Sebastian Dröge 0ee18781f9 gst: Add GstIdStr for holding structure names and field names
This is an efficient string storage for short strings without heap allocations,
and falling back to the heap for bigger allocations. Almost all structure fields
and structure names in use nowadays are short enough to not require a heap
allocation.

As structure names and fields are sometimes dynamically created, storing them in
a GQuark can create a memory leak and potentially a DoS attack by continously
triggering creating of new quarks.

Thanks to Tim for coming up with the name!

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7432>
2024-09-26 19:21:29 +03:00

332 lines
7.4 KiB
C

/* GStreamer
*
* Copyright (C) 2024 Sebastian Dröge <sebastian@centricular.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstidstr
* @title: GstIdStr
* @short_description: String type optimized for short strings
* @see_also: #GstStructure
*
* A #GstIdStr is string type optimized for short strings and used for structure
* names, structure field names and in other places.
*
* Strings up to 16 bytes (including NUL terminator) are stored inline, other
* strings are stored on the heap.
*
* ```cpp
* GstIdStr s = GST_ID_STR_INIT;
*
* gst_id_str_set (&s, "Hello, World!");
* g_print ("%s\n", gst_id_str_as_str (&s));
*
* gst_id_str_clear (&s);
* ```
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#define GST_ID_STR_DISABLE_INLINES
#include "gstidstr.h"
#include "gstidstr-private.h"
G_DEFINE_BOXED_TYPE (GstIdStr, gst_id_str, gst_id_str_copy, gst_id_str_free);
// Make sure the string type fields are in the same place for each variant
// See https://developercommunity.visualstudio.com/t/C-offsetof-an-array-item-is-accepted-by/10736612
#ifndef _MSC_VER
G_STATIC_ASSERT (G_STRUCT_OFFSET (GstIdStrPrivate,
s.string_type.t) == G_STRUCT_OFFSET (GstIdStrPrivate,
s.short_string.s[15]));
#endif
G_STATIC_ASSERT (G_STRUCT_OFFSET (GstIdStrPrivate,
s.string_type.t) == G_STRUCT_OFFSET (GstIdStrPrivate,
s.pointer_string.t));
// The overall struct should be 16 bytes large and at least pointer aligned
G_STATIC_ASSERT (sizeof (GstIdStrPrivate) == 16);
// See https://developercommunity.visualstudio.com/t/C-offsetof-an-array-item-is-accepted-by/10736612
#ifndef _MSC_VER
G_STATIC_ASSERT (G_ALIGNOF (GstIdStrPrivate) >= G_ALIGNOF (gpointer));
// Alignment and size of the private and public type must be the same
G_STATIC_ASSERT (G_ALIGNOF (GstIdStrPrivate) == G_ALIGNOF (GstIdStr));
#endif
G_STATIC_ASSERT (sizeof (GstIdStrPrivate) == sizeof (GstIdStr));
/**
* gst_id_str_init:
* @s: A %GstIdStr
*
* Initializes a (usually stack-allocated) id string @s. The newly-initialized
* id string will contain an empty string by default as value.
*
* Since: 1.26
*/
void
gst_id_str_init (GstIdStr * s)
{
_gst_id_str_init_inline (s);
}
/**
* gst_id_str_get_len:
* @s: A %GstIdStr
*
* Returns the length of @s, exluding the NUL-terminator. This is equivalent to
* calling `strcmp()` but potentially faster.
*
* Since: 1.26
*/
gsize
gst_id_str_get_len (const GstIdStr * s)
{
return _gst_id_str_get_len (s);
}
/**
* gst_id_str_set:
* @s: A %GstIdStr
* @value: A NUL-terminated string
*
* Sets @s to the string @value.
*
* Since: 1.26
*/
void
gst_id_str_set (GstIdStr * s, const gchar * value)
{
_gst_id_str_set_inline (s, value);
}
/**
* gst_id_str_set_with_len:
* @s: A %GstIdStr
* @value: A string
* @len: Length of the string
*
* Sets @s to the string @value of length @len. @value does not have to be
* NUL-terminated and @len should not include the NUL-terminator.
*
* Since: 1.26
*/
void
gst_id_str_set_with_len (GstIdStr * s, const gchar * value, gsize len)
{
_gst_id_str_set_with_len_inline (s, value, len);
}
/**
* gst_id_str_set_static_str:
* @s: A %GstIdStr
* @value: A NUL-terminated string
*
* Sets @s to the string @value. @value needs to be valid for the remaining
* lifetime of the process, e.g. has to be a static string.
*
* Since: 1.26
*/
void
gst_id_str_set_static_str (GstIdStr * s, const gchar * value)
{
_gst_id_str_set_static_str_inline (s, value);
}
/**
* gst_id_str_set_static_str_with_len:
* @s: A %GstIdStr
* @value: A string
* @len: Length of the string
*
* Sets @s to the string @value of length @len. @value needs to be valid for the
* remaining lifetime of the process, e.g. has to be a static string.
*
* @value does not have to be NUL-terminated and @len should not include the
* NUL-terminator.
*
* Since: 1.26
*/
void
gst_id_str_set_static_str_with_len (GstIdStr * s, const gchar * value,
gsize len)
{
_gst_id_str_set_static_str_with_len_inline (s, value, len);
}
/**
* gst_id_str_clear:
* @s: A %GstIdStr
*
* Clears @s and sets it to the empty string.
*
* Since: 1.26
*/
void
gst_id_str_clear (GstIdStr * s)
{
_gst_id_str_clear_inline (s);
}
/**
* gst_id_str_copy:
* @s: A %GstIdStr
*
* Copies @s into newly allocated heap memory.
*
* Returns: (transfer full): A heap-allocated copy of @s.
*
* Since: 1.26
*/
GstIdStr *
gst_id_str_copy (const GstIdStr * s)
{
return _gst_id_str_copy_inline (s);
}
/**
* gst_id_str_new:
*
* Returns a newly heap allocated empty string.
*
* Returns: (transfer full): A heap-allocated string.
*
* Since: 1.26
*/
GstIdStr *
gst_id_str_new (void)
{
return _gst_id_str_new_inline ();
}
/**
* gst_id_str_free:
* @s: A heap allocated %GstIdStr
*
* Frees @s. This should only be called for heap-allocated #GstIdStr.
*
* Since: 1.26
*/
void
gst_id_str_free (GstIdStr * s)
{
_gst_id_str_free_inline (s);
}
/**
* gst_id_str_copy_into:
* @d: The destination %GstIdStr
* @s: The source %GstIdStr
*
* Copies @s into @d.
*
* Since: 1.26
*/
void
gst_id_str_copy_into (GstIdStr * d, const GstIdStr * s)
{
_gst_id_str_copy_into_inline (d, s);
}
/**
* gst_id_str_move:
* @d: The destination %GstIdStr
* @s: The source %GstIdStr
*
* Moves @s into @d and resets @s.
*
* Since: 1.26
*/
void
gst_id_str_move (GstIdStr * d, GstIdStr * s)
{
_gst_id_str_move_inline (d, s);
}
/**
* gst_id_str_is_equal:
* @s1: A %GstIdStr
* @s2: A %GstIdStr
*
* Compares @s1 and @s2 for equality.
*
* Returns: %TRUE if @s1 and @s2 are equal.
*
* Since: 1.26
*/
gboolean
gst_id_str_is_equal (const GstIdStr * s1, const GstIdStr * s2)
{
return _gst_id_str_is_equal_inline (s1, s2);
}
/**
* gst_id_str_is_equal_to_str:
* @s1: A %GstIdStr
* @s2: A string
*
* Compares @s1 and @s2 for equality.
*
* Returns: %TRUE if @s1 and @s2 are equal.
*
* Since: 1.26
*/
gboolean
gst_id_str_is_equal_to_str (const GstIdStr * s1, const gchar * s2)
{
return _gst_id_str_is_equal_to_str_inline (s1, s2);
}
/**
* gst_id_str_is_equal_to_str_with_len:
* @s1: A %GstIdStr
* @s2: A string
* @len: Length of @s2.
*
* Compares @s1 and @s2 with length @len for equality. @s2 does not have to be
* NUL-terminated and @len should not include the NUL-terminator.
*
* This is generally faster than gst_id_str_is_equal_to_str() if the length is
* already known.
*
* Returns: %TRUE if @s1 and @s2 are equal.
*
* Since: 1.26
*/
gboolean
gst_id_str_is_equal_to_str_with_len (const GstIdStr * s1, const gchar * s2,
gsize len)
{
return _gst_id_str_is_equal_to_str_with_len_inline (s1, s2, len);
}
/**
* gst_id_str_as_str:
* @s: A %GstIdStr
*
* Returns: the NUL-terminated string representation of @s.
*
* Since: 1.26
*/
const gchar *
gst_id_str_as_str (const GstIdStr * s)
{
return _gst_id_str_as_str_inline (s);
}