[PATCH v8 2/5] box: refactor tuple_field_raw_by_path routine

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

Refactored tuple_field_raw_by_path routine as function
tuple_field_raw_by_full_path returning field data if the field
exists or NULL, instead of error index in path.
The *_by_full_path is a better name for routine because we are
going to introduce *_by_path routine in future that would work
with relative paths. const char * returning valiue is more
common result type for such routines.
Got rid of invalid path error handling in routine
lbox_tuple_field_by_path.

Needed for #1012
---
 src/box/lua/tuple.c      |  9 ++----
 src/box/tuple.h          | 51 +++++++++++++++------------------
 src/box/tuple_format.c   | 61 +++++++++++-----------------------------
 src/box/tuple_format.h   | 53 ++++++++++++++++++----------------
 test/engine/tuple.result | 16 +++++------
 5 files changed, 79 insertions(+), 111 deletions(-)

diff --git a/src/box/lua/tuple.c b/src/box/lua/tuple.c
index 1867f810f..7d377b69e 100644
--- a/src/box/lua/tuple.c
+++ b/src/box/lua/tuple.c
@@ -463,13 +463,10 @@ lbox_tuple_field_by_path(struct lua_State *L)
 	const char *field = NULL, *path = lua_tolstring(L, 2, &len);
 	if (len == 0)
 		return 0;
-	if (tuple_field_by_path(tuple, path, (uint32_t) len,
-				lua_hashstring(L, 2), &field) != 0) {
-		return luaT_error(L);
-	} else if (field == NULL) {
+	field = tuple_field_by_full_path(tuple, path, (uint32_t)len,
+					 lua_hashstring(L, 2));
+	if (field == NULL)
 		return 0;
-	}
-	assert(field != NULL);
 	luamp_decode(L, luaL_msgpack_default, &field);
 	return 1;
 }
diff --git a/src/box/tuple.h b/src/box/tuple.h
index 83e5b7013..4368dac4e 100644
--- a/src/box/tuple.h
+++ b/src/box/tuple.h
@@ -513,6 +513,23 @@ tuple_field(const struct tuple *tuple, uint32_t fieldno)
 			       tuple_field_map(tuple), fieldno);
 }
 
+/**
+ * Get a field refereed by index @part in tuple.
+ * @param tuple Tuple to get the field from.
+ * @param part Index part to use.
+ * @param path Relative JSON path to field data.
+ * @param path_len The length of the @path.
+ * @retval Field data if the field exists or NULL.
+ */
+static inline const char *
+tuple_field_by_path(const struct tuple *tuple, uint32_t fieldno,
+		    const char *path, uint32_t path_len)
+{
+	return tuple_field_raw_by_path(tuple_format(tuple), tuple_data(tuple),
+				       tuple_field_map(tuple), fieldno,
+				       path, path_len);
+}
+
 /**
  * Get a field refereed by index @part in tuple.
  * @param tuple Tuple to get the field from.
@@ -532,38 +549,16 @@ tuple_field_by_part(const struct tuple *tuple, struct key_part *part)
  * @param path Field JSON path.
  * @param path_len Length of @a path.
  * @param path_hash Hash of @a path.
- * @param[out] field Found field, or NULL, if not found.
- *
- * @retval  0 Success.
- * @retval -1 Error in JSON path.
- */
-static inline int
-tuple_field_by_path(const struct tuple *tuple, const char *path,
-                    uint32_t path_len, uint32_t path_hash,
-                    const char **field)
-{
-	return tuple_field_raw_by_path(tuple_format(tuple), tuple_data(tuple),
-	                               tuple_field_map(tuple), path, path_len,
-	                               path_hash, field);
-}
-
-/**
- * Get tuple field by its name.
- * @param tuple Tuple to get field from.
- * @param name Field name.
- * @param name_len Length of @a name.
- * @param name_hash Hash of @a name.
  *
- * @retval not NULL MessagePack field.
- * @retval     NULL No field with @a name.
+ * @retval field data if field exists or NULL
  */
 static inline const char *
-tuple_field_by_name(const struct tuple *tuple, const char *name,
-		    uint32_t name_len, uint32_t name_hash)
+tuple_field_by_full_path(const struct tuple *tuple, const char *path,
+			 uint32_t path_len, uint32_t path_hash)
 {
-	return tuple_field_raw_by_name(tuple_format(tuple), tuple_data(tuple),
-				       tuple_field_map(tuple), name, name_len,
-				       name_hash);
+	return tuple_field_raw_by_full_path(tuple_format(tuple), tuple_data(tuple),
+					    tuple_field_map(tuple),
+					    path, path_len, path_hash);
 }
 
 /**
diff --git a/src/box/tuple_format.c b/src/box/tuple_format.c
index e11b4e6f3..61b4c9734 100644
--- a/src/box/tuple_format.c
+++ b/src/box/tuple_format.c
@@ -713,15 +713,7 @@ tuple_field_go_to_key(const char **field, const char *key, int len)
 	return -1;
 }
 
-/**
- * Retrieve msgpack data by JSON path.
- * @param data Pointer to msgpack with data.
- * @param path The path to process.
- * @param path_len The length of the @path.
- * @retval 0 On success.
- * @retval >0 On path parsing error, invalid character position.
- */
-static int
+int
 tuple_field_go_to_path(const char **data, const char *path, uint32_t path_len)
 {
 	int rc;
@@ -748,11 +740,10 @@ tuple_field_go_to_path(const char **data, const char *path, uint32_t path_len)
 	return rc;
 }
 
-int
-tuple_field_raw_by_path(struct tuple_format *format, const char *tuple,
-                        const uint32_t *field_map, const char *path,
-                        uint32_t path_len, uint32_t path_hash,
-                        const char **field)
+const char *
+tuple_field_raw_by_full_path(struct tuple_format *format, const char *tuple,
+			     const uint32_t *field_map, const char *path,
+			     uint32_t path_len, uint32_t path_hash)
 {
 	assert(path_len > 0);
 	uint32_t fieldno;
@@ -763,22 +754,16 @@ tuple_field_raw_by_path(struct tuple_format *format, const char *tuple,
 	 * use the path as a field name.
 	 */
 	if (tuple_fieldno_by_name(format->dict, path, path_len, path_hash,
-				  &fieldno) == 0) {
-		*field = tuple_field_raw(format, tuple, field_map, fieldno);
-		return 0;
-	}
+				  &fieldno) == 0)
+		return tuple_field_raw(format, tuple, field_map, fieldno);
 	struct json_lexer lexer;
 	struct json_token token;
 	json_lexer_create(&lexer, path, path_len, TUPLE_INDEX_BASE);
-	int rc = json_lexer_next_token(&lexer, &token);
-	if (rc != 0)
-		goto error;
+	if (json_lexer_next_token(&lexer, &token) != 0)
+		return NULL;
 	switch(token.type) {
 	case JSON_TOKEN_NUM: {
-		int index = token.num;
-		*field = tuple_field_raw(format, tuple, field_map, index);
-		if (*field == NULL)
-			return 0;
+		fieldno = token.num;
 		break;
 	}
 	case JSON_TOKEN_STR: {
@@ -795,28 +780,16 @@ tuple_field_raw_by_path(struct tuple_format *format, const char *tuple,
 			 */
 			name_hash = field_name_hash(token.str, token.len);
 		}
-		*field = tuple_field_raw_by_name(format, tuple, field_map,
-						 token.str, token.len,
-						 name_hash);
-		if (*field == NULL)
-			return 0;
+		if (tuple_fieldno_by_name(format->dict, token.str, token.len,
+					  name_hash, &fieldno) != 0)
+			return NULL;
 		break;
 	}
 	default:
 		assert(token.type == JSON_TOKEN_END);
-		*field = NULL;
-		return 0;
+		return NULL;
 	}
-	rc = tuple_field_go_to_path(field, path + lexer.offset,
-				    path_len - lexer.offset);
-	if (rc == 0)
-		return 0;
-	/* Setup absolute error position. */
-	rc += lexer.offset;
-
-error:
-	assert(rc > 0);
-	diag_set(ClientError, ER_ILLEGAL_PARAMS,
-		 tt_sprintf("error in path on position %d", rc));
-	return -1;
+	return tuple_field_raw_by_path(format, tuple, field_map, fieldno,
+				       path + lexer.offset,
+				       path_len - lexer.offset);
 }
diff --git a/src/box/tuple_format.h b/src/box/tuple_format.h
index 30b93b610..d32bb91f2 100644
--- a/src/box/tuple_format.h
+++ b/src/box/tuple_format.h
@@ -397,27 +397,33 @@ tuple_field_raw(struct tuple_format *format, const char *tuple,
 }
 
 /**
- * Get tuple field by its name.
- * @param format Tuple format.
- * @param tuple MessagePack tuple's body.
- * @param field_map Tuple field map.
- * @param name Field name.
- * @param name_len Length of @a name.
- * @param name_hash Hash of @a name.
- *
- * @retval not NULL MessagePack field.
- * @retval     NULL No field with @a name.
+ * Retrieve msgpack data by JSON path.
+ * @param data Pointer to msgpack with data.
+ * @param path The path to process.
+ * @param path_len The length of the @path.
+ * @retval 0 On success.
+ * @retval >0 On path parsing error, invalid character position.
+ */
+int
+tuple_field_go_to_path(const char **data, const char *path, uint32_t path_len);
+
+/**
+ * Get a field at the specific position in this MessagePack
+ * array by fieldno and path.
  */
 static inline const char *
-tuple_field_raw_by_name(struct tuple_format *format, const char *tuple,
-			const uint32_t *field_map, const char *name,
-			uint32_t name_len, uint32_t name_hash)
+tuple_field_raw_by_path(struct tuple_format *format, const char *tuple,
+			const uint32_t *field_map, uint32_t fieldno,
+			const char *path, uint32_t path_len)
 {
-	uint32_t fieldno;
-	if (tuple_fieldno_by_name(format->dict, name, name_len, name_hash,
-				  &fieldno) != 0)
+	tuple = tuple_field_raw(format, tuple, field_map, fieldno);
+	if (path == NULL)
+		return tuple;
+	if (unlikely(tuple == NULL))
 		return NULL;
-	return tuple_field_raw(format, tuple, field_map, fieldno);
+	if (unlikely(tuple_field_go_to_path(&tuple, path, path_len) != 0))
+		return NULL;
+	return tuple;
 }
 
 /**
@@ -428,16 +434,13 @@ tuple_field_raw_by_name(struct tuple_format *format, const char *tuple,
  * @param path Field path.
  * @param path_len Length of @a path.
  * @param path_hash Hash of @a path.
- * @param[out] field Found field, or NULL, if not found.
  *
- * @retval  0 Success.
- * @retval -1 Error in JSON path.
+ * @retval field data if field exists or NULL
  */
-int
-tuple_field_raw_by_path(struct tuple_format *format, const char *tuple,
-                        const uint32_t *field_map, const char *path,
-                        uint32_t path_len, uint32_t path_hash,
-                        const char **field);
+const char *
+tuple_field_raw_by_full_path(struct tuple_format *format, const char *tuple,
+			     const uint32_t *field_map, const char *path,
+			     uint32_t path_len, uint32_t path_hash);
 
 /**
  * Get a tuple field pointed to by an index part.
diff --git a/test/engine/tuple.result b/test/engine/tuple.result
index 7ca3985c7..daf57d1f5 100644
--- a/test/engine/tuple.result
+++ b/test/engine/tuple.result
@@ -823,7 +823,7 @@ t[0]
 ...
 t["[0]"]
 ---
-- error: Illegal parameters, error in path on position 2
+- null
 ...
 t["[1000]"]
 ---
@@ -847,7 +847,7 @@ t["[2][6].key100"]
 ...
 t["[2][0]"] -- 0-based index in array.
 ---
-- error: Illegal parameters, error in path on position 5
+- null
 ...
 t["[4][3]"] -- Can not index string.
 ---
@@ -866,27 +866,27 @@ t["a.b.c d.e.f"]
 -- Sytax errors.
 t["[2].[5]"]
 ---
-- error: Illegal parameters, error in path on position 5
+- null
 ...
 t["[-1]"]
 ---
-- error: Illegal parameters, error in path on position 2
+- null
 ...
 t[".."]
 ---
-- error: Illegal parameters, error in path on position 2
+- null
 ...
 t["[["]
 ---
-- error: Illegal parameters, error in path on position 2
+- null
 ...
 t["]]"]
 ---
-- error: Illegal parameters, error in path on position 1
+- null
 ...
 t["{"]
 ---
-- error: Illegal parameters, error in path on position 1
+- null
 ...
 s:drop()
 ---
-- 
2.19.2