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8ca53a1a67
Closes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/3370 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6362>
222 lines
5.9 KiB
C
222 lines
5.9 KiB
C
/* GStreamer shared memory allocator
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*
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* Copyright (C) 2012 Intel Corporation
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* Copyright (C) 2012 Sreerenj Balachandran <sreerenj.balachandran@intel.com>
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* Copyright (C) 2023 Netflix Inc.
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* Author: Xavier Claessens <xavier.claessens@collabora.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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/**
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* SECTION:gstshmallocator
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* @title: GstShmAllocator
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* @short_description: Allocator for file-descriptor backed shared memory
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* @see_also: #GstMemory and #GstFdAllocator
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*
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* This is a subclass of #GstFdAllocator that implements the
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* gst_allocator_alloc() method using `memfd_create()` when available, POSIX
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* `shm_open()` otherwise. Platforms not supporting any of those (Windows) will
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* always return %NULL.
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*
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* Note that allocating new shared memories has a significant performance cost,
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* it is thus recommended to keep a pool of pre-allocated #GstMemory, using
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* #GstBufferPool. For that reason, this allocator has the
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* %GST_ALLOCATOR_FLAG_NO_COPY flag set.
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*
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* Since: 1.24
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <sys/stat.h>
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#include "gstshmallocator.h"
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#ifdef HAVE_MMAP
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#include <fcntl.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#endif
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struct _GstShmAllocator
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{
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GstFdAllocator parent;
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};
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#define GST_CAT_DEFAULT gst_shm_debug
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GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
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G_DEFINE_TYPE_WITH_CODE (GstShmAllocator, gst_shm_allocator,
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GST_TYPE_FD_ALLOCATOR,
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GST_DEBUG_CATEGORY_INIT (gst_shm_debug, "shmallocator", 0,
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"Shared memory allocator");
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);
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static GstMemory *
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gst_shm_allocator_alloc (GstAllocator * allocator, gsize size,
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GstAllocationParams * params)
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{
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#if defined(HAVE_MEMFD_CREATE) || defined(HAVE_SHM_OPEN)
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GstShmAllocator *self = GST_SHM_ALLOCATOR (allocator);
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int fd;
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GstMemory *mem;
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GstMapInfo info;
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/* See _sysmem_new_block() for details */
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gsize maxsize = size + params->prefix + params->padding;
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gsize align = params->align;
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align |= gst_memory_alignment;
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maxsize += align;
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#ifdef HAVE_MEMFD_CREATE
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fd = memfd_create ("gst-shm", MFD_CLOEXEC | MFD_ALLOW_SEALING);
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if (fd < 0) {
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GST_ERROR_OBJECT (self, "memfd_create() failed: %s", strerror (errno));
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return NULL;
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}
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#else
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{
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char filename[1024];
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static int init = 0;
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int flags = O_RDWR | O_CREAT | O_EXCL;
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int perms = S_IRUSR | S_IWUSR | S_IRGRP;
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snprintf (filename, 1024, "/gst-shm.%d.%d", getpid (), init++);
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fd = shm_open (filename, flags, perms);
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if (fd < 0) {
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GST_ERROR_OBJECT (self, "shm_open() failed: %s", strerror (errno));
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return NULL;
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}
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shm_unlink (filename);
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}
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#endif
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if (ftruncate (fd, maxsize) < 0) {
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GST_ERROR_OBJECT (self, "ftruncate failed: %s", strerror (errno));
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close (fd);
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return NULL;
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}
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mem = gst_fd_allocator_alloc (allocator, fd, maxsize,
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GST_FD_MEMORY_FLAG_KEEP_MAPPED);
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if (G_UNLIKELY (!mem)) {
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GST_ERROR_OBJECT (self, "GstFdMemory allocation failed");
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close (fd);
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return NULL;
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}
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/* We use GST_FD_MEMORY_FLAG_KEEP_MAPPED, so make sure the first map is RW. */
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if (!gst_memory_map (mem, &info, GST_MAP_READWRITE)) {
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GST_ERROR_OBJECT (self, "GstFdMemory map failed");
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gst_memory_unref (mem);
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return NULL;
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}
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/* See _sysmem_new_block() for details */
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guint8 *data = info.data;
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gsize aoffset;
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gsize asize = maxsize;
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if ((aoffset = ((guintptr) data & align))) {
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aoffset = (align + 1) - aoffset;
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data += aoffset;
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asize = maxsize - aoffset;
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}
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if (params->prefix && (params->flags & GST_MEMORY_FLAG_ZERO_PREFIXED))
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memset (data, 0, params->prefix);
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gsize padding = asize - (params->prefix + size);
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if (padding && (params->flags & GST_MEMORY_FLAG_ZERO_PADDED))
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memset (data + params->prefix + size, 0, padding);
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mem->align = align;
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mem->size = size;
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mem->offset = params->prefix + aoffset;
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gst_memory_unmap (mem, &info);
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#ifdef HAVE_MEMFD_CREATE
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fcntl (fd, F_ADD_SEALS, F_SEAL_SHRINK);
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#endif
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return mem;
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#else
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return NULL;
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#endif
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}
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static void
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gst_shm_allocator_class_init (GstShmAllocatorClass * klass)
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{
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GstAllocatorClass *alloc_class = (GstAllocatorClass *) klass;
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alloc_class->alloc = GST_DEBUG_FUNCPTR (gst_shm_allocator_alloc);
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}
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static void
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gst_shm_allocator_init (GstShmAllocator * self)
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{
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GstAllocator *alloc = GST_ALLOCATOR_CAST (self);
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alloc->mem_type = GST_ALLOCATOR_SHM;
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GST_OBJECT_FLAG_SET (self, GST_ALLOCATOR_FLAG_NO_COPY);
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}
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/**
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* gst_shm_allocator_init_once:
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*
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* Register a #GstShmAllocator using gst_allocator_register() with the name
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* %GST_ALLOCATOR_SHM. This is no-op after the first call.
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*
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* Since: 1.24
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*/
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void
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gst_shm_allocator_init_once (void)
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{
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static gsize _init = 0;
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if (g_once_init_enter (&_init)) {
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GstAllocator *alloc;
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alloc = (GstAllocator *) g_object_new (GST_TYPE_SHM_ALLOCATOR, NULL);
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gst_object_ref_sink (alloc);
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gst_allocator_register (GST_ALLOCATOR_SHM, alloc);
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g_once_init_leave (&_init, 1);
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}
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}
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/**
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* gst_shm_allocator_get:
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*
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* Get the #GstShmAllocator singleton previously registered with
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* gst_shm_allocator_init_once().
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*
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* Returns: (transfer full) (nullable): a #GstAllocator or %NULL if
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* gst_shm_allocator_init_once() has not been previously called.
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*
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* Since: 1.24
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*/
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GstAllocator *
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gst_shm_allocator_get (void)
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{
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return gst_allocator_find (GST_ALLOCATOR_SHM);
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}
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