From 08009f3f628e9c67f54535ae477b4dec4750477c Mon Sep 17 00:00:00 2001
From: stepeos <onegearmode@gmail.com>
Date: Mon, 21 Oct 2024 00:00:38 +0200
Subject: [PATCH] fix copying to not overwrite before offset

---
 runtime/src/main/java/org/capnproto/WireHelpers.java | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/runtime/src/main/java/org/capnproto/WireHelpers.java b/runtime/src/main/java/org/capnproto/WireHelpers.java
index 08370ba4..362484d2 100644
--- a/runtime/src/main/java/org/capnproto/WireHelpers.java
+++ b/runtime/src/main/java/org/capnproto/WireHelpers.java
@@ -850,7 +850,14 @@ static Data.Builder setDataPointer(int refOffset,
                                        SegmentBuilder segment,
                                        Data.Reader value) {
         Data.Builder builder = initDataPointer(refOffset, segment, value.size);
+        int originalSrcPosition = value.buffer.position();
+        int originalDstPosition = builder.buffer.position();
+        builder.buffer.position(builder.offset);
+        //# copy from src offset until src end
         builder.buffer.put(value.buffer);
+        //# restore original positions
+        builder.buffer.position(originalDstPosition);
+        value.buffer.position(originalSrcPosition);
         return builder;
     }