Thread: File I/O: Offsetting file pointer (fp) using fseek

Hello forum.

I have an issue with a program supposed to take in a user input for a file name, open it, read its contents and finally output the function name(s) and how many source lines of code (for this program, only legitimate semi-colons).

This is an example of a .txt file with a snippet of C code.

Code:

void fillAnArray(int a[]) 
BEGIN_FCN  
 int i, j; 
 fill = -3;  /* comment; <- uncounted semi-colon */ 
 for( i = 0, j=2; i < sizeof(a); i++, j--) 
   a[i] =  i + j * fill;    /* of course ; a 
  comment may be a number of 
  lines; pages, etc etc */ 
 printf (“stuff;”);
 return;
END_FCN

successfully, it should output 7 SLOCs, due to 7 counted semi-colons excluding comments.

This is my code so far. It isn't very far, but I have an issue right from the get go.

Code:

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

#define BEGIN_FCN {
#define END_FCN }
#define MAX 1000

#define INPUT_FILE "example.txt"

int main(void)
{
    char fileName[MAX];
    char str [MAX];
    int begin, end;
    int filePrev, fileCur;
    int *c, temp1, temp2, length1, length2;



    FILE *fp;
    printf ("Enter the file name to open: ");
    gets(fileName); /* get the file name from stdin */
    fp = fopen(fileName, "r");
    if (fp == NULL)
    {
        do
        {
            printf("\nFile %s could not be opened\n", fileName);
            printf ("Enter the file name to open: ");
            gets(fileName); /* get the file name from user */
            fp = fopen(fileName, "r");
        }
        while (fp == NULL);
    }
    printf("\bFile %s is successfully opened\n\n", fileName);
    /* perform desired read operations from the file in here */

    while (!feof(fp))
    {
        fgets(str, MAX, fp);
        printf("%s", str);
    }

    fseek(fp, 0, SEEK_SET);
    filePrev = fseek(fp, 0, SEEK_SET);

while (!feof(fp))
    {
        fgets(str, MAX, fp); //Get current string
        printf("%s\n", str);
        temp1 = strstr(str, "BEGIN_FCN"); //Check if BEGIN_FCN is in string
        temp2 = strstr(str, "END_FCN"); //Check if END_FCN is in string
      if (temp1 != 0)
        {
            fseek(fp, 0, SEEK_CUR); //Function name is in the line before
            fgets(str, MAX, fp); //String containing function name
            printf("%s\n", str);
            //fseek(fp, line2, SEEK_SET);
            temp1 = strchr(str,'(');
        }
    }
    printf("\n\nComplete couting SLOC of %s", fileName);
    fclose(fp);
    getchar();
    return 0;
}

My issue is after finding the BEGIN_FCN which replaces the { and the END_FCN which replaces the } of functions, finding the proper offset for fseek(fp, offset, SEEK_CUR); so it aims at the beginning of the string right above BEGIN_FCN, which is the string that contains the name of the function.

I want to get the name of the function, and find how many SLOCs there are inside.

It works for this time because if the offset is 0, it is at the start of the file which is already the beginning of the proper string.

Would I use strlen to find the lengths of the line with the function, then the line I read afterwards ("BEGIN_FCN" or "{") then subtract how much from the current fp to end up at the start of the proper string?

Originally Posted by quzah

You don't generally fseek on text files due to the way different OSs treat newlines. You would be better off reading each line into memory, and figuring out what you need to do from there.

Code:

while( fgets() != NULL )
    if strstr buf, "BEGIN_FNC"
        while( fgets() ... same as above )
            if strstr buf, "END_FNC"
                break from the loop you are done with this function
            else
                add to your line counter or whatever you are doing
        do whatever it is with your function length you just got

Quzah.

Wait, so I wouldn't need to use fseek?

How would I be able to retrieve the file name which is the string abouve BEGIN_FCN?

Originally Posted by quzah

That depends. You could store the whole file in a linked list, one line per node, or you could just use two buffers, one for current line and one for last line. When you read in a new line if it matches what you need, then last line should be your function name. If it isn't what you need, then current line becomes last line, and you read a new current line.


Quzah.

Ok. I used two buffers and if BEGIN_FCN is found in the 2nd buffer, the function name is in the 1st buffer.

How would I approach getting the name?

it could be in the form of...

Code:

void main()
void /*comment*/ main                    ()
void /**/ main /**/

and etc

Would using strtok be useable? I can output by using strtok and splitting the string, but how would you be able to store the actual string section that contains the name?