FIFO_stack_tool.c

/*
 *
 *		MIT License
 *
 *	Copyright (c) 2022 SelfTide
 *
 *	Permission is hereby granted, free of charge, to any person obtaining a copy of this 
 *	software and associated documentation files (the "Software"), to deal in the Software
 *	without restriction, including without limitation the rights to use, copy, modify, merge,
 *	publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
 *	to whom the Software is furnished to do so, subject to the following conditions:
 *
 *	The above copyright notice and this permission notice shall be included in all copies or 
 *	substantial portions of the Software.
 *
 *	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 *	BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 *	NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
 *	DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 *	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * 	FIFO stack tool 
 */

#include "FIFO_stack_tool.h"

int stack_count;
static stack *p;

// initialize new stack
void stack_init( void )
{
	p = (stack *)malloc(sizeof(stack));
	
	stack_count = 0;
	
	p->data = NULL;
	p->prev = NULL; 
	p->next = NULL;	
}

// add data to stack, append new data to end if not empty
void push_stack(void *data)
{
	stack *t = NULL;
	void *d = data;
	
	if(p != NULL)	// check to see if stack was initialized
	{
		if(p->data)	// do we already have data here? if we don't initialize the first
		{
			//if(!p->prev)	// check for null if so allocate space
			t = (stack *)malloc(sizeof(stack));

			t->next = p;
			p->prev = t;
			p = t;
			p->data = d;  // set data for current stack
			p->prev = NULL;
		}else{
			p->data = d;	// if we got here this is the first
			p->next = NULL;
			p->prev = NULL;
		}
	}
}

// pop data off the begining of the stack
void *pop_stack( void )
{
	void *data;
	stack *t = p;
	
	if(t)
	{
		if(!p)
			data = NULL;
		
		while(t->next) t = t->next;	// iterate till we get to the first in the stack
		
		data = t->data;
		
		if(t->prev)  // check to see if we got more in the FIFO stack
		{
			t->prev->next = NULL;	// set next to null and free current stack
			free(t);
		}else{
			t->data = NULL;	// don't free last stack, set data to null so stack can be used again
			t->next = NULL;
			t->prev = NULL;
		}
		return data;
	}
	return NULL;
}