decode: add support for Google Trace Event output (JSON)

[sigrok-cli.git] / decode.c

diff --git a/decode.c b/decode.c
index d27703929fe7d34a7e972627b87a5e0fd7d723e9..06400f36e87516caa56a97d2cd14e5e9bf88d9fb 100644 (file)
--- a/decode.c
+++ b/decode.c
@@ -480,6 +480,116 @@ int setup_pd_binary(char *opt_pd_binary)
        return 0;
 }
 
+/*
+ * Balance JSON object and array parentheses, and separate array items.
+ * Somewhat convoluted API to re-use the routine for individual items as
+ * well as the surrounding array and object, including deferred start of
+ * the output and late flush (and to keep the state strictly local to the
+ * routine). Some additional complexity due to JSON's inability to handle
+ * a trailing comma at the last item. Code phrased such that text literals
+ * are kept in their order of appearance in the output text.
+ */
+static void jsontrace_open_close(gboolean is_close_req)
+{
+       static gboolean is_opened;
+
+       if (!is_close_req) {
+               if (!is_opened) {
+                       printf("{\"traceEvents\": [\n");
+                       is_opened = TRUE;
+               } else {
+                       printf(",\n");
+               }
+       } else {
+               if (is_opened) {
+                       printf("\n");
+                       printf("]}\n");
+                       fflush(stdout);
+               }
+               is_opened = FALSE;
+       }
+}
+
+/* Convert uint64 sample number to double timestamp in microseconds. */
+static double jsontrace_ts_usec(uint64_t snum)
+{
+       double ts_usec;
+
+       ts_usec = snum;
+       ts_usec *= 1e6;
+       ts_usec /= pd_samplerate;
+       return ts_usec;
+}
+
+/* Emit two Google Trace Events (JSON) for one PD annotation (ss, es). */
+static void jsontrace_annotation(struct srd_decoder *dec,
+       struct srd_proto_data_annotation *pda, struct srd_proto_data *pdata)
+{
+       char *row_text;
+       GSList *lrow, *lcls;
+       struct srd_decoder_annotation_row *row;
+       int cls;
+       char **ann_descr;
+
+       /*
+        * Search for an annotation row for this index, or use the
+        * annotation's descriptor.
+        */
+       row_text = NULL;
+       if (dec->annotation_rows) {
+               for (lrow = dec->annotation_rows; lrow; lrow = lrow->next) {
+                       row = lrow->data;
+                       for (lcls = row->ann_classes; lcls; lcls = lcls->next) {
+                               cls = GPOINTER_TO_INT(lcls->data);
+                               if (cls == pda->ann_class) {
+                                       row_text = row->desc;
+                                       break;
+                               }
+                       }
+                       if (row_text)
+                               break;
+               }
+       }
+       if (!row_text) {
+               ann_descr = g_slist_nth_data(dec->annotations, pda->ann_class);
+               row_text = ann_descr[0];
+       }
+
+       /*
+        * Emit two Google Trace Events for the start and end times.
+        * Set the 'pid' (process ID) to the decoder name to group a
+        * decoder's annotations. Set the 'tid' (thread ID) to the
+        * annotation row's description. The 'ts' (timestamp) is in
+        * microseconds. Set 'name' to the longest annotation text.
+        *
+        * BEWARE of the unfortunate JSON format comma limitation. And
+        * some of the output formatting is motivated by the desire to
+        * further reduce text size, by eliminating some of the spaces.
+        *
+        * This implementation is strictly compatible to the initial
+        * implementation. Which might change in the future to increase
+        * readability of the output to humans, by generating a layout
+        * which is closer to other output modes.
+        */
+       jsontrace_open_close(FALSE);
+       printf("{");
+       printf("\"%s\": \"%s\"", "name", pda->ann_text[0]);
+       printf(", \"%s\": \"%s\"", "ph", "B");
+       printf(", \"%s\": \"%s\"", "pid", pdata->pdo->proto_id);
+       printf(", \"%s\": \"%s\"", "tid", row_text);
+       printf(", \"%s\": %lf", "ts", jsontrace_ts_usec(pdata->start_sample));
+       printf("}");
+
+       jsontrace_open_close(FALSE);
+       printf("{");
+       printf("\"%s\": \"%s\"", "name", pda->ann_text[0]);
+       printf(", \"%s\": \"%s\"", "ph", "E");
+       printf(", \"%s\": \"%s\"", "pid", pdata->pdo->proto_id);
+       printf(", \"%s\": \"%s\"", "tid", row_text);
+       printf(", \"%s\": %lf", "ts", jsontrace_ts_usec(pdata->end_sample));
+       printf("}");
+}
+
 void show_pd_annotations(struct srd_proto_data *pdata, void *cb_data)
 {
        struct srd_decoder *dec;
@@ -514,6 +624,12 @@ void show_pd_annotations(struct srd_proto_data *pdata, void *cb_data)
        if (!show_ann)
                return;
 
+       /* Google Trace Events are rather special. Use a separate code path. */
+       if (opt_pd_jsontrace) {
+               jsontrace_annotation(dec, pda, pdata);
+               return;
+       }
+
        /*
         * Determine which fields of the annotation to display. Inspect
         * user specified options as well as the verbosity of the log level:
@@ -601,4 +717,16 @@ void show_pd_binary(struct srd_proto_data *pdata, void *cb_data)
        fwrite(pdb->data, pdb->size, 1, stdout);
        fflush(stdout);
 }
+
+void show_pd_prepare(void)
+{
+       if (opt_pd_jsontrace)
+               jsontrace_open_close(TRUE);
+}
+
+void show_pd_close(void)
+{
+       if (opt_pd_jsontrace)
+               jsontrace_open_close(TRUE);
+}
 #endif