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e2a1aa44df
After a memory has been unmapped, protection mode can now be changed when mapping it again. See https://bugzilla.gnome.org/show_bug.cgi?id=789952. Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/895>
345 lines
8.1 KiB
C
345 lines
8.1 KiB
C
/* GStreamer fd backed memory
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* Copyright (C) 2013 Linaro SA
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* Author: Benjamin Gaignard <benjamin.gaignard@linaro.org> for Linaro.
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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 mordetails.
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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., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:gstfdmemory
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* @title: GstFdAllocator
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* @short_description: Memory wrapper for fd backed memory
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* @see_also: #GstMemory
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*
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* Since: 1.4
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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 "gstfdmemory.h"
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#ifdef HAVE_MMAP
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#include <sys/mman.h>
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#include <unistd.h>
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#endif
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GST_DEBUG_CATEGORY_STATIC (gst_fdmemory_debug);
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#define GST_CAT_DEFAULT gst_fdmemory_debug
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typedef struct
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{
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GstMemory mem;
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GstFdMemoryFlags flags;
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gint fd;
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gpointer data;
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gint mmapping_flags;
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gint mmap_count;
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GMutex lock;
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} GstFdMemory;
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static void
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gst_fd_mem_free (GstAllocator * allocator, GstMemory * gmem)
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{
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#ifdef HAVE_MMAP
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GstFdMemory *mem = (GstFdMemory *) gmem;
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if (mem->data) {
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if (!(mem->flags & GST_FD_MEMORY_FLAG_KEEP_MAPPED))
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g_warning (G_STRLOC ":%s: Freeing memory %p still mapped", G_STRFUNC,
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mem);
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munmap ((void *) mem->data, gmem->maxsize);
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}
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if (mem->fd >= 0 && gmem->parent == NULL
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&& !(mem->flags & GST_FD_MEMORY_FLAG_DONT_CLOSE))
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close (mem->fd);
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g_mutex_clear (&mem->lock);
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g_slice_free (GstFdMemory, mem);
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GST_DEBUG ("%p: freed", mem);
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#endif
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}
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static gpointer
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gst_fd_mem_map (GstMemory * gmem, gsize maxsize, GstMapFlags flags)
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{
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#ifdef HAVE_MMAP
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GstFdMemory *mem = (GstFdMemory *) gmem;
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gint prot;
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gpointer ret = NULL;
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if (gmem->parent)
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return gst_fd_mem_map (gmem->parent, maxsize, flags);
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prot = flags & GST_MAP_READ ? PROT_READ : 0;
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prot |= flags & GST_MAP_WRITE ? PROT_WRITE : 0;
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g_mutex_lock (&mem->lock);
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/* do not mmap twice the buffer */
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if (mem->data) {
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/* only return address if mapping flags are a subset
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* of the previous flags */
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if ((mem->mmapping_flags & prot) == prot) {
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ret = mem->data;
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mem->mmap_count++;
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} else if ((mem->flags & GST_FD_MEMORY_FLAG_KEEP_MAPPED)
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&& mem->mmap_count == 0
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&& mprotect (mem->data, gmem->maxsize, prot) == 0) {
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ret = mem->data;
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mem->mmapping_flags = prot;
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mem->mmap_count++;
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}
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goto out;
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}
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if (mem->fd != -1) {
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gint flags;
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flags =
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(mem->flags & GST_FD_MEMORY_FLAG_MAP_PRIVATE) ? MAP_PRIVATE :
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MAP_SHARED;
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mem->data = mmap (0, gmem->maxsize, prot, flags, mem->fd, 0);
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if (mem->data == MAP_FAILED) {
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GstDebugLevel level;
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mem->data = NULL;
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switch (errno) {
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case EACCES:
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level = GST_LEVEL_INFO;
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break;
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default:
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level = GST_LEVEL_ERROR;
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break;
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}
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GST_CAT_LEVEL_LOG (GST_CAT_DEFAULT, level, NULL,
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"%p: fd %d: mmap failed: %s", mem, mem->fd, g_strerror (errno));
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goto out;
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}
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}
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GST_DEBUG ("%p: fd %d: mapped %p", mem, mem->fd, mem->data);
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if (mem->data) {
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mem->mmapping_flags = prot;
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mem->mmap_count++;
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ret = mem->data;
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}
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out:
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g_mutex_unlock (&mem->lock);
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return ret;
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#else /* !HAVE_MMAP */
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return FALSE;
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#endif
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}
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static void
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gst_fd_mem_unmap (GstMemory * gmem)
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{
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#ifdef HAVE_MMAP
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GstFdMemory *mem = (GstFdMemory *) gmem;
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if (gmem->parent)
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return gst_fd_mem_unmap (gmem->parent);
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if (mem->flags & GST_FD_MEMORY_FLAG_KEEP_MAPPED) {
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g_mutex_lock (&mem->lock);
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mem->mmap_count--;
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g_mutex_unlock (&mem->lock);
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return;
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}
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g_mutex_lock (&mem->lock);
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if (mem->data && !(--mem->mmap_count)) {
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munmap ((void *) mem->data, gmem->maxsize);
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mem->data = NULL;
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mem->mmapping_flags = 0;
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GST_DEBUG ("%p: fd %d unmapped", mem, mem->fd);
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}
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g_mutex_unlock (&mem->lock);
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#endif
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}
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static GstMemory *
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gst_fd_mem_share (GstMemory * gmem, gssize offset, gssize size)
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{
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#ifdef HAVE_MMAP
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GstFdMemory *mem = (GstFdMemory *) gmem;
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GstFdMemory *sub;
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GstMemory *parent;
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GST_DEBUG ("%p: share %" G_GSSIZE_FORMAT " %" G_GSIZE_FORMAT, mem, offset,
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size);
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/* find the real parent */
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if ((parent = mem->mem.parent) == NULL)
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parent = (GstMemory *) mem;
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if (size == -1)
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size = gmem->maxsize - offset;
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sub = g_slice_new0 (GstFdMemory);
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/* the shared memory is always readonly */
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gst_memory_init (GST_MEMORY_CAST (sub), GST_MINI_OBJECT_FLAGS (parent) |
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GST_MINI_OBJECT_FLAG_LOCK_READONLY, mem->mem.allocator, parent,
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mem->mem.maxsize, mem->mem.align, mem->mem.offset + offset, size);
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sub->fd = mem->fd;
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g_mutex_init (&sub->lock);
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return GST_MEMORY_CAST (sub);
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#else /* !HAVE_MMAP */
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return NULL;
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#endif
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}
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G_DEFINE_TYPE (GstFdAllocator, gst_fd_allocator, GST_TYPE_ALLOCATOR);
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static void
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gst_fd_allocator_class_init (GstFdAllocatorClass * klass)
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{
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GstAllocatorClass *allocator_class;
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allocator_class = (GstAllocatorClass *) klass;
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allocator_class->alloc = NULL;
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allocator_class->free = gst_fd_mem_free;
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GST_DEBUG_CATEGORY_INIT (gst_fdmemory_debug, "fdmemory", 0,
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"GstFdMemory and GstFdAllocator");
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}
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static void
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gst_fd_allocator_init (GstFdAllocator * allocator)
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{
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GstAllocator *alloc = GST_ALLOCATOR_CAST (allocator);
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alloc->mem_type = GST_ALLOCATOR_FD;
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alloc->mem_map = gst_fd_mem_map;
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alloc->mem_unmap = gst_fd_mem_unmap;
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alloc->mem_share = gst_fd_mem_share;
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GST_OBJECT_FLAG_SET (allocator, GST_ALLOCATOR_FLAG_CUSTOM_ALLOC);
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}
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/**
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* gst_fd_allocator_new:
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*
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* Return a new fd allocator.
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*
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* Returns: (transfer full): a new fd allocator, or NULL if the allocator
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* isn't available. Use gst_object_unref() to release the allocator after
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* usage
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*
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* Since: 1.6
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*/
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GstAllocator *
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gst_fd_allocator_new (void)
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{
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GstAllocator *alloc;
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alloc = g_object_new (GST_TYPE_FD_ALLOCATOR, NULL);
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gst_object_ref_sink (alloc);
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return alloc;
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}
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/**
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* gst_fd_allocator_alloc:
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* @allocator: allocator to be used for this memory
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* @fd: file descriptor
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* @size: memory size
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* @flags: extra #GstFdMemoryFlags
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*
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* Return a %GstMemory that wraps a generic file descriptor.
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*
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* Returns: (transfer full): a GstMemory based on @allocator.
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* When the buffer will be released the allocator will close the @fd unless
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* the %GST_FD_MEMORY_FLAG_DONT_CLOSE flag is specified.
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* The memory is only mmapped on gst_buffer_map() request.
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*
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* Since: 1.6
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*/
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GstMemory *
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gst_fd_allocator_alloc (GstAllocator * allocator, gint fd, gsize size,
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GstFdMemoryFlags flags)
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{
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#ifdef HAVE_MMAP
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GstFdMemory *mem;
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g_return_val_if_fail (GST_IS_FD_ALLOCATOR (allocator), NULL);
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mem = g_slice_new0 (GstFdMemory);
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gst_memory_init (GST_MEMORY_CAST (mem), 0, GST_ALLOCATOR_CAST (allocator),
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NULL, size, 0, 0, size);
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mem->flags = flags;
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mem->fd = fd;
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g_mutex_init (&mem->lock);
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GST_DEBUG ("%p: fd: %d size %" G_GSIZE_FORMAT, mem, mem->fd,
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mem->mem.maxsize);
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return (GstMemory *) mem;
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#else /* !HAVE_MMAP */
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return NULL;
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#endif
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}
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/**
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* gst_is_fd_memory:
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* @mem: #GstMemory
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*
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* Check if @mem is memory backed by an fd
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*
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* Returns: %TRUE when @mem has an fd that can be retrieved with
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* gst_fd_memory_get_fd().
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*
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* Since: 1.6
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*/
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gboolean
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gst_is_fd_memory (GstMemory * mem)
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{
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g_return_val_if_fail (mem != NULL, FALSE);
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return GST_IS_FD_ALLOCATOR (mem->allocator);
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}
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/**
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* gst_fd_memory_get_fd:
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* @mem: #GstMemory
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*
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* Get the fd from @mem. Call gst_is_fd_memory() to check if @mem has
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* an fd.
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*
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* Returns: the fd of @mem or -1 when there is no fd on @mem
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*
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* Since: 1.6
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*/
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gint
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gst_fd_memory_get_fd (GstMemory * mem)
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{
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g_return_val_if_fail (mem != NULL, -1);
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g_return_val_if_fail (GST_IS_FD_ALLOCATOR (mem->allocator), -1);
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return ((GstFdMemory *) mem)->fd;
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}
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