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/* Copyright (C) 2002, 2003, 2005 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, 51 Franklin Street, Fifth Floor,

Boston, MA 02110-1301, USA.  */

#include "config.h"

#include <stdlib.h>

#include <string.h>

#include "libgfortran.h"

#include "io.h"

/* IO locking rules:

   UNIT_LOCK is a master lock, protecting UNIT_ROOT tree and UNIT_CACHE.

   Concurrent use of different units should be supported, so

   each unit has its own lock, LOCK.

   Open should be atomic with its reopening of units and list_read.c

   in several places needs find_unit another unit while holding stdin

   unit's lock, so it must be possible to acquire UNIT_LOCK while holding

   some unit's lock.  Therefore to avoid deadlocks, it is forbidden

   to acquire unit's private locks while holding UNIT_LOCK, except

   for freshly created units (where no other thread can get at their

   address yet) or when using just trylock rather than lock operation.

   In addition to unit's private lock each unit has a WAITERS counter

   and CLOSED flag.  WAITERS counter must be either only

   atomically incremented/decremented in all places (if atomic builtins

   are supported), or protected by UNIT_LOCK in all places (otherwise).

   CLOSED flag must be always protected by unit's LOCK.

   After finding a unit in UNIT_CACHE or UNIT_ROOT with UNIT_LOCK held,

   WAITERS must be incremented to avoid concurrent close from freeing

   the unit between unlocking UNIT_LOCK and acquiring unit's LOCK.

   Unit freeing is always done under UNIT_LOCK.  If close_unit sees any

   WAITERS, it doesn't free the unit but instead sets the CLOSED flag

   and the thread that decrements WAITERS to zero while CLOSED flag is

   set is responsible for freeing it (while holding UNIT_LOCK).

   flush_all_units operation is iterating over the unit tree with

   increasing UNIT_NUMBER while holding UNIT_LOCK and attempting to

   flush each unit (and therefore needs the unit's LOCK held as well).

   To avoid deadlocks, it just trylocks the LOCK and if unsuccessful,

   remembers the current unit's UNIT_NUMBER, unlocks UNIT_LOCK, acquires

   unit's LOCK and after flushing reacquires UNIT_LOCK and restarts with

   the smallest UNIT_NUMBER above the last one flushed.

   If find_unit/find_or_create_unit/find_file/get_unit routines return

   non-NULL, the returned unit has its private lock locked and when the

   caller is done with it, it must call either unlock_unit or close_unit

   on it.  unlock_unit or close_unit must be always called only with the

   private lock held.  */

/* Subroutines related to units */

#define CACHE_SIZE 3

static gfc_unit internal_unit, *unit_cache[CACHE_SIZE];

gfc_offset max_offset;

gfc_unit *unit_root;

#ifdef __GTHREAD_MUTEX_INIT

__gthread_mutex_t unit_lock = __GTHREAD_MUTEX_INIT;

#else

__gthread_mutex_t unit_lock;

#endif

/* 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 (NULL, "insert(): Duplicate key found!");

  return t;

}

/* insert_unit()-- Create a new node, insert it into the treap.  */

static gfc_unit *

insert_unit (int n)

{

  gfc_unit *u = get_mem (sizeof (gfc_unit));

  memset (u, '\0', sizeof (gfc_unit));

  u->unit_number = n;

#ifdef __GTHREAD_MUTEX_INIT

  {

    __gthread_mutex_t tmp = __GTHREAD_MUTEX_INIT;

    u->lock = tmp;

  }

#else

  __GTHREAD_MUTEX_INIT_FUNCTION (&u->lock);

#endif

  __gthread_mutex_lock (&u->lock);

  u->priority = pseudo_random ();

  unit_root = insert (u, unit_root);

  return u;

}

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)

{

  unit_root = delete_treap (old, unit_root);

}

/* get_external_unit()-- Given an integer, return a pointer to the unit

 * structure.  Returns NULL if the unit does not exist,

 * otherwise returns a locked unit. */

static gfc_unit *

get_external_unit (int n, int do_create)

{

  gfc_unit *p;

  int c, created = 0;

  __gthread_mutex_lock (&unit_lock);

retry:

  for (c = 0; c < CACHE_SIZE; c++)

    if (unit_cache[c] != NULL && unit_cache[c]->unit_number == n)

      {

        p = unit_cache[c];

        goto found;

      }

  p = 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 && do_create)

    {

      p = insert_unit (n);

      created = 1;

    }

  if (p != NULL)

    {

      for (c = 0; c < CACHE_SIZE - 1; c++)

        unit_cache[c] = unit_cache[c + 1];

      unit_cache[CACHE_SIZE - 1] = p;

    }

  if (created)

    {

      /* Newly created units have their lock held already

         from insert_unit.  Just unlock UNIT_LOCK and return.  */

      __gthread_mutex_unlock (&unit_lock);

      return p;

    }

found:

  if (p != NULL)

    {

      /* Fast path.  */

      if (! __gthread_mutex_trylock (&p->lock))

        {

          /* assert (p->closed == 0); */

          __gthread_mutex_unlock (&unit_lock);

          return p;

        }

      inc_waiting_locked (p);

    }

  __gthread_mutex_unlock (&unit_lock);

  if (p != NULL)

    {

      __gthread_mutex_lock (&p->lock);

      if (p->closed)

        {

          __gthread_mutex_lock (&unit_lock);

          __gthread_mutex_unlock (&p->lock);

          if (predec_waiting_locked (p) == 0)

            free_mem (p);

          goto retry;

        }

      dec_waiting_unlocked (p);

    }

  return p;

}

gfc_unit *

find_unit (int n)

{

  return get_external_unit (n, 0);

}

gfc_unit *

find_or_create_unit (int n)

{

  return get_external_unit (n, 1);

}

gfc_unit *

get_internal_unit (st_parameter_dt *dtp)

{

  gfc_unit * iunit;

  /* Allocate memory for a unit structure.  */

  iunit = get_mem (sizeof (gfc_unit));

  if (iunit == NULL)

    {

      generate_error (&dtp->common, ERROR_INTERNAL_UNIT, NULL);

      return NULL;

    }

  memset (iunit, '\0', sizeof (gfc_unit));

  iunit->recl = dtp->internal_unit_len;

  /* For internal units we set the unit number to -1.

     Otherwise internal units can be mistaken for a pre-connected unit or

     some other file I/O unit.  */

  iunit->unit_number = -1;

  /* Set up the looping specification from the array descriptor, if any.  */

  if (is_array_io (dtp))

    {

      iunit->rank = GFC_DESCRIPTOR_RANK (dtp->internal_unit_desc);

      iunit->ls = (array_loop_spec *)

        get_mem (iunit->rank * sizeof (array_loop_spec));

      dtp->internal_unit_len *=

        init_loop_spec (dtp->internal_unit_desc, iunit->ls);

    }

  /* Set initial values for unit parameters.  */

  iunit->s = open_internal (dtp->internal_unit, dtp->internal_unit_len);

  iunit->bytes_left = iunit->recl;

  iunit->last_record=0;

  iunit->maxrec=0;

  iunit->current_record=0;

  iunit->read_bad = 0;

  /* Set flags for the internal unit.  */

  iunit->flags.access = ACCESS_SEQUENTIAL;

  iunit->flags.action = ACTION_READWRITE;

  iunit->flags.form = FORM_FORMATTED;

  iunit->flags.pad = PAD_YES;

  iunit->flags.status = STATUS_UNSPECIFIED;

  /* Initialize the data transfer parameters.  */

  dtp->u.p.advance_status = ADVANCE_YES;

  dtp->u.p.blank_status = BLANK_UNSPECIFIED;

  dtp->u.p.seen_dollar = 0;

  dtp->u.p.skips = 0;

  dtp->u.p.pending_spaces = 0;

  dtp->u.p.max_pos = 0;

  /* This flag tells us the unit is assigned to internal I/O.  */

  dtp->u.p.unit_is_internal = 1;

  return iunit;

}

/* free_internal_unit()-- Free memory allocated for internal units if any.  */

void

free_internal_unit (st_parameter_dt *dtp)

{

  if (!is_internal_unit (dtp))

    return;

  if (dtp->u.p.current_unit->ls != NULL)

      free_mem (dtp->u.p.current_unit->ls);

  sclose (dtp->u.p.current_unit->s);

  if (dtp->u.p.current_unit != NULL)

    free_mem (dtp->u.p.current_unit);

}

/* get_unit()-- Returns the unit structure associated with the integer

 * unit or the internal file. */

gfc_unit *

get_unit (st_parameter_dt *dtp, int do_create)

{

  if ((dtp->common.flags & IOPARM_DT_HAS_INTERNAL_UNIT) != 0)

    return get_internal_unit(dtp);

  /* Has to be an external unit */

  dtp->u.p.unit_is_internal = 0;

  dtp->internal_unit_desc = NULL;

  return get_external_unit (dtp->common.unit, do_create);

}

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

int

is_internal_unit (st_parameter_dt *dtp)

{

  return dtp->u.p.unit_is_internal;

}

/* is_array_io ()-- Determine if the I/O is to/from an array */

int

is_array_io (st_parameter_dt *dtp)

{

  return dtp->internal_unit_desc != NULL;

}

/*************************/

/* Initialize everything */

void

init_units (void)

{

  gfc_unit *u;

  unsigned int i;

#ifndef __GTHREAD_MUTEX_INIT

  __GTHREAD_MUTEX_INIT_FUNCTION (&unit_lock);

#endif

#ifdef __GTHREAD_MUTEX_INIT

  {

    __gthread_mutex_t tmp = __GTHREAD_MUTEX_INIT;

    internal_unit.lock = tmp;

  }

#else

  __GTHREAD_MUTEX_INIT_FUNCTION (&internal_unit.lock);

#endif

  if (options.stdin_unit >= 0)

    {                           /* STDIN */

      u = insert_unit (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_NULL;

      u->flags.pad = PAD_YES;

      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;

      u->endfile = NO_ENDFILE;

      __gthread_mutex_unlock (&u->lock);

    }

  if (options.stdout_unit >= 0)

    {                           /* STDOUT */

      u = insert_unit (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_NULL;

      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;

      u->endfile = AT_ENDFILE;

      __gthread_mutex_unlock (&u->lock);

    }

  if (options.stderr_unit >= 0)

    {                           /* STDERR */

      u = insert_unit (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_NULL;

      u->flags.position = POSITION_ASIS;

      u->recl = options.default_recl;

      u->endfile = AT_ENDFILE;

      __gthread_mutex_unlock (&u->lock);

    }

  /* 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. */

  max_offset = 0;

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

    max_offset = max_offset + ((gfc_offset) 1 << i);

}

static int

close_unit_1 (gfc_unit *u, int locked)

{

  int i, rc;

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

  u->closed = 1;

  if (!locked)

    __gthread_mutex_lock (&unit_lock);

  for (i = 0; i < CACHE_SIZE; i++)

    if (unit_cache[i] == u)

      unit_cache[i] = NULL;

  delete_unit (u);

  if (u->file)

    free_mem (u->file);

  u->file = NULL;

  u->file_len = 0;

  if (!locked)

    __gthread_mutex_unlock (&u->lock);

  /* If there are any threads waiting in find_unit for this unit,

     avoid freeing the memory, the last such thread will free it

     instead.  */

  if (u->waiting == 0)

    free_mem (u);

  if (!locked)

    __gthread_mutex_unlock (&unit_lock);

  return rc;

}

void

unlock_unit (gfc_unit *u)

{

  __gthread_mutex_unlock (&u->lock);

}

/* close_unit()-- Close a unit.  The stream is closed, and any memory

 * associated with the stream is freed.  Returns nonzero on I/O error.

 * Should be called with the u->lock locked. */

int

close_unit (gfc_unit *u)

{

  return close_unit_1 (u, 0);

}

/* close_units()-- Delete units on completion.  We just keep deleting

 * the root of the treap until there is nothing left.

 * Not sure what to do with locking here.  Some other thread might be

 * holding some unit's lock and perhaps hold it indefinitely

 * (e.g. waiting for input from some pipe) and close_units shouldn't

 * delay the program too much.  */

void

close_units (void)

{

  __gthread_mutex_lock (&unit_lock);

  while (unit_root != NULL)

    close_unit_1 (unit_root, 1);

  __gthread_mutex_unlock (&unit_lock);

}