return nil if array index indicie is out of bounds

ruby arrays don't throw an exception; they return nil.  Lets do the
same!

this fix also includes the ability to use negative array indicies

1 files changed, 14 insertions, 6 deletions

diff --git a/ruby/ext/google/protobuf_c/repeated_field.c b/ruby/ext/google/protobuf_c/repeated_field.c
index 8cf2e29b..5148ee87 100644
--- a/ruby/ext/google/protobuf_c/repeated_field.c
+++ b/ruby/ext/google/protobuf_c/repeated_field.c
@@ -47,6 +47,15 @@ RepeatedField* ruby_to_RepeatedField(VALUE _self) {
   return self;
 }
 
+static int index_position(VALUE _index, RepeatedField* repeated_field) {
+  int index = NUM2INT(_index);
+  if (index < 0 && repeated_field->size > 0) {
+    index = repeated_field->size + index;
+  }
+  return index;
+}
+
+
 /*
  * call-seq:
  *     RepeatedField.each(&block)
@@ -74,8 +83,7 @@ VALUE RepeatedField_each(VALUE _self) {
  * call-seq:
  *     RepeatedField.[](index) => value
  *
- * Accesses the element at the given index. Throws an exception on out-of-bounds
- * errors.
+ * Accesses the element at the given index. Returns nil on out-of-bounds
  */
 VALUE RepeatedField_index(VALUE _self, VALUE _index) {
   RepeatedField* self = ruby_to_RepeatedField(_self);
@@ -83,9 +91,9 @@ VALUE RepeatedField_index(VALUE _self, VALUE _index) {
   upb_fieldtype_t field_type = self->field_type;
   VALUE field_type_class = self->field_type_class;
 
-  int index = NUM2INT(_index);
+  int index = index_position(_index, self);
   if (index < 0 || index >= self->size) {
-    rb_raise(rb_eRangeError, "Index out of range");
+    return Qnil;
   }
 
   void* memory = (void *) (((uint8_t *)self->elements) + index * element_size);
@@ -105,9 +113,9 @@ VALUE RepeatedField_index_set(VALUE _self, VALUE _index, VALUE val) {
   VALUE field_type_class = self->field_type_class;
   int element_size = native_slot_size(field_type);
 
-  int index = NUM2INT(_index);
+  int index = index_position(_index, self);
   if (index < 0 || index >= (INT_MAX - 1)) {
-    rb_raise(rb_eRangeError, "Index out of range");
+    return Qnil;
   }
   if (index >= self->size) {
     RepeatedField_reserve(self, index + 1);