deleting ifstream line

**jed** · 10-24-2006

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?

**Daved** · 10-24-2006

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.

**maxorator** · 10-25-2006

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;
}

**Daved** · 10-25-2006

Unfortunately it isn't legal C++.

**maxorator** · 10-25-2006

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;
}

**Daved** · 10-25-2006

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

**maxorator** · 10-26-2006

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;
}

**Daved** · 10-26-2006

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.

**vart** · 10-26-2006

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;
}

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