[ltt-dev] [BABELTRACE PATCH] Basic seek support

[Mathieu Desnoyers]

* Julien Desfossez (julien.desfossez at polymtl.ca) wrote:
> For now just mimic the previous behaviour of babeltrace but with a basic
> seek structure.
> We define the babeltrace_iter_seek that seeks each file_stream of an
> iterator to a given position and the babeltrace_filestream_seek function
> that does the actual seek on the file_stream and can be used internally.
> 
> Signed-off-by: Julien Desfossez <julien.desfossez at polymtl.ca>
> ---
>  converter/babeltrace-lib.c |   89 ++++++++++++++++++++++++++++++++++++++++----
>  1 files changed, 81 insertions(+), 8 deletions(-)
> 
> diff --git a/converter/babeltrace-lib.c b/converter/babeltrace-lib.c
> index d078a69..9f5e392 100644
> --- a/converter/babeltrace-lib.c
> +++ b/converter/babeltrace-lib.c
> @@ -156,7 +156,75 @@ int stream_compare(void *a, void *b)
>  		return 0;
>  }
>  
> -/* TODO: use begin_pos/end_pos */
> +/*
> + * babeltrace_filestream_seek: seek a filestream to given position.
> + */
> +static int babeltrace_filestream_seek(struct ctf_file_stream *file_stream,
> +		const struct trace_collection_pos *begin_pos)

You should not pass a struct trace_collection_pos as position parameter
for a single stream. You should pass the target stream position instead
(specific to the stream).

Thanks,

Mathieu

> +{
> +	int ret = 0;
> +
> +	switch (begin_pos->type) {
> +	case BT_SEEK_CUR:
> +		/*
> +		 * just insert into the heap we should already know
> +		 * the timestamps
> +		 */
> +		break;
> +	case BT_SEEK_BEGIN:
> +		ctf_move_pos_slow(&file_stream->pos, 0, SEEK_SET);
> +		ret = stream_read_event(file_stream);
> +		break;
> +	case BT_SEEK_TIME:
> +	case BT_SEEK_RESTORE:
> +	case BT_SEEK_END:
> +	default:
> +		assert(0); /* Not yet defined */
> +	}
> +
> +	return ret;
> +}
> +
> +/*
> + * babeltrace_iter_seek: seek iterator to given position.
> + */
> +int babeltrace_iter_seek(struct babeltrace_iter *iter,
> +	   const struct trace_collection_pos *begin_pos)
> +{
> +    int i, stream_id;
> +	int ret = 0;
> +	struct trace_collection *tc = iter->tc;
> +
> +	for (i = 0; i < tc->array->len; i++) {
> +		struct ctf_trace *tin;
> +		struct trace_descriptor *td_read;
> +
> +		td_read = g_ptr_array_index(tc->array, i);
> +		tin = container_of(td_read, struct ctf_trace, parent);
> +
> +		/* Populate heap with each stream */
> +		for (stream_id = 0; stream_id < tin->streams->len;
> +				stream_id++) {
> +			struct ctf_stream_class *stream;
> +			int filenr;
> +
> +			stream = g_ptr_array_index(tin->streams, stream_id);
> +			for (filenr = 0; filenr < stream->streams->len;
> +					filenr++) {
> +				struct ctf_file_stream *file_stream;
> +
> +				file_stream = g_ptr_array_index(stream->streams,
> +						filenr);
> +				ret = babeltrace_filestream_seek(file_stream, begin_pos);
> +				if (ret < 0)
> +					goto end;
> +			}
> +		}
> +	}
> +end:
> +	return ret;
> +}
> +
>  struct babeltrace_iter *babeltrace_iter_create(struct trace_collection *tc,
>  		struct trace_collection_pos *begin_pos,
>  		struct trace_collection_pos *end_pos)
> @@ -170,6 +238,7 @@ struct babeltrace_iter *babeltrace_iter_create(struct trace_collection *tc,
>  		goto error_malloc;
>  	iter->stream_heap = g_new(struct ptr_heap, 1);
>  	iter->tc = tc;
> +	iter->end_pos = end_pos;
>  
>  	ret = heap_init(iter->stream_heap, 0, stream_compare);
>  	if (ret < 0)
> @@ -198,12 +267,14 @@ struct babeltrace_iter *babeltrace_iter_create(struct trace_collection *tc,
>  				file_stream = g_ptr_array_index(stream->streams,
>  						filenr);
>  
> -				ret = stream_read_event(file_stream);
> -				if (ret == EOF) {
> -					ret = 0;
> -					continue;
> -				} else if (ret) {
> -					goto error;
> +				if (begin_pos) {
> +				    ret = babeltrace_filestream_seek(file_stream, begin_pos);
> +				    if (ret == EOF) {
> +					   ret = 0;
> +					   continue;
> +				    } else if (ret) {
> +					   goto error;
> +				    }
>  				}
>  				/* Add to heap */
>  				ret = heap_insert(iter->stream_heap, file_stream);
> @@ -286,12 +357,14 @@ int convert_trace(struct trace_descriptor *td_write,
>  	struct ctf_stream *stream;
>  	struct ctf_stream_event *event;
>  	struct ctf_text_stream_pos *sout;
> +	struct trace_collection_pos begin_pos;
>  	int ret = 0;
>  
>  	sout = container_of(td_write, struct ctf_text_stream_pos,
>  			trace_descriptor);
>  
> -	iter = babeltrace_iter_create(trace_collection_read, NULL, NULL);
> +	begin_pos.type = BT_SEEK_BEGIN;
> +	iter = babeltrace_iter_create(trace_collection_read, &begin_pos, NULL);
>  	while (babeltrace_iter_read_event(iter, &stream, &event) == 0) {
>  		ret = sout->parent.event_cb(&sout->parent, stream);
>  		if (ret) {
> -- 
> 1.7.5.4
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com