C语言练习 whl

题目一

　　将英文文本article-1e.txt~ article-82e.txt共82个文本文件的数据写入一个大文件article.dat，并对article.dat建立索引文件article.idx，在article.idx文件中记录每篇文章在article.dat文件中的起始位置和长度（此为子程序1：建立索引程序）；

　　实现文档检索：通过控制台输入文档编号，程序可通过article.idx查询到该文档在article.dat中的位置，读出该文档并输出到控制台（此为子程序2：检索程序）。

参考方法：

index.cpp

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <memory.h>
 4 #define MAXFILESIZE 20480
 5 struct idx_t//索引结构体
 6 {
 7     long pos;
 8     int len;
 9 }idx;
10 /* 本程序只为说明过程，因而去掉了所有错误判断过程（如文件打开失败等）,仅供参考 */
11 int main()
12 {
13     FILE *srcfp,*datfp,*idxfp;//源文件指针、dat文件指针、index文件指针
14     int len,i,count;
15     char *content;
16     char filename[50];//存储要打开文件的“文件路径”
17 
18     content=(char*)malloc(MAXFILESIZE);
19 
20     datfp = fopen("data.dat", "wb+");
21     idxfp = fopen("data.idx", "wb+");
22 
23     for (i=1;i<=82;i++)
24     {
25         sprintf(filename,"data\\article-%de.txt",i);//格式化要打开文件的“文件路径”到filename[]中
26 
27         srcfp = fopen(filename, "rb+");
28 
29         //读取源文件的长度
30         fseek(srcfp,0L,SEEK_END);
31         len = ftell(srcfp);
32         fseek(srcfp,0L,SEEK_SET);
33         memset(content,0,MAXFILESIZE);//初始化动态申请空间为0
34         fread(content,len,1,srcfp);//从源文件读的内存
35         idx.pos=ftell(datfp);//保存该文件在dat文件中的的起始位置
36         fwrite(content,len,1,datfp);//从内存写到dat文件
37         idx.len = len;//保存该文件在dat文件中的长度
38         fwrite(&idx,sizeof(struct idx_t),1,idxfp);//将索引写入index文件
39         fclose(srcfp);
40     }
41     free(content);
42     fclose(datfp); 
43     fclose(idxfp); 
44     return 0;
45 }

search.cpp

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

#define MAXFILESIZE 20480
struct idx_t
{
    long pos;
    int len;
}idx;
/* 本程序只为说明过程，因而去掉了所有错误判断过程,仅供参考 */
int main()
{
    FILE *datfp,*idxfp;
    int len,num,ret;
    char *content;

    printf("input file number:");
    scanf("%d",&num);

    datfp = fopen("data.dat", "rb");
    idxfp = fopen("data.idx", "rb");

    fseek(idxfp,sizeof(struct idx_t)*(num-1),SEEK_SET);
    fread(&idx,sizeof(struct idx_t),1,idxfp);

    content=(char*)malloc(MAXFILESIZE);
    memset(content,0,MAXFILESIZE);

    ret=fseek(datfp,idx.pos,SEEK_SET);
    ret=fread(content,1,idx.len,datfp);

    printf("%s",content);

    free(content);
    fclose(datfp); 
    fclose(idxfp); 
    system("pause");
    return 0;
}

myself方法：

myself.cpp

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 
  5 struct index 
  6 {
  7     char filename[20];
  8     long start;
  9     long end;
 10 }strindex[83];
 11 
 12 void BuildIndex()
 13 {
 14     FILE *fromfp,*to_datfp,*indexfp; 
 15     long len,temp_dat_start,temp_dat_end;
 16     char *content;
 17     int i,j,temp;
 18     for (i=1; i<83; i++)
 19     {
 20         char path[100] = "data\\article-";
 21         strcpy(strindex[i].filename,"article-");
 22         temp = i / 10;        
 23         if (temp == 0)
 24         {
 25             j = strlen(path);
 26             path[j] = (char)(i+48);
 27             path[j+1] = '\0';
 28             strcat(path,"e.txt");
 29 
 30             strindex[i].filename[8]= (char)(i+48);
 31             strindex[i].filename[9]= '\0';
 32         }
 33         else
 34         {
 35             j = strlen(path);
 36             path[j] = (char)(i/10+48);
 37             path[j+1] = (char)(i%10+48);
 38             path[j+2] = '\0';
 39             strcat(path,"e.txt");
 40 
 41             strindex[i].filename[8]= (char)(i/10+48);
 42             strindex[i].filename[9]= (char)(i%10+48);
 43             strindex[i].filename[10]= '\0';
 44 
 45         }
 46 
 47         fromfp = fopen(path,"r");
 48         if (i == 1)
 49         {
 50             to_datfp = fopen("article.dat", "w");
 51             indexfp = fopen("article.idx", "w");
 52         } 
 53         else
 54         {
 55             to_datfp = fopen("article.dat", "a");
 56             indexfp = fopen("article.idx", "a");
 57         }
 58 
 59         //获取插入到article.dat文件中的article-xe.txt文件的大小
 60         fseek(fromfp,0L,SEEK_END);
 61         len = ftell(fromfp);
 62         fseek(fromfp,0L,SEEK_SET);//将文件位置置为“文件开始位置”
 63 
 64         //更新索引表中strindex[i]文件的开始位置
 65         fseek(to_datfp,0L,SEEK_END);
 66         temp_dat_start = ftell(to_datfp);
 67         strindex[i].start = temp_dat_start;
 68 
 69         //拷贝article-xe.txt文件内容到article.dat文件中
 70         content=(char*)malloc(len+1);//动态申请“article-xe.txt”大小的空间
 71         memset(content,0,len+1);//置0
 72         fread(content,len,1,fromfp);//读
 73         fwrite(content,len,1,to_datfp);//写
 74         free(content);
 75 
 76         //更新索引表中strindex[i]文件的结束位置
 77         fseek(to_datfp,0L,SEEK_END);
 78         temp_dat_end = ftell(to_datfp);
 79         strindex[i].end = temp_dat_end;
 80 
 81         fwrite(&strindex[i],sizeof(struct index),1,indexfp);//将strindex[i]内容写入索引文件article.idx中
 82 
 83         fclose(fromfp);
 84         fclose(to_datfp);
 85         fclose(indexfp);
 86     }
 87 }
 88 void search(int num)
 89 {
 90     FILE *indexfp,*datafp;
 91     indexfp = fopen("article.idx","r");
 92     datafp = fopen("article.dat", "r");
 93     int i;
 94     for(i=num-1;i<num;i++)
 95     {
 96         fseek(indexfp,i*(sizeof(struct index)),SEEK_SET);
 97         fread(&strindex[i],sizeof(struct index),1, indexfp);
 98     }
 99     i--;
100     int length;
101     length = strindex[i].end-strindex[i].start;
102     char *content;
103     fseek(datafp,(strindex[i].start),SEEK_SET);//文件开始位置
104     content=(char*)malloc(length+1);//动态申请“article-1e.txt”大小的空间
105     memset(content,0,length+1);//置0
106     fread(content,length +1,1,datafp);//读
107     printf("%s",content);
108     free(content);
109 
110     fclose(datafp);
111     fclose(indexfp);
112 }
113 
114 int main()
115 {
116     int order;
117     BuildIndex();
118     printf("请输入要检索的文件序号（1~82）：");
119     while (scanf("%d",&order))
120     {
121         search(order);
122         printf("请输入要检索的文件序号（1~82）：");
123     }
124     system("pause");
125     return 0;
126 }

myself方法(改进版)：

使用sprintf()改进文件路径；

myself—better.cpp

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 
  5 struct index 
  6 {
  7     char filename[20];
  8     long start;
  9     long end;
 10 }strindex[83];
 11 
 12 void BuildIndex()
 13 {
 14     FILE *fromfp,*to_datfp,*indexfp; 
 15     long len,temp_dat_start,temp_dat_end;
 16     char *content;
 17     int i,j,temp;
 18     for (i=1; i<83; i++)
 19     {
 20         char path[100];
 21 
 22         sprintf(path,"data\\article-%de.txt",i);//myself改进
 23         sprintf(strindex[i].filename,"article-%de",i);//myself改进
 24 
 25         fromfp = fopen(path,"r");
 26         if (i == 1)
 27         {
 28             to_datfp = fopen("article.dat", "w");
 29             indexfp = fopen("article.idx", "w");
 30         } 
 31         else
 32         {
 33             to_datfp = fopen("article.dat", "a");
 34             indexfp = fopen("article.idx", "a");
 35         }
 36 
 37         //获取插入到article.dat文件中的article-xe.txt文件的大小
 38         fseek(fromfp,0L,SEEK_END);
 39         len = ftell(fromfp);
 40         fseek(fromfp,0L,SEEK_SET);//将文件位置置为“文件开始位置”
 41 
 42         //更新索引表中strindex[i]文件的开始位置
 43         fseek(to_datfp,0L,SEEK_END);
 44         temp_dat_start = ftell(to_datfp);
 45         strindex[i].start = temp_dat_start;
 46 
 47         //拷贝article-xe.txt文件内容到article.dat文件中
 48         content=(char*)malloc(len+1);//动态申请“article-xe.txt”大小的空间
 49         memset(content,0,len+1);//置0
 50         fread(content,len,1,fromfp);//读
 51         fwrite(content,len,1,to_datfp);//写
 52         free(content);
 53 
 54         //更新索引表中strindex[i]文件的结束位置
 55         fseek(to_datfp,0L,SEEK_END);
 56         temp_dat_end = ftell(to_datfp);
 57         strindex[i].end = temp_dat_end;
 58 
 59         fwrite(&strindex[i],sizeof(struct index),1,indexfp);//将strindex[i]内容写入索引文件article.idx中
 60 
 61         fclose(fromfp);
 62         fclose(to_datfp);
 63         fclose(indexfp);
 64     }
 65 }
 66 void search(int num)
 67 {
 68     FILE *indexfp,*datafp;
 69     indexfp = fopen("article.idx","r");
 70     datafp = fopen("article.dat", "r");
 71     int i;
 72     for(i=num-1;i<num;i++)
 73     {
 74         fseek(indexfp,i*(sizeof(struct index)),SEEK_SET);
 75         fread(&strindex[i],sizeof(struct index),1, indexfp);
 76     }
 77     i--;
 78     int length;
 79     length = strindex[i].end-strindex[i].start;
 80     char *content;
 81     fseek(datafp,(strindex[i].start),SEEK_SET);//文件开始位置
 82     content=(char*)malloc(length+1);//动态申请“article-1e.txt”大小的空间
 83     memset(content,0,length+1);//置0
 84     fread(content,length +1,1,datafp);//读
 85     printf("%s",content);
 86     free(content);
 87 
 88     fclose(datafp);
 89     fclose(indexfp);
 90 }
 91 
 92 int main()
 93 {
 94     int order;
 95     BuildIndex();
 96     printf("请输入要检索的文件序号（1~82）：");
 97     while (scanf("%d",&order))
 98     {
 99         search(order);
100         printf("请输入要检索的文件序号（1~82）：");
101     }
102     system("pause");
103     return 0;
104 }