deleting ifstream line

This is a discussion on deleting ifstream line within the C++ Programming forums, part of the General Programming Boards category; hello, I have a scanner that I need to tweak. This one section scans a line and I need it ...

  1. #1
    jed
    jed is offline
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    deleting ifstream line

    hello,
    I have a scanner that I need to tweak. This one section scans a line and I need it to delete what ever it takes in if its between the comment sign. { delete this}. here is the block of code that I messing with.

    Code:
     
    else if( ch == '{' ) 
        {
           ch = rfile.get();
           tokenIndex = 0;
           while(ch != '}' && ! rfile.eof () )
           {
             tokString[ tokenIndex ++ ] = ch;
             ch = rfile.get();
           }
           tokString [ tokenIndex ] = 0;
           ch = rfile.get(); 
           currentToken = OUTPUT;
        }
    Is there a get and delete in ifstream? I couldn't find anything online. can I set "ch" to null?

  2. #2
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    Do you mean you want to delete it from the file, or delete it from your string representation. You can't exactly delete it from the file without reading in the entire file and then writing it back out except for the parts you don't want. I don't think that's what you want to do here, though.

    It looks like all you need to do is ignore the text you want to "delete". Just don't add it to tokString or whatever you are doing with it. You could just keep calling rfile.get() until you reach the closing brace without the rest of the code.

  3. #3
    Reverse Engineer maxorator's Avatar
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    This function removes bracketed things from buffers
    Code:
    char* delquotes(char* source,int szsource){
        char temp[szsource];
        int tempc=0;
        bool del=false;
        for(int i=0;source[i]!='\0';i++){
            if(source[i]=='{'&& !del){
                del=true;
            }
            else if(del==false){
                temp[tempc]=source[i];
                tempc++;
            }
            if(source[i]=='}' && del){
                del=false;
            }
        }
        temp[tempc]='\0';
        strcpy(source,temp);
        return source;
    }
    "The Internet treats censorship as damage and routes around it." - John Gilmore

  4. #4
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    Unfortunately it isn't legal C++.

  5. #5
    Reverse Engineer maxorator's Avatar
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    Why?
    You don't like strcpy?
    Fine, I'll replace it:
    Code:
    char* delquotes(char* source,int szsource){
        char temp[szsource];
        int tempc=0,n;
        bool del=false;
        for(int i=0;source[i]!='\0';i++){
            if(source[i]=='{'&& !del){
                del=true;
            }
            else if(del==false){
                temp[tempc]=source[i];
                tempc++;
            }
            if(source[i]=='}' && del){
                del=false;
            }
        }
        temp[tempc]='\0';
        for(n=0;temp[n]!='\0';n++){
            source[n]=temp[n];
        }
        source[n]='\0';
        return source;
    }
    Last edited by maxorator; 10-25-2006 at 10:06 AM.
    "The Internet treats censorship as damage and routes around it." - John Gilmore

  6. #6
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    strcpy is fine and completely legal in C++. I was referring to the non-constant array sizes.

  7. #7
    Reverse Engineer maxorator's Avatar
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    Code:
    char* delquotes(char* source,int szsource){
        char *temp=new char[szsource];
        int tempc=0,n;
        bool del=false;
        for(int i=0;source[i]!='\0';i++){
            if(source[i]=='{'&& !del){
                del=true;
            }
            else if(del==false){
                temp[tempc]=source[i];
                tempc++;
            }
            if(source[i]=='}' && del){
                del=false;
            }
        }
        temp[tempc]='\0';
        for(n=0;temp[n]!='\0';n++){
            source[n]=temp[n];
        }
        source[n]='\0';
        delete[] temp;
        return source;
    }
    "The Internet treats censorship as damage and routes around it." - John Gilmore

  8. #8
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    Usually functions that take a C style string and a size assume that the size is the size of the string, not the size of the array. If you are going to do something different you should make it clear in a comment at the very least.

  9. #9
    CSharpener vart's Avatar
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    And better to test that there is no buffer overrun.

    Mpreover - you don't need the temp string everithing can be done inplace

    Code:
    char* remove(char* stringSrc, char char2remove)
    {
       char* src = stringSrc;
       char* dst = stringSrc;
       while(*src)
       {
          if(*src == char2remove)
             src++;
          else
          {
             if(src != dst)
             {
                *dst = *src; 
             }
             dst++;
             src++;
          }
       }
       *dst = 0;
       return stringSrc;
    }
    Last edited by vart; 10-26-2006 at 03:03 PM.

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