[lttng-dev] [BABELTRACE PATCH] Fix data_offset when importing the indexes

[lttng-dev] [BABELTRACE PATCH] Fix data_offset when importing the indexes

[Julien Desfossez]

When importing an index, we don't have the data_offset and we want to
mmap the tracefile only when needed, so we introduce a new function to
only compute this information when we are going to use a new packet.

Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
---
 formats/ctf/ctf.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 105 insertions(+), 1 deletion(-)

diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
index 5cf8097..b8103c5 100644
--- a/formats/ctf/ctf.c
+++ b/formats/ctf/ctf.c
@@ -627,6 +627,103 @@ error:
 	return ret;
 }
 
+static
+int find_data_offset(struct ctf_stream_pos *pos,
+		struct ctf_file_stream *file_stream,
+		struct packet_index *packet_index)
+{
+	uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len;
+	struct stat filestats;
+	int ret;
+	size_t filesize;
+
+	pos = &file_stream->pos;
+
+	ret = fstat(pos->fd, &filestats);
+	if (ret < 0)
+		return ret;
+	filesize = filestats.st_size;
+
+	/* Deal with empty files */
+	if (!filesize) {
+		return 0;
+	}
+
+begin:
+	if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) {
+		packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT;
+	}
+
+	if (pos->base_mma) {
+		/* unmap old base */
+		ret = munmap_align(pos->base_mma);
+		if (ret) {
+			fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+					strerror(errno));
+			return ret;
+		}
+		pos->base_mma = NULL;
+	}
+	/* map new base. Need mapping length from header. */
+	pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ,
+			MAP_PRIVATE, pos->fd, pos->mmap_offset);
+	assert(pos->base_mma != MAP_FAILED);
+
+	pos->content_size = packet_map_len;
+	pos->packet_size = packet_map_len;
+	pos->offset = 0;	/* Position of the packet header */
+
+	/* update trace_packet_header and stream_packet_context */
+	if (pos->prot != PROT_WRITE && file_stream->parent.trace_packet_header) {
+		/* Read packet header */
+		ret = generic_rw(&pos->parent, &file_stream->parent.trace_packet_header->p);
+		if (ret) {
+			if (ret == -EFAULT)
+				goto retry;
+		}
+	}
+	if (pos->prot != PROT_WRITE && file_stream->parent.stream_packet_context) {
+		/* Read packet context */
+		ret = generic_rw(&pos->parent, &file_stream->parent.stream_packet_context->p);
+		if (ret) {
+			if (ret == -EFAULT)
+				goto retry;
+		}
+	}
+	packet_index->data_offset = pos->offset;
+
+	/* unmap old base */
+	ret = munmap_align(pos->base_mma);
+	if (ret) {
+		fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+				strerror(errno));
+		return ret;
+	}
+	pos->base_mma = NULL;
+
+	return 0;
+
+	/* Retry with larger mapping */
+retry:
+	if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) {
+		/*
+		 * Reached EOF, but still expecting header/context data.
+		 */
+		fprintf(stderr, "[error] Reached end of file, but still expecting header or context fields.\n");
+		return -EFAULT;
+	}
+	/* Double the mapping len, and retry */
+	tmp_map_len = packet_map_len << 1;
+	if (tmp_map_len >> 1 != packet_map_len) {
+		/* Overflow */
+		fprintf(stderr, "[error] Packet mapping length overflow\n");
+		return -EFAULT;
+	}
+	packet_map_len = tmp_map_len;
+	goto begin;
+}
+
+
 int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor *trace,
 		int fd, int open_flags)
 {
@@ -845,11 +942,17 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos, size_t index, int whence)
 				struct packet_index,
 				pos->cur_index);
 		file_stream->parent.real_timestamp = packet_index->timestamp_begin;
-		pos->mmap_offset = packet_index->offset;
 
 		/* Lookup context/packet size in index */
+		if (packet_index->data_offset == -1) {
+			ret = find_data_offset(pos, file_stream, packet_index);
+			if (ret < 0) {
+				return;
+			}
+		}
 		pos->content_size = packet_index->content_size;
 		pos->packet_size = packet_index->packet_size;
+		pos->mmap_offset = packet_index->offset;
 		if (packet_index->data_offset < packet_index->content_size) {
 			pos->offset = 0;	/* will read headers */
 		} else if (packet_index->data_offset == packet_index->content_size) {
@@ -1748,6 +1851,7 @@ int import_stream_packet_index(struct ctf_trace *td,
 		index.timestamp_end = be64toh(ctf_index.timestamp_end);
 		index.events_discarded = be64toh(ctf_index.events_discarded);
 		index.events_discarded_len = 64;
+		index.data_offset = -1;
 		stream_id = be64toh(ctf_index.stream_id);
 
 		if (!first_packet) {
-- 
1.8.3.2

[lttng-dev] [BABELTRACE PATCH] Fix data_offset when importing the indexes

[Mathieu Desnoyers]

----- Original Message -----
> From: "Julien Desfossez" <jdesfossez@efficios.com>
> To: "mathieu desnoyers" <mathieu.desnoyers at efficios.com>
> Cc: lttng-dev at lists.lttng.org, "Julien Desfossez" <jdesfossez at efficios.com>
> Sent: Friday, November 29, 2013 11:43:39 PM
> Subject: [BABELTRACE PATCH] Fix data_offset when importing the indexes
> 
> When importing an index, we don't have the data_offset and we want to
> mmap the tracefile only when needed, so we introduce a new function to
> only compute this information when we are going to use a new packet.

Merged with tiny cleanup.

Thanks!

Mathieu

> 
> Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
> ---
>  formats/ctf/ctf.c | 106
>  +++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 105 insertions(+), 1 deletion(-)
> 
> diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
> index 5cf8097..b8103c5 100644
> --- a/formats/ctf/ctf.c
> +++ b/formats/ctf/ctf.c
> @@ -627,6 +627,103 @@ error:
>  	return ret;
>  }
>  
> +static
> +int find_data_offset(struct ctf_stream_pos *pos,
> +		struct ctf_file_stream *file_stream,
> +		struct packet_index *packet_index)
> +{
> +	uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len;
> +	struct stat filestats;
> +	int ret;
> +	size_t filesize;
> +
> +	pos = &file_stream->pos;
> +
> +	ret = fstat(pos->fd, &filestats);
> +	if (ret < 0)
> +		return ret;
> +	filesize = filestats.st_size;
> +
> +	/* Deal with empty files */
> +	if (!filesize) {
> +		return 0;
> +	}
> +
> +begin:
> +	if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) {
> +		packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT;
> +	}
> +
> +	if (pos->base_mma) {
> +		/* unmap old base */
> +		ret = munmap_align(pos->base_mma);
> +		if (ret) {
> +			fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
> +					strerror(errno));
> +			return ret;
> +		}
> +		pos->base_mma = NULL;
> +	}
> +	/* map new base. Need mapping length from header. */
> +	pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ,
> +			MAP_PRIVATE, pos->fd, pos->mmap_offset);
> +	assert(pos->base_mma != MAP_FAILED);
> +
> +	pos->content_size = packet_map_len;
> +	pos->packet_size = packet_map_len;
> +	pos->offset = 0;	/* Position of the packet header */
> +
> +	/* update trace_packet_header and stream_packet_context */
> +	if (pos->prot != PROT_WRITE && file_stream->parent.trace_packet_header) {
> +		/* Read packet header */
> +		ret = generic_rw(&pos->parent,
> &file_stream->parent.trace_packet_header->p);
> +		if (ret) {
> +			if (ret == -EFAULT)
> +				goto retry;
> +		}
> +	}
> +	if (pos->prot != PROT_WRITE && file_stream->parent.stream_packet_context) {
> +		/* Read packet context */
> +		ret = generic_rw(&pos->parent,
> &file_stream->parent.stream_packet_context->p);
> +		if (ret) {
> +			if (ret == -EFAULT)
> +				goto retry;
> +		}
> +	}
> +	packet_index->data_offset = pos->offset;
> +
> +	/* unmap old base */
> +	ret = munmap_align(pos->base_mma);
> +	if (ret) {
> +		fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
> +				strerror(errno));
> +		return ret;
> +	}
> +	pos->base_mma = NULL;
> +
> +	return 0;
> +
> +	/* Retry with larger mapping */
> +retry:
> +	if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) {
> +		/*
> +		 * Reached EOF, but still expecting header/context data.
> +		 */
> +		fprintf(stderr, "[error] Reached end of file, but still expecting header
> or context fields.\n");
> +		return -EFAULT;
> +	}
> +	/* Double the mapping len, and retry */
> +	tmp_map_len = packet_map_len << 1;
> +	if (tmp_map_len >> 1 != packet_map_len) {
> +		/* Overflow */
> +		fprintf(stderr, "[error] Packet mapping length overflow\n");
> +		return -EFAULT;
> +	}
> +	packet_map_len = tmp_map_len;
> +	goto begin;
> +}
> +
> +
>  int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor
>  *trace,
>  		int fd, int open_flags)
>  {
> @@ -845,11 +942,17 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos,
> size_t index, int whence)
>  				struct packet_index,
>  				pos->cur_index);
>  		file_stream->parent.real_timestamp = packet_index->timestamp_begin;
> -		pos->mmap_offset = packet_index->offset;
>  
>  		/* Lookup context/packet size in index */
> +		if (packet_index->data_offset == -1) {
> +			ret = find_data_offset(pos, file_stream, packet_index);
> +			if (ret < 0) {
> +				return;
> +			}
> +		}
>  		pos->content_size = packet_index->content_size;
>  		pos->packet_size = packet_index->packet_size;
> +		pos->mmap_offset = packet_index->offset;
>  		if (packet_index->data_offset < packet_index->content_size) {
>  			pos->offset = 0;	/* will read headers */
>  		} else if (packet_index->data_offset == packet_index->content_size) {
> @@ -1748,6 +1851,7 @@ int import_stream_packet_index(struct ctf_trace *td,
>  		index.timestamp_end = be64toh(ctf_index.timestamp_end);
>  		index.events_discarded = be64toh(ctf_index.events_discarded);
>  		index.events_discarded_len = 64;
> +		index.data_offset = -1;
>  		stream_id = be64toh(ctf_index.stream_id);
>  
>  		if (!first_packet) {
> --
> 1.8.3.2
> 
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

[lttng-dev] [BABELTRACE PATCH] Fix data_offset when importing the indexes

[Mathieu Desnoyers]

----- Original Message -----
> From: "Julien Desfossez" <jdesfossez@efficios.com>
> To: "mathieu desnoyers" <mathieu.desnoyers at efficios.com>
> Cc: lttng-dev at lists.lttng.org, "Julien Desfossez" <jdesfossez at efficios.com>
> Sent: Friday, November 29, 2013 5:12:02 PM
> Subject: [BABELTRACE PATCH] Fix data_offset when importing the indexes
> 
> The data_offset is the same for all the packets of a stream and is
> computed from reading the headers and context of the first packet in a
> stream.

This assumption is wrong. You can have variants, sequences or string
in a packet header/context, which makes it impossible to know the size
of those structures for all packets by just reading the first packet.

Thanks,

Mathieu

> When importing an index, we don't have this information and we want to
> mmap the tracefile only when needed, so we introduce a new function to
> only compute this information when we are going to use the first packet
> of a stream. Once we find the data_offset, we copy it to the
> ctf_stream_pos to avoid recomputing it for each packet (since it won't
> be written in the index at open time).
> 
> Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
> ---
>  formats/ctf/ctf.c              | 102
>  +++++++++++++++++++++++++++++++++++++++++
>  include/babeltrace/ctf/types.h |   1 +
>  2 files changed, 103 insertions(+)
> 
> diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
> index 5cf8097..5e7ae17 100644
> --- a/formats/ctf/ctf.c
> +++ b/formats/ctf/ctf.c
> @@ -627,10 +627,103 @@ error:
>  	return ret;
>  }
>  
> +static
> +int find_data_offset(struct ctf_stream_pos *pos,
> +		struct ctf_file_stream *file_stream)
> +{
> +	uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len;
> +	struct stat filestats;
> +	int ret;
> +	size_t filesize;
> +
> +	pos = &file_stream->pos;
> +
> +	ret = fstat(pos->fd, &filestats);
> +	if (ret < 0)
> +		return ret;
> +	filesize = filestats.st_size;
> +
> +	/* Deal with empty files */
> +	if (!filesize) {
> +		return 0;
> +	}
> +
> +begin:
> +	if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) {
> +		packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT;
> +	}
> +
> +	if (pos->base_mma) {
> +		/* unmap old base */
> +		ret = munmap_align(pos->base_mma);
> +		if (ret) {
> +			fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
> +					strerror(errno));
> +			return ret;
> +		}
> +		pos->base_mma = NULL;
> +	}
> +	/* map new base. Need mapping length from header. */
> +	pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ,
> +			MAP_PRIVATE, pos->fd, pos->mmap_offset);
> +	assert(pos->base_mma != MAP_FAILED);
> +
> +	/* update trace_packet_header and stream_packet_context */
> +	if (pos->prot != PROT_WRITE && file_stream->parent.trace_packet_header) {
> +		/* Read packet header */
> +		ret = generic_rw(&pos->parent,
> &file_stream->parent.trace_packet_header->p);
> +		if (ret) {
> +			if (ret == -EFAULT)
> +				goto retry;
> +		}
> +	}
> +	if (pos->prot != PROT_WRITE && file_stream->parent.stream_packet_context) {
> +		/* Read packet context */
> +		ret = generic_rw(&pos->parent,
> &file_stream->parent.stream_packet_context->p);
> +		if (ret) {
> +			if (ret == -EFAULT)
> +				goto retry;
> +		}
> +	}
> +	pos->data_offset = pos->offset;
> +
> +	/* unmap old base */
> +	ret = munmap_align(pos->base_mma);
> +	if (ret) {
> +		fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
> +				strerror(errno));
> +		return ret;
> +	}
> +	pos->base_mma = NULL;
> +
> +	return 0;
> +
> +	/* Retry with larger mapping */
> +retry:
> +	if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) {
> +		/*
> +		 * Reached EOF, but still expecting header/context data.
> +		 */
> +		fprintf(stderr, "[error] Reached end of file, but still expecting header
> or context fields.\n");
> +		return -EFAULT;
> +	}
> +	/* Double the mapping len, and retry */
> +	tmp_map_len = packet_map_len << 1;
> +	if (tmp_map_len >> 1 != packet_map_len) {
> +		/* Overflow */
> +		fprintf(stderr, "[error] Packet mapping length overflow\n");
> +		return -EFAULT;
> +	}
> +	packet_map_len = tmp_map_len;
> +	goto begin;
> +}
> +
> +
>  int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor
>  *trace,
>  		int fd, int open_flags)
>  {
>  	pos->fd = fd;
> +	pos->data_offset = -1;
>  	if (fd >= 0) {
>  		pos->packet_cycles_index = g_array_new(FALSE, TRUE,
>  						sizeof(struct packet_index));
> @@ -850,6 +943,14 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos,
> size_t index, int whence)
>  		/* Lookup context/packet size in index */
>  		pos->content_size = packet_index->content_size;
>  		pos->packet_size = packet_index->packet_size;
> +		if (pos->data_offset != -1) {
> +			packet_index->data_offset = pos->data_offset;
> +		} else {
> +			ret = find_data_offset(pos, file_stream);
> +			if (ret < 0) {
> +				return;
> +			}
> +		}
>  		if (packet_index->data_offset < packet_index->content_size) {
>  			pos->offset = 0;	/* will read headers */
>  		} else if (packet_index->data_offset == packet_index->content_size) {
> @@ -1593,6 +1694,7 @@ begin:
>  
>  	/* Save position after header and context */
>  	packet_index.data_offset = pos->offset;
> +	pos->data_offset = pos->offset;
>  
>  	/* add index to packet array */
>  	g_array_append_val(file_stream->pos.packet_cycles_index, packet_index);
> diff --git a/include/babeltrace/ctf/types.h b/include/babeltrace/ctf/types.h
> index e90464d..5f32b9b 100644
> --- a/include/babeltrace/ctf/types.h
> +++ b/include/babeltrace/ctf/types.h
> @@ -78,6 +78,7 @@ struct ctf_stream_pos {
>  	int64_t last_offset;	/* offset before the last read_event */
>  	uint64_t cur_index;	/* current index in packet index */
>  	uint64_t last_events_discarded;	/* last known amount of event discarded */
> +	int64_t data_offset;	/* offset of data within the packet, in bits */
>  	void (*packet_seek)(struct bt_stream_pos *pos, size_t index,
>  			int whence); /* function called to switch packet */
>  
> --
> 1.8.3.2
> 
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

[lttng-dev] [BABELTRACE PATCH] Fix data_offset when importing the indexes

[Julien Desfossez]

The data_offset is the same for all the packets of a stream and is
computed from reading the headers and context of the first packet in a
stream.
When importing an index, we don't have this information and we want to
mmap the tracefile only when needed, so we introduce a new function to
only compute this information when we are going to use the first packet
of a stream. Once we find the data_offset, we copy it to the
ctf_stream_pos to avoid recomputing it for each packet (since it won't
be written in the index at open time).

Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
---
 formats/ctf/ctf.c              | 102 +++++++++++++++++++++++++++++++++++++++++
 include/babeltrace/ctf/types.h |   1 +
 2 files changed, 103 insertions(+)

diff --git a/formats/ctf/ctf.c b/formats/ctf/ctf.c
index 5cf8097..5e7ae17 100644
--- a/formats/ctf/ctf.c
+++ b/formats/ctf/ctf.c
@@ -627,10 +627,103 @@ error:
 	return ret;
 }
 
+static
+int find_data_offset(struct ctf_stream_pos *pos,
+		struct ctf_file_stream *file_stream)
+{
+	uint64_t packet_map_len = DEFAULT_HEADER_LEN, tmp_map_len;
+	struct stat filestats;
+	int ret;
+	size_t filesize;
+
+	pos = &file_stream->pos;
+
+	ret = fstat(pos->fd, &filestats);
+	if (ret < 0)
+		return ret;
+	filesize = filestats.st_size;
+
+	/* Deal with empty files */
+	if (!filesize) {
+		return 0;
+	}
+
+begin:
+	if (filesize - pos->mmap_offset < (packet_map_len >> LOG2_CHAR_BIT)) {
+		packet_map_len = (filesize - pos->mmap_offset) << LOG2_CHAR_BIT;
+	}
+
+	if (pos->base_mma) {
+		/* unmap old base */
+		ret = munmap_align(pos->base_mma);
+		if (ret) {
+			fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+					strerror(errno));
+			return ret;
+		}
+		pos->base_mma = NULL;
+	}
+	/* map new base. Need mapping length from header. */
+	pos->base_mma = mmap_align(packet_map_len >> LOG2_CHAR_BIT, PROT_READ,
+			MAP_PRIVATE, pos->fd, pos->mmap_offset);
+	assert(pos->base_mma != MAP_FAILED);
+
+	/* update trace_packet_header and stream_packet_context */
+	if (pos->prot != PROT_WRITE && file_stream->parent.trace_packet_header) {
+		/* Read packet header */
+		ret = generic_rw(&pos->parent, &file_stream->parent.trace_packet_header->p);
+		if (ret) {
+			if (ret == -EFAULT)
+				goto retry;
+		}
+	}
+	if (pos->prot != PROT_WRITE && file_stream->parent.stream_packet_context) {
+		/* Read packet context */
+		ret = generic_rw(&pos->parent, &file_stream->parent.stream_packet_context->p);
+		if (ret) {
+			if (ret == -EFAULT)
+				goto retry;
+		}
+	}
+	pos->data_offset = pos->offset;
+
+	/* unmap old base */
+	ret = munmap_align(pos->base_mma);
+	if (ret) {
+		fprintf(stderr, "[error] Unable to unmap old base: %s.\n",
+				strerror(errno));
+		return ret;
+	}
+	pos->base_mma = NULL;
+
+	return 0;
+
+	/* Retry with larger mapping */
+retry:
+	if (packet_map_len == ((filesize - pos->mmap_offset) << LOG2_CHAR_BIT)) {
+		/*
+		 * Reached EOF, but still expecting header/context data.
+		 */
+		fprintf(stderr, "[error] Reached end of file, but still expecting header or context fields.\n");
+		return -EFAULT;
+	}
+	/* Double the mapping len, and retry */
+	tmp_map_len = packet_map_len << 1;
+	if (tmp_map_len >> 1 != packet_map_len) {
+		/* Overflow */
+		fprintf(stderr, "[error] Packet mapping length overflow\n");
+		return -EFAULT;
+	}
+	packet_map_len = tmp_map_len;
+	goto begin;
+}
+
+
 int ctf_init_pos(struct ctf_stream_pos *pos, struct bt_trace_descriptor *trace,
 		int fd, int open_flags)
 {
 	pos->fd = fd;
+	pos->data_offset = -1;
 	if (fd >= 0) {
 		pos->packet_cycles_index = g_array_new(FALSE, TRUE,
 						sizeof(struct packet_index));
@@ -850,6 +943,14 @@ void ctf_packet_seek(struct bt_stream_pos *stream_pos, size_t index, int whence)
 		/* Lookup context/packet size in index */
 		pos->content_size = packet_index->content_size;
 		pos->packet_size = packet_index->packet_size;
+		if (pos->data_offset != -1) {
+			packet_index->data_offset = pos->data_offset;
+		} else {
+			ret = find_data_offset(pos, file_stream);
+			if (ret < 0) {
+				return;
+			}
+		}
 		if (packet_index->data_offset < packet_index->content_size) {
 			pos->offset = 0;	/* will read headers */
 		} else if (packet_index->data_offset == packet_index->content_size) {
@@ -1593,6 +1694,7 @@ begin:
 
 	/* Save position after header and context */
 	packet_index.data_offset = pos->offset;
+	pos->data_offset = pos->offset;
 
 	/* add index to packet array */
 	g_array_append_val(file_stream->pos.packet_cycles_index, packet_index);
diff --git a/include/babeltrace/ctf/types.h b/include/babeltrace/ctf/types.h
index e90464d..5f32b9b 100644
--- a/include/babeltrace/ctf/types.h
+++ b/include/babeltrace/ctf/types.h
@@ -78,6 +78,7 @@ struct ctf_stream_pos {
 	int64_t last_offset;	/* offset before the last read_event */
 	uint64_t cur_index;	/* current index in packet index */
 	uint64_t last_events_discarded;	/* last known amount of event discarded */
+	int64_t data_offset;	/* offset of data within the packet, in bits */
 	void (*packet_seek)(struct bt_stream_pos *pos, size_t index,
 			int whence); /* function called to switch packet */
 
-- 
1.8.3.2