gstfilesrc源文件.doc

/* GStreamer * Copyright (C) 1999,2000 Erik Walthinsen * 2000,2005 Wim Taymans * * gstfilesrc.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., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. */* * SECTION:element-filesrc * see_also: #GstFileSrc * * Read data from a file in the local file system. */#ifdef HAVE_CONFIG_H# include config.h#endif#include #include gstfilesrc.h#include #include #ifdef G_OS_WIN32#include /* lseek, open, close, read */* On win32, stat* default to 32 bit; we need the 64-bit * variants, so explicitly define it that way. */#define stat _stat64#define fstat _fstat64#undef lseek#define lseek _lseeki64#undef off_t#define off_t guint64/* Prevent stat.h from defining the stat* functions as * _stat*, since were explicitly overriding that */#undef _INC_STAT_INL#endif#include #include #ifdef HAVE_UNISTD_H# include #endif#ifdef HAVE_MMAP# include #endif#include #include #include ././gst/gst-i18n-lib.hstatic GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE (src, GST_PAD_SRC, GST_PAD_ALWAYS, GST_STATIC_CAPS_ANY);/* FIXME we should be using glib for this */#ifndef S_ISREG#define S_ISREG(mode) (mode)&_S_IFREG)#endif#ifndef S_ISDIR#define S_ISDIR(mode) (mode)&_S_IFDIR)#endif#ifndef S_ISSOCK#define S_ISSOCK(x) (0)#endif#ifndef O_BINARY#define O_BINARY (0)#endif/* Copy of glibs g_open due to win32 libc/cross-DLL brokenness: we cant * use the file descriptor opened in glib (and returned from this function) * in this library, as they may have unrelated C runtimes. */intgst_open (const gchar * filename, int flags, int mode)#ifdef G_OS_WIN32 wchar_t *wfilename = g_utf8_to_utf16 (filename, -1, NULL, NULL, NULL); int retval; int save_errno; if (wfilename = NULL) errno = EINVAL; return -1; retval = _wopen (wfilename, flags, mode); save_errno = errno; g_free (wfilename); errno = save_errno; return retval;#else return open (filename, flags, mode);#endif/* * GStreamer Default File Source * Theory of Operation * * Update: see GstFileSrc:use-mmap property documentation below * for why use of mmap() is disabled by default. * * This source uses mmap(2) to efficiently load data from a file. * To do this without seriously polluting the applications memory * space, it must do so in smaller chunks, say 1-4MB at a time. * Buffers are then subdivided from these mmapd chunks, to directly * make use of the mmap. * * To handle refcounting so that the mmap can be freed at the appropriate * time, a buffer will be created for each mmapd region, and all new * buffers will be sub-buffers of this top-level buffer. As they are * freed, the refcount goes down on the mmapd buffer and its free() * function is called, which will call munmap(2) on itself. * * If a buffer happens to cross the boundaries of an mmapd region, we * have to decide whether its more efficient to copy the data into a * new buffer, or mmap() just that buffer. There will have to be a * breakpoint size to determine which will be done. The mmap() size * has a lot to do with this as well, because you end up in double- * jeopardy: the larger the outgoing buffer, the more data to copy when * it overlaps, *and* the more frequently youll have buffers that *do* * overlap. * * Seeking is another tricky aspect to do efficiently. The initial * implementation of this source wont make use of these features, however. * The issue is that if an application seeks backwards in a file, *and* * that region of the file is covered by an mmap that hasnt been fully * deallocated, we really should re-use it. But keeping track of these * regions is tricky because we have to lock the structure that holds * them. We need to settle on a locking primitive (GMutex seems to be * a really good option.), then we can do that. */GST_DEBUG_CATEGORY_STATIC (gst_file_src_debug);#define GST_CAT_DEFAULT gst_file_src_debug/* FileSrc signals and args */enum /* FILL ME */ LAST_SIGNAL;#define DEFAULT_BLOCKSIZE 4*1024#define DEFAULT_MMAPSIZE 4*1024*1024#define DEFAULT_TOUCH TRUE#define DEFAULT_USEMMAP FALSE#define DEFAULT_SEQUENTIAL FALSEenum ARG_0, ARG_LOCATION, ARG_FD, ARG_MMAPSIZE, ARG_SEQUENTIAL, ARG_TOUCH, ARG_USEMMAP;static void gst_file_src_finalize (GObject * object);/设置属性的虚函数static void gst_file_src_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec);/获取属性的虚函数static void gst_file_src_get_property (GObject * object, guint prop_id, GValue * value, GParamSpec * pspec);static gboolean gst_file_src_start (GstBaseSrc * basesrc);static gboolean gst_file_src_stop (GstBaseSrc * basesrc);static gboolean gst_file_src_is_seekable (GstBaseSrc * src);static gboolean gst_file_src_get_size (GstBaseSrc * src, guint64 * size);static GstFlowReturn gst_file_src_create (GstBaseSrc * src, guint64 offset, guint length, GstBuffer * buffer);static gboolean gst_file_src_query (GstBaseSrc * src, GstQuery * query);static void gst_file_src_uri_handler_init (gpointer g_iface, gpointer iface_data);static void_do_init (GType filesrc_type) static const GInterfaceInfo urihandler_info = gst_file_src_uri_handler_init, NULL, NULL ; g_type_add_interface_static (filesrc_type, GST_TYPE_URI_HANDLER, &urihandler_info); GST_DEBUG_CATEGORY_INIT (gst_file_src_debug, filesrc, 0, filesrc element);GST_BOILERPLATE_FULL (GstFileSrc, gst_file_src, GstBaseSrc, GST_TYPE_BASE_SRC, _do_init);/初始化类结构，定义父类，定义类成员（子类），类详细信息。/元件细节在_base_init ()函数中被注册到插件中/：_base_init()用来在创建每个新的子类时，初始化类和子类的属性static voidgst_file_src_base_init (gpointer g_class) GstElementClass *gstelement_class = GST_ELEMENT_CLASS (g_class); gst_element_class_set_details_simple (gstelement_class, File Source, Source/File, Read from arbitrary point in a file, Erik Walthinsen ); /将pad模板注册到element中 gst_element_class_add_pad_template (gstelement_class, gst_static_pad_template_get (&srctemplate);/定义类成员变量：1、定义信号及其响应函数；2、定义虚函数等等。/_class_init()用来对类进行初始化（指定类的信号，参数和虚函数，设定全局状态），该初始化过程只进行一次static voidgst_file_src_class_init (GstFileSrcClass * klass) GObjectClass *gobject_class; GstBaseSrcClass *gstbasesrc_class; gobject_class = G_OBJECT_CLASS (klass); gstbasesrc_class = GST_BASE_SRC_CLASS (klass); gobject_class-set_property = gst_file_src_set_property; gobject_class-get_property = gst_file_src_get_property; g_object_class_install_property (gobject_class, ARG_FD, g_param_spec_int (fd, File-descriptor, File-descriptor for the file being mmap()d, 0, G_MAXINT, 0, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS); g_object_class_install_property (gobject_class, ARG_LOCATION, g_param_spec_string (location, File Location, Location of the file to read, NULL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_MUTABLE_READY); g_object_class_install_property (gobject_class, ARG_MMAPSIZE, g_param_spec_ulong (mmapsize, mmap() Block Size, Size in bytes of mmap()d regions, 0, G_MAXULONG, DEFAULT_MMAPSIZE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_MUTABLE_PLAYING); g_object_class_install_property (gobject_class, ARG_TOUCH, g_param_spec_boolean (touch, Touch mapped region read data, Touch mmapped data regions to force them to be read from disk, DEFAULT_TOUCH, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_MUTABLE_PLAYING); /* * GstFileSrc:use-mmap * * Whether to use mmap(). Set to TRUE to force use of mmap() instead of * read() for reading data. * * Use of mmap() is disabled by default since with mmap() there are a * number of occasions where the process/application will be notified of * read errors via a SIGBUS signal from the kernel, which will lead to * the application being killed if not handled by the application. This * is something that is difficult to work around for a library like * GStreamer, hence use of mmap() is disabled by default. Said errors * can occur for example when an external device (e.g. an external hard * drive or a portable music player) are unplugged while in use, or when * a CD/DVD medium cannot be be read because the medium is scratched or * otherwise damaged. * */ g_object_class_install_property (gobject_class, ARG_USEMMAP, g_param_spec_boolean (use-mmap, Use mmap to read data, Whether to use mmap() instead of read(), DEFAULT_USEMMAP, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_MUTABLE_READY); g_object_class_install_property (gobject_class, ARG_SEQUENTIAL, g_param_spec_boolean (sequential, Optimise for sequential mmap access, Whether to use madvise to hint to the kernel that access to mmap pages will be sequential, DEFAULT_SEQUENTIAL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_MUTABLE_PLAYING); gobject_class-finalize = GST_DEBUG_FUNCPTR (gst_file_src_finalize); gstbasesrc_class-start = GST_DEBUG_FUNCPTR (gst_file_src_start); gstbasesrc_class-stop = GST_DEBUG_FUNCPTR (gst_file_src_stop); gstbasesrc_class-is_seekable = GST_DEBUG_FUNCPTR (gst_file_src_is_seekable); gstbasesrc_class-get_size = GST_DEBUG_FUNCPTR (gst_file_src_get_size); gstbasesrc_class-create = GST_DEBUG_FUNCPTR (gst_file_src_create); gstbasesrc_class-query = GST_DEBUG_FUNCPTR (gst_file_src_query); if (sizeof (off_t) pagesize = getpagesize ();#endif src-filename = NULL; src-fd = 0; src-uri = NULL; src-touch = DEFAULT_TOUCH; src-mapbuf = NULL; src-mapsize = DEFAULT_MMAPSIZE; /* default is 4MB */ src-use_mmap = DEFAULT_USEMMAP; src-sequential = DEFAULT_SEQUENTIAL; src-is_regular = FALSE;static voidgst_file_src_finalize (GObject * object) GstFileSrc *src; src = GST_FILE_SRC (object); g_free (src-filename); g_free (src-uri); G_OBJECT_CLASS (parent_class)-finalize (object);static gbooleangst_file_src_set_location (GstFileSrc * src, const gchar * location) GstState state; /* the element must be stopped in order to do this */ GST_OBJECT_LOCK (src); state = GST_STATE (src); if (state != GST_STATE_READY & state != GST_STATE_NULL) goto wrong_state; GST_OBJECT_UNLOCK (src); g_free (src-filename); g_free (src-uri); /* clear the filename if we get a NULL (is that possible?) */ if (location = NULL) src-filename = NULL; src-uri = NULL; else /* we store the filename as received by the application. On Windoes this * should be UTF8 */ src-filename = g_strdup (location); src-uri = gst_uri_construct (file, src-filename); g_object_notify (G_OBJECT (src), location); gst_uri_handler_new_uri (GST_URI_HANDLER (src), src-uri); return TRUE; /* ERROR */wrong_state: GST_DEBUG_OBJECT (src, setting location in wrong state); GST_OBJECT_UNLOCK (src); return FALSE; /设置属性static voidgst_file_src_set_property (GObject * object, guint prop_id, const GValue * value, GParamSpec * pspec) GstFileSrc *src; g_return_if_fail (GST_IS_FILE_SRC (object); src = GST_FILE_SRC (object); switch (prop_id) case ARG_LOCATION: gst_file_src_set_location (src, g_value_get_string (value); break; case ARG_MMAPSIZE: if (src-mapsize % src-pagesize) = 0) src-mapsize = g_value_get_ulong (value); else GST_INFO_OBJECT (src, invalid mapsize, must be a multiple of pagesize, which is %d, src-pagesize); break; case ARG_TOUCH: src-touch = g_value_get_boolean (value); break; case ARG_SEQUENTIAL: src-sequential = g_value_get_boolean (value); break; case ARG_USEMMAP: src-use_mmap = g_value_get_boolean (value); break; default: G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec); break; /获取属性static voidgst_file_src_get_property (GObject * object, guint prop_id, GValue * value, GParamSpec * pspec) GstFileSrc *src; g_return_if_fail (GST_IS_FILE_SRC (object); src = GST_FILE_SRC (object); switch (prop_id) case ARG_LOCATION: g_value_set_string (value, src-filename); break; case ARG_FD: g_value_set_int (value, src-fd); break; case ARG_MMAPSIZE: g_value_set_ulong (value, src-mapsize); break; case ARG_TOUCH: g_value_set_boolean (value, src-touch); break; case ARG_SEQUENTIAL: g_value_set_boolean (value, src-sequential); break; case ARG_USEMMAP: g_value_set_boolean (value, src-use_mmap); break; default: G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec); break; /* * mmap code below */#ifdef HAVE_MMAP/* GstMmapBuffer */typedef struct _GstMmapBuffer GstMmapBuffer;typedef struct _GstMmapBufferClass GstMmapBufferClass;#define GST_TYPE_MMAP_BUFFER (gst_mmap_buffer_get_type()#define GST_IS_MMAP_BUFFER(obj) (G_TYPE_CHECK_INSTANCE_TYPE (obj), GST_TYPE_MMAP_BUFFER)#define GST_IS_MMAP_BUFFER_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE (klass), GST_TYPE_MMAP_BUFFER)#define GST_MMAP_BUFFER_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS (obj), GST_TYPE_MMAP_BUFFER, GstMmapBufferClass)#define GST_MMAP_BUFFER(obj) (G_TYPE_CHECK_INSTANCE_CAST (obj), GST_TYPE_MMAP_BUFFER, GstMmapBuffer)#define GST_MMAP_BUFFER_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST (klass), GST_TYPE_MMAP_BUFFER, GstMmapBufferClass)struct _GstMmapBuffer GstBuffer buffer; GstFileSrc *filesrc;struct _GstMmapBufferClass GstBufferClass buffer_class;static void gst_mmap_buffer_init (GTypeInstance * instance, gpointer g_class);static void gst_mmap_buffer_class_init (gpointer g_class, gpointer class_data);static void gst_mmap_buffer_finalize (GstMmapBuffer * mmap_buffer);static GstBufferClass *mmap_buffer_parent_class = NULL;static GTypegst_mmap_buffer_get_type (void) static GType _gst_mmap_buffer_type; if (G_UNLIKELY (_gst_mmap_buffer_type = 0) static const GTypeInfo mmap_buffer_info = sizeof (GstMmapBufferClass), NULL, NULL, gst_mmap_buffer_class_init, NULL, NULL, sizeof (GstMmapBuffer), 0, gst_mmap_buffer_init, NULL ; _gst_mmap_buffer_type = g_type_register_static (GST_TYPE_BUFFER, GstMmapBuffer, &mmap_buffer_info, 0); return _gst_mmap_buffer_type;static voidgst_mmap_buffer_class_init (gpointer g_class, gpointer class_data) GstMiniObjectClass *mini_object_class = GST_MINI_OBJECT_CLASS (g_class); mmap_buffer_parent_class = g_type_class_peek_parent (g_class); mini_object_class-finalize = (GstMiniObjectFinalizeFunction) gst_mmap_buffer_finalize;static voidgst_mmap_buffer_init (GTypeInstance * instance, gpointer g_class) GstBuffer *buf = (GstBuffer *) instance; GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_READONLY); /* before we re-enable this flag, we probably need to fix _copy() * _make_writable(), etc. in GstMiniObject/GstBuffer as well */ /* GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_ORIGINAL); */static voidgst_mmap_buffer_finalize (GstMmapBuffer * mmap_buffer) guint size; gpointer data; guint64 offset; GstFileSrc *src; GstBuffer *buffer = GST_BUFFER (mmap_buffer); /* get info */ size = GST_BUFFER_SIZE (buffer); offset = GST_BUFFER_OFFSET (buffer); data = GST_BUFFER_DATA (buffer); src = mmap_buffer-filesrc; GST_LOG (freeing mmap()d buf