#pragma once

#include<pthread.h>
#include<stdio.h>

typedef struct
{
    pthread_mutex_t rw_mutex;
    pthread_cond_t  rw_condreaders;
    pthread_cond_t  rw_condwriters;
    int             rw_magic;
    int             rw_nwaitreaders;
    int             rw_nwaitwriters;
    int             rw_refcount;       // 0 >0 ==-1
}my_pthread_rwlock_t;

#define  RW_MAGIC  0x20180326

#define MY_PTHREAD_RWLOCK_INITIALIZER {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, PTHREAD_COND_INITIALIZER,\
RW_MAGIC,0,0,0}

typedef int  my_pthread_rwlockattr_t;


int my_pthread_rwlock_init(my_pthread_rwlock_t *rw, my_pthread_rwlockattr_t *attr);
int my_pthread_rwlock_destroy(my_pthread_rwlock_t *rw);
int my_pthread_rwlock_rdlock(my_pthread_rwlock_t *rw);
int my_pthread_rwlock_wrlock(my_pthread_rwlock_t *rw);
int my_pthread_rwlock_unlock(my_pthread_rwlock_t *rw);
int my_pthread_rwlock_tryrdlock(my_pthread_rwlock_t *rw);
int my_pthread_rwlock_trywrlock(my_pthread_rwlock_t *rw);
 

#include"my_pthread_rwlock.h"
#include<errno.h>

int my_pthread_rwlock_rdlock(my_pthread_rwlock_t *rw)
{
    int result;
    if(rw->rw_magic != RW_MAGIC)
        return -1;
    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
        return result;

    while(rw->rw_refcount<0)
    {
        rw->rw_nwaitreaders++;
        result = pthread_cond_wait(&rw->rw_condreaders, &rw->rw_mutex);
        rw->rw_nwaitreaders--;
        if(result != 0)
            break;
    }
    if(result == 0)
        rw->rw_refcount++;
    pthread_mutex_unlock(&rw->rw_mutex);
    return result;
}

int my_pthread_rwlock_wrlock(my_pthread_rwlock_t *rw)
{
    int result;
    if(rw->rw_magic != RW_MAGIC)
        return -1;

    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
        return result;

    while(rw->rw_refcount != 0 || rw->rw_nwaitreaders >0)
    {
        rw->rw_nwaitwriters++;
        result = pthread_cond_wait(&rw->rw_condwriters, &rw->rw_mutex);
        rw->rw_nwaitwriters--;
        if(result != 0)
            break;
    }
    if(result == 0)
        rw->rw_refcount = -1;

    pthread_mutex_unlock(&rw->rw_mutex);
    return result;
}

int my_pthread_rwlock_unlock(my_pthread_rwlock_t *rw)
{
    int result;
    if(rw->rw_magic != RW_MAGIC)
        return -1;
    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
        return result;

    if(rw->rw_refcount > 0)
        rw->rw_refcount--;
    else if(rw->rw_refcount == -1)
        rw->rw_refcount = 0;
    else
        printf("unlock error.\n");
    if(rw->rw_nwaitreaders > 0)
        result = pthread_cond_broadcast(&rw->rw_condreaders);
    else if(rw->rw_nwaitwriters > 0)
    {
        if(rw->rw_refcount == 0)
        {
            result = pthread_cond_signal(&rw->rw_condwriters);
        }
    }
   // else if(rw->rw_nwaitreaders > 0)
        //result = pthread_cond_broadcast(&rw->rw_condreaders);

    pthread_mutex_unlock(&rw->rw_mutex);
    return result;
}

int my_phread_rwlock_destroy(my_pthread_rwlock_t *rw)
{
    if(rw->rw_magic != RW_MAGIC)
        return (EINVAL);
    if(rw->rw_refcount != 0 || rw->rw_nwaitreaders != 0 || rw->rw_nwaitwriters != 0)
        return (EBUSY);
    pthread_mutex_destroy(&rw->rw_mutex);
    pthread_cond_destroy(&rw->rw_condreaders);
    pthread_cond_destroy(&rw->rw_condwriters);
    rw->rw_magic = 0;
    return 0;
}

my_pthread_rwlock_tryrdlock(my_pthread_rwlock_t *rw)
{
    int result;
    if(rw->rw_magic != RW_MAGIC)
        return (EINVAL);
    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
        return result;
    if(rw->rw_refcount <0 || rw->rw_nwaitwriters > 0)
        result = (EBUSY);
    else
        rw->rw_refcount++;
    pthread_mutex_unlock(&rw->rw_mutex);
    return result;
}

my_pthread_rwlock_trywrlock(my_pthread_rwlock_t *rw)
{
    int result;
    if(rw->rw_magic != RW_MAGIC)
        return (EINVAL);
    if((result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
        return result;
    if(rw->rw_refcount != 0)
        return (EBUSY);
    else
        rw->rw_refcount = -1;
    pthread_mutex_unlock(&rw->rw_mutex);
    return result;
}

#include<stdio.h>
#include<unistd.h>
#include<pthread.h>
#include"my_pthread_rwlock.h"
#include"my_pthread_rwlock1.c"

my_pthread_rwlock_t rwlock = MY_PTHREAD_RWLOCK_INITIALIZER;

void * thread_fun1(void *arg)
{
    my_pthread_rwlock_wrlock(&rwlock);
    printf("thread 1 wrlock.\n");
    sleep(3);
    my_pthread_rwlock_unlock(&rwlock);
}
void * thread_fun2(void *arg)
{
      my_pthread_rwlock_wrlock(&rwlock);
    //my_pthread_rwlock_trywrlock(&rwlock);
    //printf("thread 2 trywrlock\n");
      printf("thread 2 wrlock.\n");
    my_pthread_rwlock_unlock(&rwlock);
}
void * thread_fun3(void *arg)
{
      my_pthread_rwlock_rdlock(&rwlock);
    //my_pthread_rwlock_tryrdlock(&rwlock);
    //printf("thread 3 tryrdlock.\n");
      printf("thread 3 rdlock.\n");
    my_pthread_rwlock_unlock(&rwlock);
}

int main()
{
    pthread_t tid1, tid2, tid3;
    pthread_create(&tid1, NULL, thread_fun1, NULL);
    sleep(1);
    pthread_create(&tid2, NULL, thread_fun2, NULL);
    pthread_create(&tid3, NULL, thread_fun3, NULL);

    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL);
    pthread_join(tid3, NULL);

    return 0;
}