From fa16153fd58a0a5c36037c81119072f1a0623e48 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Sun, 2 Nov 2014 18:02:25 +0100
Subject: [PATCH] store: Let the JSON formatter know about arrays at top level.

There's no reason to require this to be handled separately.
---
 src/core/store_json.c         | 20 +++++++++++++++++---
 src/frontend/query.c          |  5 +----
 src/include/core/store.h      |  6 ++++--
 t/unit/core/store_json_test.c |  7 ++++---
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/src/core/store_json.c b/src/core/store_json.c
index d9fc37c..b4b7b6a 100644
--- a/src/core/store_json.c
+++ b/src/core/store_json.c
@@ -52,6 +52,8 @@ struct sdb_store_json_formatter {
 	 * the path pointing to the current object */
 	int context[8];
 	size_t current;
+
+	int flags;
 };
 
 /*
@@ -105,7 +107,7 @@ json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj)
  */
 
 sdb_store_json_formatter_t *
-sdb_store_json_formatter(sdb_strbuf_t *buf)
+sdb_store_json_formatter(sdb_strbuf_t *buf, int flags)
 {
 	sdb_store_json_formatter_t *f;
 
@@ -119,6 +121,7 @@ sdb_store_json_formatter(sdb_strbuf_t *buf)
 	f->buf = buf;
 	f->context[0] = 0;
 	f->current = 0;
+	f->flags = flags;
 	return f;
 } /* sdb_store_json_formatter */
 
@@ -130,6 +133,8 @@ sdb_store_json_emit(sdb_store_json_formatter_t *f, sdb_store_obj_t *obj)
 
 	/* first host */
 	if (! f->context[0]) {
+		if (f->flags & SDB_WANT_ARRAY)
+			sdb_strbuf_append(f->buf, "[");
 		assert(f->current == 0);
 		f->context[0] = SDB_HOST;
 		return json_emit(f, obj);
@@ -228,12 +233,21 @@ sdb_store_json_finish(sdb_store_json_formatter_t *f)
 	if (! f)
 		return -1;
 
+	if (! f->context[0]) {
+		/* no content */
+		if (f->flags & SDB_WANT_ARRAY)
+			sdb_strbuf_append(f->buf, "[]");
+		return 0;
+	}
+
 	while (f->current > 0) {
 		sdb_strbuf_append(f->buf, "}]");
 		--f->current;
 	}
-	if (f->context[0])
-		sdb_strbuf_append(f->buf, "}");
+
+	sdb_strbuf_append(f->buf, "}");
+	if (f->flags & SDB_WANT_ARRAY)
+		sdb_strbuf_append(f->buf, "]");
 	return 0;
 } /* sdb_store_json_finish */
 
diff --git a/src/frontend/query.c b/src/frontend/query.c
index dddf842..1ef36b3 100644
--- a/src/frontend/query.c
+++ b/src/frontend/query.c
@@ -390,7 +390,7 @@ sdb_fe_exec_lookup(sdb_conn_t *conn, int type,
 		sdb_strbuf_sprintf(conn->errbuf, "Out of memory");
 		return -1;
 	}
-	f = sdb_store_json_formatter(buf);
+	f = sdb_store_json_formatter(buf, SDB_WANT_ARRAY);
 	if (! f) {
 		char errbuf[1024];
 		sdb_log(SDB_LOG_ERR, "frontend: Failed to create "
@@ -403,7 +403,6 @@ sdb_fe_exec_lookup(sdb_conn_t *conn, int type,
 	}
 
 	sdb_strbuf_memcpy(buf, &res_type, sizeof(uint32_t));
-	sdb_strbuf_append(buf, "[");
 
 	if (sdb_store_scan(SDB_HOST, m, filter, lookup_tojson, f)) {
 		sdb_log(SDB_LOG_ERR, "frontend: Failed to lookup hosts");
@@ -414,8 +413,6 @@ sdb_fe_exec_lookup(sdb_conn_t *conn, int type,
 	}
 	sdb_store_json_finish(f);
 
-	sdb_strbuf_append(buf, "]");
-
 	sdb_connection_send(conn, CONNECTION_DATA,
 			(uint32_t)sdb_strbuf_len(buf), sdb_strbuf_string(buf));
 	sdb_strbuf_destroy(buf);
diff --git a/src/include/core/store.h b/src/include/core/store.h
index 6dd7d1a..df959ea 100644
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
@@ -89,7 +89,7 @@ typedef struct sdb_store_matcher sdb_store_matcher_t;
 #define SDB_STORE_MATCHER(obj) ((sdb_store_matcher_t *)(obj))
 
 /*
- * A JSON formatter converts a stored object into the JSON format.
+ * A JSON formatter converts stored objects into the JSON format.
  * See http://www.ietf.org/rfc/rfc4627.txt
  */
 struct sdb_store_json_formatter;
@@ -577,6 +577,8 @@ sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
  * out. The SKIP_EMPTY flags may be used to skip host objects entirely.
  */
 enum {
+	SDB_WANT_ARRAY              = 1 << 0,
+
 	SDB_SKIP_ATTRIBUTES         = 1 << 0,
 	SDB_SKIP_SERVICES           = 1 << 1,
 	SDB_SKIP_METRICS            = 1 << 2,
@@ -624,7 +626,7 @@ sdb_store_host_tojson(sdb_store_obj_t *host, sdb_strbuf_t *buf,
  * Create a JSON formatter writing to the specified buffer.
  */
 sdb_store_json_formatter_t *
-sdb_store_json_formatter(sdb_strbuf_t *buf);
+sdb_store_json_formatter(sdb_strbuf_t *buf, int flags);
 
 /*
  * sdb_store_json_emit:
diff --git a/t/unit/core/store_json_test.c b/t/unit/core/store_json_test.c
index ee0db2f..c544633 100644
--- a/t/unit/core/store_json_test.c
+++ b/t/unit/core/store_json_test.c
@@ -236,6 +236,9 @@ START_TEST(test_store_tojson)
 				"{\"name\": \"h2\", \"last_update\": \"1970-01-01 00:00:00 +0000\", "
 					"\"update_interval\": \"0s\", \"backends\": []}"
 			"]" },
+		{ { sdb_store_lt_matcher, SDB_FIELD_LAST_UPDATE,
+				{ SDB_TYPE_DATETIME, { .datetime = 0 } } }, scan_tojson_full,
+			"[]" },
 	};
 
 	buf = sdb_strbuf_create(0);
@@ -269,17 +272,15 @@ START_TEST(test_store_tojson)
 		}
 
 		sdb_strbuf_clear(buf);
-		f = sdb_store_json_formatter(buf);
+		f = sdb_store_json_formatter(buf, SDB_WANT_ARRAY);
 		assert(f);
 
-		sdb_strbuf_append(buf, "[");
 		status = sdb_store_scan(SDB_HOST, /* m = */ NULL, filter,
 				golden_data[i].f, f);
 		fail_unless(status == 0,
 				"sdb_store_scan(HOST, ..., tojson) = %d; expected: 0",
 				status);
 		sdb_store_json_finish(f);
-		sdb_strbuf_append(buf, "]");
 
 		verify_json_output(buf, golden_data[i].expected);
 		free(f);
-- 
2.30.2