Thread: code review request: stack implementation

  1. #1
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    code review request: stack implementation

    I'm looking for some input on my stack implementation. Anything goes -- style, structure, functionality. Anything I should have done differently?

    stack.h
    Code:
    #include <stdio.h>
    
    typedef int stackElementT;
    
    typedef struct {
    
      stackElementT *contents;
      int size;
      int count;
    
    } stackT;
    
    void STACKinit(stackT *stack, unsigned int);
    void STACKpush(stackT *stack, int value);
    int STACKpop(stackT *stack);
    void STACKempty(stackT *stack);
    stack.c

    Code:
    #include <stdio.h>                                               
    #include <stdlib.h>                                              
    #include "stack.h"                                               
    
    void                                                             
    STACKinit(stackT *stack, unsigned int size) {
      
      stack->contents = malloc(sizeof(stackElementT) * size);        
      stack->size = size;                                            
      stack->count = 0;                                              
                                                                     
    }
    
    void                                                             
    STACKpush(stackT *stack, const stackElementT value) {            
                                                                     
      if (stack->count >= stack->size) {
        
        fprintf(stderr, "Cannot push onto a full stack.\n");         
        exit(1);                                                     
                                                                     
      }
                                                                     
      stack->contents[stack->count++] = value;                       
                                                                     
    }
    
    stackElementT                                                    
    STACKpop(stackT *stack) {
                                                                     
      if (stack->count <= 0) {
        
        fprintf(stderr, "Cannot pop off empty stack.\n");            
        exit(1);                                                     
                                                                     
      }
                                                                     
      return stack->contents[--stack->count];                        
                                                                     
    }
    
    void 
    STACKempty(stackT *stack) {                                      
      STACKinit(stack, stack->size);                                 
    }

  2. #2
    Hurry Slowly vart's Avatar
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    I do not see why your header file needs
    #include <stdio.h>

    you should check the malloc return
    exit is too harsh way of notifying the caller that he did something wrong - better return error code

    You do not provide function that will free allocated memory
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  3. #3
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    Quote Originally Posted by vart View Post
    exit is too harsh way of notifying the caller that he did something wrong - better return error code
    How would you do this with functions that already have a return type, i.e. STACKpop?

    You do not provide function that will free allocated memory
    How is this typically done?

  4. #4
    Woof, woof! zacs7's Avatar
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    A few things, some personal

    * the function names are a little 'odd' and hard to read. stackPop() or stack_pop() would be nicer to use IMO.
    * --stack->count I'd use parenthesis to avoid operator precedence... just me --(stack->count). Same for stack->count++ -- I find (stack->count)++ easier to read.
    * use inclusion guards in stack.h
    * no free()?
    * STACKinit(stackT *stack, unsigned int size)... consider using 'size_t size' instead of 'unsigned int size'.
    * Check malloc doesn't return NULL before proceeding.

    EDIT:

    > How would you do this with functions that already have a return type, i.e. STACKpop?
    Return something that isn't going to occur -1 for example. Or, give it a success flag (example)... Or put the stackElement as an arg
    Code:
    stackElementT STACKpop(stackT * stack, int * result)
    {
        if(stack->count <= 0)
        {
            fprintf(stderr, "Cannot pop off empty stack.\n");
            *result = 1;
            /* garbage */
            return 0;                                                    
        }
        
        *result = 0;
        return stack->contents[--stack->count];                        
    }
    Then you'd only use the return value if result == 0.

    > How is this typically done?
    Code:
    ptr = malloc(blah);
    
    /* use ptr */
    
    free(ptr);
    Last edited by zacs7; 02-24-2008 at 03:49 AM.

  5. #5
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    Thanks for reviewing!

    Quote Originally Posted by zacs7 View Post
    * use inclusion guards in stack.h
    What do you mean?

  6. #6
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    Quote Originally Posted by cs32 View Post
    Thanks for reviewing!



    What do you mean?
    http://en.wikipedia.org/wiki/Include_guard

  7. #7
    Woof, woof! zacs7's Avatar
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