/* GIO - GLib Input, Output and Streaming Library

 * 

 * Copyright (C) 2006-2007 Red Hat, Inc.

 * Copyright (C) 2007 Jürg Billeter

 * Copyright © 2009 Codethink Limited

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General

 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Alexander Larsson <alexl@redhat.com>

 */

#include "config.h"

#include "gdatainputstream.h"

#include "gtask.h"

#include "gcancellable.h"

#include "gioenumtypes.h"

#include "gioerror.h"

#include "glibintl.h"

#include "gstrfuncsprivate.h"

#include <string.h>

/**

 * SECTION:gdatainputstream

 * @short_description: Data Input Stream

 * @include: gio/gio.h

 * @see_also: #GInputStream

 * 

 * Data input stream implements #GInputStream and includes functions for 

 * reading structured data directly from a binary input stream.

 *

 **/

struct _GDataInputStreamPrivate {

  GDataStreamByteOrder byte_order;

  GDataStreamNewlineType newline_type;

};

enum {

  PROP_0,

  PROP_BYTE_ORDER,

  PROP_NEWLINE_TYPE

};

static void g_data_input_stream_set_property (GObject      *object,

					      guint         prop_id,

					      const GValue *value,

					      GParamSpec   *pspec);

static void g_data_input_stream_get_property (GObject      *object,

					      guint         prop_id,

					      GValue       *value,

					      GParamSpec   *pspec);

G_DEFINE_TYPE_WITH_PRIVATE (GDataInputStream,

                            g_data_input_stream,

                            G_TYPE_BUFFERED_INPUT_STREAM)

static void

g_data_input_stream_class_init (GDataInputStreamClass *klass)

{

  GObjectClass *object_class;

  object_class = G_OBJECT_CLASS (klass);

  object_class->get_property = g_data_input_stream_get_property;

  object_class->set_property = g_data_input_stream_set_property;

  /**

   * GDataStream:byte-order:

   *

   * The ::byte-order property determines the byte ordering that

   * is used when reading multi-byte entities (such as integers)

   * from the stream.

   */ 

  g_object_class_install_property (object_class,

                                   PROP_BYTE_ORDER,

                                   g_param_spec_enum ("byte-order",

                                                      P_("Byte order"),

                                                      P_("The byte order"),

                                                      G_TYPE_DATA_STREAM_BYTE_ORDER,

                                                      G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN,

                                                      G_PARAM_READWRITE|G_PARAM_STATIC_NAME|G_PARAM_STATIC_BLURB));

  /**

   * GDataStream:newline-type:

   *

   * The :newline-type property determines what is considered

   * as a line ending when reading complete lines from the stream.

   */ 

  g_object_class_install_property (object_class,

                                   PROP_NEWLINE_TYPE,

                                   g_param_spec_enum ("newline-type",

                                                      P_("Newline type"),

                                                      P_("The accepted types of line ending"),

                                                      G_TYPE_DATA_STREAM_NEWLINE_TYPE,

                                                      G_DATA_STREAM_NEWLINE_TYPE_LF,

                                                      G_PARAM_READWRITE|G_PARAM_STATIC_NAME|G_PARAM_STATIC_BLURB));

}

static void

g_data_input_stream_set_property (GObject      *object,

				  guint         prop_id,

				  const GValue *value,

				  GParamSpec   *pspec)

{

  GDataInputStream        *dstream;

  dstream = G_DATA_INPUT_STREAM (object);

   switch (prop_id)

    {

    case PROP_BYTE_ORDER:

      g_data_input_stream_set_byte_order (dstream, g_value_get_enum (value));

      break;

    case PROP_NEWLINE_TYPE:

      g_data_input_stream_set_newline_type (dstream, g_value_get_enum (value));

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static void

g_data_input_stream_get_property (GObject    *object,

                                  guint       prop_id,

                                  GValue     *value,

                                  GParamSpec *pspec)

{

  GDataInputStreamPrivate *priv;

  GDataInputStream        *dstream;

  dstream = G_DATA_INPUT_STREAM (object);

  priv = dstream->priv;

  switch (prop_id)

    { 

    case PROP_BYTE_ORDER:

      g_value_set_enum (value, priv->byte_order);

      break;

    case PROP_NEWLINE_TYPE:

      g_value_set_enum (value, priv->newline_type);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

      break;

    }

}

static void

g_data_input_stream_init (GDataInputStream *stream)

{

  stream->priv = g_data_input_stream_get_instance_private (stream);

  stream->priv->byte_order = G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN;

  stream->priv->newline_type = G_DATA_STREAM_NEWLINE_TYPE_LF;

}

/**

 * g_data_input_stream_new:

 * @base_stream: a #GInputStream.

 * 

 * Creates a new data input stream for the @base_stream.

 * 

 * Returns: a new #GDataInputStream.

 **/

GDataInputStream *

g_data_input_stream_new (GInputStream *base_stream)

{

  GDataInputStream *stream;

  g_return_val_if_fail (G_IS_INPUT_STREAM (base_stream), NULL);

  stream = g_object_new (G_TYPE_DATA_INPUT_STREAM,

                         "base-stream", base_stream,

                         NULL);

  return stream;

}

/**

 * g_data_input_stream_set_byte_order:

 * @stream: a given #GDataInputStream.

 * @order: a #GDataStreamByteOrder to set.

 * 

 * This function sets the byte order for the given @stream. All subsequent

 * reads from the @stream will be read in the given @order.

 *  

 **/

void

g_data_input_stream_set_byte_order (GDataInputStream     *stream,

				    GDataStreamByteOrder  order)

{

  GDataInputStreamPrivate *priv;

  g_return_if_fail (G_IS_DATA_INPUT_STREAM (stream));

  priv = stream->priv;

  if (priv->byte_order != order)

    {

      priv->byte_order = order;

      g_object_notify (G_OBJECT (stream), "byte-order");

    }

}

/**

 * g_data_input_stream_get_byte_order:

 * @stream: a given #GDataInputStream.

 * 

 * Gets the byte order for the data input stream.

 * 

 * Returns: the @stream's current #GDataStreamByteOrder. 

 **/

GDataStreamByteOrder

g_data_input_stream_get_byte_order (GDataInputStream *stream)

{

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN);

  return stream->priv->byte_order;

}

/**

 * g_data_input_stream_set_newline_type:

 * @stream: a #GDataInputStream.

 * @type: the type of new line return as #GDataStreamNewlineType.

 * 

 * Sets the newline type for the @stream.

 * 

 * Note that using G_DATA_STREAM_NEWLINE_TYPE_ANY is slightly unsafe. If a read

 * chunk ends in "CR" we must read an additional byte to know if this is "CR" or

 * "CR LF", and this might block if there is no more data available.

 *  

 **/

void

g_data_input_stream_set_newline_type (GDataInputStream       *stream,

				      GDataStreamNewlineType  type)

{

  GDataInputStreamPrivate *priv;

  g_return_if_fail (G_IS_DATA_INPUT_STREAM (stream));

  priv = stream->priv;

  if (priv->newline_type != type)

    {

      priv->newline_type = type;

      g_object_notify (G_OBJECT (stream), "newline-type");

    }

}

/**

 * g_data_input_stream_get_newline_type:

 * @stream: a given #GDataInputStream.

 * 

 * Gets the current newline type for the @stream.

 * 

 * Returns: #GDataStreamNewlineType for the given @stream.

 **/

GDataStreamNewlineType

g_data_input_stream_get_newline_type (GDataInputStream *stream)

{

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), G_DATA_STREAM_NEWLINE_TYPE_ANY);

  return stream->priv->newline_type;

}

static gboolean

read_data (GDataInputStream  *stream,

           void              *buffer,

           gsize              size,

           GCancellable      *cancellable,

           GError           **error)

{

  gsize available;

  gssize res;

  while ((available = g_buffered_input_stream_get_available (G_BUFFERED_INPUT_STREAM (stream))) < size)

    {

      res = g_buffered_input_stream_fill (G_BUFFERED_INPUT_STREAM (stream),

					  size - available,

					  cancellable, error);

      if (res < 0)

	return FALSE;

      if (res == 0)

	{

	  g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_FAILED,

                               _("Unexpected early end-of-stream"));

	  return FALSE;

	}

    }

  /* This should always succeed, since it's in the buffer */

  res = g_input_stream_read (G_INPUT_STREAM (stream),

			     buffer, size,

			     NULL, NULL);

  g_warn_if_fail (res == size);

  return TRUE;

}

/**

 * g_data_input_stream_read_byte:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads an unsigned 8-bit/1-byte value from @stream.

 *

 * Returns: an unsigned 8-bit/1-byte value read from the @stream or %0 

 * if an error occurred.

 **/

guchar

g_data_input_stream_read_byte (GDataInputStream  *stream,

			       GCancellable       *cancellable,

			       GError            **error)

{

  guchar c;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), '\0');

  if (read_data (stream, &c, 1, cancellable, error))

      return c;

  return 0;

}

/**

 * g_data_input_stream_read_int16:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads a 16-bit/2-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order() and g_data_input_stream_set_byte_order().

 * 

 * Returns: a signed 16-bit/2-byte value read from @stream or %0 if 

 * an error occurred.

 **/

gint16

g_data_input_stream_read_int16 (GDataInputStream  *stream,

			       GCancellable       *cancellable,

			       GError            **error)

{

  gint16 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 2, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GINT16_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GINT16_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

/**

 * g_data_input_stream_read_uint16:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 *

 * Reads an unsigned 16-bit/2-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order() and g_data_input_stream_set_byte_order(). 

 * 

 * Returns: an unsigned 16-bit/2-byte value read from the @stream or %0 if 

 * an error occurred. 

 **/

guint16

g_data_input_stream_read_uint16 (GDataInputStream  *stream,

				 GCancellable       *cancellable,

				 GError            **error)

{

  guint16 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 2, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GUINT16_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GUINT16_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

/**

 * g_data_input_stream_read_int32:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads a signed 32-bit/4-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order() and g_data_input_stream_set_byte_order().

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. 

 *   

 * Returns: a signed 32-bit/4-byte value read from the @stream or %0 if 

 * an error occurred. 

 **/

gint32

g_data_input_stream_read_int32 (GDataInputStream  *stream,

				GCancellable       *cancellable,

				GError            **error)

{

  gint32 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 4, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GINT32_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GINT32_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

/**

 * g_data_input_stream_read_uint32:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads an unsigned 32-bit/4-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order() and g_data_input_stream_set_byte_order().

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. 

 * 

 * Returns: an unsigned 32-bit/4-byte value read from the @stream or %0 if 

 * an error occurred. 

 **/

guint32

g_data_input_stream_read_uint32 (GDataInputStream  *stream,

				 GCancellable       *cancellable,

				 GError            **error)

{

  guint32 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 4, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GUINT32_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GUINT32_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

/**

 * g_data_input_stream_read_int64:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads a 64-bit/8-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order() and g_data_input_stream_set_byte_order().

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. 

 * 

 * Returns: a signed 64-bit/8-byte value read from @stream or %0 if 

 * an error occurred.  

 **/

gint64

g_data_input_stream_read_int64 (GDataInputStream  *stream,

			       GCancellable       *cancellable,

			       GError            **error)

{

  gint64 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 8, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GINT64_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GINT64_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

/**

 * g_data_input_stream_read_uint64:

 * @stream: a given #GDataInputStream.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 * 

 * Reads an unsigned 64-bit/8-byte value from @stream.

 *

 * In order to get the correct byte order for this read operation, 

 * see g_data_input_stream_get_byte_order().

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. 

 * 

 * Returns: an unsigned 64-bit/8-byte read from @stream or %0 if 

 * an error occurred. 

 **/

guint64

g_data_input_stream_read_uint64 (GDataInputStream  *stream,

				GCancellable       *cancellable,

				GError            **error)

{

  guint64 v;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), 0);

  if (read_data (stream, &v, 8, cancellable, error))

    {

      switch (stream->priv->byte_order)

	{

	case G_DATA_STREAM_BYTE_ORDER_BIG_ENDIAN:

	  v = GUINT64_FROM_BE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_LITTLE_ENDIAN:

	  v = GUINT64_FROM_LE (v);

	  break;

	case G_DATA_STREAM_BYTE_ORDER_HOST_ENDIAN:

	default:

	  break;

	}

      return v;

    }

  return 0;

}

static gssize

scan_for_newline (GDataInputStream *stream,

		  gsize            *checked_out,

		  gboolean         *last_saw_cr_out,

		  int              *newline_len_out)

{

  GBufferedInputStream *bstream;

  GDataInputStreamPrivate *priv;

  const char *buffer;

  gsize start, end, peeked;

  int i;

  gssize found_pos;

  int newline_len;

  gsize available, checked;

  gboolean last_saw_cr;

  priv = stream->priv;

  bstream = G_BUFFERED_INPUT_STREAM (stream);

  checked = *checked_out;

  last_saw_cr = *last_saw_cr_out;

  found_pos = -1;

  newline_len = 0;

  start = checked;

  buffer = (const char*)g_buffered_input_stream_peek_buffer (bstream, &available) + start;

  end = available;

  peeked = end - start;

  for (i = 0; checked < available && i < peeked; i++)

    {

      switch (priv->newline_type)

	{

	case G_DATA_STREAM_NEWLINE_TYPE_LF:

	  if (buffer[i] == 10)

	    {

	      found_pos = start + i;

	      newline_len = 1;

	    }

	  break;

	case G_DATA_STREAM_NEWLINE_TYPE_CR:

	  if (buffer[i] == 13)

	    {

	      found_pos = start + i;

	      newline_len = 1;

	    }

	  break;

	case G_DATA_STREAM_NEWLINE_TYPE_CR_LF:

	  if (last_saw_cr && buffer[i] == 10)

	    {

	      found_pos = start + i - 1;

	      newline_len = 2;

	    }

	  break;

	default:

	case G_DATA_STREAM_NEWLINE_TYPE_ANY:

	  if (buffer[i] == 10) /* LF */

	    {

	      if (last_saw_cr)

		{

		  /* CR LF */

		  found_pos = start + i - 1;

		  newline_len = 2;

		}

	      else

		{

		  /* LF */

		  found_pos = start + i;

		  newline_len = 1;

		}

	    }

	  else if (last_saw_cr)

	    {

	      /* Last was cr, this is not LF, end is CR */

	      found_pos = start + i - 1;

	      newline_len = 1;

	    }

	  /* Don't check for CR here, instead look at last_saw_cr on next byte */

	  break;

	}

      last_saw_cr = (buffer[i] == 13);

      if (found_pos != -1)

	{

	  *newline_len_out = newline_len;

	  return found_pos;

	}

    }

  checked = end;

  *checked_out = checked;

  *last_saw_cr_out = last_saw_cr;

  return -1;

}

/**

 * g_data_input_stream_read_line:

 * @stream: a given #GDataInputStream.

 * @length: (out) (optional): a #gsize to get the length of the data read in.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 *

 * Reads a line from the data input stream.  Note that no encoding

 * checks or conversion is performed; the input is not guaranteed to

 * be UTF-8, and may in fact have embedded NUL characters.

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned.

 *

 * Returns: (nullable) (transfer full) (array zero-terminated=1) (element-type guint8):

 *  a NUL terminated byte array with the line that was read in

 *  (without the newlines).  Set @length to a #gsize to get the length

 *  of the read line.  On an error, it will return %NULL and @error

 *  will be set. If there's no content to read, it will still return

 *  %NULL, but @error won't be set.

 **/

char *

g_data_input_stream_read_line (GDataInputStream  *stream,

			       gsize             *length,

			       GCancellable      *cancellable,

			       GError           **error)

{

  GBufferedInputStream *bstream;

  gsize checked;

  gboolean last_saw_cr;

  gssize found_pos;

  gssize res;

  int newline_len;

  char *line;

  g_return_val_if_fail (G_IS_DATA_INPUT_STREAM (stream), NULL);  

  bstream = G_BUFFERED_INPUT_STREAM (stream);

  newline_len = 0;

  checked = 0;

  last_saw_cr = FALSE;

  while ((found_pos = scan_for_newline (stream, &checked, &last_saw_cr, &newline_len)) == -1)

    {

      if (g_buffered_input_stream_get_available (bstream) ==

	  g_buffered_input_stream_get_buffer_size (bstream))

	g_buffered_input_stream_set_buffer_size (bstream,

						 2 * g_buffered_input_stream_get_buffer_size (bstream));

      res = g_buffered_input_stream_fill (bstream, -1, cancellable, error);

      if (res < 0)

	return NULL;

      if (res == 0)

	{

	  /* End of stream */

	  if (g_buffered_input_stream_get_available (bstream) == 0)

	    {

	      if (length)

		*length = 0;

	      return NULL;

	    }

	  else

	    {

	      found_pos = checked;

	      newline_len = 0;

	      break;

	    }

	}

    }

  line = g_malloc (found_pos + newline_len + 1);

  res = g_input_stream_read (G_INPUT_STREAM (stream),

			     line,

			     found_pos + newline_len,

			     NULL, NULL);

  if (length)

    *length = (gsize)found_pos;

  g_warn_if_fail (res == found_pos + newline_len);

  line[found_pos] = 0;

  return line;

}

/**

 * g_data_input_stream_read_line_utf8:

 * @stream: a given #GDataInputStream.

 * @length: (out) (optional): a #gsize to get the length of the data read in.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @error: #GError for error reporting.

 *

 * Reads a UTF-8 encoded line from the data input stream.

 *

 * If @cancellable is not %NULL, then the operation can be cancelled by

 * triggering the cancellable object from another thread. If the operation

 * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned.

 *

 * Returns: (nullable) (transfer full): a NUL terminated UTF-8 string

 *  with the line that was read in (without the newlines).  Set

 *  @length to a #gsize to get the length of the read line.  On an

 *  error, it will return %NULL and @error will be set.  For UTF-8

 *  conversion errors, the set error domain is %G_CONVERT_ERROR.  If

 *  there's no content to read, it will still return %NULL, but @error

 *  won't be set.

 *

 * Since: 2.30

 **/

char *

g_data_input_stream_read_line_utf8 (GDataInputStream  *stream,

				    gsize             *length,

				    GCancellable      *cancellable,

				    GError           **error)

{

  char *res;

  res = g_data_input_stream_read_line (stream, length, cancellable, error);

  if (!res)

    return NULL;

  if (!g_utf8_validate (res, -1, NULL))

    {

      g_set_error_literal (error, G_CONVERT_ERROR,

			   G_CONVERT_ERROR_ILLEGAL_SEQUENCE,

			   _("Invalid byte sequence in conversion input"));

      g_free (res);

      return NULL;

    }

  return res;

}

static gssize

scan_for_chars (GDataInputStream *stream,

		gsize            *checked_out,

		const char       *stop_chars,

                gsize             stop_chars_len)

{

  GBufferedInputStream *bstream;

  const char *buffer;

  gsize start, end, peeked;

  int i;

  gsize available, checked;

  const char *stop_char;

  const char *stop_end;

  bstream = G_BUFFERED_INPUT_STREAM (stream);

  stop_end = stop_chars + stop_chars_len;

  checked = *checked_out;

  start = checked;

  buffer = (const char *)g_buffered_input_stream_peek_buffer (bstream, &available) + start;

  end = available;

  peeked = end - start;

  for (i = 0; checked < available && i < peeked; i++)