size of buffer

This is a discussion on size of buffer within the C Programming forums, part of the General Programming Boards category; I'm asking for a stream of numbers and want to store each number in an array. The number of #'s ...

  1. #1
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    size of buffer

    I'm asking for a stream of numbers and want to store each number in an array. The number of #'s is variable, so I want to check how many #'s a user has entered so I can allocate the necessary amount of memory for my array.

    Thanks

  2. #2
    Banned master5001's Avatar
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    You can either allocate a lot of memory and shoot for the best, or create a queue if you need to be more exact.

  3. #3
    Jack of many languages Dino's Avatar
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    You can't put the cart before the horse. You have to plan in advance for some number of responses, and then act accordingly when that number is exceeded. That number could be 1 or 50 million - you don't know. My point being is that whatever you choose, when you get one more response than you planned for, you'll have to regroup.

    The lazy person's choice might be to plan for 100 responses. If that or fewer are received, you are done. If more than 100 are received, then you'll need to pull out the heavy artillery and get some storage from the heap and create a new array that is larger than your initial pick (by some degree larger - you're choice).

    Another way might be to get a hunk of heap from the get-go, and instead of defining it as an array, just treat it as an array, and when it's not big enough any more, realloc() that hunk to some amount larger than the first, and keep going with adding more entries.
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    Mmm.. makes sense, but how do I know I've read all the entries?

    for instance:

    numbers: 1 2 3 4 5 6 7 8

    code:
    a loop?...
    scanf("%d", store in array);
    ...

    How do I know when to stop?

    Thanks

  5. #5
    Jack of many languages Dino's Avatar
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    The read routine you use will set the EOF (end of file) indicator, and you will test it and act accordingly.
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
    12/20: Mario F.:I never was, am not, and never will be, one to shut up in the face of something I think is fundamentally wrong.

    Amen brother!

  6. #6
    Banned master5001's Avatar
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    The queue idea that I mentioned would be something more like:

    Example:
    Code:
    #include <stdlib.h>
    
    struct item
    {
      int value;
      struct item *next;
    };
    
    int push(struct item **q, int value)
    {
      struct item *node = malloc(sizeof(*node)), *tmp;
    
      if(!node)
        return EXIT_FAILURE;
    
      node->value = value;
      node->next = 0;
    
      if(*q)
      {
        for(tmp = *q; tmp->next; tmp = tmp->next)
          ;
        tmp->next = node;
      } else
        *q = node;
    
      return EXIT_SUCCESS;
    }
    
    int pop(struct item **q, int *r)
    {
      struct item *tmp;
    
      if(!r || !q)
        return EXIT_FAILURE;
    
      if(!*q)
        return EXIT_FAILURE;
    
      tmp = *q;
      *q = (*q)->next;
      *r = tmp->value;
      free(tmp);
      
      return EXIT_SUCCESS;
    }
    
    int main(int argc, char **argv)
    {
      struct item *q = 0;
      int i;
    
      for(i = 1; i < argc; i++)
        push(&q, atoi(argv[i]);
    
      while(pop(&q, &i) == EXIT_SUCCESS)
        printf("&#37;d ", i);
    
     return EXIT_SUCCESS;
    }
    Last edited by master5001; 10-28-2008 at 01:12 PM.

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    Great, thanks

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    I dunno who that was directed at, but I will give it to you, Todd. You were a little more distinct than I was on this one.

  9. #9
    Jack of many languages Dino's Avatar
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    Let's give it to Salem. I think Salem needs it.
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
    12/20: Mario F.:I never was, am not, and never will be, one to shut up in the face of something I think is fundamentally wrong.

    Amen brother!

  10. #10
    Banned master5001's Avatar
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    True. Salem takes more crap than any of us. Todd, did you read the post within my link. I am so going to reference it everytime someone gets overly frustrated. At least I got that particular student's attitude turned around.

  11. #11
    Jack of many languages Dino's Avatar
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    I wish somedays I could just "give up" on a problem I'm working on at work!!
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
    12/20: Mario F.:I never was, am not, and never will be, one to shut up in the face of something I think is fundamentally wrong.

    Amen brother!

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