From d4bd7c741756f299ce32dcd4ef1cae72f1040b8c Mon Sep 17 00:00:00 2001
From: "slav.babanin" <slav.babanin@mongodb.com>
Date: Thu, 17 Apr 2025 16:38:52 -0700
Subject: [PATCH 1/2] Fix ByteBufferBsonOutput buffer caching logic.

Replaced getNextByteBuffer with getCurrentByteBuffer in writeOnBuffers to correct
buffer state management. getNextByteBuffer failed to update currentByteBuffer,
causing encoding errors.

JAVA-5816
---
 .../mongodb/internal/connection/ByteBufferBsonOutput.java | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java b/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
index 89075a0c0f..87778276b5 100644
--- a/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
+++ b/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
@@ -176,6 +176,7 @@ private ByteBuf getCurrentByteBuffer() {
         if (currentByteBuffer == null) {
             currentByteBuffer = getByteBufferAtIndex(curBufferIndex);
         }
+
         if (currentByteBuffer.hasRemaining()) {
             return currentByteBuffer;
         }
@@ -185,11 +186,6 @@ private ByteBuf getCurrentByteBuffer() {
         return currentByteBuffer;
     }
 
-    private ByteBuf getNextByteBuffer() {
-        assertFalse(bufferList.get(curBufferIndex).hasRemaining());
-        return getByteBufferAtIndex(++curBufferIndex);
-    }
-
     private ByteBuf getByteBufferAtIndex(final int index) {
         if (bufferList.size() < index + 1) {
             ByteBuf buffer = bufferProvider.getBuffer(index >= (MAX_SHIFT - INITIAL_SHIFT)
@@ -459,7 +455,7 @@ private int writeOnBuffers(final String str,
 
             if (c < 0x80) {
                 if (remaining == 0) {
-                    curBuffer = getNextByteBuffer();
+                    curBuffer = getCurrentByteBuffer();
                     curBufferPos = 0;
                     curBufferLimit = curBuffer.limit();
                 }

From ae0965436453d8b0ceb50e4481819c25de0690c9 Mon Sep 17 00:00:00 2001
From: "slav.babanin" <slav.babanin@mongodb.com>
Date: Thu, 17 Apr 2025 16:53:11 -0700
Subject: [PATCH 2/2] Remove unused imports.

---
 .../com/mongodb/internal/connection/ByteBufferBsonOutput.java    | 1 -
 1 file changed, 1 deletion(-)

diff --git a/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java b/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
index 87778276b5..c684eddf9f 100644
--- a/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
+++ b/driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java
@@ -26,7 +26,6 @@
 import java.util.ArrayList;
 import java.util.List;
 
-import static com.mongodb.assertions.Assertions.assertFalse;
 import static com.mongodb.assertions.Assertions.assertTrue;
 import static com.mongodb.assertions.Assertions.notNull;
 import static java.lang.String.format;