#ifndef INCLUDED_OS_PRIORITY_H
#define INCLUDED_OS_PRIORITY_H

#ifndef INCLUDED_OS_TYPES_H
#include <os_types.h>
#endif /*INCLUDED_OS_TYPES_H*/

#ifndef INCLUDED_OS_COMPILER_H
#include <os_compiler.h>
#endif /*INCLUDED_OS_COMPILER_H*/

#ifndef INCLUDED_CPU_CLZ_H
#include <cpu_clz.h>
#endif /*INCLUDED_CPU_CLZ_H*/


/* ======================================================================================================================== */
/* 常量 */

#define OS_PRIORITY_TABLE_SIZE ((OS_CFG_PRIORITY_MAX - 1u)/(OS_CFG_CPU_INT_NBITS) + 1u)   // 优先级位图表的大小，单位为os_uint_t的数量


#define OS_PRIORITY_CMP_HIGH  (1)
#define OS_PRIORITY_CMP_EQUAL (0)
#define OS_PRIORITY_CMP_LOW   (-1)

#define OS_PRIORITY_IDLE            OS_PRIORITY_LOWEST
#define OS_PRIORITY_LOWEST          (OS_CFG_PRIORITY_MAX-1)                                                 /*31*/
#define OS_PRIORITY_HIGHEST         (1)                                                                     /*1*/
#define OS_PRIORITY_NORMAL          ((OS_PRIORITY_LOWEST-OS_PRIORITY_HIGHEST)>>1)                           /*15*/
#define OS_PRIORITY_BELOW_NORMAL    (((OS_PRIORITY_LOWEST-OS_PRIORITY_NORMAL)>>1)+OS_PRIORITY_NORMAL)       /*23*/
#define OS_PRIORITY_ABOVE_NORMAL    ((OS_PRIORITY_NORMAL-OS_PRIORITY_HIGHEST)>>1)                           /*7*/


/* ======================================================================================================================== */
/* 类型 */

typedef os_uint_t os_priority_t;

extern volatile os_priority_t g_os_priority_table[OS_PRIORITY_TABLE_SIZE];

/* ======================================================================================================================== */
/* 接口 */

OS_STATIC_FORCE_INLINE
void os_priority_init(void){
    for(os_uint_t i = 0; i < OS_PRIORITY_TABLE_SIZE; i++){
        g_os_priority_table[i] = 0u;   // 初始化优先级位图表，将所有优先级位都设置为0，表示所有优先级都没有线程占用
    }
}

OS_STATIC_FORCE_INLINE
void os_priority_set(os_priority_t priority){
    os_size_t index = priority / OS_CFG_CPU_INT_NBITS;              // 计算优先级在优先级位图表中的索引位置
    os_size_t bit_idx = priority & (OS_CFG_CPU_INT_NBITS - 1u);     // 计算优先级在索引位置的位偏移 0 - 31
    os_uint_t bit = 1u << (OS_CFG_CPU_INT_NBITS - 1u - bit_idx);    // 计算对应位的掩码，优先级0对应最高位，优先级31对应最低位
    g_os_priority_table[index] |= bit;                                // 将对应位设置为1，表示该优先级被占用
}

OS_STATIC_FORCE_INLINE
void os_priority_clear(os_priority_t priority){
    os_size_t index = priority / OS_CFG_CPU_INT_NBITS;              // 计算优先级在优先级位图表中的索引位置
    os_size_t bit_idx = priority & (OS_CFG_CPU_INT_NBITS - 1u);     // 计算优先级在索引位置的位偏移 0 - 31
    os_uint_t bit = 1u << (OS_CFG_CPU_INT_NBITS - 1u - bit_idx);    // 计算对应位的掩码，优先级0对应最高位，优先级31对应最低位
    g_os_priority_table[index] &= ~bit;                               // 将对应位清零，表示该优先级被释放
}

OS_STATIC_FORCE_INLINE
os_priority_t os_priority_get_highest(void){
    os_priority_t* p_table = (os_priority_t*)&g_os_priority_table[0];   // 从优先级位图表的第一个元素开始查找
    os_priority_t priority = 0;

    while(*p_table == 0u){                      // 如果当前元素为0，表示该范围内的优先级都没有线程占用
        p_table++;                              // 移动到下一个元素
        priority += OS_CFG_CPU_INT_NBITS;       // 增加优先级偏移量，跳过当前范围
    }

    priority += cpu_clz(*p_table);              // 使用内置函数计算当前元素中最高位1的索引位置，得到最高优先级的偏移量
    return priority;                            // 返回最高优先级，优先级0对应最高位，没有线程占用时返回OS_CFG_PRIORITY_MAX
}


OS_STATIC_FORCE_INLINE
os_bool_t os_priority_is_high(os_priority_t prio_a, os_priority_t prio_b){
    return (prio_a < prio_b)?OS_TRUE:OS_FALSE;    // 优先级数值越小表示优先级越高，因此比较两个优先级的数值大小来判断哪个优先级更高
}

OS_STATIC_FORCE_INLINE
int os_priority_cmp(os_priority_t prio_a, os_priority_t prio_b){
    return (int)((prio_a == prio_b)?OS_PRIORITY_CMP_EQUAL:((prio_a < prio_b)?OS_PRIORITY_CMP_HIGH:OS_PRIORITY_CMP_LOW));
}


#endif /* INCLUDED_OS_PRIORITY_H */