/*

 * Copyright © 2009, 2010 Codethink Limited

 * Copyright © 2011 Collabora Ltd.

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * 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: Ryan Lortie <desrt@desrt.ca>

 *         Stef Walter <stefw@collabora.co.uk>

 */

#include "config.h"

#include "gbytes.h"

#include <glib/garray.h>

#include <glib/gstrfuncs.h>

#include <glib/gatomic.h>

#include <glib/gslice.h>

#include <glib/gtestutils.h>

#include <glib/gmem.h>

#include <glib/gmessages.h>

#include <glib/grefcount.h>

#include <string.h>

/**

 * GBytes:

 *

 * A simple refcounted data type representing an immutable sequence of zero or

 * more bytes from an unspecified origin.

 *

 * The purpose of a #GBytes is to keep the memory region that it holds

 * alive for as long as anyone holds a reference to the bytes.  When

 * the last reference count is dropped, the memory is released. Multiple

 * unrelated callers can use byte data in the #GBytes without coordinating

 * their activities, resting assured that the byte data will not change or

 * move while they hold a reference.

 *

 * A #GBytes can come from many different origins that may have

 * different procedures for freeing the memory region.  Examples are

 * memory from g_malloc(), from memory slices, from a #GMappedFile or

 * memory from other allocators.

 *

 * #GBytes work well as keys in #GHashTable. Use g_bytes_equal() and

 * g_bytes_hash() as parameters to g_hash_table_new() or g_hash_table_new_full().

 * #GBytes can also be used as keys in a #GTree by passing the g_bytes_compare()

 * function to g_tree_new().

 *

 * The data pointed to by this bytes must not be modified. For a mutable

 * array of bytes see #GByteArray. Use g_bytes_unref_to_array() to create a

 * mutable array for a #GBytes sequence. To create an immutable #GBytes from

 * a mutable #GByteArray, use the g_byte_array_free_to_bytes() function.

 *

 * Since: 2.32

 **/

/* Keep in sync with glib/tests/bytes.c */

struct _GBytes

{

  gconstpointer data;  /* may be NULL iff (size == 0) */

  gsize size;  /* may be 0 */

  gatomicrefcount ref_count;

  GDestroyNotify free_func;

  gpointer user_data;

};

/**

 * g_bytes_new:

 * @data: (transfer none) (array length=size) (element-type guint8) (nullable):

 *        the data to be used for the bytes

 * @size: the size of @data

 *

 * Creates a new #GBytes from @data.

 *

 * @data is copied. If @size is 0, @data may be %NULL.

 *

 * Returns: (transfer full): a new #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_new (gconstpointer data,

             gsize         size)

{

  g_return_val_if_fail (data != NULL || size == 0, NULL);

  return g_bytes_new_take (g_memdup2 (data, size), size);

}

/**

 * g_bytes_new_take:

 * @data: (transfer full) (array length=size) (element-type guint8) (nullable):

 *        the data to be used for the bytes

 * @size: the size of @data

 *

 * Creates a new #GBytes from @data.

 *

 * After this call, @data belongs to the bytes and may no longer be

 * modified by the caller.  g_free() will be called on @data when the

 * bytes is no longer in use. Because of this @data must have been created by

 * a call to g_malloc(), g_malloc0() or g_realloc() or by one of the many

 * functions that wrap these calls (such as g_new(), g_strdup(), etc).

 *

 * For creating #GBytes with memory from other allocators, see

 * g_bytes_new_with_free_func().

 *

 * @data may be %NULL if @size is 0.

 *

 * Returns: (transfer full): a new #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_new_take (gpointer data,

                  gsize    size)

{

  return g_bytes_new_with_free_func (data, size, g_free, data);

}

/**

 * g_bytes_new_static: (skip)

 * @data: (transfer full) (array length=size) (element-type guint8) (nullable):

 *        the data to be used for the bytes

 * @size: the size of @data

 *

 * Creates a new #GBytes from static data.

 *

 * @data must be static (ie: never modified or freed). It may be %NULL if @size

 * is 0.

 *

 * Returns: (transfer full): a new #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_new_static (gconstpointer data,

                    gsize         size)

{

  return g_bytes_new_with_free_func (data, size, NULL, NULL);

}

/**

 * g_bytes_new_with_free_func: (skip)

 * @data: (array length=size) (element-type guint8) (nullable):

 *        the data to be used for the bytes

 * @size: the size of @data

 * @free_func: the function to call to release the data

 * @user_data: data to pass to @free_func

 *

 * Creates a #GBytes from @data.

 *

 * When the last reference is dropped, @free_func will be called with the

 * @user_data argument.

 *

 * @data must not be modified after this call is made until @free_func has

 * been called to indicate that the bytes is no longer in use.

 *

 * @data may be %NULL if @size is 0.

 *

 * Returns: (transfer full): a new #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_new_with_free_func (gconstpointer  data,

                            gsize          size,

                            GDestroyNotify free_func,

                            gpointer       user_data)

{

  GBytes *bytes;

  g_return_val_if_fail (data != NULL || size == 0, NULL);

  bytes = g_slice_new (GBytes);

  bytes->data = data;

  bytes->size = size;

  bytes->free_func = free_func;

  bytes->user_data = user_data;

  g_atomic_ref_count_init (&bytes->ref_count);

  return (GBytes *)bytes;

}

/**

 * g_bytes_new_from_bytes:

 * @bytes: a #GBytes

 * @offset: offset which subsection starts at

 * @length: length of subsection

 *

 * Creates a #GBytes which is a subsection of another #GBytes. The @offset +

 * @length may not be longer than the size of @bytes.

 *

 * A reference to @bytes will be held by the newly created #GBytes until

 * the byte data is no longer needed.

 *

 * Since 2.56, if @offset is 0 and @length matches the size of @bytes, then

 * @bytes will be returned with the reference count incremented by 1. If @bytes

 * is a slice of another #GBytes, then the resulting #GBytes will reference

 * the same #GBytes instead of @bytes. This allows consumers to simplify the

 * usage of #GBytes when asynchronously writing to streams.

 *

 * Returns: (transfer full): a new #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_new_from_bytes (GBytes  *bytes,

                        gsize    offset,

                        gsize    length)

{

  gchar *base;

  /* Note that length may be 0. */

  g_return_val_if_fail (bytes != NULL, NULL);

  g_return_val_if_fail (offset <= bytes->size, NULL);

  g_return_val_if_fail (offset + length <= bytes->size, NULL);

  /* Avoid an extra GBytes if all bytes were requested */

  if (offset == 0 && length == bytes->size)

    return g_bytes_ref (bytes);

  base = (gchar *)bytes->data + offset;

  /* Avoid referencing intermediate GBytes. In practice, this should

   * only loop once.

   */

  while (bytes->free_func == (gpointer)g_bytes_unref)

    bytes = bytes->user_data;

  g_return_val_if_fail (bytes != NULL, NULL);

  g_return_val_if_fail (base >= (gchar *)bytes->data, NULL);

  g_return_val_if_fail (base <= (gchar *)bytes->data + bytes->size, NULL);

  g_return_val_if_fail (base + length <= (gchar *)bytes->data + bytes->size, NULL);

  return g_bytes_new_with_free_func (base, length,

                                     (GDestroyNotify)g_bytes_unref, g_bytes_ref (bytes));

}

/**

 * g_bytes_get_data:

 * @bytes: a #GBytes

 * @size: (out) (optional): location to return size of byte data

 *

 * Get the byte data in the #GBytes. This data should not be modified.

 *

 * This function will always return the same pointer for a given #GBytes.

 *

 * %NULL may be returned if @size is 0. This is not guaranteed, as the #GBytes

 * may represent an empty string with @data non-%NULL and @size as 0. %NULL will

 * not be returned if @size is non-zero.

 *

 * Returns: (transfer none) (array length=size) (element-type guint8) (nullable):

 *          a pointer to the byte data, or %NULL

 *

 * Since: 2.32

 */

gconstpointer

g_bytes_get_data (GBytes *bytes,

                  gsize *size)

{

  g_return_val_if_fail (bytes != NULL, NULL);

  if (size)

    *size = bytes->size;

  return bytes->data;

}

/**

 * g_bytes_get_size:

 * @bytes: a #GBytes

 *

 * Get the size of the byte data in the #GBytes.

 *

 * This function will always return the same value for a given #GBytes.

 *

 * Returns: the size

 *

 * Since: 2.32

 */

gsize

g_bytes_get_size (GBytes *bytes)

{

  g_return_val_if_fail (bytes != NULL, 0);

  return bytes->size;

}

/**

 * g_bytes_ref:

 * @bytes: a #GBytes

 *

 * Increase the reference count on @bytes.

 *

 * Returns: the #GBytes

 *

 * Since: 2.32

 */

GBytes *

g_bytes_ref (GBytes *bytes)

{

  g_return_val_if_fail (bytes != NULL, NULL);

  g_atomic_ref_count_inc (&bytes->ref_count);

  return bytes;

}

/**

 * g_bytes_unref:

 * @bytes: (nullable): a #GBytes

 *

 * Releases a reference on @bytes.  This may result in the bytes being

 * freed. If @bytes is %NULL, it will return immediately.

 *

 * Since: 2.32

 */

void

g_bytes_unref (GBytes *bytes)

{

  if (bytes == NULL)

    return;

  if (g_atomic_ref_count_dec (&bytes->ref_count))

    {

      if (bytes->free_func != NULL)

        bytes->free_func (bytes->user_data);

      g_slice_free (GBytes, bytes);

    }

}

/**

 * g_bytes_equal:

 * @bytes1: (type GLib.Bytes): a pointer to a #GBytes

 * @bytes2: (type GLib.Bytes): a pointer to a #GBytes to compare with @bytes1

 *

 * Compares the two #GBytes values being pointed to and returns

 * %TRUE if they are equal.

 *

 * This function can be passed to g_hash_table_new() as the @key_equal_func

 * parameter, when using non-%NULL #GBytes pointers as keys in a #GHashTable.

 *

 * Returns: %TRUE if the two keys match.

 *

 * Since: 2.32

 */

gboolean

g_bytes_equal (gconstpointer bytes1,

               gconstpointer bytes2)

{

  const GBytes *b1 = bytes1;

  const GBytes *b2 = bytes2;

  g_return_val_if_fail (bytes1 != NULL, FALSE);

  g_return_val_if_fail (bytes2 != NULL, FALSE);

  return b1->size == b2->size &&

         (b1->size == 0 || memcmp (b1->data, b2->data, b1->size) == 0);

}

/**

 * g_bytes_hash:

 * @bytes: (type GLib.Bytes): a pointer to a #GBytes key

 *

 * Creates an integer hash code for the byte data in the #GBytes.

 *

 * This function can be passed to g_hash_table_new() as the @key_hash_func

 * parameter, when using non-%NULL #GBytes pointers as keys in a #GHashTable.

 *

 * Returns: a hash value corresponding to the key.

 *

 * Since: 2.32

 */

guint

g_bytes_hash (gconstpointer bytes)

{

  const GBytes *a = bytes;

  const signed char *p, *e;

  guint32 h = 5381;

  g_return_val_if_fail (bytes != NULL, 0);

  for (p = (signed char *)a->data, e = (signed char *)a->data + a->size; p != e; p++)

    h = (h << 5) + h + *p;

  return h;

}

/**

 * g_bytes_compare:

 * @bytes1: (type GLib.Bytes): a pointer to a #GBytes

 * @bytes2: (type GLib.Bytes): a pointer to a #GBytes to compare with @bytes1

 *

 * Compares the two #GBytes values.

 *

 * This function can be used to sort GBytes instances in lexicographical order.

 *

 * If @bytes1 and @bytes2 have different length but the shorter one is a

 * prefix of the longer one then the shorter one is considered to be less than

 * the longer one. Otherwise the first byte where both differ is used for

 * comparison. If @bytes1 has a smaller value at that position it is

 * considered less, otherwise greater than @bytes2.

 *

 * Returns: a negative value if @bytes1 is less than @bytes2, a positive value

 *          if @bytes1 is greater than @bytes2, and zero if @bytes1 is equal to

 *          @bytes2

 *

 *

 * Since: 2.32

 */

gint

g_bytes_compare (gconstpointer bytes1,

                 gconstpointer bytes2)

{

  const GBytes *b1 = bytes1;

  const GBytes *b2 = bytes2;

  gint ret;

  g_return_val_if_fail (bytes1 != NULL, 0);

  g_return_val_if_fail (bytes2 != NULL, 0);

  ret = memcmp (b1->data, b2->data, MIN (b1->size, b2->size));

  if (ret == 0 && b1->size != b2->size)

      ret = b1->size < b2->size ? -1 : 1;

  return ret;

}

static gpointer

try_steal_and_unref (GBytes         *bytes,

                     GDestroyNotify  free_func,

                     gsize          *size)

{

  gpointer result;

  if (bytes->free_func != free_func || bytes->data == NULL ||

      bytes->user_data != bytes->data)

    return NULL;

  /* Are we the only reference? */

  if (g_atomic_ref_count_compare (&bytes->ref_count, 1))

    {

      *size = bytes->size;

      result = (gpointer)bytes->data;

      g_slice_free (GBytes, bytes);

      return result;

    }

  return NULL;

}

/**

 * g_bytes_unref_to_data:

 * @bytes: (transfer full): a #GBytes

 * @size: (out): location to place the length of the returned data

 *

 * Unreferences the bytes, and returns a pointer the same byte data

 * contents.

 *

 * As an optimization, the byte data is returned without copying if this was

 * the last reference to bytes and bytes was created with g_bytes_new(),

 * g_bytes_new_take() or g_byte_array_free_to_bytes(). In all other cases the

 * data is copied.

 *

 * Returns: (transfer full) (array length=size) (element-type guint8)

 *          (not nullable): a pointer to the same byte data, which should be

 *          freed with g_free()

 *

 * Since: 2.32

 */

gpointer

g_bytes_unref_to_data (GBytes *bytes,

                       gsize  *size)

{

  gpointer result;

  g_return_val_if_fail (bytes != NULL, NULL);

  g_return_val_if_fail (size != NULL, NULL);

  /*

   * Optimal path: if this is was the last reference, then we can return

   * the data from this GBytes without copying.

   */

  result = try_steal_and_unref (bytes, g_free, size);

  if (result == NULL)

    {

      /*

       * Copy: Non g_malloc (or compatible) allocator, or static memory,

       * so we have to copy, and then unref.

       */

      result = g_memdup2 (bytes->data, bytes->size);

      *size = bytes->size;

      g_bytes_unref (bytes);

    }

  return result;

}

/**

 * g_bytes_unref_to_array:

 * @bytes: (transfer full): a #GBytes

 *

 * Unreferences the bytes, and returns a new mutable #GByteArray containing

 * the same byte data.

 *

 * As an optimization, the byte data is transferred to the array without copying

 * if this was the last reference to bytes and bytes was created with

 * g_bytes_new(), g_bytes_new_take() or g_byte_array_free_to_bytes(). In all

 * other cases the data is copied.

 *

 * Do not use it if @bytes contains more than %G_MAXUINT

 * bytes. #GByteArray stores the length of its data in #guint, which

 * may be shorter than #gsize, that @bytes is using.

 *

 * Returns: (transfer full): a new mutable #GByteArray containing the same byte data

 *

 * Since: 2.32

 */

GByteArray *

g_bytes_unref_to_array (GBytes *bytes)

{

  gpointer data;

  gsize size;

  g_return_val_if_fail (bytes != NULL, NULL);

  data = g_bytes_unref_to_data (bytes, &size);

  return g_byte_array_new_take (data, size);

}

/**

 * g_bytes_get_region:

 * @bytes: a #GBytes

 * @element_size: a non-zero element size

 * @offset: an offset to the start of the region within the @bytes

 * @n_elements: the number of elements in the region

 *

 * Gets a pointer to a region in @bytes.

 *

 * The region starts at @offset many bytes from the start of the data

 * and contains @n_elements many elements of @element_size size.

 *

 * @n_elements may be zero, but @element_size must always be non-zero.

 * Ideally, @element_size is a static constant (eg: sizeof a struct).

 *

 * This function does careful bounds checking (including checking for

 * arithmetic overflows) and returns a non-%NULL pointer if the

 * specified region lies entirely within the @bytes. If the region is

 * in some way out of range, or if an overflow has occurred, then %NULL

 * is returned.

 *

 * Note: it is possible to have a valid zero-size region. In this case,

 * the returned pointer will be equal to the base pointer of the data of

 * @bytes, plus @offset.  This will be non-%NULL except for the case

 * where @bytes itself was a zero-sized region.  Since it is unlikely

 * that you will be using this function to check for a zero-sized region

 * in a zero-sized @bytes, %NULL effectively always means "error".

 *

 * Returns: (nullable): the requested region, or %NULL in case of an error

 *

 * Since: 2.70

 */

gconstpointer

g_bytes_get_region (GBytes *bytes,

                    gsize   element_size,

                    gsize   offset,

                    gsize   n_elements)

{

  gsize total_size;

  gsize end_offset;

  g_return_val_if_fail (element_size > 0, NULL);

  /* No other assertion checks here.  If something is wrong then we will

   * simply crash (via NULL dereference or divide-by-zero).

   */

  if (!g_size_checked_mul (&total_size, element_size, n_elements))

    return NULL;

  if (!g_size_checked_add (&end_offset, offset, total_size))

    return NULL;

  /* We now have:

   *

   *   0 <= offset <= end_offset

   *

   * So we need only check that end_offset is within the range of the

   * size of @bytes and we're good to go.

   */

  if (end_offset > bytes->size)

    return NULL;

  /* We now have:

   *

   *   0 <= offset <= end_offset <= bytes->size

   */

  return ((guchar *) bytes->data) + offset;

}