better escape code support

compiler/lexer/lexer.odin

@@ -8,6 +8,10 @@ is_identifier_start :: proc(value: byte) -> bool {
 	return value == '_' || value >= 'a' && value <= 'z' || value >= 'A' && value <= 'Z'
 }
 
+is_hex_digit :: proc(value: byte) -> bool {
+	return value >= '0' && value <= '9' || value >= 'a' && value <= 'f' || value >= 'A' && value <= 'F'
+}
+
 is_identifier_continue :: proc(value: byte) -> bool {
 	return is_identifier_start(value) || value >= '0' && value <= '9'
 }
@@ -319,13 +323,21 @@ lex :: proc(
 			for cursor < len(bytes) && bytes[cursor] != '"' && bytes[cursor] != '\n' {
 				if bytes[cursor] == '\\' {
 					cursor += 1
-					if cursor >= len(bytes) ||
-					   (bytes[cursor] != '\\' && bytes[cursor] != '"' && bytes[cursor] != 'n' &&
-					    bytes[cursor] != 'r' && bytes[cursor] != 't' && bytes[cursor] != '0') {
+					valid_escape := cursor < len(bytes) &&
+						(bytes[cursor] == '\\' || bytes[cursor] == '"' || bytes[cursor] == 'n' ||
+						 bytes[cursor] == 'r' || bytes[cursor] == 't' || bytes[cursor] == '0')
+					if cursor < len(bytes) && bytes[cursor] == 'x' {
+						valid_escape = cursor+2 < len(bytes) &&
+							is_hex_digit(bytes[cursor+1]) && is_hex_digit(bytes[cursor+2])
+						if valid_escape {
+							cursor += 2
+						}
+					}
+					if !valid_escape {
 						source.add(
 							diagnostics,
-							source.Span{file=source_file.id, start=source.Offset(max(cursor-1, start)), end=source.Offset(min(cursor+1, len(bytes)))},
-							"strings only support '\\\\', '\\\"', '\\n', '\\r', '\\t', and '\\0' escapes",
+							source.Span{file=source_file.id, start=source.Offset(max(cursor-1, start)), end=source.Offset(min(cursor+3, len(bytes)))},
+							"strings only support '\\\\', '\\\"', '\\n', '\\r', '\\t', '\\0', and '\\xNN' escapes",
 						)
 						valid = false
 					}