedCompareExchange( &atomic->i, desired, expected );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return (int)__sync_val_compare_and_swap( &atomic->i, expected, desired );
    
    #else 
        #error Unknown platform.
    #endif
    }


void* thread_atomic_ptr_load( thread_atomic_ptr_t* atomic )
    {
    #if defined( _WIN32 )
    
        return InterlockedCompareExchangePointer( &atomic->ptr, 0, 0 );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return __sync_fetch_and_add( &atomic->ptr, 0 );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_atomic_ptr_store( thread_atomic_ptr_t* atomic, void* desired )
    {
    #if defined( _WIN32 )
    
        #pragma warning( push )
        #pragma warning( disable: 4302 ) // 'type cast' : truncation from 'void *' to 'LONG'
        #pragma warning( disable: 4311 ) // pointer truncation from 'void *' to 'LONG'
        #pragma warning( disable: 4312 ) // conversion from 'LONG' to 'PVOID' of greater size
        InterlockedExchangePointer( &atomic->ptr, desired );
        #pragma warning( pop )

    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        __sync_lock_test_and_set( &atomic->ptr, desired );
        __sync_lock_release( &atomic->ptr );
    
    #else 
        #error Unknown platform.
    #endif
    }


void* thread_atomic_ptr_swap( thread_atomic_ptr_t* atomic, void* desired )
    {
    #if defined( _WIN32 )
    
        #pragma warning( push )
        #pragma warning( disable: 4302 ) // 'type cast' : truncation from 'void *' to 'LONG'
        #pragma warning( disable: 4311 ) // pointer truncation from 'void *' to 'LONG'
        #pragma warning( disable: 4312 ) // conversion from 'LONG' to 'PVOID' of greater size
        return InterlockedExchangePointer( &atomic->ptr, desired );
        #pragma warning( pop )
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        void* old = __sync_lock_test_and_set( &atomic->ptr, desired );
        __sync_lock_release( &atomic->ptr );
        return old;
    
    #else 
        #error Unknown platform.
    #endif
    }


void* thread_atomic_ptr_compare_and_swap( thread_atomic_ptr_t* atomic, void* expected, void* desired )
    {
    #if defined( _WIN32 )
    
        return InterlockedCompareExchangePointer( &atomic->ptr, desired, expected );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return __sync_val_compare_and_swap( &atomic->ptr, expected, desired );

    #else 
        #error Unknown platform.
    #endif
    }


void thread_timer_init( thread_timer_t* timer )
    {
    #if defined( _WIN32 )

        // Compile-time size check
        #pragma warning( push )
        #pragma warning( disable: 4214 ) // nonstandard extension used: bit field types other than int
        struct x { char thread_timer_type_too_small : ( sizeof( thread_mutex_t ) < sizeof( HANDLE ) ? 0 : 1 ); }; 
        #pragma warning( pop )

        TIMECAPS tc;
        if( timeGetDevCaps( &tc, sizeof( TIMECAPS ) ) == TIMERR_NOERROR ) 
            timeBeginPeriod( tc.wPeriodMin );

        *(HANDLE*)timer = CreateWaitableTimer( NULL, TRUE, NULL );

    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        // Nothing

    #else 
        #error Unknown platform.
    #endif
    }


void thread_timer_term( thread_timer_t* timer )
    {
    #if defined( _WIN32 )

        CloseHandle( *(HANDLE*)timer );
    
        TIMECAPS tc;
        if( timeGetDevCaps( &tc, sizeof( TIMECAPS ) ) == TIMERR_NOERROR ) 
            timeEndPeriod( tc.wPeriodMin );

    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        // Nothing
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_timer_wait( thread_timer_t* timer, THREAD_U64 nanoseconds )
    {
    #if defined( _WIN32 )

        LARGE_INTEGER due_time;
        due_time.QuadPart = - (LONGLONG) ( nanoseconds / 100 );
        BOOL b = SetWaitableTimer( *(HANDLE*)timer, &due_time, 0, 0, 0, FALSE );
        (void) b;
        WaitForSingleObject( *(HANDLE*)timer, INFINITE ); 
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        struct timespec rem;
        struct timespec req;
        req.tv_sec = nanoseconds / 1000000000ULL;
        req.tv_nsec = nanoseconds - req.tv_sec * 1000000000ULL;
        while( nanosleep( &req, &rem ) )
            req = rem;
    
    #else 
        #error Unknown platform.
    #endif
    }


thread_tls_t thread_tls_create( void )
    {
    #if defined( _WIN32 )

        DWORD tls = TlsAlloc();      
        if( tls == TLS_OUT_OF_INDEXES )
            return NULL;
        else
            return (thread_tls_t) (uintptr_t) tls;
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_key_t tls;
        if( pthread_key_create( &tls, NULL ) == 0 )
            return (thread_tls_t) tls;
        else
            return NULL;

    #else 
        #error Unknown platform.
    #endif
    }


void thread_tls_destroy( thread_tls_t tls )
    {
    #if defined( _WIN32 )

        TlsFree( (DWORD) (uintptr_t) tls );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_key_delete( (pthread_key_t) (uintptr_t) tls );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_tls_set( thread_tls_t tls, void* value )
    {
    #if defined( _WIN32 )

        TlsSetValue( (DWORD) (uintptr_t) tls, value );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        pthread_setspecific( (pthread_key_t) (uintptr_t) tls, value );
    
    #else 
        #error Unknown platform.
    #endif
    }


void* thread_tls_get( thread_tls_t tls )
    {
    #if defined( _WIN32 )

        return TlsGetValue( (DWORD) (uintptr_t) tls );
    
    #elif defined( __linux__ ) || defined( __APPLE__ ) || defined( __ANDROID__ )

        return pthread_getspecific( (pthread_key_t) (uintptr_t) tls );
    
    #else 
        #error Unknown platform.
    #endif
    }


void thread_queue_init( thread_queue_t* queue, int size, void** values, int count )
    {
    queue->values = values;
    thread_signal_init( &queue->data_ready );
    thread_signal_init( &queue->space_open );
    thread_atomic_int_store( &queue->head, 0 );
    thread_atomic_int_store( &queue->tail, count > size ? size : count );
    thread_atomic_int_store( &queue->count, count > size ? size : count );
    queue->size = size;
    #ifndef NDEBUG
        thread_atomic_int_store( &queue->id_produce_is_set, 0 );
        thread_atomic_int_store( &queue->id_consume_is_set, 0 );
    #endif
    }


void thread_queue_term( thread_queue_t* queue )
    {
    thread_signal_term( &queue->space_open );
    thread_signal_term( &queue->data_ready );
    }


int thread_queue_produce( thread_queue_t* queue, void* value, int timeout_ms )
    {
    #ifndef NDEBUG
        if( thread_atomic_int_compare_and_swap( &queue->id_produce_is_set, 0, 1 ) == 0 )
            queue->id_produce = thread_current_thread_id();
        THREAD_ASSERT( thread_current_thread_id() == queue->id_produce, "thread_queue_produce called from multiple threads" );
    #endif
    while( thread_atomic_int_load( &queue->count ) == queue->size )  // TODO: fix signal so that this can be an "if" instead of "while"
        {
        if( timeout_ms == 0 ) return 0;
        if( thread_signal_wait( &queue->space_open, timeout_ms == THREAD_QUEUE_WAIT_INFINITE ? THREAD_SIGNAL_WAIT_INFINITE : timeout_ms ) == 0 )
            return 0;
        }
    int tail = thread_atomic_int_inc( &queue->tail );
    queue->values[ tail % queue->size ] = value;
    if( thread_atomic_int_inc( &queue->count ) == 0 )
        thread_signal_raise( &queue->data_ready );
    return 1;
    }


void* thread_queue_consume( thread_queue_t* queue, int timeout_ms )
    {
    #ifndef NDEBUG
        if( thread_atomic_int_compare_and_swap( &queue->id_consume_is_set, 0, 1 ) == 0 )
            queue->id_consume = thread_current_thread_id();
        THREAD_ASSERT( thread_current_thread_id() == queue->id_consume, "thread_queue_consume called from multiple threads" );
    #endif
    while( thread_atomic_int_load( &queue->count ) == 0 ) // TODO: fix signal so that this can be an "if" instead of "while"
        {
        if( timeout_ms == 0 ) return NULL;
        if( thread_signal_wait( &queue->data_ready, timeout_ms == THREAD_QUEUE_WAIT_INFINITE ? THREAD_SIGNAL_WAIT_INFINITE : timeout_ms ) == 0 )
            return NULL;
        }
    int head = thread_atomic_int_inc( &queue->head );
    void* retval = queue->values[ head % queue->size ];
    if( thread_atomic_int_dec( &queue->count ) == queue->size )
        thread_signal_raise( &queue->space_open );
    return retval;
    }

    
int thread_queue_count( thread_queue_t* queue )
    {
    return thread_atomic_int_load( &queue->count );
    }


#endif /* THREAD_IMPLEMENTATION */

/*
revision history:
    0.3     set_high_priority API change. Fixed spurious wakeup bug in signal. Added 
            timeout param to queue produce/consume. Various cleanup and trivial fixes.
    0.2     first publicly released version 
*/

/*
------------------------------------------------------------------------------

This software is available under 2 licenses - you may choose the one you like.

------------------------------------------------------------------------------

ALTERNATIVE A - MIT License

Copyright (c) 2015 Mattias Gustavsson

Permission is hereby granted, free of charge, to any person obtaining a copy of 
this software and associated documentation files (the "Software"), to deal in 
the Software without restriction, including without limitation the rights to 
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 
of the Software, and to permit persons to whom the Software is furnished to do 
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all 
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.

------------------------------------------------------------------------------

ALTERNATIVE B - Public Domain (www.unlicense.org)

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this 
software, either in source code form or as a compiled binary, for any purpose, 
commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this 
software dedicate any and all copyright interest in the software to the public 
domain. We make this dedication for the benefit of the public at large and to 
the detriment of our heirs and successors. We intend this dedication to be an 
overt act of relinquishment in perpetuity of all present and future rights to 
this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

------------------------------------------------------------------------------
*/