optimize clearing lines by using pointers to define the row order

src/game/game.c

@@ -3,7 +3,9 @@
 #include <SDL_scancode.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 #include "../main.h"
 #include "../window/colour.h"
@@ -11,32 +13,58 @@
 #include "tetromino/placing.h"
 
 
-static void clear_row(Row* row, uint8_t y) {
-    // move the rows down from the specified height
-    for (; y > 0; y--)
-        memcpy(row[y].columns, row[y - 1].columns, COLUMNS * sizeof(Colour));
+void game_init(GameData* const game_data) {
+    // zero-initialize the game data
+    *game_data = (GameData){0};
 
-    memset(row[0].columns, NONE, sizeof(Colour));
+    // write the pointer information for the rows
+    for (uint8_t i = 0; i < ROWS; i++)
+        game_data->row[i] = game_data->row_raw[i];
+
+    // set a random seed using the system clock
+    srand(time(NULL));
+}
+
+static bool is_filled(CRow row) {
+    for (uint8_t x = 0; x < COLUMNS; x++) {
+        if (row[x].packed == NONE) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static inline void set_row(Row* rows, const uint8_t y, Row row) {
+    rows[(ROWS - 1) - y] = row;
 }
 
 static void clear_rows(Row* row) {
-    // start at the lowest row
-    // integer will wrap
-    for (uint8_t y = ROWS - 1; y < ROWS; y--) {
-        Row* crow = &row[y];  // the current row
-        bool nfilled = false; // whether this row is filled
+    uint8_t filled_rows = 0;
 
-        // loop through all the columns or till nfilled is true
-        for (uint8_t x = 0; x < COLUMNS; x++) {
-            if (crow->columns[x].packed == NONE) {
-                nfilled = true;
-                break;
-            }
+    // loop through each row
+    for (uint8_t y = 0; y < ROWS; y++) {
+        // zero out the row instead if we've reached the top rows
+        if ((ROWS - y) <= filled_rows) {
+            for (uint8_t x = 0; x < COLUMNS; x++)
+                row[filled_rows--][x].packed = 0; // use filled_rows as the y index and decrease them as we go.
+            continue;
         }
 
-        // continue if the row isn;t filled
-        if (!nfilled)
-            clear_row(crow, y);
+        // get the row we currently need to check
+        Row crow = filled_rows > 0
+                       ? row[y + filled_rows]
+                       : row[y];
+
+        // set the current y to the current row
+        Row row_cache = row[y];
+        set_row(row, y, crow);
+
+        if (!is_filled(crow)) continue;
+
+        // write the cached row to the top if we know that the current row pointer will be lost
+        row[filled_rows] = row_cache;
+        filled_rows++;
     }
 }
 
@@ -66,5 +94,5 @@ void game_update(GameData* game_data, const uint8_t* keys) {
     update_input(game_data, keys);
 
     // tmp_set_random(game_data);
-    // tmp_set_all(game_data);
+    tmp_set_all(game_data);
 }