/* GStreamer
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* Copyright (C) 2000,2005 Wim Taymans <wim@fluendo.com>
* Copyright (C) 2006 Tim-Philipp Müller <tim centricular net>
*
* gsttypefindhelper.c:
*
* 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:gsttypefindhelper
* @title: GstTypeFindHelper
* @short_description: Utility functions for typefinding
*
* Utility functions for elements doing typefinding:
* gst_type_find_helper() does typefinding in pull mode, while
* gst_type_find_helper_for_buffer() is useful for elements needing to do
* typefinding in push mode from a chain function.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdlib.h>
#include <string.h>
#include "gsttypefindhelper.h"
/* ********************** typefinding in pull mode ************************ */
static void
helper_find_suggest (gpointer data, guint probability, GstCaps * caps);
typedef struct
{
GstBuffer *buffer;
GstMapInfo map;
} GstMappedBuffer;
typedef struct
{
GSList *buffers; /* buffer cache */
guint64 size;
guint64 last_offset;
GstTypeFindHelperGetRangeFunction func;
GstTypeFindProbability best_probability;
GstCaps *caps;
GstTypeFindFactory *factory; /* for logging */
GstObject *obj; /* for logging */
GstObject *parent;
} GstTypeFindHelper;
/*
* helper_find_peek:
* @data: helper data struct
* @off: stream offset
* @size: block size
*
* Get data pointer within a stream. Keeps a cache of read buffers (partly
* for performance reasons, but mostly because pointers returned by us need
* to stay valid until typefinding has finished)
*
* Returns: (nullable): address of the data or %NULL if buffer does not cover
* the requested range.
*/
static const guint8 *
helper_find_peek (gpointer data, gint64 offset, guint size)
{
GstTypeFindHelper *helper;
GstBuffer *buffer;
GstFlowReturn ret;
GSList *insert_pos = NULL;
gsize buf_size;
guint64 buf_offset;
GstMappedBuffer *bmap;
#if 0
GstCaps *caps;
#endif
helper = (GstTypeFindHelper *) data;
GST_LOG_OBJECT (helper->obj, "'%s' called peek (%" G_GINT64_FORMAT
", %u)", GST_OBJECT_NAME (helper->factory), offset, size);
if (size == 0)
return NULL;
if (offset < 0) {
if (helper->size == -1 || helper->size < -offset)
return NULL;
offset += helper->size;
}
/* see if we have a matching buffer already in our list */
if (size > 0 && offset <= helper->last_offset) {
GSList *walk;
for (walk = helper->buffers; walk; walk = walk->next) {
GstMappedBuffer *bmp = (GstMappedBuffer *) walk->data;
GstBuffer *buf = GST_BUFFER_CAST (bmp->buffer);
buf_offset = GST_BUFFER_OFFSET (buf);
buf_size = bmp->map.size;
/* buffers are kept sorted by end offset (highest first) in the list, so
* at this point we save the current position and stop searching if
* we're after the searched end offset */
if (buf_offset <= offset) {
if ((offset + size) < (buf_offset + buf_size)) {
/* must already have been mapped before */
return (guint8 *) bmp->map.data + (offset - buf_offset);
}
} else if (offset + size >= buf_offset + buf_size) {
insert_pos = walk;
break;
}
}
}
buffer = NULL;
/* some typefinders go in 1 byte steps over 1k of data and request
* small buffers. It is really inefficient to pull each time, and pulling
* a larger chunk is almost free. Trying to pull a larger chunk at the end
* of the file is also not a problem here, we'll just get a truncated buffer
* in that case (and we'll have to double-check the size we actually get
* anyway, see below) */
ret =
helper->func (helper->obj, helper->parent, offset, MAX (size, 4096),
&buffer);
if (ret != GST_FLOW_OK)
goto error;
#if 0
caps = GST_BUFFER_CAPS (buffer);
if (caps && !gst_caps_is_empty (caps) && !gst_caps_is_any (caps)) {
GST_DEBUG ("buffer has caps %" GST_PTR_FORMAT ", suggest max probability",
caps);
gst_caps_replace (&helper->caps, caps);
helper->best_probability = GST_TYPE_FIND_MAXIMUM;
gst_buffer_unref (buffer);
return NULL;
}
#endif
/* getrange might silently return shortened buffers at the end of a file,
* we must, however, always return either the full requested data or %NULL */
buf_offset = GST_BUFFER_OFFSET (buffer);
buf_size = gst_buffer_get_size (buffer);
if (buf_size < size) {
GST_DEBUG ("dropping short buffer of size %" G_GSIZE_FORMAT ","
"requested size was %u", buf_size, size);
gst_buffer_unref (buffer);
return NULL;
}
if (buf_offset != -1 && buf_offset != offset) {
GST_DEBUG ("dropping buffer with unexpected offset %" G_GUINT64_FORMAT ", "
"expected offset was %" G_GUINT64_FORMAT, buf_offset, offset);
gst_buffer_unref (buffer);
return NULL;
}
bmap = g_slice_new0 (GstMappedBuffer);
if (!gst_buffer_map (buffer, &bmap->map, GST_MAP_READ))
goto map_failed;
bmap->buffer = buffer;
if (insert_pos) {
helper->buffers = g_slist_insert_before (helper->buffers, insert_pos, bmap);
} else {
/* if insert_pos is not set, our offset is bigger than the largest offset
* we have so far; since we keep the list sorted with highest offsets
* first, we need to prepend the buffer to the list */
helper->last_offset = GST_BUFFER_OFFSET (buffer) + buf_size;
helper->buffers = g_slist_prepend (helper->buffers, bmap);
}
return bmap->map.data;
error:
{
GST_INFO ("typefind function returned: %s", gst_flow_get_name (ret));
return NULL;
}
map_failed:
{
GST_ERROR ("map failed");
gst_buffer_unref (buffer);
g_slice_free (GstMappedBuffer, bmap);
return NULL;
}
}
/*
* helper_find_suggest:
* @data: helper data struct
* @probability: probability of the match
* @caps: caps of the type
*
* If given @probability is higher, replace previously store caps.
*/
static void
helper_find_suggest (gpointer data, guint probability, GstCaps * caps)
{
GstTypeFindHelper *helper = (GstTypeFindHelper *) data;
GST_LOG_OBJECT (helper->obj,
"'%s' called suggest (%u, %" GST_PTR_FORMAT ")",
GST_OBJECT_NAME (helper->factory), probability, caps);
if (probability > helper->best_probability) {
gst_caps_replace (&helper->caps, caps);
helper->best_probability = probability;
}
}
static guint64
helper_find_get_length (gpointer data)
{
GstTypeFindHelper *helper = (GstTypeFindHelper *) data;
GST_LOG_OBJECT (helper->obj, "'%s' called get_length, returning %"
G_GUINT64_FORMAT, GST_OBJECT_NAME (helper->factory), helper->size);
return helper->size;
}
/**
* gst_type_find_helper_get_range:
* @obj: A #GstObject that will be passed as first argument to @func
* @parent: (allow-none): the parent of @obj or %NULL
* @func: (scope call): A generic #GstTypeFindHelperGetRangeFunction that will
* be used to access data at random offsets when doing the typefinding
* @size: The length in bytes
* @extension: extension of the media
* @prob: (out) (allow-none): location to store the probability of the found
* caps, or %NULL
*
* Utility function to do pull-based typefinding. Unlike gst_type_find_helper()
* however, this function will use the specified function @func to obtain the
* data needed by the typefind functions, rather than operating on a given
* source pad. This is useful mostly for elements like tag demuxers which
* strip off data at the beginning and/or end of a file and want to typefind
* the stripped data stream before adding their own source pad (the specified
* callback can then call the upstream peer pad with offsets adjusted for the
* tag size, for example).
*
* When @extension is not %NULL, this function will first try the typefind
* functions for the given extension, which might speed up the typefinding
* in many cases.
*
* Free-function: gst_caps_unref
*
* Returns: (transfer full) (nullable): the #GstCaps corresponding to the data
* stream. Returns %NULL if no #GstCaps matches the data stream.
*/
GstCaps *
gst_type_find_helper_get_range (GstObject * obj, GstObject * parent,
GstTypeFindHelperGetRangeFunction func, guint64 size,
const gchar * extension, GstTypeFindProbability * prob)
{
GstTypeFindHelper helper;
GstTypeFind find;
GSList *walk;
GList *l, *type_list;
GstCaps *result = NULL;
gint pos = 0;
g_return_val_if_fail (GST_IS_OBJECT (obj), NULL);
g_return_val_if_fail (func != NULL, NULL);
helper.buffers = NULL;
helper.size = size;
helper.last_offset = 0;
helper.func = func;
helper.best_probability = GST_TYPE_FIND_NONE;
helper.caps = NULL;
helper.obj = obj;
helper.parent = parent;
find.data = &helper;
find.peek = helper_find_peek;
find.suggest = helper_find_suggest;
if (size == 0 || size == (guint64) - 1) {
find.get_length = NULL;
} else {
find.get_length = helper_find_get_length;
}
type_list = gst_type_find_factory_get_list ();
/* move the typefinders for the extension first in the list. The idea is that
* when one of them returns MAX we don't need to search further as there is a
* very high chance we got the right type. */
if (extension) {
GList *next;
GST_LOG_OBJECT (obj, "sorting typefind for extension %s to head",
extension);
for (l = type_list; l; l = next) {
const gchar *const *ext;
GstTypeFindFactory *factory;
next = l->next;
factory = GST_TYPE_FIND_FACTORY (l->data);
ext = gst_type_find_factory_get_extensions (factory);
if (ext == NULL)
continue;
GST_LOG_OBJECT (obj, "testing factory %s for extension %s",
GST_OBJECT_NAME (factory), extension);
while (*ext != NULL) {
if (strcmp (*ext, extension) == 0) {
/* found extension, move in front */
GST_LOG_OBJECT (obj, "moving typefind for extension %s to head",
extension);
/* remove entry from list */
type_list = g_list_delete_link (type_list, l);
/* insert at the position */
type_list = g_list_insert (type_list, factory, pos);
/* next element will be inserted after this one */
pos++;
break;
}
++ext;
}
}
}
for (l = type_list; l; l = l->next) {
helper.factory = GST_TYPE_FIND_FACTORY (l->data);
gst_type_find_factory_call_function (helper.factory, &find);
if (helper.best_probability >= GST_TYPE_FIND_MAXIMUM)
break;
}
gst_plugin_feature_list_free (type_list);
for (walk = helper.buffers; walk; walk = walk->next) {
GstMappedBuffer *bmap = (GstMappedBuffer *) walk->data;
gst_buffer_unmap (bmap->buffer, &bmap->map);
gst_buffer_unref (bmap->buffer);
g_slice_free (GstMappedBuffer, bmap);
}
g_slist_free (helper.buffers);
if (helper.best_probability > 0)
result = helper.caps;
if (prob)
*prob = helper.best_probability;
GST_LOG_OBJECT (obj, "Returning %" GST_PTR_FORMAT " (probability = %u)",
result, (guint) helper.best_probability);
return result;
}
/**
* gst_type_find_helper:
* @src: A source #GstPad
* @size: The length in bytes
*
* Tries to find what type of data is flowing from the given source #GstPad.
*
* Free-function: gst_caps_unref
*
* Returns: (transfer full) (nullable): the #GstCaps corresponding to the data
* stream. Returns %NULL if no #GstCaps matches the data stream.
*/
GstCaps *
gst_type_find_helper (GstPad * src, guint64 size)
{
GstTypeFindHelperGetRangeFunction func;
g_return_val_if_fail (GST_IS_OBJECT (src), NULL);
g_return_val_if_fail (GST_PAD_GETRANGEFUNC (src) != NULL, NULL);
func = (GstTypeFindHelperGetRangeFunction) (GST_PAD_GETRANGEFUNC (src));
return gst_type_find_helper_get_range (GST_OBJECT (src),
GST_OBJECT_PARENT (src), func, size, NULL, NULL);
}
/* ********************** typefinding for buffers ************************* */
typedef struct
{
const guint8 *data; /* buffer data */
gsize size;
GstTypeFindProbability best_probability;
GstCaps *caps;
GstTypeFindFactory *factory; /* for logging */
GstObject *obj; /* for logging */
} GstTypeFindBufHelper;
/*
* buf_helper_find_peek:
* @data: helper data struct
* @off: stream offset
* @size: block size
*
* Get data pointer within a buffer.
*
* Returns: (nullable): address inside the buffer or %NULL if buffer does not
* cover the requested range.
*/
static const guint8 *
buf_helper_find_peek (gpointer data, gint64 off, guint size)
{
GstTypeFindBufHelper *helper;
helper = (GstTypeFindBufHelper *) data;
GST_LOG_OBJECT (helper->obj, "'%s' called peek (%" G_GINT64_FORMAT ", %u)",
GST_OBJECT_NAME (helper->factory), off, size);
if (size == 0)
return NULL;
if (off < 0) {
GST_LOG_OBJECT (helper->obj, "'%s' wanted to peek at end; not supported",
GST_OBJECT_NAME (helper->factory));
return NULL;
}
/* If we request beyond the available size, we're sure we can't return
* anything regardless of the requested offset */
if (size > helper->size)
return NULL;
/* Only return data if there's enough room left for the given offset.
* This is the same as "if (off + size <= helper->size)" except that
* it doesn't exceed type limits */
if (off <= helper->size - size)
return helper->data + off;
return NULL;
}
/*
* buf_helper_find_suggest:
* @data: helper data struct
* @probability: probability of the match
* @caps: caps of the type
*
* If given @probability is higher, replace previously store caps.
*/
static void
buf_helper_find_suggest (gpointer data, guint probability, GstCaps * caps)
{
GstTypeFindBufHelper *helper = (GstTypeFindBufHelper *) data;
GST_LOG_OBJECT (helper->obj,
"'%s' called suggest (%u, %" GST_PTR_FORMAT ")",
GST_OBJECT_NAME (helper->factory), probability, caps);
/* Note: not >= as we call typefinders in order of rank, highest first */
if (probability > helper->best_probability) {
gst_caps_replace (&helper->caps, caps);
helper->best_probability = probability;
}
}
/**
* gst_type_find_helper_for_data:
* @obj: (allow-none): object doing the typefinding, or %NULL (used for logging)
* @data: (transfer none) (array length=size): * a pointer with data to typefind
* @size: the size of @data
* @prob: (out) (allow-none): location to store the probability of the found
* caps, or %NULL
*
* Tries to find what type of data is contained in the given @data, the
* assumption being that the data represents the beginning of the stream or
* file.
*
* All available typefinders will be called on the data in order of rank. If
* a typefinding function returns a probability of %GST_TYPE_FIND_MAXIMUM,
* typefinding is stopped immediately and the found caps will be returned
* right away. Otherwise, all available typefind functions will the tried,
* and the caps with the highest probability will be returned, or %NULL if
* the content of @data could not be identified.
*
* Free-function: gst_caps_unref
*
* Returns: (transfer full) (nullable): the #GstCaps corresponding to the data,
* or %NULL if no type could be found. The caller should free the caps
* returned with gst_caps_unref().
*/
GstCaps *
gst_type_find_helper_for_data (GstObject * obj, const guint8 * data, gsize size,
GstTypeFindProbability * prob)
{
GstTypeFindBufHelper helper;
GstTypeFind find;
GList *l, *type_list;
GstCaps *result = NULL;
g_return_val_if_fail (data != NULL, NULL);
helper.data = data;
helper.size = size;
helper.best_probability = GST_TYPE_FIND_NONE;
helper.caps = NULL;
helper.obj = obj;
if (helper.data == NULL || helper.size == 0)
return NULL;
find.data = &helper;
find.peek = buf_helper_find_peek;
find.suggest = buf_helper_find_suggest;
find.get_length = NULL;
type_list = gst_type_find_factory_get_list ();
for (l = type_list; l; l = l->next) {
helper.factory = GST_TYPE_FIND_FACTORY (l->data);
gst_type_find_factory_call_function (helper.factory, &find);
if (helper.best_probability >= GST_TYPE_FIND_MAXIMUM)
break;
}
gst_plugin_feature_list_free (type_list);
if (helper.best_probability > 0)
result = helper.caps;
if (prob)
*prob = helper.best_probability;
GST_LOG_OBJECT (obj, "Returning %" GST_PTR_FORMAT " (probability = %u)",
result, (guint) helper.best_probability);
return result;
}
/**
* gst_type_find_helper_for_buffer:
* @obj: (allow-none): object doing the typefinding, or %NULL (used for logging)
* @buf: (in) (transfer none): a #GstBuffer with data to typefind
* @prob: (out) (allow-none): location to store the probability of the found
* caps, or %NULL
*
* Tries to find what type of data is contained in the given #GstBuffer, the
* assumption being that the buffer represents the beginning of the stream or
* file.
*
* All available typefinders will be called on the data in order of rank. If
* a typefinding function returns a probability of %GST_TYPE_FIND_MAXIMUM,
* typefinding is stopped immediately and the found caps will be returned
* right away. Otherwise, all available typefind functions will the tried,
* and the caps with the highest probability will be returned, or %NULL if
* the content of the buffer could not be identified.
*
* Free-function: gst_caps_unref
*
* Returns: (transfer full) (nullable): the #GstCaps corresponding to the data,
* or %NULL if no type could be found. The caller should free the caps
* returned with gst_caps_unref().
*/
GstCaps *
gst_type_find_helper_for_buffer (GstObject * obj, GstBuffer * buf,
GstTypeFindProbability * prob)
{
GstCaps *result;
GstMapInfo info;
g_return_val_if_fail (buf != NULL, NULL);
g_return_val_if_fail (GST_IS_BUFFER (buf), NULL);
g_return_val_if_fail (GST_BUFFER_OFFSET (buf) == 0 ||
GST_BUFFER_OFFSET (buf) == GST_BUFFER_OFFSET_NONE, NULL);
if (!gst_buffer_map (buf, &info, GST_MAP_READ))
return NULL;
result = gst_type_find_helper_for_data (obj, info.data, info.size, prob);
gst_buffer_unmap (buf, &info);
return result;
}
/**
* gst_type_find_helper_for_extension:
* @obj: (allow-none): object doing the typefinding, or %NULL (used for logging)
* @extension: an extension
*
* Tries to find the best #GstCaps associated with @extension.
*
* All available typefinders will be checked against the extension in order
* of rank. The caps of the first typefinder that can handle @extension will be
* returned.
*
* Free-function: gst_caps_unref
*
* Returns: (transfer full) (nullable): the #GstCaps corresponding to
* @extension, or %NULL if no type could be found. The caller should free
* the caps returned with gst_caps_unref().
*/
GstCaps *
gst_type_find_helper_for_extension (GstObject * obj, const gchar * extension)
{
GList *l, *type_list;
GstCaps *result = NULL;
g_return_val_if_fail (extension != NULL, NULL);
GST_LOG_OBJECT (obj, "finding caps for extension %s", extension);
type_list = gst_type_find_factory_get_list ();
for (l = type_list; l; l = g_list_next (l)) {
GstTypeFindFactory *factory;
const gchar *const *ext;
factory = GST_TYPE_FIND_FACTORY (l->data);
/* we only want to check those factories without a function */
if (gst_type_find_factory_has_function (factory))
continue;
/* get the extension that this typefind factory can handle */
ext = gst_type_find_factory_get_extensions (factory);
if (ext == NULL)
continue;
/* there are extension, see if one of them matches the requested
* extension */
while (*ext != NULL) {
if (strcmp (*ext, extension) == 0) {
/* we found a matching extension, take the caps */
if ((result = gst_type_find_factory_get_caps (factory))) {
gst_caps_ref (result);
goto done;
}
}
++ext;
}
}
done:
gst_plugin_feature_list_free (type_list);
GST_LOG_OBJECT (obj, "Returning %" GST_PTR_FORMAT, result);
return result;
}