help can't find a way to make this work

This is a discussion on help can't find a way to make this work within the C Programming forums, part of the General Programming Boards category; hi, I'm doing a very simple program in which I want to remove comments from a .c file, so I ...

  1. #1
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    help can't find a way to make this work

    hi, I'm doing a very simple program in which I want to remove comments from a .c file, so I started with something simple and tried to make a program that changed ' ' to a '.' except that I can't make it work, every time the program finds a ' ' it ends the search cycle and the '.' is somehow written at the end of the file. :S It must have a very simple solution please help.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    FILE *file;
    int o = 1;
    
    void time()
    {
    	int i;
    	for(i=0; i<10000000; i++);
    }
    
    
    void commentremover(FILE *tmp)
    {
    	char o;
    	int i = 0;
    	char input[] = ".";
    	//FILE *tmp2;
    	//tmp2=tmp;
    	while((o=fgetc(tmp)) != EOF)
    	{
    	if(o=='\n')
    	{
    		printf(" %d \t:*LF*:\n", i , o);
    	}
    	else
    	{
    		if(o=='\x0D')
    		{
    			printf(" %d \t:*CR*:\n");
    		}
    		else
    		{
    			if(o==' ')
    			{
    				fwrite(input,1,1,tmp);
    			}
    			else
    			{
    			printf(" %d \t:%c:\n", i , o);
    			}
    		}
    	}
    	i++;
    	fflush(stdout);
    	}
    }
    
    void printer(FILE *tmp)
    {
    	char o;
    	o = fgetc(tmp);
    	while(o != EOF)
    	{
    		time(1);
    		printf("%c", o);
    	o = fgetc(tmp);
    	}
    }
    
    int main()
    {
    	file = fopen("out.txt", "r+");
    	commentremover(file);
    	return 0;
    }

    edit: The printf sequence is part of the 'seach throu the file bit' they will be removed after I get the writing working
    Last edited by Pe6r0; 12-02-2006 at 03:07 PM.

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    Code:
    char o;
    /* ... */
    while((o=fgetc(tmp)) != EOF)
    EOF is an int value, and as such should be stored in an int.

    Calling a function time() is a bad idea, because there's a function of the same name in the standard library. In any rate, your time() function takes no parameters, so passing it one as printer() does is a bad idea.
    Code:
    time(1);
    In between reads and writes of a FILE* file, you need to fflush() it. fflush(file), not fflush(stdout).
    dwk

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  3. #3
    and the hat of wrongness Salem's Avatar
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    Read up on finite state machines.

    You basically have two states
    - in a comment
    - not in a comment.

    You also have two transitional states
    - entering a comment
    - leaving a comment.

    You decide these things based on finding a / followed by a * and a * followed by a /
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  4. #4
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    thanks for all the input ppl! it helped a lot

  5. #5
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    well I did do a fflush of the file between read and write but the end result was the same. I keep getting the stuff written at the end only

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    FILE *file;
    
    void commentremover(FILE *tmp)
    {
    	char o;
    	int i = 0;
    	char input[] = ".";
    	while((o=fgetc(tmp)) != EOF)
    	{
    	if(o=='\n')
    	{
    		printf(" %d \t:*LF*:\n", i , o);
    	}
    	else
    	{
    		if(o=='\x0D')
    		{
    			printf(" %d \t:*CR*:\n");
    		}
    		else
    		{
    			if(o==' ')
    			{
    				fflush(tmp);
    				fopen("out.txt", "r+");
    				fwrite(input,1,1,tmp);
    			}
    			else
    			{
    			printf(" %d \t:%c:\n", i , o);
    			}
    		}
    	}
    	i++;
    	fflush(stdout);
    	}
    }
    
    int main()
    {
    	file = fopen("out.txt", "r+");
    	commentremover(file);
    	return 0;
    }

    I havent reached the part of recognizing a comment yet since my first task would be to succesfully identify a character and substitute it for any other.

    Code:
    			if(o==' ')
    			{
    				fflush(tmp);
    				fopen("out.txt", "r+");
    				fwrite(input,1,1,tmp);
    			}
    EDIT: reseting the pointer tmp seems like a bad ideia since we do need to know where in the file we need to write. So I dropped that ideia. Any other thoughts? I also used fputc which produced the same result. I read the help files (man) on both functions and since I'm not using append mode the only other reason that comes to mind would be that something goes wrong with the writing (fputc writes in append mode when that happens). The ideia of this test part would be to substitute the spaces with dots in a .txt file. I also made some printf to monitor the advance of the search across the file (it stops at the first space)

    out.txt:
    Code:
    Beggining of the file
    Second line
    
    /* comment one */
    
    // line comment
    
    END OF FILE
    I get at stout (after I disregard the fflush and the fopen):

    0 :B:
    1 :e:
    2 :g:
    3 :g:
    4 :i:
    5 :n:
    6 :i:
    7 :n:
    8 :g:

    and ends there
    Last edited by Pe6r0; 12-02-2006 at 08:39 PM.

  6. #6
    CSharpener vart's Avatar
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    Code:
    if(o==' ')
    			{
    				fflush(tmp);
    				fopen("out.txt", "r+");
    				fwrite(input,1,1,tmp);
    			}
    What does the selected line do here?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  7. #7
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    As I said I already disregarded the second fopen (it was suggested earlier) that line is now:

    Code:
    			if(o==' ')
    			{
    			fwrite(input,1,1,tmp);
    			}

  8. #8
    Registered User ssharish2005's Avatar
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    did you see Salems post. It gives u the basic idea of what to do and how to approch.

    1. loop around the file reading each char
    2. check is that char read is '/' if so check for next char read is '/' if so then just discard the line which mean that line is been commented.

    this methods is for the // commenting method. Try solving this problem first

    ssharish2005

  9. #9
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    I did read it My plan is to make a program that searches throu the comments AND removes them. The searching part is easy since I already have the program searching for specific characters. My problem is that I can't write where I want! that program writes always at the end and exits the cycle when I find a "key" character

  10. #10
    CSharpener vart's Avatar
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    My problem is that I can't write where I want
    REad all file into buffer long enogh
    Modify the buffer in the memory
    Write the resulting buffer to the disk
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  11. #11
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    THANKS! I never even thought about it in that way

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