gstreamer/libs/gst/bytestream/bytestream.c

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/* GStreamer
* Copyright (C) 2001 Erik Walthinsen <omega@temple-baptist.com>
*
* gstbytestream.c: adds a convenient bytestream based API to a pad.
*
* 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.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <gst/gstinfo.h>
#include <gst/gstplugin.h>
#include <gst/gstversion.h>
#include "bytestream.h"
GST_DEBUG_CATEGORY_STATIC (debug_bs);
#define GST_CAT_DEFAULT debug_bs
static guint8 *gst_bytestream_assemble (GstByteStream * bs, guint32 len);
static inline void
gst_bytestream_init (GstByteStream * bs)
{
bs->event = NULL;
bs->buflist = NULL;
bs->headbufavail = 0;
bs->listavail = 0;
bs->assembled = NULL;
bs->offset = 0LL;
bs->in_seek = FALSE;
}
static inline void
gst_bytestream_exit (GstByteStream * bs)
{
GSList *walk;
if (bs->event)
gst_event_unref (bs->event);
walk = bs->buflist;
while (walk) {
gst_buffer_unref (GST_BUFFER (walk->data));
walk = g_slist_next (walk);
}
g_slist_free (bs->buflist);
g_free (bs->assembled);
}
/**
* gst_bytestream_new:
* @pad: the pad to attach the bytestream to
*
* creates a bytestream from the given pad
*
* Returns: a new #GstByteStream object.
*/
GstByteStream *
gst_bytestream_new (GstPad * pad)
{
GstByteStream *bs = g_new (GstByteStream, 1);
bs->pad = pad;
gst_bytestream_init (bs);
return bs;
}
/**
* gst_bytestream_destroy:
* @bs: the bytestream object to destroy
*
* destroy the bytestream object and free its resources.
*/
void
gst_bytestream_destroy (GstByteStream * bs)
{
gst_bytestream_exit (bs);
g_free (bs);
}
void
gst_bytestream_reset (GstByteStream * bs)
{
/* free all data */
gst_bytestream_exit (bs);
/* reset data to clean state */
gst_bytestream_init (bs);
}
/* HOW THIS WORKS:
*
* The fundamental structure is a singly-linked list of buffers. The
* buffer on the front is the oldest, and thus the first to read data
* from. The number of bytes left to be read in this buffer is stored
* in bs->headbufavail. The number of bytes available in the entire
* list (including the head buffer) is in bs->listavail.
*
* When a request is made for data (peek), _fill_bytes is called with
* the number of bytes needed, but only if the listavail indicates
* that there aren't already enough. This calls _get_next_buf until
* the listavail is sufficient to satisfy the demand.
*
* _get_next_buf pulls a buffer from the pad the bytestream is attached
* to, and shoves it in the list. There are actually two things it can
* do. If there's already a buffer in the list, and the _is_span_fast()
* test returns true, it will merge it with that last buffer. Otherwise
* it will simply tack it onto the end of the list.
*
* The _peek itself first checks the simple case of the request fitting
* within the head buffer, and if so creates a subbuffer and returns.
* Otherwise, it creates a new buffer and allocates space for the request
* and calls _assemble to fill it. We know we have to copy because this
* case only happens when the _merge wasn't feasible during _get_next_buf.
*
* The _flush method repeatedly inspects the head buffer and flushes as
* much data from it as it needs to, up to the size of the buffer. If
* the flush decimates the buffer, it's stripped, unref'd, and removed.
*/
/* get the next buffer
* if the buffer can be merged with the head buffer, do so
* else add it onto the head of the
*/
static gboolean
gst_bytestream_get_next_buf (GstByteStream * bs)
{
GstBuffer *nextbuf, *lastbuf, *headbuf;
GSList *end;
/* if there is an event pending, return FALSE */
if (bs->event)
return FALSE;
GST_DEBUG ("get_next_buf: pulling buffer");
nextbuf = GST_BUFFER (gst_pad_pull (bs->pad));
if (!nextbuf)
return FALSE;
if (GST_IS_EVENT (nextbuf)) {
bs->event = GST_EVENT (nextbuf);
return FALSE;
}
if (GST_BUFFER_TIMESTAMP_IS_VALID (nextbuf))
bs->last_ts = GST_BUFFER_TIMESTAMP (nextbuf);
GST_DEBUG ("get_next_buf: got buffer of %d bytes", GST_BUFFER_SIZE (nextbuf));
/* first see if there are any buffers in the list at all */
if (bs->buflist) {
GST_DEBUG ("gst_next_buf: there is at least one buffer in the list");
/* now find the end of the list */
end = g_slist_last (bs->buflist);
/* get the buffer that's there */
lastbuf = GST_BUFFER (end->data);
/* see if we can marge cheaply */
if (gst_buffer_is_span_fast (lastbuf, nextbuf)) {
GST_DEBUG ("get_next_buf: merging new buffer with last buf on list");
/* it is, let's merge them (this is really an append, but...) */
end->data = gst_buffer_merge (lastbuf, nextbuf);
/* add to the length of the list */
bs->listavail += GST_BUFFER_SIZE (nextbuf);
/* have to check to see if we merged with the head buffer */
if (end == bs->buflist) {
bs->headbufavail += GST_BUFFER_SIZE (nextbuf);
}
gst_buffer_unref (lastbuf);
gst_buffer_unref (nextbuf);
/* if we can't, we just append this buffer */
} else {
GST_DEBUG ("get_next_buf: adding new buffer to the end of the list");
end = g_slist_append (end, nextbuf);
/* also need to increment length of list and buffer count */
bs->listavail += GST_BUFFER_SIZE (nextbuf);
}
/* if there are no buffers in the list */
} else {
GST_DEBUG ("get_next_buf: buflist is empty, adding new buffer to list");
/* put this on the end of the list */
bs->buflist = g_slist_append (bs->buflist, nextbuf);
/* and increment the number of bytes in the list */
bs->listavail = GST_BUFFER_SIZE (nextbuf);
/* set the head buffer avail to the size */
bs->headbufavail = GST_BUFFER_SIZE (nextbuf);
}
/* a zero offset is a indication that we might need to set the timestamp */
if (bs->offset == 0LL) {
headbuf = GST_BUFFER (bs->buflist->data);
bs->offset = GST_BUFFER_OFFSET (headbuf);
}
return TRUE;
}
static gboolean
gst_bytestream_fill_bytes (GstByteStream * bs, guint32 len)
{
/* as long as we don't have enough, we get more buffers */
while (bs->listavail < len) {
GST_DEBUG ("fill_bytes: there are %d bytes in the list, we need %d",
bs->listavail, len);
if (!gst_bytestream_get_next_buf (bs))
return FALSE;
}
return TRUE;
}
/**
* gst_bytestream_peek:
* @bs: the bytestream to peek
* @buf: pointer to a variable that can hold a buffer pointer.
* @len: the number of bytes to peek
*
* Peeks len bytes into the bytestream, the result is returned as
* a #GstBuffer. Unref the buffer after usage.
* This function can return less bytes than requested. In that case,
* an event might have happened which you can retrieve with
* gst_bytestream_get_status().
*
* Returns: The number of bytes successfully peeked.
*/
guint32
gst_bytestream_peek (GstByteStream * bs, GstBuffer ** buf, guint32 len)
{
GstBuffer *headbuf, *retbuf = NULL;
g_return_val_if_fail (bs != NULL, 0);
g_return_val_if_fail (buf != NULL, 0);
if (len == 0)
return 0;
GST_DEBUG ("peek: asking for %d bytes", len);
/* make sure we have enough */
GST_DEBUG ("peek: there are %d bytes in the list", bs->listavail);
if (len > bs->listavail) {
if (!gst_bytestream_fill_bytes (bs, len)) {
/* we must have an event coming up */
if (bs->listavail > 0) {
/* we have some data left, len will be shrunk to the amount of data available */
len = bs->listavail;
} else {
/* there is no data */
*buf = retbuf;
return 0;
}
}
GST_DEBUG ("peek: there are now %d bytes in the list", bs->listavail);
}
gst_bytestream_print_status (bs);
/* extract the head buffer */
headbuf = GST_BUFFER (bs->buflist->data);
/* if the requested bytes are in the current buffer */
GST_DEBUG ("peek: headbufavail is %d", bs->headbufavail);
if (len <= bs->headbufavail) {
GST_DEBUG ("peek: there are enough bytes in headbuf (need %d, have %d)",
len, bs->headbufavail);
/* create a sub-buffer of the headbuf */
retbuf =
gst_buffer_create_sub (headbuf,
GST_BUFFER_SIZE (headbuf) - bs->headbufavail, len);
GST_BUFFER_OFFSET (retbuf) =
GST_BUFFER_OFFSET (headbuf) + GST_BUFFER_SIZE (headbuf) -
bs->headbufavail;
}
/* otherwise we need to figure out how to assemble one */
else {
GST_DEBUG ("peek: current buffer is not big enough for len %d", len);
retbuf = gst_buffer_new ();
GST_BUFFER_SIZE (retbuf) = len;
GST_BUFFER_DATA (retbuf) = gst_bytestream_assemble (bs, len);
GST_BUFFER_TIMESTAMP (retbuf) = bs->last_ts;
}
*buf = retbuf;
return len;
}
/**
* gst_bytestream_peek_bytes:
* @bs: the bytestream to peek
* @data: pointer to a variable that can hold a guint8 pointer.
* @len: the number of bytes to peek
*
* Peeks len bytes into the bytestream, the result is returned as
* a pointer to a guint8*. The data pointed to be data should not
* be freed and will become invalid after performing the next bytestream
* operation.
* This function can return less bytes than requested. In that case,
* an event might have happened which you can retrieve with
* gst_bytestream_get_status().
*
* Returns: The number of bytes successfully peeked.
*/
guint32
gst_bytestream_peek_bytes (GstByteStream * bs, guint8 ** data, guint32 len)
{
GstBuffer *headbuf;
g_return_val_if_fail (bs != NULL, 0);
g_return_val_if_fail (data != NULL, 0);
g_return_val_if_fail (len > 0, 0);
GST_DEBUG ("peek_bytes: asking for %d bytes", len);
if (bs->assembled) {
if (bs->assembled_len >= len) {
*data = bs->assembled;
return len;
}
g_free (bs->assembled);
bs->assembled = NULL;
}
/* make sure we have enough */
GST_DEBUG ("peek_bytes: there are %d bytes in the list", bs->listavail);
if (len > bs->listavail) {
if (!gst_bytestream_fill_bytes (bs, len)) {
/* we must have an event coming up */
if (bs->listavail > 0) {
/* we have some data left, len will be shrunk to the amount of data available */
len = bs->listavail;
} else {
/* there is no data */
*data = NULL;
return 0;
}
}
GST_DEBUG ("peek_bytes: there are now %d bytes in the list", bs->listavail);
}
gst_bytestream_print_status (bs);
/* extract the head buffer */
headbuf = GST_BUFFER (bs->buflist->data);
/* if the requested bytes are in the current buffer */
GST_DEBUG ("peek_bytes: headbufavail is %d", bs->headbufavail);
if (len <= bs->headbufavail) {
GST_DEBUG
("peek_bytes: there are enough bytes in headbuf (need %d, have %d)",
len, bs->headbufavail);
/* create a sub-buffer of the headbuf */
*data =
GST_BUFFER_DATA (headbuf) + (GST_BUFFER_SIZE (headbuf) -
bs->headbufavail);
}
/* otherwise we need to figure out how to assemble one */
else {
GST_DEBUG ("peek_bytes: current buffer is not big enough for len %d", len);
*data = gst_bytestream_assemble (bs, len);
bs->assembled = *data;
bs->assembled_len = len;
}
return len;
}
static guint8 *
gst_bytestream_assemble (GstByteStream * bs, guint32 len)
{
guint8 *data = g_malloc (len);
GSList *walk;
guint32 copied = 0;
GstBuffer *buf;
/* copy the data from the curbuf */
buf = GST_BUFFER (bs->buflist->data);
GST_DEBUG ("assemble: copying %d bytes from curbuf at %d to *data",
bs->headbufavail, GST_BUFFER_SIZE (buf) - bs->headbufavail);
memcpy (data,
GST_BUFFER_DATA (buf) + GST_BUFFER_SIZE (buf) - bs->headbufavail,
bs->headbufavail);
copied += bs->headbufavail;
/* asumption is made that the buffers all exist in the list */
walk = g_slist_next (bs->buflist);
while (copied < len) {
buf = GST_BUFFER (walk->data);
if (GST_BUFFER_SIZE (buf) < (len - copied)) {
GST_DEBUG ("assemble: copying %d bytes from buf to output offset %d",
GST_BUFFER_SIZE (buf), copied);
memcpy (data + copied, GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (buf));
copied += GST_BUFFER_SIZE (buf);
} else {
GST_DEBUG ("assemble: copying %d bytes from buf to output offset %d",
len - copied, copied);
memcpy (data + copied, GST_BUFFER_DATA (buf), len - copied);
copied = len;
}
walk = g_slist_next (walk);
}
return data;
}
/**
* gst_bytestream_flush:
* @bs: the bytestream to flush
* @len: the number of bytes to flush
*
* Flush len bytes from the bytestream.
* This function can return FALSE when the number of
* bytes could not be flushed due to an event. In that case,
* you can get the number of available bytes before the event
* with gst_bytestream_get_status().
*
* Returns: TRUE if the number of bytes could be flushed.
*/
gboolean
gst_bytestream_flush (GstByteStream * bs, guint32 len)
{
GST_DEBUG ("flush: flushing %d bytes", len);
if (len == 0)
return TRUE;
/* make sure we have enough */
GST_DEBUG ("flush: there are %d bytes in the list", bs->listavail);
if (len > bs->listavail) {
if (!gst_bytestream_fill_bytes (bs, len)) {
return FALSE;
}
GST_DEBUG ("flush: there are now %d bytes in the list", bs->listavail);
}
gst_bytestream_flush_fast (bs, len);
return TRUE;
}
/**
* gst_bytestream_flush_fast:
* @bs: the bytestream to flush
* @len: the number of bytes to flush
*
* Flushes len bytes from the bytestream. This function
* is faster than gst_bytestream_flush() but only works
* when you have recently peeked no less than len bytes
* with gst_bytestream_peek() or gst_bytestream_peek_bytes().
*/
void
gst_bytestream_flush_fast (GstByteStream * bs, guint32 len)
{
GstBuffer *headbuf;
if (len == 0)
return;
g_assert (len <= bs->listavail);
if (bs->assembled) {
g_free (bs->assembled);
bs->assembled = NULL;
}
/* update the byte offset */
bs->offset += len;
/* repeat until we've flushed enough data */
while (len > 0) {
headbuf = GST_BUFFER (bs->buflist->data);
GST_DEBUG ("flush: analyzing buffer that's %d bytes long, offset %"
G_GUINT64_FORMAT, GST_BUFFER_SIZE (headbuf),
GST_BUFFER_OFFSET (headbuf));
/* if there's enough to complete the flush */
if (bs->headbufavail > len) {
/* just trim it off */
GST_DEBUG ("flush: trimming %d bytes off end of headbuf", len);
bs->headbufavail -= len;
bs->listavail -= len;
len = 0;
/* otherwise we have to trim the whole buffer */
} else {
GST_DEBUG ("flush: removing head buffer completely");
/* remove it from the list */
bs->buflist = g_slist_delete_link (bs->buflist, bs->buflist);
/* trim it from the avail size */
bs->listavail -= bs->headbufavail;
/* record that we've trimmed this many bytes */
len -= bs->headbufavail;
/* unref it */
gst_buffer_unref (headbuf);
/* record the new headbufavail */
if (bs->buflist) {
bs->headbufavail = GST_BUFFER_SIZE (GST_BUFFER (bs->buflist->data));
GST_DEBUG ("flush: next headbuf is %d bytes", bs->headbufavail);
} else {
GST_DEBUG ("flush: no more bytes at all");
}
}
GST_DEBUG ("flush: bottom of while(), len is now %d", len);
}
}
/**
* gst_bytestream_seek:
* @bs: the bytestream to seek
* @offset: the byte offset to seek to
* @method: the seek method.
*
* Perform a seek on the bytestream to the given offset.
* The method can be one of GST_SEEK_METHOD_CUR, GST_SEEK_METHOD_SET,
* GST_SEEK_METHOD_END.
* This seek will also flush any pending data in the bytestream or
* peer elements.
*
* Returns: TRUE when the seek succeeded.
*/
gboolean
gst_bytestream_seek (GstByteStream * bs, gint64 offset, GstSeekType method)
{
GstRealPad *peer;
g_return_val_if_fail (bs != NULL, FALSE);
peer = GST_RPAD_PEER (bs->pad);
GST_DEBUG ("bs: send event");
if (gst_pad_send_event (GST_PAD (peer), gst_event_new_seek (GST_FORMAT_BYTES |
(method & GST_SEEK_METHOD_MASK) |
GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE, offset))) {
gst_bytestream_flush_fast (bs, bs->listavail);
/* we set the seek flag here. We cannot pull the pad here
* bacause a seek might occur outisde of the pads cothread context */
bs->in_seek = TRUE;
return TRUE;
}
GST_DEBUG ("bs: send event failed\n");
return FALSE;
}
/**
* gst_bytestream_tell
* @bs: a bytestream
*
* Get the current byteoffset in the bytestream.
*
* Returns: the offset or -1 on error.
*/
guint64
gst_bytestream_tell (GstByteStream * bs)
{
GstFormat format;
gint64 value;
g_return_val_if_fail (bs != NULL, -1);
format = GST_FORMAT_BYTES;
if (gst_pad_query (GST_PAD_PEER (bs->pad), GST_QUERY_POSITION, &format,
&value)) {
return value - bs->listavail;
}
return -1;
}
/**
* gst_bytestream_length
* @bs: a bytestream
*
* Get the total length of the bytestream.
*
* Returns: the total length or -1 on error.
*/
guint64
gst_bytestream_length (GstByteStream * bs)
{
GstFormat format;
gint64 value;
g_return_val_if_fail (bs != NULL, -1);
format = GST_FORMAT_BYTES;
if (gst_pad_query (GST_PAD_PEER (bs->pad), GST_QUERY_TOTAL, &format, &value))
return value;
return -1;
}
/**
* gst_bytestream_read:
* @bs: the bytestream to read
* @buf: pointer to a variable that can hold a buffer pointer.
* @len: the number of bytes to read
*
* Read len bytes from the bytestream, the result is returned as
* a #GstBuffer. Unref the buffer after usage.
* This function can return less bytes than requested. In that case,
* an event might have happened which you can retrieve with
* gst_bytestream_get_status().
*
* Returns: The number of bytes successfully read.
*/
guint32
gst_bytestream_read (GstByteStream * bs, GstBuffer ** buf, guint32 len)
{
guint32 len_peeked;
g_return_val_if_fail (bs != NULL, -1);
len_peeked = gst_bytestream_peek (bs, buf, len);
if (len_peeked == 0)
return 0;
gst_bytestream_flush_fast (bs, len_peeked);
return len_peeked;
}
/**
* gst_bytestream_size_hint
* @bs: a bytestream
* @size: the size to hint
*
* Give a hint that we are going to read chunks of the given size.
* Giving size hints to the peer element might improve performance
* since less buffers need to be merged.
*
* Returns: TRUE if the hint was accepted.
*/
gboolean
gst_bytestream_size_hint (GstByteStream * bs, guint32 size)
{
GstEvent *event;
g_return_val_if_fail (bs != NULL, FALSE);
event = gst_event_new_size (GST_FORMAT_BYTES, size);
return gst_pad_send_event (GST_PAD_PEER (bs->pad), event);
}
/**
* gst_bytestream_get_status
* @bs: a bytestream
* @avail_out: total number of bytes buffered
* @event_out: an event
*
* When an event occurs, the bytestream operations return a value less
* than the requested length. You must retrieve the event using this API
* before reading more bytes from the stream.
*/
void
gst_bytestream_get_status (GstByteStream * bs,
guint32 * avail_out, GstEvent ** event_out)
{
if (avail_out)
*avail_out = bs->listavail;
if (event_out) {
*event_out = bs->event;
bs->event = NULL;
}
}
/**
* gst_bytestream_get_timestamp
* @bs: a bytestream
*
* Get the timestamp of the first data in the bytestream. If no data
* exists 1 byte is read to load a new buffer.
*
* This function will not check input buffer boundries. It is possible
* the next read could span two or more input buffers with different
* timestamps.
*
* Returns: a timestamp.
*/
guint64
gst_bytestream_get_timestamp (GstByteStream * bs)
{
GstBuffer *headbuf;
g_return_val_if_fail (bs != NULL, 0);
GST_DEBUG ("get_timestamp: getting timestamp");
/* make sure we have a buffer */
if (bs->listavail == 0) {
GST_DEBUG ("gst_timestamp: fetching a buffer");
if (!gst_bytestream_fill_bytes (bs, 1))
return 0;
}
/* extract the head buffer */
headbuf = GST_BUFFER (bs->buflist->data);
return GST_BUFFER_TIMESTAMP (headbuf);
}
/**
* gst_bytestream_print_status
* @bs: a bytestream
*
* Print the current status of the bytestream object. mainly
* used for debugging purposes.
*/
void
gst_bytestream_print_status (GstByteStream * bs)
{
GSList *walk;
GstBuffer *buf;
GST_DEBUG ("STATUS: head buffer has %d bytes available", bs->headbufavail);
GST_DEBUG ("STATUS: list has %d bytes available", bs->listavail);
walk = bs->buflist;
while (walk) {
buf = GST_BUFFER (walk->data);
walk = g_slist_next (walk);
GST_DEBUG ("STATUS: buffer starts at %" G_GUINT64_FORMAT
" and is %d bytes long", GST_BUFFER_OFFSET (buf),
GST_BUFFER_SIZE (buf));
}
}
static gboolean
plugin_init (GstPlugin * plugin)
{
GST_DEBUG_CATEGORY_INIT (debug_bs, "bytestream", 0, "bytestream library");
return TRUE;
}
GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,
GST_VERSION_MINOR,
"gstbytestream",
"a byte-oriented layer on top of buffer-passing",
plugin_init, VERSION, GST_LICENSE, GST_PACKAGE, GST_ORIGIN)