C语言结构体嵌套二级指针和文件读写相关函数

　　1.结构体嵌套二级指针#define _CRT_SECURE_NO_WARNINGS #include #include #include #include   struct Teacher {     char* name;     char** Stduents; };  static void allocateSpace(struct Teacher***teachers) { 	struct Teacher** pArray = malloc(sizeof(struct Teacher) * 3);      for (int i = 0; i < 3; i++)     {         //给每个老师分配空间         pArray[i] = malloc(sizeof(struct Teacher));          //给每个老师姓名分配空间         pArray[i]->name = malloc(sizeof(char) * 64);         sprintf(pArray[i]->name, ＂Teacher_%d＂, i + 1);          //给老师带的学生的数组分配空间         pArray[i]->Stduents = malloc(sizeof(char*) * 4);          //给四个学生分配内存，并且赋值         for (int j = 0; j < 4; j++)         {             pArray[i]->Stduents[j] = malloc(sizeof(char) * 64);             sprintf(pArray[i]->Stduents[j], ＂%s_Student_%d＂, pArray[i]->name, j + 1);         }     }         *teachers = pArray; }  void showArray(struct Teacher** pArray, int len) {     for (int i = 0; i < len; i++)     {         printf(＂%s ＂, pArray[i]->name);         for (int j = 0; j < 4; j++)         {             printf(＂     %s ＂, pArray[i]->Stduents[j]);         }     } }  static void freeSpace(struct Teacher**pArray,int len) {     for (int i = 0; i < len; i++)     {         //释放老师姓名         if (pArray[i]->name != NULL)         {             free(pArray[i]->name);             pArray[i]->name = NULL;         }          //释放每个学生         for (int j = 0; j < len; j++)         { 			if (pArray[i]->Stduents[j] != NULL) 			{                 free(pArray[i]->Stduents[j]);                 pArray[i]->Stduents = NULL; 			}         }          //释放学生数组         free(pArray[i]->Stduents);         pArray[i]->Stduents = NULL;          //释放老师         free(pArray[i]);         pArray[i] = NULL;     }     //释放老师数组     free(pArray);     pArray = NULL; }  static void test01() {     struct Teacher** pArray = NULL;     //分配内存     allocateSpace(&pArray);      //打印数组     showArray(pArray, 3);      //释放内存     freeSpace(pArray, 3);     pArray = NULL; }   int main01() {     test01();      return 0; }  /*   打印结果 Teacher_1      Teacher_1_Student_1      Teacher_1_Student_2      Teacher_1_Student_3      Teacher_1_Student_4 Teacher_2      Teacher_2_Student_1      Teacher_2_Student_2      Teacher_2_Student_3      Teacher_2_Student_4 Teacher_3      Teacher_3_Student_1      Teacher_3_Student_2      Teacher_3_Student_3      Teacher_3_Student_4 */
　　2.结构体偏移量#define _CRT_SECURE_NO_WARNINGS #include #include #include #include   struct person {     char a;//0~3     int b;//4~7 };  static void test01() {     struct person p1;     struct person* p = &p1;      printf(＂b的偏移量为:%d ＂, (int)&(p->b) - (int)p);     printf(＂b的偏移量为:%d ＂, offsetof(struct person, b)); }  //通过偏移量获取数据 static void test02() {     struct person p1 = { ＂a＂,10 };      printf(＂p.b=%d ＂, *(int*)((char*)&p1 + offsetof(struct person, b)));      printf(＂p.b=%d ＂, *(int*)((int*)&p1 + 1)); }  //结构体嵌套结构体 struct person2 {     char a;     int b;     struct person c; };  static void test03() {     struct person2 p = { ＂a＂,10,＂b＂,20 };           int offset1 = offsetof(struct person2, c);     int offset2 = offsetof(struct person, b);      printf(＂%d ＂, *(int*)((char*)&p + offset1 + offset2));//10      printf(＂%d ＂, ((struct person*) ((char*)&p + offset1))->b);//10 }  int main02() {     //test01();     test02();      return 0; }
　　3.内存的对齐方式#define _CRT_SECURE_NO_WARNINGS #include #include #include #include   //#pragma pack(1)  对齐模式修改为1 #pragma pack(show)//默认对齐模数为8  该值可以改为2的n次方   //对于自定义数据类型 内存的对齐规则： /* 1、从第一个属性开始 偏移为0 2、第二个属性开始，地址要放在该类型的整数倍， 与对齐模数比 取小的值 的整数倍上。 3、所有的属性都计算结束后，整体做二次对齐， 整体需放在属性中最大类型与对齐模数比取小的值的整数倍上。 */ typedef struct _STUDENT {     int a;     char b;     double c;     float d; }Student static void test01() {     printf(＂sizeof=%d ＂, sizeof(Student));//24 } //结构体嵌套结构体时，只需看子结构体中最大数据类型即可 typedef struct _STUDENT2 {     char a;//0~7     Student b;//8~31  子结构体最大数据类型是8     double c;//32~39 }Student2; static void test02() {     printf(＂sizeof=%d ＂, sizeof(Student2)); } int main03() {     //test01();     test02();     return 0; }
　　4.文件的读写
　　fgetc、fputc、fgets、fputs、fread、fwrite、fprintf、fscanf等函数的使用#define _CRT_SECURE_NO_WARNINGS #include #include #include #include  //1、字符的读写回顾 fgetc()、fputc() static void test01() {     //写文件  fputc     FILE* f_write = fopen(＂f:/a.txt＂, ＂w＂);      if (f_write == NULL)     {         return;     }     char buf[] = ＂hello world＂;     for (int i = 0; i < strlen(buf); i++)     {         fputc(buf[i], f_write);     }     fclose(f_write);      //读文件  fgetc     FILE* f_read = fopen(＂f:/a.txt＂, ＂r＂);      if (f_read == NULL)     {         return;     }     char ch;     while ((ch = fgetc(f_read) != EOF))//EOF即  END  OF  FILE     {         printf(＂%c ＂, ch);     }          fclose(f_read); }  //2、按行读写文件 static void test02() {     //写文件  fputs()     FILE* f_write = fopen(＂f:/a.txt＂, ＂w+＂);     if (f_write == NULL)     {         return;     }     char* buf[] =     {           ＂君不见黄河之水天上来，奔流到海不复回 ＂          ＂君不见高堂明镜悲白发，朝如青丝暮成雪 ＂          ＂人生得意须尽欢，莫使金樽空对月 ＂          ＂天生我材必有用，千金散尽还复来 ＂     };      for (int i = 0; i < 4; i++)     {         fputs(buf[i], f_write);     }     fclose(f_write);          //读文件  fgets()     FILE* f_read = fopen(＂f:/a.txt＂, ＂r＂);     if (f_read == NULL)     {         return;     }     while (!feof(f_read))     {         char temp[1024] = { 0 };          fgets(temp, 1024, f_read);          printf(＂%s ＂, temp);     }     fclose(f_read); }  //3、按块进行读写 fread()、fwrite() struct hero {     char name[64];     int age; };  static void test03() {     //写文件  fwrite()     FILE* f_write = fopen(＂f:/a.txt＂, ＂wb＂);     if (f_write == NULL)     {         return;     }     struct hero heros[] =     {         {＂孙悟空＂,111},         {＂曹操＂,222},         {＂赵云＂,333},         {＂鲁班＂,444},     };      for(int i=0;i<4;i++)     {         fwrite(&heros[i], sizeof(struct hero), 1, f_write);     }     fclose(f_write);      //读文件  fread()     FILE* f_read = fopen(＂f:/a.txt＂, ＂rb＂);     if (f_read == NULL)     {         return;     }      struct hero temp[4];     fread(&temp, sizeof(struct hero), 4, f_read);     for (int i = 0; i < 4; i++)     {         printf(＂姓名：%s  年龄：%d ＂, temp[i].name, temp[i].age);     }     fclose(f_read); }  //4、格式化读写 static void test04() {     //写文件  fprintf()     FILE* f_write = fopen(＂f:/a.txt＂, ＂w＂);     if (f_write = NULL)     {         return;     }     fprintf(f_write, ＂hello world %s＂, ＂abcd＂);     fclose(f_write);      //读文件 fscanf()     FILE* f_read = fopen(＂f:/a.txt＂, ＂r＂);     if (f_read = NULL)     {         return;     }     char temp[1024] = { 0 };     while (!feof(f_read))     {         fscanf(f_read, ＂%s＂, temp);         printf(＂%s ＂, temp);     }      fclose(f_read); }  static void test05() {     //写文件     FILE* f_write = fopen(＂f:/a.txt＂, ＂wb＂);     if (f_write == NULL)     {         return;     }     struct hero heros[] =     {         {＂孙悟空＂,111},         {＂曹操＂,222},         {＂赵云＂,333},         {＂鲁班＂,444},     };      for (int i = 0; i < 4; i++)     {         fwrite(&heros[i], sizeof(struct hero), 1, f_write);     }     fclose(f_write);      //读文件     FILE* f_read = fopen(＂f:/a.txt＂, ＂rb＂);     if (f_read == NULL)     {         //error 宏         //printf(＂文件加载失败 ＂);         perror(＂文件加载失败＂);//用户提示信息+系统提供信息         return;     }     struct hero temphero;     //移动光标     //fseek(f_read, sizeof(struct hero) * 3, SEEK_SET);     fseek(f_read, -(long)sizeof(struct hero) * 1, SEEK_END);//sizeof的返回值是无符号的 需强转为long类型     rewind(f_read);//将光标置到文件开头     fread(&temphero, sizeof(struct hero), 1, f_read);     printf(＂姓名:%s,年龄:%d ＂, temphero.name, temphero.age);//鲁班 444     fclose(f_read); } int main04() {     //test01();     //test02();     //test03();     //test04();     test05();     return 0; }
　　5.文件读写的注意事项#define _CRT_SECURE_NO_WARNINGS #include #include #include #include  static void test01() {     FILE* file = fopen(＂f:/a.txt＂, ＂r＂);      if (file == NULL)     {         return;     }     char ch;  #if 0     while (!feof(file))     {         ch = fgetc(file);          //滞后性         if (feof(file))         {             break;         }         printf(＂%c＂, ch);     } #endif     char ch;     while ((ch = fgetc(file)) != EOF)     {         printf(＂%c＂, ch);     }     fclose(file); } //注意事项2 struct person {     char* name;//不要将指针写入到文件中     int age; }; int main05() {     test01();     return 0; }
　　6.配置文件的读写#pragma  once #define _CRT_SECURE_NO_WARNINGS #include #include #include  struct ConfigInfo { 	char key[64]; //索引值 	char value[64]; //实值 };   //获取有效行数 int getFileLine(char* fileName);  //判断当前行是否有效 int isValidLine(char* str);  //解析文件 void parseFile(char* filePath, int lines, struct ConfigInfo** configInfo);  //根据索引值 获取 实值  char* getInfoByKey(char* key, struct ConfigInfo* configInfo, int line);  //释放信息 void freeSpace(struct ConfigInfo* configInfo); #include ＂config.h＂  //获取有效行数 int getFileLine(char* fileName) { 	FILE* file = fopen(fileName, ＂r＂); 	if (file == NULL) 	{ 		return -1; 	}  	char buf[1024] = { 0 }; 	int lines = 0; 	while (fgets(buf, 1024, file) != NULL) 	{ 		//如果是有效行 才统计 		if (isValidLine(buf)) 		{ 			lines++; 		}  	} 	fclose(file);  	return lines; }  //判断当前行是否有效 int isValidLine(char* str) { 	if (str[0] == ＂ ＂ || str[0] == ＂＂ || strchr(str, ＂:＂) == NULL) 	{ 		return 0; //无效数据 都返回假 	} 	return 1; }   //解析文件 void parseFile(char* filePath, int lines, struct ConfigInfo** configInfo) {  	struct ConfigInfo* info = malloc(sizeof(struct ConfigInfo) * lines);  	if (info == NULL) 	{ 		return; 	}  	FILE* file = fopen(filePath, ＂r＂);  	char buf[1024] = { 0 }; 	int index = 0; 	while (fgets(buf, 1024, file) != NULL) 	{ 		//解析数据  有效数据才解析 		// heroName:aaaa  		if (isValidLine(buf)) 		{ 			memset(info[index].key, 0, 64); 			memset(info[index].value, 0, 64);  			char* pos = strchr(buf, ＂:＂); //pos代表冒号所在位置  			strncpy(info[index].key, buf, pos - buf); //将key截取到 结构体中 最后-1的原因是不需要截取换行符 			strncpy(info[index].value, pos + 1, strlen(pos + 1) - 1);  			/*printf(＂key =  %s ＂, info[index].key); 			printf(＂value =  %s＂, info[index].value);*/ 			index++;  		}  		memset(buf, 0, 1024);  	}   	*configInfo = info; }   //根据索引值 获取 实值  char* getInfoByKey(char* key, struct ConfigInfo* configInfo, int line) { 	for (int i = 0; i < line; i++) 	{ 		if (strcmp(key, configInfo[i].key) == 0) 		{ 			return configInfo[i].value; 		} 	} 	return NULL; }   //释放信息 void freeSpace(struct ConfigInfo* configInfo) { 	if (configInfo != NULL) 	{ 		free(configInfo); 		configInfo = NULL; 	}  }#define _CRT_SECURE_NO_WARNINGS #include #include #include #include ＂config.h＂  struct Person { 	char a; 	int b; };  void test01() { 	char* filePath = ＂./config.txt＂;  	int line = getFileLine(filePath);  	printf(＂文件的有效行数为：%d ＂, line);  	struct ConfigInfo* pArray = NULL;  	parseFile(filePath, line, &pArray);  	//测试 根据key 访问value 	printf(＂heroId = %s ＂, getInfoByKey(＂heroId＂, pArray, line)); 	printf(＂heroName = %s ＂, getInfoByKey(＂heroName＂, pArray, line)); 	printf(＂heroAtk = %s ＂, getInfoByKey(＂heroAtk＂, pArray, line)); 	printf(＂heroDef = %s ＂, getInfoByKey(＂heroDef＂, pArray, line)); 	printf(＂heroInfo = %s ＂, getInfoByKey(＂heroInfo＂, pArray, line));   	//释放内存 	freeSpace(pArray); 	pArray = NULL;   	//文件加密 codeFile( sourceFile ,  destFile ) 	// #  35  转为 short 	// 0000 0000 0010 0011   << 4 	// 0000 0010 0011 0000    	// 1000 0000 0000 0000    |  	// 1000 0010 0011 0000  + 0000 ~ 1111 随机数  rand()%16     0~ 15 	// 1000 0010 0011 1010   	//解密  decodeFile ( sourceFile ,  destFile ) 	// 1000 0010 0011 1010  <<1  	// 000  0010 0011 10100  >> 5 	// 0000 0000  0010 0011 }  int main()  { 	test01(); 	system(＂pause＂); 	return EXIT_SUCCESS; }