Simplify SavepointBuffer implementation

kitty/data-types.h

@@ -235,8 +235,7 @@ typedef struct {
 
 typedef struct {
     Savepoint buf[SAVEPOINTS_SZ];
-    Savepoint *start_of_data;
-    Savepoint *end_of_data;
+    index_type start_of_data, count;
 } SavepointBuffer;
 
 #define PARSER_BUF_SZ 8192
@@ -296,7 +295,6 @@ uint16_t* translation_table(char);
 uint32_t decode_utf8(uint32_t*, uint32_t*, uint8_t byte);
 Savepoint* savepoints_pop(SavepointBuffer *);
 Savepoint* savepoints_push(SavepointBuffer *);
-void savepoints_init(SavepointBuffer *);
 void cursor_reset(Cursor*);
 Cursor* cursor_copy(Cursor*);
 void cursor_copy_to(Cursor *src, Cursor *dest);

kitty/savepoints.c

@@ -7,26 +7,15 @@
 
 #include "data-types.h"
 
-#define ADVANCE(x) \
-    self->x = (self->x >= self->buf + SAVEPOINTS_SZ - 1) ? self->buf : self->x + 1;
-
-#define RETREAT(x) \
-    self->x = self->x == self->buf ? self->buf + SAVEPOINTS_SZ - 1 : self->x - 1;
-
 Savepoint* savepoints_push(SavepointBuffer *self) {
-    Savepoint *ans = self->end_of_data;
-    ADVANCE(end_of_data);
-    if (self->end_of_data == self->start_of_data) ADVANCE(start_of_data);
+    Savepoint *ans = self->buf + ((self->start_of_data + self->count) % SAVEPOINTS_SZ);
+    if (self->count == SAVEPOINTS_SZ) self->start_of_data = (self->start_of_data + 1) % SAVEPOINTS_SZ;
+    else self->count++;
     return ans;
 }
 
 Savepoint* savepoints_pop(SavepointBuffer *self) {
-    if (self->start_of_data == self->end_of_data) return NULL;
-    RETREAT(end_of_data);
-    return self->end_of_data;
-}
-
-void savepoints_init(SavepointBuffer *self) {
-    self->end_of_data = self->buf;
-    self->start_of_data = self->buf;
+    if (self->count == 0) return NULL;
+    self->count--;
+    return self->buf + ((self->start_of_data + self->count) % SAVEPOINTS_SZ);
 }

kitty/screen.c

@@ -39,7 +39,6 @@ new(PyTypeObject *type, PyObject *args, PyObject UNUSED *kwds) {
         if (self->cursor == NULL || self->main_linebuf == NULL || self->alt_linebuf == NULL || self->change_tracker == NULL || self->tabstops == NULL) {
             Py_CLEAR(self); return NULL;
         }
-        savepoints_init(&self->main_savepoints); savepoints_init(&self->alt_savepoints);
     }
     return (PyObject*) self;
 }