[vlc-devel] [RFC 03/10] core: add stream_extractor module type
Rémi Denis-Courmont
remi at remlab.net
Mon Nov 28 12:12:58 CET 2016
On November 28, 2016 4:22:22 AM GMT+02:00, "Filip Roséen" <filip at atch.se> wrote:
>These changes introduces a new module type named stream_extractor. The
>added documentation should explain when such module should be used,
>but in short it allows for extraction of data within a stream,
>effectively resulting in a new stream that refers to the extracted
>data.
>
>Interaction with the stream-extractor shall never happen directly,
>instead the module-backend is written in a way so that it exposes a
>stream_t to the public.
>
> [ access ] -> [ stream_t ] -> [ stream consumer ]
> '- [ stream extractor ]
>
>Future changes are necessary in order to make modules of this type
>usable in practice, but has been split into individual commits so that
>the changes are easier to follow.
>---
> include/vlc_stream_extractor.h | 76 +++++++++++++++
> modules/Makefile.am | 1 +
> modules/stream_extractor/Makefile.am | 0
> src/Makefile.am | 2 +
>src/input/stream_extractor.c | 173
>+++++++++++++++++++++++++++++++++++
> 5 files changed, 252 insertions(+)
> create mode 100644 include/vlc_stream_extractor.h
> create mode 100644 modules/stream_extractor/Makefile.am
> create mode 100644 src/input/stream_extractor.c
>
>diff --git a/include/vlc_stream_extractor.h
>b/include/vlc_stream_extractor.h
>new file mode 100644
>index 0000000..f01dc9b
>--- /dev/null
>+++ b/include/vlc_stream_extractor.h
>@@ -0,0 +1,76 @@
>+#ifndef VLC_STREAM_EXTRACTOR_H
>+#define VLC_STREAM_EXTRACTOR_H
>+
>+#ifdef __cplusplus
>+extern "C" {
>+#endif
>+
>+/**
>+ * \defgroup stream_extractor Stream Extractor
>+ * \ingroup input
>+ *
>+ * If a stream can be viewed as a directory, such as when opening a
>+ * compressed archive, a \em stream-extractor is used to get access to
>+ * the entities inside said stream.
>+ *
>+ * A \em stream-extractor can do one of two things;
>+ *
>+ * - either it lists the logical entries within a stream, or;
>+ * - it extracts the data associated with one of those entries based
>+ * on a unique identifier.
>+ *
>+ * @{
>+ *
>+ **/
>+struct stream_extractor_t {
>+ VLC_COMMON_MEMBERS;
>+
>+ union {
>+ /**
>+ * Callbacks for entity extraction
>+ *
>+ * The following callbacks shall be populated if the
>stream_extractor is
>+ * used to extract a specific entity from the source-stream.
>Each
>+ * callback shall behave as those, with the same name,
>specified in \ref
>+ * stream_t.
>+ *
>+ **/
>+ struct {
>+ ssize_t (*pf_read)(struct stream_extractor_t *, void
>*buf, size_t len);
>+ block_t* (*pf_block)(struct stream_extractor_t *, bool
>*eof);
>+ int (*pf_seek)(struct stream_extractor_t *,
>uint64_t);
>+ int (*pf_control)(struct stream_extractor_t *, int
>i_query, va_list);
>+
>+ } stream;
>+
>+ /**
>+ * Callbacks for stream directory listing
>+ *
>+ * These callbacks are used when a stream is to be treated as
>a
>+ * directory, it shall behave as those, with the same name,
>specified
>+ * in \ref stream_t.
>+ *
>+ **/
>+ struct {
>+ int (*pf_readdir)(struct stream_extractor_t *,
>input_item_node_t *);
>+
>+ } directory;
>+
>+ };
>+
>+ void* p_sys; /**< Private data pointer */
>+ stream_t* source; /**< The source stream */
>+ char* identifier; /**< name of requested entity to extract, or
>NULL
>+ ** when requested to list directories */
>+};
>+
>+typedef struct stream_extractor_t stream_extractor_t;
>+
>+/**
>+ * @}
>+ */
>+
>+#ifdef __cplusplus
>+} /* extern "C" */
>+#endif
>+#endif /* include-guard */
>diff --git a/modules/Makefile.am b/modules/Makefile.am
>index a291e33..57dc49c 100644
>--- a/modules/Makefile.am
>+++ b/modules/Makefile.am
>@@ -42,6 +42,7 @@ include packetizer/Makefile.am
> include services_discovery/Makefile.am
> include spu/Makefile.am
> include stream_filter/Makefile.am
>+include stream_extractor/Makefile.am
> include text_renderer/Makefile.am
> include video_chroma/Makefile.am
> include video_filter/Makefile.am
>diff --git a/modules/stream_extractor/Makefile.am
>b/modules/stream_extractor/Makefile.am
>new file mode 100644
>index 0000000..e69de29
>diff --git a/src/Makefile.am b/src/Makefile.am
>index 60f5fac..ccc8dfb 100644
>--- a/src/Makefile.am
>+++ b/src/Makefile.am
>@@ -87,6 +87,7 @@ pluginsinclude_HEADERS = \
> ../include/vlc_sout.h \
> ../include/vlc_spu.h \
> ../include/vlc_stream.h \
>+ ../include/vlc_stream_extractor.h \
> ../include/vlc_strings.h \
> ../include/vlc_subpicture.h \
> ../include/vlc_text_style.h \
>@@ -257,6 +258,7 @@ libvlccore_la_SOURCES = \
> input/stats.c \
> input/stream.c \
> input/stream_fifo.c \
>+ input/stream_extractor.c \
> input/stream_filter.c \
> input/stream_memory.c \
> input/subtitles.c \
>diff --git a/src/input/stream_extractor.c
>b/src/input/stream_extractor.c
>new file mode 100644
>index 0000000..a926363
>--- /dev/null
>+++ b/src/input/stream_extractor.c
>@@ -0,0 +1,173 @@
>+#ifndef STREAM_EXTRACTOR_H
>+#define STREAM_EXTRACTOR_H
>+
>+#ifdef HAVE_CONFIG_H
>+# include "config.h"
>+#endif
>+
>+#include <vlc_common.h>
>+#include <vlc_stream.h>
>+#include <vlc_stream_extractor.h>
>+#include <vlc_modules.h>
>+#include <vlc_url.h>
>+#include <vlc_memstream.h>
>+#include <libvlc.h>
>+#include <assert.h>
>+
>+#include "stream.h"
>+
>+/**
>+ * \defgroup stream_extractor_Private Stream Extractor Private
>+ * \ingroup stream_extractor
>+ * \internal
>+ * @{
>+ * \file
>+ **/
>+
>+struct stream_extractor_private {
>+ stream_extractor_t public;
>+ stream_t* stream;
>+ module_t* module;
>+
>+ vlc_object_t* owner;
>+};
>+
>+/**
>+ * Release the private data associated with a stream-extractor
>+ *
>+ * \param priv pointer to the private section
>+ */
>+static void se_Release( struct stream_extractor_private* priv )
>+{
>+ free( priv->public.identifier );
>+
>+ if( priv->module )
>+ {
>+ module_unneed( &priv->public, priv->module );
>+ vlc_stream_Delete( priv->public.source );
>+ }
>+
>+ vlc_object_release( &priv->public );
>+}
>+
>+/**
>+ * \defgroup stream_extractor_Callbacks Stream Extractor Callbacks
>+ * \ingroup stream_extractor
>+ * @{
>+ * \file
>+ * These functions simply forwards the relevant stream-request to
>+ * the underlying stream-extractor. They are a basic form of
>+ * type-erasure in that the outside world sees a stream_t, but the
>+ * work is actually done by a stream_extractor_t.
>+ */
>+
>+static void
>+se_StreamDelete( stream_t* stream )
>+{
>+ se_Release( stream->p_sys );
>+}
>+
>+static ssize_t
>+se_StreamRead( stream_t* stream, void* buf, size_t len )
>+{
>+ struct stream_extractor_private* priv = stream->p_sys;
>+ stream_extractor_t* extractor = &priv->public;
>+ return extractor->stream.pf_read( extractor, buf, len );
>+}
>+
>+static block_t*
>+se_StreamBlock( stream_t* stream, bool* eof )
>+{
>+ struct stream_extractor_private* priv = stream->p_sys;
>+ stream_extractor_t* extractor = &priv->public;
>+ return extractor->stream.pf_block( extractor, eof );
>+}
>+
>+static int
>+se_StreamSeek( stream_t* stream, uint64_t offset )
>+{
>+ struct stream_extractor_private* priv = stream->p_sys;
>+ stream_extractor_t* extractor = &priv->public;
>+ return extractor->stream.pf_seek( extractor, offset );
>+}
>+
>+static int
>+se_StreamReadDir( stream_t* stream, input_item_node_t* node )
>+{
>+ struct stream_extractor_private* priv = stream->p_sys;
>+ stream_extractor_t* extractor = &priv->public;
>+ return extractor->directory.pf_readdir( extractor, node );
>+}
>+
>+static int
>+se_StreamControl( stream_t* stream, int req, va_list args )
>+{
>+ struct stream_extractor_private* priv = stream->p_sys;
>+ stream_extractor_t* extractor = &priv->public;
>+
>+ if( extractor->identifier )
>+ return extractor->stream.pf_control( extractor, req, args );
>+
>+ if( req == STREAM_IS_DIRECTORY )
>+ {
>+ *va_arg( args, bool* ) = true;
>+ return VLC_SUCCESS;
>+ }
>+
>+ return VLC_EGENERIC;
>+}
>+/**
>+ * @}
>+ **/
>+
>+/**
>+ * Initialize the public stream_t for a stream_extractor_t
>+ *
>+ * This function simply initializes the relevant data-members of the
>+ * public stream_t which is a handle to the internal
>+ * stream_extractor_t.
>+ *
>+ * \param obj the private section of the stream_extractor_t
>+ * \param source the source stream which the stream_extractor_t should
>+ * will read from
>+ * \return VLC_SUCCESS on success, an error-code on failure.
>+ **/
>+static int
>+se_InitStream( struct stream_extractor_private* priv, stream_t* source
>)
>+{
>+ stream_t* s = vlc_stream_CommonNew( priv->public.obj.parent,
>+ se_StreamDelete );
>+ if( unlikely( !s ) )
>+ return VLC_EGENERIC;
>+
>+ if( priv->public.identifier )
>+ {
>+ if( priv->public.stream.pf_read ) s->pf_read = se_StreamRead;
>+ else s->pf_block =
>se_StreamBlock;
>+
>+ s->pf_seek = se_StreamSeek;
>+ s->psz_url = NULL;
>+ }
>+ else
>+ {
>+ s->pf_readdir = se_StreamReadDir;
>+ s->psz_url = source->psz_url ? strdup( source->psz_url ) :
>NULL;
>+ }
>+
>+
>+ if( source->psz_url && unlikely( !s->psz_url ) )
>+ return VLC_EGENERIC;
>+
>+ priv->stream = s;
>+ priv->stream->pf_control = se_StreamControl;
>+ priv->stream->p_input = source->p_input;
>+ priv->stream->p_sys = priv;
>+
>+ return VLC_SUCCESS;
>+}
>+
>+/**
>+ * @}
>+ **/
>+
>+#endif /* include-guard */
>--
>2.10.2
>
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VLC already relies on anonymous unions (nominally a C11 feature, but supported by compilers for a long time). Don't feel obliged to name them.
--
Rémi Denis-Courmont
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