From 6e3d30e41be915193874455411a0866d26dc1aca Mon Sep 17 00:00:00 2001
From: Jonas Herzig <me@johni0702.de>
Date: Sun, 17 Jul 2022 16:28:56 +0200
Subject: [PATCH] Fix thread unsafety in OpenGlToBitmapProcessor

Sharing the temporary `row` and `rowSwap` buffers between different calls to the
processor is not safe because it will be used by multiple threads.
As a result some of the rows in the image could randomly get corrupted.

This commit gets rid of the cached buffers (the value of which questionable
anyway) and simply re-uses the same code which other processors use.
---
 .../processor/OpenGlToBitmapProcessor.java    | 37 +++++--------------
 1 file changed, 10 insertions(+), 27 deletions(-)

diff --git a/src/main/java/com/replaymod/render/processor/OpenGlToBitmapProcessor.java b/src/main/java/com/replaymod/render/processor/OpenGlToBitmapProcessor.java
index 6cb60f5e..8740716d 100644
--- a/src/main/java/com/replaymod/render/processor/OpenGlToBitmapProcessor.java
+++ b/src/main/java/com/replaymod/render/processor/OpenGlToBitmapProcessor.java
@@ -2,42 +2,25 @@ package com.replaymod.render.processor;
 
 import com.replaymod.render.frame.OpenGlFrame;
 import com.replaymod.render.frame.BitmapFrame;
+import com.replaymod.render.utils.ByteBufferPool;
+import de.johni0702.minecraft.gui.utils.lwjgl.Dimension;
 import de.johni0702.minecraft.gui.utils.lwjgl.ReadableDimension;
 
 import java.nio.ByteBuffer;
 
-public class OpenGlToBitmapProcessor extends AbstractFrameProcessor<OpenGlFrame, BitmapFrame> {
+import static com.replaymod.render.utils.Utils.openGlBytesToBitmap;
 
-    private byte[] row, rowSwap;
+public class OpenGlToBitmapProcessor extends AbstractFrameProcessor<OpenGlFrame, BitmapFrame> {
 
     @Override
     public BitmapFrame process(OpenGlFrame rawFrame) {
-        // Flip whole image in place
-
         ReadableDimension size = rawFrame.getSize();
+        int width = size.getWidth();
+        int height = size.getHeight();
         int bpp = rawFrame.getBytesPerPixel();
-        int rowSize = size.getWidth() * bpp;
-        if (row == null || row.length < rowSize) {
-            row = new byte[rowSize];
-            rowSwap = new byte[rowSize];
-        }
-        ByteBuffer buffer = rawFrame.getByteBuffer();
-        int rows = size.getHeight();
-        byte[] row = this.row;
-        byte[] rowSwap = this.rowSwap;
-        for (int i = 0; i < rows / 2; i++) {
-            int from = rowSize * i;
-            int to = rowSize * (rows - i - 1);
-            buffer.position(from);
-            buffer.get(row);
-            buffer.position(to);
-            buffer.get(rowSwap);
-            buffer.position(to);
-            buffer.put(row);
-            buffer.position(from);
-            buffer.put(rowSwap);
-        }
-        buffer.rewind();
-        return new BitmapFrame(rawFrame.getFrameId(), size, bpp, buffer);
+        ByteBuffer result = ByteBufferPool.allocate(width * height * bpp);
+        openGlBytesToBitmap(rawFrame, 0, 0, result, width);
+        ByteBufferPool.release(rawFrame.getByteBuffer());
+        return new BitmapFrame(rawFrame.getFrameId(), new Dimension(width, height), bpp, result);
     }
 }