From f7ed656326285831256061407c2c533c16c50f36 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Fri, 17 Aug 2012 00:01:54 -0400 Subject: [PATCH] Add BT_SEEK_LAST type to bt_iter_pos Inspired from patch by Francis Deslauriers and Julien Desfossez. Acked-by: Julien Desfossez Signed-off-by: Mathieu Desnoyers --- include/babeltrace/iterator.h | 8 ++ lib/iterator.c | 166 ++++++++++++++++++++++++++++++++++ 2 files changed, 174 insertions(+) diff --git a/include/babeltrace/iterator.h b/include/babeltrace/iterator.h index aa6470e7..e658eeec 100644 --- a/include/babeltrace/iterator.h +++ b/include/babeltrace/iterator.h @@ -40,6 +40,13 @@ struct bt_saved_pos; * is expressed in nanoseconds * - restore is a position saved with bt_iter_get_pos, it is used with * BT_SEEK_RESTORE. + * + * Note about BT_SEEK_LAST: if many events happen to be at the last + * timestamp, it is implementation-defined which event will be the last, + * and the order of events with the same timestamp may not be the same + * as normal iteration on the trace. Therefore, it is recommended to + * only use BT_SEEK_LAST to get the timestamp of the last event(s) in + * the trace. */ struct bt_iter_pos { enum { @@ -48,6 +55,7 @@ struct bt_iter_pos { BT_SEEK_CUR, BT_SEEK_BEGIN, BT_SEEK_END, + BT_SEEK_LAST, } type; union { uint64_t seek_time; diff --git a/lib/iterator.c b/lib/iterator.c index 2dbd77c0..927444f4 100644 --- a/lib/iterator.c +++ b/lib/iterator.c @@ -103,6 +103,10 @@ void bt_iter_free_pos(struct bt_iter_pos *iter_pos) * * Return 0 if the seek succeded, EOF if we didn't find any packet * containing the timestamp, or a positive integer for error. + * + * TODO: this should be turned into a binary search! It is currently + * doing a linear search in the packets. This is a O(n) operation on a + * very frequent code path. */ static int seek_file_stream_by_timestamp(struct ctf_file_stream *cfs, uint64_t timestamp) @@ -187,6 +191,148 @@ static int seek_ctf_trace_by_timestamp(struct ctf_trace *tin, return found ? 0 : EOF; } +/* + * Find timestamp of last event in the stream. + * + * Return value: 0 if OK, positive error value on error, EOF if no + * events were found. + */ +static int find_max_timestamp_ctf_file_stream(struct ctf_file_stream *cfs, + uint64_t *timestamp_end) +{ + int ret, count = 0, i; + uint64_t timestamp = 0; + struct ctf_stream_pos *stream_pos; + + stream_pos = &cfs->pos; + /* + * We start by the last packet, and iterate backwards until we + * either find at least one event, or we reach the first packet + * (some packets can be empty). + */ + for (i = stream_pos->packet_real_index->len - 1; i >= 0; i--) { + stream_pos->packet_seek(&stream_pos->parent, i, SEEK_SET); + count = 0; + /* read each event until we reach the end of the stream */ + do { + ret = stream_read_event(cfs); + if (ret == 0) { + count++; + timestamp = cfs->parent.real_timestamp; + } + } while (ret == 0); + + /* Error */ + if (ret > 0) + goto end; + assert(ret == EOF); + if (count) + break; + } + + if (count) { + *timestamp_end = timestamp; + ret = 0; + } else { + /* Return EOF if no events were found */ + ret = EOF; + } +end: + return ret; +} + +/* + * Find the stream within a stream class that contains the event with + * the largest timestamp, and save that timestamp. + * + * Return 0 if OK, EOF if no events were found in the streams, or + * positive value on error. + */ +static int find_max_timestamp_ctf_stream_class( + struct ctf_stream_declaration *stream_class, + struct ctf_file_stream **cfsp, + uint64_t *max_timestamp) +{ + int ret = EOF, i; + + for (i = 0; i < stream_class->streams->len; i++) { + struct ctf_stream_definition *stream; + struct ctf_file_stream *cfs; + uint64_t current_max_ts = 0; + + stream = g_ptr_array_index(stream_class->streams, i); + if (!stream) + continue; + cfs = container_of(stream, struct ctf_file_stream, parent); + ret = find_max_timestamp_ctf_file_stream(cfs, ¤t_max_ts); + if (ret == EOF) + continue; + if (ret != 0) + break; + if (current_max_ts >= *max_timestamp) { + *max_timestamp = current_max_ts; + *cfsp = cfs; + } + } + assert(ret >= 0 || ret == EOF); + return ret; +} + +/* + * seek_last_ctf_trace_collection: seek trace collection to last event. + * + * Return 0 if OK, EOF if no events were found, or positive error value + * on error. + */ +static int seek_last_ctf_trace_collection(struct trace_collection *tc, + struct ctf_file_stream **cfsp) +{ + int i, j, ret; + int found = 0; + uint64_t max_timestamp = 0; + + if (!tc) + return 1; + + /* For each trace in the trace_collection */ + 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); + if (!td_read) + continue; + tin = container_of(td_read, struct ctf_trace, parent); + /* For each stream_class in the trace */ + for (j = 0; j < tin->streams->len; j++) { + struct ctf_stream_declaration *stream_class; + + stream_class = g_ptr_array_index(tin->streams, j); + if (!stream_class) + continue; + ret = find_max_timestamp_ctf_stream_class(stream_class, + cfsp, &max_timestamp); + if (ret > 0) + goto end; + if (ret == 0) + found = 1; + assert(ret == EOF || ret == 0); + } + } + /* + * Now we know in which file stream the last event is located, + * and we know its timestamp. + */ + if (!found) { + ret = EOF; + } else { + ret = seek_file_stream_by_timestamp(*cfsp, max_timestamp); + assert(ret == 0); + } +end: + return ret; +} + int bt_iter_set_pos(struct bt_iter *iter, const struct bt_iter_pos *iter_pos) { struct trace_collection *tc; @@ -332,6 +478,26 @@ int bt_iter_set_pos(struct bt_iter *iter, const struct bt_iter_pos *iter_pos) } } break; + case BT_SEEK_LAST: + { + struct ctf_file_stream *cfs; + + tc = iter->ctx->tc; + ret = seek_last_ctf_trace_collection(tc, &cfs); + if (ret != 0) + goto error; + /* remove all streams from the heap */ + heap_free(iter->stream_heap); + /* Create a new empty heap */ + ret = heap_init(iter->stream_heap, 0, stream_compare); + if (ret < 0) + goto error; + /* Insert the stream that contains the last event */ + ret = heap_insert(iter->stream_heap, cfs); + if (ret) + goto error; + break; + } default: /* not implemented */ return -EINVAL; -- 2.34.1