[lttng-dev] [RFC PATCH lttng-tools v2 08/20] Add serialized versions of lttng_channel structs

[Yannick Lamarre]

Serialized versions of lttng_channel and lttng_channel_extended are
packed structures to be used in communication protocols for consistent
sizes across platforms. The serialized versions are stripped of pointers
and padding.

Pointers are removed since their size can vary across processes on
platforms supporting multiple pointer sizes (32bits vs 64bits) and this
creates mismatches in structure sizes.
Padding is also removed since it defeats the purpose of a packed struct
and is not used to extend the protocols.

Signed-off-by: Yannick Lamarre <ylamarre at efficios.com>
---
Reworded commit message to better justify removal of pointer and padding
fields.

 include/lttng/channel-internal.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/include/lttng/channel-internal.h b/include/lttng/channel-internal.h
index 030b4701..c956c19d 100644
--- a/include/lttng/channel-internal.h
+++ b/include/lttng/channel-internal.h
@@ -20,11 +20,41 @@
 
 #include <common/macros.h>
 
+struct lttng_channel_attr_serialized {
+	int overwrite;                      /* -1: session default, 1: overwrite, 0: discard */
+	uint64_t subbuf_size;               /* bytes, power of 2 */
+	uint64_t num_subbuf;                /* power of 2 */
+	unsigned int switch_timer_interval; /* usec */
+	unsigned int read_timer_interval;   /* usec */
+	uint32_t output; /* enum lttng_event_output */
+	/* LTTng 2.1 padding limit */
+	uint64_t tracefile_size;            /* bytes */
+	uint64_t tracefile_count;           /* number of tracefiles */
+	/* LTTng 2.3 padding limit */
+	unsigned int live_timer_interval;   /* usec */
+	/* LTTng 2.7 padding limit */
+
+} LTTNG_PACKED;
+
+struct lttng_channel_serialized {
+	char name[LTTNG_SYMBOL_NAME_LEN];
+	uint32_t enabled;
+	struct lttng_channel_attr_serialized attr;
+
+} LTTNG_PACKED;
+
 struct lttng_channel_extended {
 	uint64_t discarded_events;
 	uint64_t lost_packets;
 	uint64_t monitor_timer_interval;
 	int64_t blocking_timeout;
+};
+
+struct lttng_channel_extended_serialized {
+	uint64_t discarded_events;
+	uint64_t lost_packets;
+	uint64_t monitor_timer_interval;
+	int64_t blocking_timeout;
 } LTTNG_PACKED;
 
 #endif /* LTTNG_CHANNEL_INTERNAL_H */
-- 
2.11.0