libubox: Add getters for the cursor and its parent

JSON might not be generated serial if it's synthesized from another
source such as UCI with a different organizational structure.  In
that case, being able to randomly access arrays and objects in the
synthetic JSON simplifies passes over the source material.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

Author: pprindeville

sh/jshn.sh

@@ -211,6 +211,28 @@ json_get_index() {
 	eval "export -- \"$__dest=\${$__seq}\"; [ -n \"\${$__seq+x}\" ]"
 }
 
+json_get_position() {
+	local __dest="$1"
+	eval "export -- \"$__dest=\${JSON_CUR}\"; [ -n \"\${JSON_CUR+x}\" ]"
+}
+
+json_move_to() {
+	local __cur="$1"
+	_json_set_var JSON_CUR "$cur"
+}
+
+json_get_parent_position() {
+	local __dest="$1" __cur __parent
+	_json_get_var __cur JSON_CUR
+	__parent="U_$__cur"
+	eval "export -- \"$__dest=\${$__parent}\"; [ -n \"\${$__parent+x}\" ]"
+}
+
+json_get_root_position() {
+	local __dest="$1" __cur="J_V"
+	eval "export -- \"$__dest=\${__cur}\"; [ -n \"\${__cur+x}\" ]"
+}
+
 # functions read access to json variables
 
 json_compact() {

tests/shunit2/tests.sh

@@ -510,4 +510,124 @@ test_jshn_get_index() {
 	set -u
 }
 
+test_jshn_get_root_position() {
+	JSON_PREFIX="${JSON_PREFIX:-}"
+	. ../../sh/jshn.sh
+
+	# __SHUNIT_SHELL_FLAGS='u' results in 'line 6: JSON_UNSET: unbound variable' in json_cleanup()
+	set +u
+
+	local root
+
+	# Test getting the root position
+	json_init
+	json_add_object "obj"
+	json_add_array "arr"
+	json_get_root_position root
+	assertEquals "J_V" "$root"
+
+	set -u
+}
+
+test_jshn_get_parent_position() {
+	JSON_PREFIX="${JSON_PREFIX:-}"
+	. ../../sh/jshn.sh
+
+	# __SHUNIT_SHELL_FLAGS='u' results in 'line 6: JSON_UNSET: unbound variable' in json_cleanup()
+	set +u
+
+	local cur
+
+	json_init
+
+	json_add_object "obj"
+	json_add_array "arr"
+
+	local obj="$cur"
+
+	json_get_parent_position cur
+	assertEquals "J_T1" "$cur"
+
+	set -u
+}
+
+test_jshn_get_position() {
+	JSON_PREFIX="${JSON_PREFIX:-}"
+	. ../../sh/jshn.sh
+
+	# __SHUNIT_SHELL_FLAGS='u' results in 'line 6: JSON_UNSET: unbound variable' in json_cleanup()
+	set +u
+
+	local cur
+
+	# Test getting the root position
+	json_init
+	json_get_position cur
+	assertEquals "J_V" "$cur"
+
+	local root="$cur"
+
+	# ... and the object position
+	json_add_object "obj"
+	json_get_position cur
+	assertEquals "J_T1" "$cur"
+
+	local obj="$cur"
+
+	# ... and the array position
+	json_add_array "arr"
+	json_get_position cur
+	assertEquals "J_A2" "$cur"
+
+	local arr="$cur"
+
+	# ... still within the array
+	json_add_string "first" "one"
+	json_get_position cur
+	assertEquals "J_A2" "$cur"
+
+	# ... still within the array
+	json_add_string "second" "two"
+	json_get_position cur
+	assertEquals "J_A2" "$cur"
+
+	# ... now back to the object
+	json_select ..
+	json_get_position cur
+	assertEquals "$obj" "$cur"
+
+	# ... and at the root
+	json_select ..
+	json_get_position cur
+	assertEquals "$root" "$cur"
+
+	set -u
+}
+
+test_jshn_move_to() {
+	JSON_PREFIX="${JSON_PREFIX:-}"
+	. ../../sh/jshn.sh
+
+	# __SHUNIT_SHELL_FLAGS='u' results in 'line 6: JSON_UNSET: unbound variable' in json_cleanup()
+	set +u
+
+	local cur cur2
+
+	json_init
+	json_add_object "obj"
+	json_get_position cur
+
+	json_add_array "arr"
+	json_add_string "first" "one"
+	json_add_string "second" "two"
+
+	json_move_to "$cur"
+
+	json_get_position cur2
+
+	assertEquals "J_T1" "$cur2"
+
+	set -u
+}
+
 . ./shunit2/shunit2