/*
   f98stack.c for fbbi.c
   Stack ANSI C Functions - source.
   v0.98 Oct 1 1998 Chris Pressey
   v0.98a Mar 26 2003 Chris Pressey

   Copyright (c)1998, 2001, 2003, Cat's Eye Technologies.
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

     Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.

     Neither the name of Cat's Eye Technologies nor the names of its
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission. 

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
   OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
   OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
   ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE. 

*/

/*
   Why use this package?
   - It's ANSI C
   - You need to store one or more stack stacks,
     as defined in Funge-98 (http://www.catseye.mb.ca/projects/funge98-+)

   Changes in v0.98:
   - FSS_DATATYPE is replaced with void * and dc (size in bytes)
   - stack stack is built upon stack with stack * as the cell type
*/

#include <string.h>
#include <stdlib.h>

#include <stdio.h>

#include "f98stack.h"

/* Given the number of cells (sc) and bytes per cell (dc), */
/* allocate a new stack */
stack * stack_alloc(long int sc, long int dc)
{
  stack * u;
  u = (stack *)malloc(sizeof(stack));
  if (u != NULL)
  {
    u->mem = malloc(sc * dc);
    if (u->mem != NULL)
    {
      u->sp = -1;
      u->sc = sc;
      u->dc = dc;
    } else return NULL;
  } else return NULL;
  SDEBUG("Successful Allocate", u);
  return u;
}

/* Given a pointer to a stack, remove and return the top cell */
void * stack_pop(stack * s)
{
  SDEBUG("Before Pop", s);
  if (s->sp >= 0)
  {
    return ((char *)s->mem + (s->sp-- * s->dc));
  } else return NULL;
}

/* Given a pointer to a stack and a value, place it on the */
/* top of the stack */
int stack_push(stack * s, void * val)
{
  SDEBUG("Before Push", s);
  if(s->sp < s->sc-1)
  {
    memcpy(((char *)s->mem + (++s->sp * s->dc)), val, s->dc);
    SDEBUG("Successful Push", s);
    return 1;
  } else return 0;
}

/* Pop a series of cells off the stack as chars until a 0 cell */
void stack_pop_string(stack * s, char * str)
{
  int i = 0;
  void * x = NULL;
  SDEBUG("Before Pop String", s);
  x = stack_pop(s);
  while ((s->sp >= 0) && (x != NULL) && (*(char *)x != 0))
  {
    str[i++] = *(char *)x;
    x = stack_pop(s);
  }
  str[i] = (char)'\0';
}

/* Push a series of chars onto the stack as cells until a 0 char */
void stack_push_string(stack * s, char * str)
{
  int i = strlen(str) + 1;
  long int l = 0;
  SDEBUG("Before Push String", s);
  while (i > 0)
  {
    l = (long)0 | str[--i]; /* pad */
    stack_push(s, &l);
  }
}

/* Given a pointer to a stack and a number of cells from the top */
/* cell, return an indexed cell without removing it */
void * stack_read(stack * s, int offset /* 0 = TOS */ )
{
  void * k = NULL;
  if(offset < 0) offset *= -1;
  SDEBUG("Before Read", s);
  if (s->sp >= offset)
  {
    k = (void *)((char *)s->mem + (s->sp - offset) * s->dc);
    return k;
  } else return NULL;
}

/* Return the number of elements on a given stack */
int stack_measure(stack * s)
{
  SDEBUG("Before Measure", s);
  if (s != NULL) return s->sp + 1; else return 0;
}

/* Remove all cells from a given stack */
void stack_clear(stack * s)
{
  SDEBUG("Before Clear", s);
  if (s != NULL) s->sp = -1;
}

/* Release all the memory used by a stack, invalidating the stack */
void stack_free(stack * s)
{
  SDEBUG("Before Free", s);
  if (s != NULL)
  {
    free(s->mem);
    free(s);
  }
}

/* Stack of stacks - transfer elements a la f98's {} instructions */
int stack_stack_transfer (stack * t, int count, void * zero)
{
  int i;
  stack * toss; stack * soss;
  void * q;

  SDEBUG("Before Transfer", t);
  if (stack_measure(t) > 1)
  {
    toss = (stack *)stack_read(t, 0);
    soss = (stack *)stack_read(t, 1);
    if (toss != NULL && soss != NULL)
    {
      if (count > 0) /* from SOSS to TOSS */
      {
        for(i=0;i<count;i++)
        {
          q = stack_read(soss, count - 1 - i);
          if (q != NULL) stack_push(toss, q); else stack_push(toss, zero);
        }
        soss->sp -= count;
        if (soss->sp < 0) soss->sp = -1;
      } else
      if (count < 0) /* from TOSS to SOSS */
      {
        count *= -1;
        for(i=0;i<count;i++)
        {
          q = stack_read(toss, count - 1 - i);
          if (q != NULL) stack_push(soss, q); else stack_push(soss, zero);
        }
        toss->sp -= count;
        if (toss->sp <= 0) toss->sp = -1;
      }
      return 1;
    }
  }
  return 0;
}