/* GSL - Generic Sound Layer
 * Copyright (C) 2002 Tim Janik
 *
 * This library 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 of the License, or
 * (at your option) any later version.
 *
 * This library 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
#include "gslfilehash.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>


/* macros */
#if (GLIB_SIZEOF_LONG > 4)
#define HASH_LONG(l)	(l + (l >> 32))
#else
#define HASH_LONG(l)	(l)
#endif


/* --- variables --- */
static GslMutex    fdpool_mutex = { 0, };
static GHashTable *hfile_ht = NULL;


/* --- functions --- */
static guint
hfile_hash (gconstpointer key)
{
  const GslHFile *hfile = key;
  guint h;

  h = HASH_LONG (hfile->mtime);
  h ^= g_str_hash (hfile->file_name);
  h ^= HASH_LONG (hfile->n_bytes);

  return h;
}

static gboolean
hfile_equals (gconstpointer key1,
	      gconstpointer key2)
{
  const GslHFile *hfile1 = key1;
  const GslHFile *hfile2 = key2;

  return (hfile1->mtime == hfile2->mtime &&
	  hfile1->n_bytes == hfile2->n_bytes &&
	  strcmp (hfile1->file_name, hfile2->file_name) == 0);
}

void
_gsl_init_fd_pool (void)
{
  g_assert (hfile_ht == NULL);

  gsl_mutex_init (&fdpool_mutex);
  hfile_ht = g_hash_table_new (hfile_hash, hfile_equals);
}

static gboolean
stat_fd (gint     fd,
	 GTime   *mtime,
	 GslLong *n_bytes)
{
  struct stat statbuf = { 0, };

  if (fstat (fd, &statbuf) < 0)
    return FALSE;	/* have errno */
  if (mtime)
    *mtime = statbuf.st_mtime;
  if (n_bytes)
    *n_bytes = statbuf.st_size;
  return TRUE;
}

static gboolean
stat_file (const gchar *file_name,
	   GTime       *mtime,
	   GslLong     *n_bytes)
{
  struct stat statbuf = { 0, };

  if (stat (file_name, &statbuf) < 0)
    return FALSE;	/* have errno */
  if (mtime)
    *mtime = statbuf.st_mtime;
  if (n_bytes)
    *n_bytes = statbuf.st_size;
  return TRUE;
}

/**
 * gsl_hfile_open
 * @file_name: name of the file to open
 * @RETURNS:   a new opened #GslHFile or NULL if an error occoured (errno set)
 *
 * Open a file for reading and return the associated GSL hashed file.
 * The motivation for using a #GslHFile over normal unix file
 * descriptors is to reduce the amount of opened unix file descriptors and
 * to ensure thread safety upon reading offset relative byte blocks.
 * Multiple open #GslHFiles with equal file names will share a
 * single unix file descriptor as long as the file wasn't modified meanwhile.
 * This function is MT-safe and may be called from any thread.
 */
GslHFile*
gsl_hfile_open (const gchar *file_name)
{
  GslHFile key, *hfile;
  gint ret_errno;

  errno = EFAULT;
  g_return_val_if_fail (file_name != NULL, NULL);

  key.file_name = (gchar*) file_name;
  if (!stat_file (file_name, &key.mtime, &key.n_bytes))
    return NULL;	/* errno from stat() */

  GSL_SYNC_LOCK (&fdpool_mutex);
  hfile = g_hash_table_lookup (hfile_ht, &key);
  if (hfile)
    {
      GSL_SYNC_LOCK (&hfile->mutex);
      hfile->ocount++;
      GSL_SYNC_UNLOCK (&hfile->mutex);
      ret_errno = 0;
    }
  else
    {
      gint fd;

      fd = open (file_name, O_RDONLY | O_NOCTTY, 0);
      if (fd >= 0)
	{
	  hfile = gsl_new_struct0 (GslHFile, 1);
	  hfile->file_name = g_strdup (file_name);
	  hfile->mtime = key.mtime;
	  hfile->n_bytes = key.n_bytes;
	  hfile->cpos = 0;
	  hfile->fd = fd;
	  hfile->ocount = 1;
	  gsl_mutex_init (&hfile->mutex);
	  g_hash_table_insert (hfile_ht, hfile, hfile);
	  ret_errno = 0;
	}
      else
	ret_errno = errno;
    }
  GSL_SYNC_UNLOCK (&fdpool_mutex);

  errno = ret_errno;
  return hfile;
}

/**
 * gsl_hfile_close
 * @hfile:     valid #GslHFile
 *
 * Close and destroy a #GslHFile.
 * This function is MT-safe and may be called from any thread.
 */
void
gsl_hfile_close (GslHFile *hfile)
{
  gboolean destroy = FALSE;

  g_return_if_fail (hfile != NULL);
  g_return_if_fail (hfile->ocount > 0);

  GSL_SYNC_LOCK (&fdpool_mutex);
  GSL_SYNC_LOCK (&hfile->mutex);
  if (hfile->ocount > 1)
    hfile->ocount--;
  else
    {
      if (!g_hash_table_remove (hfile_ht, hfile))
	g_warning ("%s: failed to unlink hashed file (%p)",
		   G_STRLOC, hfile);
      else
	{
	  hfile->ocount = 0;
	  destroy = TRUE;
	}
    }
  GSL_SYNC_UNLOCK (&hfile->mutex);
  GSL_SYNC_UNLOCK (&fdpool_mutex);

  if (destroy)
    {
      gsl_mutex_destroy (&hfile->mutex);
      close (hfile->fd);
      g_free (hfile->file_name);
      gsl_delete_struct (GslHFile, hfile);
    }
  errno = 0;
}

/**
 * gsl_hfile_pread
 * @hfile:   valid GslHFile
 * @offset:  offset in bytes within 0 and file end
 * @n_bytes: number of bytes to read
 * @bytes:   buffer to store read bytes
 * @error_p: pointer to GslErrorType location
 * @RETURNS: amount of bytes read or -1 if an error occoured (errno set)
 *
 * Read a block of bytes from a GslHFile.
 * This function is MT-safe and may be called from any thread.
 */
GslLong
gsl_hfile_pread (GslHFile *hfile,
		 GslLong   offset,
		 GslLong   n_bytes,
		 gpointer  bytes)
{
  GslLong ret_bytes = -1;
  gint ret_errno;

  errno = EFAULT;
  g_return_val_if_fail (hfile != NULL, -1);
  g_return_val_if_fail (hfile->ocount > 0, -1);
  g_return_val_if_fail (offset >= 0, -1);
  if (offset >= hfile->n_bytes || n_bytes < 1)
    {
      errno = 0;
      return 0;
    }
  g_return_val_if_fail (bytes != NULL, -1);

  GSL_SYNC_LOCK (&hfile->mutex);
  if (hfile->ocount)
    {
      if (hfile->cpos != offset)
	{
	  hfile->cpos = lseek (hfile->fd, offset, SEEK_SET);
	  if (hfile->cpos < 0 && errno != EINVAL)
	    {
	      ret_errno = errno;
	      GSL_SYNC_UNLOCK (&hfile->mutex);
	      errno = ret_errno;
	      return -1;
	    }
	}
      if (hfile->cpos == offset)
	{
	  do
	    ret_bytes = read (hfile->fd, bytes, n_bytes);
	  while (ret_bytes < 0 && errno == EINTR);
	  if (ret_bytes < 0)
	    {
	      ret_errno = errno;
	      ret_bytes = -1;
	    }
	  else
	    {
	      ret_errno = 0;
	      hfile->cpos += ret_bytes;
	    }
	}
      else	/* this should only happen if the file changed since open() */
	{
	  hfile->cpos = -1;
	  if (offset + n_bytes > hfile->n_bytes)
	    n_bytes = hfile->n_bytes - offset;
	  memset (bytes, 0, n_bytes);
	  ret_bytes = n_bytes;
	  ret_errno = 0;
	}
    }
  else
    ret_errno = EFAULT;
  GSL_SYNC_UNLOCK (&hfile->mutex);

  errno = ret_errno;
  return ret_bytes;
}

/**
 * gsl_rfile_open
 * @file_name: name of the file to open
 * @RETURNS:   a new opened #GslRFile or NULL if an error occoured (errno set)
 *
 * Open a file for reading and create a GSL read only file handle for it.
 * The motivation for using a #GslRFile over normal unix files
 * is to reduce the amount of opened unix file descriptors by using
 * a #GslHFile for the actual IO.
 */
GslRFile*
gsl_rfile_open (const gchar *file_name)
{
  GslHFile *hfile = gsl_hfile_open (file_name);
  GslRFile *rfile;

  if (!hfile)
    rfile = NULL;
  else
    {
      rfile = gsl_new_struct0 (GslRFile, 1);
      rfile->hfile = hfile;
      rfile->offset = 0;
    }
  return rfile;
}

/**
 * gsl_rfile_name
 * @rfile:   valid #GslRFile
 * @RETURNS: the file name used to open this file
 *
 * Retrive the file name used to open @rfile.
 */
gchar*
gsl_rfile_name (GslRFile *rfile)
{
  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, NULL);

  errno = 0;
  return rfile->hfile->file_name;
}

/**
 * gsl_rfile_seek_set
 * @rfile:   valid #GslRFile
 * @offset:  new seek position within 0 and gsl_rfile_length()+1
 * @RETURNS: resulting position within 0 and gsl_rfile_length()+1
 *
 * Set the current #GslRFile seek position.
 */
GslLong
gsl_rfile_seek_set (GslRFile *rfile,
		    GslLong   offset)
{
  GslLong l;

  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, 0);

  l = rfile->hfile->n_bytes;
  rfile->offset = CLAMP (offset, 0, l);

  errno = 0;
  return rfile->offset;
}

/**
 * gsl_rfile_position
 * @rfile:   valid #GslRFile
 * @RETURNS: current position within 0 and gsl_rfile_length()
 *
 * Retrive the current #GslRFile seek position.
 */
GslLong
gsl_rfile_position (GslRFile *rfile)
{
  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, 0);

  errno = 0;
  return rfile->offset;
}

/**
 * gsl_rfile_length
 * @rfile:   valid #GslRFile
 * @RETURNS: total length of the #GslRFile in bytes
 *
 * Retrive the file length of @rfile in bytes.
 */
GslLong
gsl_rfile_length (GslRFile *rfile)
{
  GslLong l;

  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, 0);

  l = rfile->hfile->n_bytes;

  errno = 0;
  return l;
}

/**
 * gsl_rfile_pread
 * @rfile:   valid GslRFile
 * @offset:  offset in bytes within 0 and gsl_rfile_length()
 * @n_bytes: number of bytes to read
 * @bytes:   buffer to store read bytes
 * @error_p: pointer to GslErrorType location
 * @RETURNS: amount of bytes read or -1 if an error occoured (errno set)
 *
 * Read a block of bytes from a GslRFile at a specified position.
 */
GslLong
gsl_rfile_pread (GslRFile *rfile,
		 GslLong   offset,
		 GslLong   n_bytes,
		 gpointer  bytes)
{
  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, -1);

  return gsl_hfile_pread (rfile->hfile, offset, n_bytes, bytes);
}

/**
 * gsl_rfile_read
 * @rfile:   valid GslRFile
 * @n_bytes: number of bytes to read
 * @bytes:   buffer to store read bytes
 * @error_p: pointer to GslErrorType location
 * @RETURNS: amount of bytes read or -1 if an error occoured (errno set)
 *
 * Read a block of bytes from a GslRFile from the current seek position
 * and advance the seek position.
 */
GslLong
gsl_rfile_read (GslRFile *rfile,
		GslLong   n_bytes,
		gpointer  bytes)
{
  GslLong l;

  errno = EFAULT;
  g_return_val_if_fail (rfile != NULL, -1);

  l = gsl_hfile_pread (rfile->hfile, rfile->offset, n_bytes, bytes);
  if (l > 0)
    rfile->offset += l;
  return l;
}

/**
 * gsl_rfile_close
 * @rfile:     valid #GslRFile
 *
 * Close and destroy a #GslRFile.
 */
void
gsl_rfile_close (GslRFile *rfile)
{
  errno = EFAULT;
  g_return_if_fail (rfile != NULL);

  gsl_hfile_close (rfile->hfile);
  gsl_delete_struct (GslRFile, rfile);
  errno = 0;
}