文本文件大数据查询

小鱼儿 2022-07-17 01:15 220阅读 0赞

大数据查询的步骤：

//读入到内存、排序、写入到文件、创建索引、二分查找

下面代码听课时写的有点乱，可以按上面的 步骤来实现。

#define _CRT_SECURE_NO_WARNINGS
    #include<stdio.h>
    #include<stdlib.h>
    #include<string.h>
    #include<Windows.h>
    
    #define LINE 10000000
    
    //读入到内存、排序、写入到文件、创建索引、二分查找
    
    char **g_pp;	//保存指针数组
    char *sorpath = "E:\\qqok.txt";
    char *despath = "E:\\qsort.txt";
    char *indexpath = "E:\\qindex.txt";
    
    struct index	//索引的数据结构
    {
    	int *pindex;		//保存每行的首地址
    	int length;			//行数
    }allindex;
    
    int getLine(char *path)
    {
    	int line = 0;
    	FILE *pfr = fopen(path, "rb");
    	if (pfr == NULL)
    	{
    		printf("文件打开失败！\n");
    		return 0;
    	}
    	else
    	{
    		while (!feof(pfr))
    		{
    			char str[256] = { 0 };
    			fgets(str, 256, pfr);
    			line++;
    		}
    	}
    	fclose(pfr);
    	return line;
    }
    
    void eatq(char *str)
    {
    	for (char *ptemp = str; *ptemp != '\0'; ptemp++)
    	{
    		if (*ptemp == '-')
    		{
    
    			*ptemp = '\0';
    		}
    	}
    }
    
    //去掉 \n
    void eatN(char *str)
    {
    	while (*str != '\0')
    	{
    		if (*str == '\r' || *str == '\n')
    		{
    			*str = '\0';
    		}
    		str++;
    	}
    }
    
    
    void initmem(char *path)
    {
    	printf("\n开始读取...\n");
    	g_pp = calloc(LINE, sizeof(char *));
    	FILE *pfr = fopen(path, "rb");
    	if (pfr == NULL)
    	{
    		printf("文件打开失败！\n");
    		return ;
    	}
    	else
    	{
    		for (int i = 0; i < LINE;i++)
    		{
    			char str[256] = { 0 };
    			fgets(str, 256, pfr);
    			g_pp[i] = calloc(strlen(str) + 1, sizeof(char));
    			//printf("%s", str);
    			
    			if (g_pp[i])
    			{
    				//strcpy(g_pp[i], str);	//拷贝数据
    				sprintf(g_pp[i], str);	//在大数据使用时不稳定
    				strcpy(g_pp[i], str);
    				//printf("%d  ", strlen(str));
    				eatN(g_pp[i]);	//去掉 \n 因为这儿可能有次使用 \n
    				//printf("%d \n ", strlen(g_pp[i]));
    
    			}
    		
    		}
    	}
    	fclose(pfr);
    	printf("\n结束读取...\n");
    }
    
    int com(void *p1, void *p2)
    {
    	char **pstr1 = p1;
    	char **pstr2 = p2;
    	int res = strcmp(*pstr1, *pstr2);
    	
    	return res;
    }
    
    void sort()
    {
    	qsort(g_pp, LINE, sizeof(char*), com);
    }
    
    
    
    void writetofile(char *path)
    {
    	FILE *pfw = fopen(path, "wb");
    	if (pfw == NULL)
    	{
    		printf("文件打开失败！\n");
    		return ;
    	}
    	else
    	{
    		for (int i = 0; i < LINE; i++)
    		{
    			char tempstr[100] = { 0 };
    			sprintf(tempstr, "%s\n", g_pp[i]);
    			//strcat(g_pp[i], '\n');
    			//写进去字符串前先要配上个 \n，因为上面我们把 \n 去掉了
    			fputs(tempstr, pfw);	//得到一个有序的文件
    			//printf("%s", tempstr);
    		}
    	}
    	fclose(pfw);
    
    }
    
    void show()
    {
    	for (int i = 0; i < LINE; i++)
    	{
    		printf("%s\n", g_pp[i]);
    	}
    }
    
    //初始化数据
    void initindex(char *path)
    {
    	printf("索引数组开始分配...\n");
    	allindex.length = LINE+1;
    	allindex.pindex = calloc(allindex.length, sizeof(int));		//开辟内存空间
    	printf("索引数组完成分配。\n");
    
    	printf("开始读取...\n");
    	FILE *pfr = fopen(path, "rb");
    	FILE *pfw = fopen(indexpath, "wb");	//索引文件
    	if (pfr == NULL || pfw == NULL)
    	{
    		printf("文件打开失败！\n");
    		return;
    	}
    	else
    	{
    		int alllength = 0;
    		int i = 0;
    		while (!feof(pfr))
    		{
    			char str[256] = { 0 };
    			fgets(str, 256, pfr);
    			//记录每行数据所占用的长度，方便后面指针查询的跳转
    			allindex.pindex[i] = alllength;			
    			//printf("%d ", allindex.pindex[i]);
    			int length = strlen(str);
    			alllength += length;
    
    			i++;
    		}
    		fclose(pfr);
    	}
    	printf("结束读取...\n");
    
    	//把索引写入到文件中
    	printf("索引写入...\n");
    	fwrite(allindex.pindex, sizeof(int), allindex.length, pfw);
    	
    	fclose(pfw);
    	printf("索引写入结束。\n");
    
    	//释放内存
    	free(allindex.pindex);
    
    }
    
    //快速读取,就是建立好索引文件后，直接读取索引文件
    void qucik(char *path)
    {
    	printf("索引数组开始分配...\n");
    	allindex.length = LINE;
    	allindex.pindex = calloc(allindex.length, sizeof(int));		//开辟内存空间
    	printf("索引数组完成分配。\n");
    
    	printf("开始读取...\n");
    	FILE *pfr = fopen(indexpath, "rb");
    	if (pfr == NULL)
    	{
    		printf("文件打开失败！\n");
    		return;
    	}
    	fread(allindex.pindex, sizeof(int), allindex.length, pfr);
    	fclose(pfr);
    	
    	printf("结束读取...\n");
    }
    
    //把索引读入到内存。
    void main内存索引查询()
    {
    	//printf("%d\n", getLine(sorpath));
    	//initmem(sorpath);
    	show();
    	//printf("\n排序后：\n");
    	//sort();
    	show();
    
    	//writetofile(despath);
    	//printf("%d\n", getLine(despath));
    	//创建索引
    	//initindex(despath);
    	/*qucik(indexpath);
    	FILE *pfr = fopen(despath, "rb");
    
    	while (1)
    	{
    		printf("请输入要查询的行号：");
    		int num = 0;
    		scanf("%d", &num);
    		fseek(pfr, allindex.pindex[num], SEEK_SET);
    		
    		char str[256] = { 0 };
    		fgets(str, 256, pfr);
    		printf("%s", str);
    
    	}
    	fclose(pfr);*/
    
    
    
    	system("pause");
    }
    
    //文件索引，即打开二个文件，先查询索引文件的内容，
    //然后根据索引的内容来查询相应的行
    void main索引文件查询()
    {
    	FILE *pfindex = fopen(indexpath, "rb");
    	FILE *pfsortq = fopen(despath, "rb");
    
    	while (1)
    	{
    		printf("请输入要查询的行数：");
    		int num = 0;
    		scanf("%d", &num);
    		fseek(pfindex, num*sizeof(int), SEEK_SET);
    		int data;
    		fread(&data, sizeof(int), 1, pfindex);
    		//printf("%d", data);
    		char str[256] = { 0 };
    		fseek(pfsortq, sizeof(char)*data, SEEK_SET);
    		fgets(str, 256, pfsortq);
    		printf("%s", str);
    
    	}
    
    	fclose(pfindex);
    	fclose(pfsortq);
    
    
    
    	system("pause");
    }
    
    void searchstr(char *str)
    {
    	FILE *pfindex = fopen(indexpath, "rb");
    	FILE *pfdes = fopen(despath, "rb");
    	if (pfindex == NULL || pfdes == NULL)
    	{
    		printf("cannot file !\n");
    		return;
    	}
    	int flag = 0;
    	int start = 0;
    	int end = LINE - 1;
    	while (start <= end)
    	{
    		int mid = (start + end) / 2;
    		int data = 0;
    		fseek(pfindex, mid*sizeof(int), SEEK_SET);
    		fread(&data, sizeof(1), 1, pfindex);
    		
    		char pstr[256] = { 0 };
    		fseek(pfdes, data, SEEK_SET);
    		fgets(pstr, 256, pfdes);
    		eatN(pstr);	//去掉 \n
    		//如果按 QQ 号，这时就需要把前的QQ号取出来
    		//eatq(pstr);  这样会把原字符串直接截断，无法打印出全部数据。
    		char ptemp[256] = { 0 };
    		strcpy(ptemp, pstr);
    		eatq(ptemp);
    
    		int res = strcmp(ptemp, str); //这个比较是完全比较，连 \n 也比较
    		if (res == 0)
    		{
    			flag = 1;
    			printf("%s", pstr);
    			break;
    		}
    		else if (res == 1)
    		{
    			end = mid - 1;
    		}
    		else if (res == -1)
    		{
    			start = mid + 1;
    		}
    	}
    	if (flag)
    	{
    		printf("\nfind\n");
    	}
    	else
    	{
    		printf("\nnot find");
    	}
    
    	fclose(pfindex);
    	fclose(pfdes);
    }
    
    
    
    //二分查找法
    void main()
    {
    	
    	
    	while (1)
    	{
    		char str[256];
    		printf("请输入要查询的QQ号：");
    		scanf("%s", str);
    
    		searchstr(str);
    	}
    	
    
    
    	system("pause");
    }