c - 读取简单数据声明并响应分配给该变量的内存量的程序

Question

我编写了一个程序，它读取简单的数据声明并返回分配给该变量的内存量。

每个输入行应包含 - 一个类型名称，它必须是以下之一:char、int、short、long、float 或 double。 - 一个或多个单独的声明规范，以逗号分隔。 - 标记行尾的分号。

在我的代码中，我还添加了对文件的使用(见下文)。

我想问你如何使用 sizeof 代替我对要分配的数据类型的大小进行编码的方式。我也想问你我在文件中的使用是否正确。

#define _CRT_SECURE_NO_WARNINGS

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

void bytesPerValue(char str[], char* filename) ;
int theSizeOf(char *str);
 int strToNumber(char *str);

void main()
{
     char str[50];

     gets(str);

     bytesPerValue(str,"input.txt");

}

void bytesPerValue(char str[], char* filename) 
{
        int i = 0, j = 0;
        int temp = 1;
        int size;
        char* tempChar = (char*)malloc((strlen(str))*sizeof(tempChar));
        FILE *f=fopen(filename,"w");
        if (f==NULL)
            exit(1);
        while (str[i]!=' ' || str[i]=='*') //checking the type of the variables//
        {
                tempChar[j] = str[i];
                i++;
                j++;   
        }
        tempChar[j] = '\0';
        size = theSizeOf(tempChar);
        j = 0;
        i++;
        while (str[i] != ';')
        {

                if (isalpha(str[i]) || str[i]=='_') // for  variables and arrays//
                {
                        while (str[i] != ',' && str[i] != ';') //runs until ', ' or '; ' //
                        {
                                if (str[i]==' ')
                                {
                                        while (str[i]==' ')
                                                i++;
                                }

                                if (str[i] == '[') //checks if it is array//
                                {
                                        printf("%c", str[i]);
                                        i++;
                                        while (str[i] != ']')
                                        {
                                                tempChar[j] = str[i]; //copies the value in the string//
                                                i++;
                                                j++;
                                        }

                                        tempChar[j] = '\0';
                                        temp = strToNumber(tempChar); //converting to number in order to valuate the bytes//
                                }
                                printf("%c", str[i]);
                                i++;

                                if (isspace(str[i]))
                                {
                                        while (isspace(str[i]))
                                                i++;
                                }
                        }
                        fprintf(f," requires %d bytes \n", temp*(sizeof(temp)));
                }


                if (str[i] == '*') //for pointers//
                {
                        while (str[i] != ',' && str[i] != ';')
                        {
                                printf("%c", str[i]);
                                i++;
                                if (str[i]==' ')
                                {
                                        while (str[i]==' ')
                                                i++;
                                }
                        }
                        fprintf(f," requires %d bytes \n", 4);
                }
                if (str[i] != ';')
                        i++;
        }

 fclose(f);
}

int theSizeOf(char* str) // checking the size of the variable
{
        if (strcmp(str, "int")==0 || strcmp(str, "long")==0 || strcmp(str, "float")==0)
                return 4;
        else if (strcmp(str, "char")==0)
                return 1;
        else if (strcmp(str, "double")==0)
                return 8;
        else if (strcmp(str, "short")==0)
                return 2;
        else 
            return 0;
}


int strToNumber(char* str) //converting the string to number//
{
        int temp=1;
        int num=0;
        int t;
        int i;
        int length = strlen(str);
        for (i = length-1; i >= 0; i--)
        {
                t = str[i] - '0';
                num += t * temp;
                temp *= 10;
        }
        return num;
} 

Answer 1

how can I use sizeof instead the way I coded the size of data types to be allocated?

size_t theSizeOf(const char* str) {
  if (strcmp(str, "char"  )==0) return sizeof(char);
  if (strcmp(str, "short" )==0) return sizeof(short);
  if (strcmp(str, "int"   )==0) return sizeof(int);
  if (strcmp(str, "long"  )==0) return sizeof(long);
  if (strcmp(str, "float" )==0) return sizeof(float);
  if (strcmp(str, "double")==0) return sizeof(double);
  return 0;
}

或者使用数组

size_t theSizeOf(const char* str) {
  const struct {
    const char *type;
    size_t size;
  } types[] =  {
     {"char", sizeof(char) },
     {"int", sizeof(int) },
     // Add others as needed.
     {"double", sizeof(double) },
  };
  for (size_t i=0; i< sizeof types /sizeof types[0]; i++) {
     if (strcmp(str, types[i].type)==0) return types[i].size;
  }
  return 0;
}

---

I also would like to ask you whether my use in file is right.

很多问题比如

    // No need for cast
    // buffer allocation 1 too short
    // wrong sizeof argument
    char* tempChar = (char*)malloc((strlen(str))*sizeof(tempChar));
    // instead use
    char* tempChar = malloc(strlen(str) + 1);

    // potential infinite loop as code does not check for null character
    while (str[i]!=' ' || str[i]=='*') {
      ...

    // Does not handle negative numbers nor overflow of `temp`.
    strToNumber()