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2019 mateusz.vi 1 
/*
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 *  STACK.C - Stack management functions.
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 *  Written 1995,96 by Andrew Clarke and released to the public domain.
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 *
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 *  Slightly modified for inclusion in pdTree
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 *  by Jeremy Davis <jeremyd@computer.org> Jan. 2001
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 */
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#include <stdlib.h>  // for malloc
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#include "stack.h"
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// initialize stack structure to known initial values.
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void stackDefaults(STACK * p_stack)
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{
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    p_stack->p_top = NULL;
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    p_stack->items = 0L;
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}
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#if defined __BORLANDC__ || __TURBOC__
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#pragma argsused
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#endif
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// place any extra stack initialization here
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void stackInit(STACK * p_stack)
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{
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}
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// ensures stack is empty and all allocated memory freed
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void stackTerm(STACK * p_stack)
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{
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    while (!stackIsEmpty(p_stack))
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    {
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        stackPopItem(p_stack);
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    }
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}
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// add an item to the stack, allocating memory for STACKNODE
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int stackPushItem(STACK * p_stack, void *p_item)
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{
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    STACKNODE *p_node;
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    p_node = malloc(sizeof(STACKNODE));
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    if (!p_node)
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        return 0;
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    p_node->p_item = p_item;
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    if (!p_stack->p_top)
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        p_node->p_prev = NULL;
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    else
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        p_node->p_prev = p_stack->p_top;
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    p_stack->p_top = p_node;
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    p_stack->items++;
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    return 1;
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}
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// removes item from the stack, freeing memory allocated for STACKNODE
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void *stackPopItem(STACK * p_stack)
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{
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    void *p_item;
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    STACKNODE *p_node;
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    if (!p_stack->items)
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        return NULL;
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    p_item = p_stack->p_top->p_item;
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    p_node = p_stack->p_top;
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    p_stack->p_top = p_stack->p_top->p_prev;
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    free(p_node);
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    p_stack->items--;
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    return p_item;
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}
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// returns the current size of (items on) the stack
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unsigned long stackTotalItems(STACK * p_stack)
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{
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    return p_stack->items;
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}
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// returns true if the stack is empty, nonzero otherwise
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int stackIsEmpty(STACK * p_stack)
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{
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    return p_stack->items == 0;
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}
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/*
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 *  The rest of this file is a sample program to show how
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 *  to use the stack functions and also to test the stack functions.
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 *
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 */
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#ifdef TEST_STACK
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#include <stdio.h>
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int main(void)
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{
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    STACK p_stack;
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    char *str;
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    stackDefaults(&p_stack);
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    stackInit(&p_stack);
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    stackPushItem(&p_stack, "One banana");
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    stackPushItem(&p_stack, "Two banana");
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    stackPushItem(&p_stack, "Three banana");
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    stackPushItem(&p_stack, "Four banana");
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    stackPushItem(&p_stack, "Five banana");
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    str = stackPopItem(&p_stack);
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    while (str)
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    {
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        printf("%s\n", str);
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        str = stackPopItem(&p_stack);
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    }
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    stackTerm(&p_stack);
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    return 0;
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}
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#endif
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