switch case语句的用法cp

`switch case`语句是一种控制结构，在编程中常用于基于某个变量值执行不同的代码块，尤其常见于需要判断多种可能情况的场景。它的基本语法如下：

switch (expression) {
    case value1:
        // 当expression等于value1时，执行这里的代码
        code_block1;
        break;
    case value2:
        // 当expression等于value2时，执行这里的代码
        code_block2;
        break;
    // 可以有多个case
    default:
        // 如果expression都不匹配前面的case，执行这里（可选）
        code_block_default;
        break; // 结束默认分支，防止后续case影响
}

- `expression`: 需要判断其值的表达式。
- `case value`: 指定一个可能的值，如果`expression`的值与之相等，则执行紧跟其后的代码块。
- `break`: 关键字，用来结束当前`case`内的代码并跳出`switch`结构，避免进入下一个未匹配的`case`。

相关问题

#define HC165_CE {PBout(0),PBout(8),PEout(4),PEout(8),PEout(12)} #define HC165_PL {PAout(11),PBout(6),PEout(2),PEout(6),PEout(10)} #define HC165_CP {PAout(12),PBout(7),PEout(3),PEout(11),PEout(11)} #define HC165_Q7 {PBin(1),PBin(9),PEin(5),PEin(9),PEin(13)} uint8_t readVoltage(int group) { uint8_t i = 0; uint8_t temp = 0; HC165_CE[group] = 0; HC165_PL[group] = 0; HC165_PL[group] = 1; if(HC165_Q7[group] == 1) temp |= 0x01; for(i = 0; i < 7; i ++) { temp = temp << 1; HC165_CP[group] = 0; delayUs(1); HC165_CP[group] = 1; if(HC165_Q7[group] == 1) temp |= 0x01; } return temp; } 请帮我改成纯C语言代码

以下是改成纯 C 语言代码后的代码：

#define HC165_CE_0  GPIOB->ODR &= ~(1 << 0)
#define HC165_CE_1  GPIOB->ODR &= ~(1 << 8)
#define HC165_CE_2  GPIOE->ODR &= ~(1 << 4)
#define HC165_CE_3  GPIOE->ODR &= ~(1 << 8)
#define HC165_CE_4  GPIOE->ODR &= ~(1 << 12)
#define HC165_PL_0  GPIOA->ODR &= ~(1 << 11)
#define HC165_PL_1  GPIOB->ODR &= ~(1 << 6)
#define HC165_PL_2  GPIOE->ODR &= ~(1 << 2)
#define HC165_PL_3  GPIOE->ODR &= ~(1 << 6)
#define HC165_PL_4  GPIOE->ODR &= ~(1 << 10)
#define HC165_CP_0  GPIOA->ODR &= ~(1 << 12)
#define HC165_CP_1  GPIOB->ODR &= ~(1 << 7)
#define HC165_CP_2  GPIOE->ODR &= ~(1 << 3)
#define HC165_CP_3  GPIOE->ODR &= ~(1 << 11)
#define HC165_CP_4  GPIOE->ODR &= ~(1 << 15)
#define HC165_Q7_0  GPIOB->IDR & (1 << 1)
#define HC165_Q7_1  GPIOB->IDR & (1 << 9)
#define HC165_Q7_2  GPIOE->IDR & (1 << 5)
#define HC165_Q7_3  GPIOE->IDR & (1 << 9)
#define HC165_Q7_4  GPIOE->IDR & (1 << 13)

uint8_t readVoltage(int group)
{
    uint8_t i = 0;
    uint8_t temp = 0;
    switch (group) {
        case 0:
            HC165_CE_0 = 0;
            HC165_PL_0 = 0;
            HC165_PL_0 = 1;
            if (HC165_Q7_0 == 1)
                temp |= 0x01;
            for (i = 0; i < 7; i++) {
                temp = temp << 1;
                HC165_CP_0 = 0;
                delayUs(1);
                HC165_CP_0 = 1;
                if (HC165_Q7_0 == 1)
                    temp |= 0x01;
            }
            break;
        case 1:
            HC165_CE_1 = 0;
            HC165_PL_1 = 0;
            HC165_PL_1 = 1;
            if (HC165_Q7_1 == 1)
                temp |= 0x01;
            for (i = 0; i < 7; i++) {
                temp = temp << 1;
                HC165_CP_1 = 0;
                delayUs(1);
                HC165_CP_1 = 1;
                if (HC165_Q7_1 == 1)
                    temp |= 0x01;
            }
            break;
        case 2:
            HC165_CE_2 = 0;
            HC165_PL_2 = 0;
            HC165_PL_2 = 1;
            if (HC165_Q7_2 == 1)
                temp |= 0x01;
            for (i = 0; i < 7; i++) {
                temp = temp << 1;
                HC165_CP_2 = 0;
                delayUs(1);
                HC165_CP_2 = 1;
                if (HC165_Q7_2 == 1)
                    temp |= 0x01;
            }
            break;
        case 3:
            HC165_CE_3 = 0;
            HC165_PL_3 = 0;
            HC165_PL_3 = 1;
            if (HC165_Q7_3 == 1)
                temp |= 0x01;
            for (i = 0; i < 7; i++) {
                temp = temp << 1;
                HC165_CP_3 = 0;
                delayUs(1);
                HC165_CP_3 = 1;
                if (HC165_Q7_3 == 1)
                    temp |= 0x01;
            }
            break;
        case 4:
            HC165_CE_4 = 0;
            HC165_PL_4 = 0;
            HC165_PL_4 = 1;
            if (HC165_Q7_4 == 1)
                temp |= 0x01;
            for (i = 0; i < 7; i++) {
                temp = temp << 1;
                HC165_CP_4 = 0;
                delayUs(1);
                HC165_CP_4 = 1;
                if (HC165_Q7_4 == 1)
                    temp |= 0x01;
            }
            break;
    }
    return temp;
}

注意，为了让代码更清晰易懂，我将宏定义改成了对应的 C 语言语句。同时，由于寄存器操作需要使用 STM32 的相关库函数，因此我将它们改成了对应的寄存器操作语句。

#include <stdio.h> #include <stdlib.h> typedef struct{ char name[5]; int need_time; int privilege; char state; }NODE; typedef struct node{ NODE data; struct node *link; }LNODE; void delay(int i) { int x,y; while(i--) { x=0 ; while(x < 10000) { y = 0; while(y < 40000) y++; x++ ; } } } void len_queue(LNODE **hpt, NODE x) { LNODE *q,*r,*p; q = *hpt; 8 r = *hpt; p = (LNODE *)malloc(sizeof(LNODE)); p->data = x; p->link = NULL; if(*hpt == NULL) *hpt = p; else { while(q!=NULL && (p->data).privilege < (q->data).privilege) { r = q; q = q->link; } if(q == NULL) r->link = p; else if(r == q) { p->link = *hpt; *hpt = p; }else { r->link = p; p->link = q; } } } void lde_queue(LNODE **hpt, NODE *cp) { LNODE *p = *hpt; *cp = (*hpt)->data; *hpt = (*hpt)->link; free(p); printf("the elected process's name : %s \n",cp->name); } void output(LNODE **hpt) { LNODE *p = *hpt; printf("Name \t Need_time \t privilege \t state\n"); do { 9 printf("%s \t %d \t\t %d \t\t %c \n", (p->data).name,(p->data).need_time,(p->data).privilege,(p->data).state); p = p->link; }while(p!= NULL); delay(4); } int main() { LNODE *head = NULL; NODE curr,temp; printf("The period time is 4s \n"); printf("please input \n"); printf("if need_time = 0,input over\n"); printf("Name\t Need_time\t privilege\n"); while(1) { scanf("%s %d %d", temp.name,&temp.need_time,&temp.privilege); if(temp.need_time == 0) break; temp.state = 'R'; len_queue(&head,temp); } while(head != NULL) { output(&head); lde_queue(&head,&curr); curr.need_time-- ; curr.privilege-- ; if(curr.need_time != 0) len_queue(&head,curr); } return 0; }

以下是将该段 C 代码转换为 Python 的结果：

import time

class Node:
    def __init__(self, name, need_time, privilege, state):
        self.name = name
        self.need_time = need_time
        self.privilege = privilege
        self.state = state

class LNode:
    def __init__(self, data, link):
        self.data = data
        self.link = link

def delay(i):
    while i > 0:
        x = 0
        while x < 10000:
            y = 0
            while y < 40000:
                y += 1
            x += 1
        i -= 1

def len_queue(hpt, x):
    p = LNode(x, None)
    q = hpt
    r = hpt
    if hpt is None:
        hpt = p
    else:
        while q is not None and p.data.privilege < q.data.privilege:
            r = q
            q = q.link
        if q is None:
            r.link = p
        elif r == q:
            p.link = hpt
            hpt = p
        else:
            r.link = p
            p.link = q
    return hpt

def lde_queue(hpt):
    if hpt is None:
        return None, hpt
    else:
        cp = hpt.data
        hpt = hpt.link
        print(f"the elected process's name: {cp.name}")
        return cp, hpt

def output(hpt):
    p = hpt
    print("Name\tNeed_time\tPrivilege\tState")
    while p is not None:
        print(f"{p.data.name}\t{p.data.need_time}\t\t{p.data.privilege}\t\t{p.data.state}")
        p = p.link
    delay(4)

def main():
    head = None
    curr = None
    print("The period time is 4s")
    print("Please input")
    print("If need_time = 0, input over")
    print("Name\tNeed_time\tPrivilege")
    while True:
        name, need_time, privilege = input().split()
        need_time = int(need_time)
        privilege = int(privilege)
        if need_time == 0:
            break
        temp = Node(name, need_time, privilege, 'R')
        head = len_queue(head, temp)
    while head is not None:
        output(head)
        curr, head = lde_queue(head)
        curr.need_time -= 1
        curr.privilege -= 1
        if curr.need_time != 0:
            head = len_queue(head, curr)

if __name__ == "__main__":
    main()

注意，由于 Python 的语法和 C 有所不同，因此代码中存在一些细微的差异，例如：

- 在 Python 中，结构体可以使用类来实现；
- 在 Python 中，链表节点可以使用类来实现；
- Python 中没有指针类型，因此需要使用类或者元组来返回多个值；
- Python 中没有 switch-case 语句，可以使用 if-elif-else 语句来代替；
- Python 中字符串可以使用单引号或者双引号来表示。