[ruby/yarp] Add a yp_location_for_node function to the C API

yp_location_for_node takes a parser and a node and returns the
location in a way that can be punned into ruby/ruby types

ruby/prism@75e06016a7

yarp/yarp.c

@@ -12900,6 +12900,40 @@ yp_parse_serialize(const char *source, size_t size, yp_buffer_t *buffer) {
     yp_parser_free(&parser);
 }
 
+static yp_code_position_t
+yp_code_position(yp_newline_list_t newline_list, size_t loc) {
+    int line = 0;
+    while (line < (int)newline_list.size && newline_list.offsets[line] < loc) {
+        line++;
+    }
+
+    if (line > 0) {
+        line--;
+    }
+
+    int column = (int) (loc - newline_list.offsets[line]);
+
+    yp_code_position_t position;
+    position.lineno = line;
+    position.column = column;
+
+    return position;
+}
+
+yp_code_location_t
+yp_location_for_node(yp_parser_t *parser, yp_node_t *node) {
+    yp_newline_list_t newline_list = parser->newline_list;
+
+    yp_code_position_t start = yp_code_position(newline_list, (size_t)(node->location.start - parser->start));
+    yp_code_position_t end = yp_code_position(newline_list, (size_t)(node->location.end - parser->start));
+
+    yp_code_location_t location;
+    location.beg_pos = start;
+    location.end_pos = end;
+
+    return location;
+}
+
 #undef YP_CASE_KEYWORD
 #undef YP_CASE_OPERATOR
 #undef YP_CASE_WRITABLE

yarp/yarp.h

@@ -66,4 +66,23 @@ YP_EXPORTED_FUNCTION void yp_parse_serialize(const char *source, size_t size, yp
 // Returns a string representation of the given token type.
 YP_EXPORTED_FUNCTION const char * yp_token_type_to_str(yp_token_type_t token_type);
 
+// This reprsents a line, column position in the parsed source code
+// The layouts of this struct should not change because they mirror
+// rb_code_position_struct in ruby/ruby which allows us to type pun
+typedef struct yp_code_position_struct {
+    int lineno;
+    int column;
+} yp_code_position_t;
+
+// This reprsents a begin and end of anything in the AST that has a
+// location from the parsed source code.
+// The layouts of this struct should not change because they mirror
+// rb_code_position_struct in ruby/ruby which allows us to type pun
+typedef struct yp_code_location_struct {
+    yp_code_position_t beg_pos;
+    yp_code_position_t end_pos;
+} yp_code_location_t;
+
+yp_code_location_t yp_location_for_node(yp_parser_t *parser, yp_node_t *node);
+
 #endif