c - 使用 sscanf 解析不会保留数组以供后续使用

Question

我正在开发一个模拟 n 路关联缓存映射的项目。然而，当尝试在后续方程中使用 address[i] 数组时，就会出现问题。我想我不明白为什么不保留数组。任何帮助将非常感激。我不是最擅长 C 编码的。现在的问题是从文件中读取并将这些值扫描到数组中。其他一切我相信我都能弄清楚。

代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>


/*global variables */
int mainSize, cacheSize, blockSize, cmSet, cnumBlocks, mnumBlocks,address[50],mmBlkNum[50], mappedCMset[50],hit_miss[50],address[50];
char mode[50];
int totMemRefs=0;


int main(void)
{
    /*Variables */

    int i;
    char replacePolicy;
    char filename[50];
    char *result = NULL;
    char line[50];
    FILE *fp;
    fp = fopen(filename, "r");


    /*Gathers input from user */
    printf("Enter the main memory size between between 4 and 32K bytes: ");
    scanf("%d",&mainSize);
    if (mainSize < 4 || mainSize > 32768)
    {
        printf("Invalid main memory size.");
        //errorCheck()
    }

    printf("Enter the size of the cache between 2 and 32K bytes: ");
    scanf("%d", &cacheSize);
    if (cacheSize < 2 || cacheSize > 32768)
    {
        printf("Invalid cache memory size.");
        //errorCheck()
    } 


    printf("Enter the size of the block/line between 2 and 32K bytes: ");
    scanf("%d",&blockSize);
    if (blockSize < 2 || blockSize > 32768)
    {
        printf("Invalid block/line size.");
        //errorCheck
    }

    printf("Enter the degree of set-associativity: ");
    scanf("%d", &cmSet);


    cnumBlocks = cacheSize/blockSize;
    printf("Number of blocks in cache = %d\n", cnumBlocks);

    mnumBlocks = mainSize/blockSize;
    printf("Number of blocks in main memory = %d\n", mnumBlocks);

    printf("Enter replacement policy (L = LRU, F = FIFO): ");
    scanf("%s", &replacePolicy);




    printf("Enter the name of the file containing the list of memory    referenced: ");
    scanf("%s", filename);


    /* checks if filename is valid/exits */
    if ((fp = fopen(filename, "r")) == NULL)
    {
        printf("Invalid input.");
        //errorCheck();
    }

    /* gets total number of mem references from first line of file and stores in variable totMemRefs*/
    fgets(line,sizeof(line),fp);
    result = strtok(line,"\n");
    totMemRefs = atoi(result);
    printf("Total Mem Refs = %d\n", totMemRefs);


    /*skips second line of white space */
    fgets(line, sizeof(line),fp);

    i=0;
    //reads each line of file and tokenizes into mode and address
    while (fgets(line, sizeof(line), fp)!=NULL)
    {

        if (sscanf(line,"%s %d",&mode[i],&address[i]) == 2)
        {
            printf("Mode: %c  Address: %d\n",mode[i],address[i]);
            i++;
        }


    }//end of parsing while loop

    fclose(fp); //close file after reading


    for (i=0; i<totMemRefs; i++)
    {
        /* calculates the corresponding block number of the address */
        mmBlkNum[i]=address[i]/blockSize;

        /* calculates the corresponding cache mem set that mm block is in */
        mappedCMset[i]=mmBlkNum[i]%cnumBlocks;
        printf("Mode = %c  Address = %d  MM Block Num = %d  Cm Set = %d\n",    mode[i],address[i],mmBlkNum[i],mappedCMset[i]);

    }

}//end of main

这是 example_test_data.txt 的内容:

6

R 0
R 1
R 4
R 36
R 0
R 4

以下是主存储器和高速缓冲存储器的特性:

main mem size = 128 bytes
cache mem size = 32 bytes
block size = 4 bytes
set associativity = 2
filename = example_test_data.txt  

这是 while 循环中数组的输出:

    Mode: R  Address: 0
    Mode: R  Address: 1
    Mode: R  Address: 4
    Mode: R  Address: 36
    Mode: R  Address: 0
    Mode: R  Address: 4

这是解析后数组的输出 - 在以下 for 循环中:

    Mode = R  Address = 4  MM Block Num = 1  Cm Set = 1
    Mode =    Address = 0  MM Block Num = 0  Cm Set = 0
    Mode =    Address = 0  MM Block Num = 0  Cm Set = 0
    Mode =    Address = 0  MM Block Num = 0  Cm Set = 0
    Mode =    Address = 0  MM Block Num = 0  Cm Set = 0
    Mode =    Address = 0  MM Block Num = 0  Cm Set = 0

如您所见，模式和地址数组的第二次迭代与文件 while 循环中的不同。我很困惑为什么会出现这种情况。我尝试尽可能地进行描述。我也不知道为什么格式没有显示。抱歉，如果这会使阅读变得更加困难。再次强调，任何帮助或插入正确的方向将不胜感激!

编辑:输出应该是:

    Mode = R   Address = 0   MM Blk Num = 0   CM Set = 0
    Mode = R   Address = 1   MM Blk Num = 0   CM Set = 0
    Mode = R   Address = 4   MM Blk Num = 1   CM Set = 1
    Mode = R   Address = 36  MM Blk Num = 9   CM Set = 1
    Mode = R   Address = 0   MM Blk Num = 0   CM Set = 0
    Mode = R   Address = 4   MM Blk Num = 1   CM Set = 1

我知道获得正确值所需的方程式。我知道如何手工处理这些，没问题。因此，知道结果应该是什么并不是问题。以前，我使用过 fscanf 和 strtok，但它们都没有产生预期的结果。基本上，当我在扫描时在 while 循环中打印它时，它可以工作，但是一旦我尝试计算 mmBlkNum 和mappedCMset，数组中的值就不同了。

代码已更新!

Answer 1

我看到的第一个错误:

scanf("%s", &filename);

替换为正确的参数:

scanf("%s", filename);

请使用-Wall进行编译，这样编译器就会说出这些内容。与-Werror结合使用。还推荐-Wextra。

我的编译器与您的程序的输出:

stackoverflow.c: In function 'main':
stackoverflow.c:246:11: error: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[50]' [-Werror=format=]
     scanf("%s", &filename);
           ^
cc1.exe: all warnings being treated as errors

我看到的第二个错误:您将所有读取的内容放在 while 循环中的同一索引 i = 0 处。正确使用 for 或使用 while:

    i = 0;
    while (fgets(line, sizeof(line), fp)!=NULL && i < totMemRefs)
    {
        if (sscanf(line,"%s %d",&mode[i],&address[i]) == 2)
        {
            printf("Mode: %c  Address: %d\n",mode[i],address[i]);
            i++;
        }


    }//end of parsing while loop

    if (i < totMemRefs)
    {
        fprintf(stderr, "Missing inputs.\n");
        return 1;
    }

我还添加了验证输入不超出用户所说的将提供的输入数量，并且验证用户提供所有行。考虑在程序开头添加类似的内容:

#define MAX_INPUT_LINES 50

并使用MAX_INPUT_LINES而不是50。