lightningd: don't bother pretty-printing JSON.

This doesn't result in a speedup for our benchmark, since we use the
cli tool which does the formatting.

MCP results from 5 runs, min-max(mean +/- stddev):
	store_load_msec:33422-36830(35196.2+/-1.2e+03)
	vsz_kb:2637488
	store_rewrite_sec:36.030000-37.630000(36.794+/-0.52)
	listnodes_sec:0.720000-0.950000(0.86+/-0.077)
	listchannels_sec:40.300000-41.080000(40.668+/-0.29)
	routing_sec:30.440000-31.030000(30.69+/-0.2)
	peer_write_all_sec:50.060000-52.800000(51.416+/-0.91)

MCP notable changes from 2 patches ago (>1 stddev):
	-listchannels_sec:48.560000-55.680000(52.642+/-2.7)
	+listchannels_sec:40.300000-41.080000(40.668+/-0.29)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/json_stream.c

@@ -14,9 +14,6 @@ struct json_stream {
 	/* tal_arr of types (JSMN_OBJECT/JSMN_ARRAY) we're enclosed in. */
 	jsmntype_t *wrapping;
 #endif
-	/* How far to indent. */
-	size_t indent;
-
 	/* True if we haven't yet put an element in current wrapping */
 	bool empty;
 
@@ -61,7 +58,6 @@ struct json_stream *new_json_stream(const tal_t *ctx,
 #if DEVELOPER
 	js->wrapping = tal_arr(js, jsmntype_t, 0);
 #endif
-	js->indent = 0;
 	js->empty = true;
 	js->log = log;
 	return js;
@@ -179,29 +175,11 @@ static void check_fieldname(const struct json_stream *js,
 #endif
 }
 
-static void js_append_indent(struct json_stream *js)
-{
-	static const char indent_buf[] = "                                ";
-	size_t len;
-
-	for (size_t i = 0; i < js->indent * 2; i += len) {
-		len = js->indent * 2;
-		if (len > sizeof(indent_buf)-1)
-			len = sizeof(indent_buf)-1;
-		/* Use tail of indent_buf string. */
-		json_stream_append(js, indent_buf + sizeof(indent_buf) - 1 - len);
-	}
-}
-
 static void json_start_member(struct json_stream *js, const char *fieldname)
 {
 	/* Prepend comma if required. */
 	if (!js->empty)
-		json_stream_append(js, ", \n");
-	else
-		json_stream_append(js, "\n");
-
-	js_append_indent(js);
+		json_stream_append(js, ",");
 
 	check_fieldname(js, fieldname);
 	if (fieldname)
@@ -215,19 +193,17 @@ static void js_indent(struct json_stream *js, jsmntype_t type)
 	tal_arr_expand(&js->wrapping, type);
 #endif
 	js->empty = true;
-	js->indent++;
 }
 
 static void js_unindent(struct json_stream *js, jsmntype_t type)
 {
-	assert(js->indent);
 #if DEVELOPER
-	assert(tal_count(js->wrapping) == js->indent);
-	assert(js->wrapping[js->indent-1] == type);
-	tal_resize(&js->wrapping, js->indent-1);
+	size_t indent = tal_count(js->wrapping);
+	assert(indent > 0);
+	assert(js->wrapping[indent-1] == type);
+	tal_resize(&js->wrapping, indent-1);
 #endif
 	js->empty = false;
-	js->indent--;
 }
 
 void json_array_start(struct json_stream *js, const char *fieldname)
@@ -239,9 +215,7 @@ void json_array_start(struct json_stream *js, const char *fieldname)
 
 void json_array_end(struct json_stream *js)
 {
-	json_stream_append(js, "\n");
 	js_unindent(js, JSMN_ARRAY);
-	js_append_indent(js);
 	json_stream_append(js, "]");
 }
 
@@ -254,9 +228,7 @@ void json_object_start(struct json_stream *js, const char *fieldname)
 
 void json_object_end(struct json_stream *js)
 {
-	json_stream_append(js, "\n");
 	js_unindent(js, JSMN_OBJECT);
-	js_append_indent(js);
 	json_stream_append(js, "}");
 }
 

lightningd/test/run-jsonrpc.c

@@ -149,12 +149,12 @@ static void test_json_escape(void)
 		if (i == '\\' || i == '"'
 		    || i == '\n' || i == '\r' || i == '\b'
 		    || i == '\t' || i == '\f')
-			assert(strstarts(str, "\n{\n  \"x\": \"\\"));
+			assert(strstarts(str, "{\"x\":\"\\"));
 		else if (i < 32 || i == 127) {
-			assert(strstarts(str, "\n{\n  \"x\": \"\\u00"));
+			assert(strstarts(str, "{\"x\":\"\\u00"));
 		} else {
-			char expect[] = "\n{\n  \"x\": \"?\"\n}";
-			expect[11] = i;
+			char expect[] = "{\"x\":\"?\"}";
+			expect[6] = i;
 			assert(streq(str, expect));
 		}
 		tal_free(result);

tools/bench-gossipd.sh

@@ -130,7 +130,7 @@ if [ -z "${TARGETS##* routing_sec *}" ]; then
     echo "$DIV" | tr -d \\n; DIV=","
     # shellcheck disable=SC2046
     # shellcheck disable=SC2005
-    echo $(grep nodeid "$DIR"/listnodes.json | cut -d'"' -f4 | sort | head -n2) | while read -r from to; do
+    echo $(tr '{}' '\n' < "$DIR"/listnodes.json | grep nodeid | cut -d'"' -f4 | sort | head -n2) | while read -r from to; do
 	# shellcheck disable=SC2086
 	/usr/bin/time --quiet --append -f %e $LCLI1 getroute $from 1 1 6 $to 2>&1 > /dev/null | print_stat routing_sec # FIXME: this shouldn't fail
     done