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glib2.0/glib/gbytes.c

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/*
* 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 #GBytes and may no longer be
* modified by the caller. The memory of @data has to be dynamically
* allocated and will eventually be freed with g_free().
*
* 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;
}
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