/* ------------------------------------------------------------------------- 
 * stack.c
 * A stack of pointers. 
 * Copyright 2010 QTronic GmbH. All rights reserved. 
 * -------------------------------------------------------------------------*/ 

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "stack.h"

Stack* stackNew(int initialSize, int inc){
    Stack* s = (Stack*)malloc(sizeof(Stack));
    s->stack = NULL;
    s->stackSize = 0;
    s->stackPos = -1;
    s->initialSize = initialSize;
    s->inc = inc;
    return s;
}

int stackIsEmpty(Stack* s) {
    return s->stackPos == -1;
}

// add an element to stack and grow stack if required
// returns 1 to indicate success and 0 for error
int stackPush(Stack* s, void* e) {
    s->stackPos++;
    if (s->stackPos==s->stackSize){
		s->stackSize += (s->stack ? s->inc: s->initialSize);
        s->stack = (void**) realloc(s->stack, s->stackSize * sizeof(void*));
        if (!s->stack) return 0; // error;
    }
    s->stack[s->stackPos] = e;
    return 1; // success
}

// return top element (possibly NULL), if stack not empty
// runtime error if stack is empty
void* stackPeek(Stack* s){
    assert(!stackIsEmpty(s));
    return s->stack[s->stackPos];
}

// remove top element (possibly NULL) from stack and return it
// runtime error if stack is empty
void* stackPop(Stack* s){
    assert(!stackIsEmpty(s));
    return s->stack[s->stackPos--];
}

// return the last n elements as null terminated array, 
// or NULL if memory allocation fails
void** stackLastPopedAsArray0(Stack* s, int n){
    int i;
    void** array = (void**)malloc((n + 1)*sizeof(void*));
    if (! array) return NULL; // failure
    for (i=0; i<n; i++) {
        array[i] = s->stack[i+ s->stackPos + 1];
    }
    array[n]=NULL; // terminating NULL
    return array;
}

// return stack as possibly empty array, or NULL if memory allocation fails
// On sucessful return, the stack is empty.
void** stackPopAllAsArray(Stack* s, int *size) {
    int i;
    void** array = (void**)malloc((s->stackPos + 1)*sizeof(void*));
    if (! array) return NULL; // failure
    *size = s->stackPos + 1;
    for (i=0; i<*size; i++) 
        array[i] = s->stack[i];
    s->stackPos = -1;
    return array; 
}

// release the given stack
void stackFree(Stack* s){
    if (s->stack) free(s->stack);
    free(s);
}