/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
   Contributed by Andy Vaught

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file.  (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)

Libgfortran is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Libgfortran; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "config.h"
#include <stdlib.h>
#include <string.h>
#include "libgfortran.h"
#include "io.h"


/* Subroutines related to units */


#define CACHE_SIZE 3
static gfc_unit internal_unit, *unit_cache[CACHE_SIZE];


/* This implementation is based on Stefan Nilsson's article in the
 * July 1997 Doctor Dobb's Journal, "Treaps in Java". */

/* pseudo_random()-- Simple linear congruential pseudorandom number
 * generator.  The period of this generator is 44071, which is plenty
 * for our purposes.  */

static int
pseudo_random (void)
{
  static int x0 = 5341;

  x0 = (22611 * x0 + 10) % 44071;
  return x0;
}


/* rotate_left()-- Rotate the treap left */

static gfc_unit *
rotate_left (gfc_unit * t)
{
  gfc_unit *temp;

  temp = t->right;
  t->right = t->right->left;
  temp->left = t;

  return temp;
}


/* rotate_right()-- Rotate the treap right */

static gfc_unit *
rotate_right (gfc_unit * t)
{
  gfc_unit *temp;

  temp = t->left;
  t->left = t->left->right;
  temp->right = t;

  return temp;
}


static int
compare (int a, int b)
{
  if (a < b)
    return -1;
  if (a > b)
    return 1;

  return 0;
}


/* insert()-- Recursive insertion function.  Returns the updated treap. */

static gfc_unit *
insert (gfc_unit * new, gfc_unit * t)
{
  int c;

  if (t == NULL)
    return new;

  c = compare (new->unit_number, t->unit_number);

  if (c < 0)
    {
      t->left = insert (new, t->left);
      if (t->priority < t->left->priority)
	t = rotate_right (t);
    }

  if (c > 0)
    {
      t->right = insert (new, t->right);
      if (t->priority < t->right->priority)
	t = rotate_left (t);
    }

  if (c == 0)
    internal_error ("insert(): Duplicate key found!");

  return t;
}


/* insert_unit()-- Given a new node, insert it into the treap.  It is
 * an error to insert a key that already exists. */

void
insert_unit (gfc_unit * new)
{
  new->priority = pseudo_random ();
  g.unit_root = insert (new, g.unit_root);
}


static gfc_unit *
delete_root (gfc_unit * t)
{
  gfc_unit *temp;

  if (t->left == NULL)
    return t->right;
  if (t->right == NULL)
    return t->left;

  if (t->left->priority > t->right->priority)
    {
      temp = rotate_right (t);
      temp->right = delete_root (t);
    }
  else
    {
      temp = rotate_left (t);
      temp->left = delete_root (t);
    }

  return temp;
}


/* delete_treap()-- Delete an element from a tree.  The 'old' value
 * does not necessarily have to point to the element to be deleted, it
 * must just point to a treap structure with the key to be deleted.
 * Returns the new root node of the tree. */

static gfc_unit *
delete_treap (gfc_unit * old, gfc_unit * t)
{
  int c;

  if (t == NULL)
    return NULL;

  c = compare (old->unit_number, t->unit_number);

  if (c < 0)
    t->left = delete_treap (old, t->left);
  if (c > 0)
    t->right = delete_treap (old, t->right);
  if (c == 0)
    t = delete_root (t);

  return t;
}


/* delete_unit()-- Delete a unit from a tree */

static void
delete_unit (gfc_unit * old)
{
  g.unit_root = delete_treap (old, g.unit_root);
}


/* find_unit()-- Given an integer, return a pointer to the unit
 * structure.  Returns NULL if the unit does not exist. */

gfc_unit *
find_unit (int n)
{
  gfc_unit *p;
  int c;

  for (c = 0; c < CACHE_SIZE; c++)
    if (unit_cache[c] != NULL && unit_cache[c]->unit_number == n)
      {
	p = unit_cache[c];
	return p;
      }

  p = g.unit_root;
  while (p != NULL)
    {
      c = compare (n, p->unit_number);
      if (c < 0)
	p = p->left;
      if (c > 0)
	p = p->right;
      if (c == 0)
	break;
    }

  if (p != NULL)
    {
      for (c = 0; c < CACHE_SIZE - 1; c++)
	unit_cache[c] = unit_cache[c + 1];

      unit_cache[CACHE_SIZE - 1] = p;
    }

  return p;
}

/* get_unit()-- Returns the unit structure associated with the integer
 * unit or the internal file. */

gfc_unit *
get_unit (int read_flag)
{
  if (ioparm.internal_unit != NULL)
    {
      internal_unit.s =
	open_internal (ioparm.internal_unit, ioparm.internal_unit_len);

      /* Set flags for the internal unit */

      internal_unit.flags.access = ACCESS_SEQUENTIAL;
      internal_unit.flags.action = ACTION_READWRITE;
      internal_unit.flags.form = FORM_FORMATTED;
      internal_unit.flags.delim = DELIM_NONE;

      return &internal_unit;
    }

  /* Has to be an external unit */

  return find_unit (ioparm.unit);
}


/* is_internal_unit()-- Determine if the current unit is internal or
 * not */

int
is_internal_unit ()
{
  return current_unit == &internal_unit;
}


/*************************/
/* Initialize everything */

void
init_units (void)
{
  gfc_offset m, n;
  gfc_unit *u;
  int i;

  if (options.stdin_unit >= 0)
    {				/* STDIN */
      u = get_mem (sizeof (gfc_unit));
      memset (u, '\0', sizeof (gfc_unit));

      u->unit_number = options.stdin_unit;
      u->s = input_stream ();

      u->flags.action = ACTION_READ;

      u->flags.access = ACCESS_SEQUENTIAL;
      u->flags.form = FORM_FORMATTED;
      u->flags.status = STATUS_OLD;
      u->flags.blank = BLANK_ZERO;
      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;
      u->endfile = NO_ENDFILE;

      insert_unit (u);
    }

  if (options.stdout_unit >= 0)
    {				/* STDOUT */
      u = get_mem (sizeof (gfc_unit));
      memset (u, '\0', sizeof (gfc_unit));

      u->unit_number = options.stdout_unit;
      u->s = output_stream ();

      u->flags.action = ACTION_WRITE;

      u->flags.access = ACCESS_SEQUENTIAL;
      u->flags.form = FORM_FORMATTED;
      u->flags.status = STATUS_OLD;
      u->flags.blank = BLANK_ZERO;
      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;
      u->endfile = AT_ENDFILE;

      insert_unit (u);
    }

  if (options.stderr_unit >= 0)
    {				/* STDERR */
      u = get_mem (sizeof (gfc_unit));
      memset (u, '\0', sizeof (gfc_unit));

      u->unit_number = options.stderr_unit;
      u->s = error_stream ();

      u->flags.action = ACTION_WRITE;

      u->flags.access = ACCESS_SEQUENTIAL;
      u->flags.form = FORM_FORMATTED;
      u->flags.status = STATUS_OLD;
      u->flags.blank = BLANK_ZERO;
      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;
      u->endfile = AT_ENDFILE;

      insert_unit (u);
    }

  /* Calculate the maximum file offset in a portable manner.
   * max will be the largest signed number for the type gfc_offset.
   *
   * set a 1 in the LSB and keep a running sum, stopping at MSB-1 bit. */

  g.max_offset = 0;
  for (i=0; i < sizeof(g.max_offset) * 8 - 1; i++)
    g.max_offset = g.max_offset + ((gfc_offset) 1 << i);

}


/* close_unit()-- Close a unit.  The stream is closed, and any memory
 * associated with the stream is freed.  Returns nonzero on I/O error. */

int
close_unit (gfc_unit * u)
{
  int i, rc;

  for (i = 0; i < CACHE_SIZE; i++)
    if (unit_cache[i] == u)
      unit_cache[i] = NULL;

  rc = (u->s == NULL) ? 0 : sclose (u->s) == FAILURE;

  delete_unit (u);
  free_mem (u);

  return rc;
}


/* close_units()-- Delete units on completion.  We just keep deleting
 * the root of the treap until there is nothing left. */

void
close_units (void)
{
  while (g.unit_root != NULL)
    close_unit (g.unit_root);
}