From d621df28d34d08a3499f47318480c8d3d7b993d8 Mon Sep 17 00:00:00 2001
From: Andrei Tokar <andrei.tokar@gmail.com>
Date: Sun, 7 Jul 2024 23:07:09 -0400
Subject: [PATCH] fix backup duplication error

---
 h2/src/main/org/h2/mvstore/SingleFileStore.java |  4 ++--
 h2/src/main/org/h2/util/IOUtils.java            | 10 +++++-----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/h2/src/main/org/h2/mvstore/SingleFileStore.java b/h2/src/main/org/h2/mvstore/SingleFileStore.java
index 9794c4faff..c4d42533bd 100644
--- a/h2/src/main/org/h2/mvstore/SingleFileStore.java
+++ b/h2/src/main/org/h2/mvstore/SingleFileStore.java
@@ -238,11 +238,11 @@ public void backup(ZipOutputStream out) throws IOException {
         boolean before = mvStore.setReuseSpace(false);
         try {
 
-            IOUtils.copy(in, out);
+            long copied = IOUtils.copy(in, 0, out);
 
             mvStore.executeFilestoreOperation(() -> {
                 try {
-                    IOUtils.copy(in, out);
+                    IOUtils.copy(in, copied, out);
                 } catch (IOException ex) {
                     throw new RuntimeException(ex);
                 }
diff --git a/h2/src/main/org/h2/util/IOUtils.java b/h2/src/main/org/h2/util/IOUtils.java
index 40bb727bec..128bba0fed 100644
--- a/h2/src/main/org/h2/util/IOUtils.java
+++ b/h2/src/main/org/h2/util/IOUtils.java
@@ -198,9 +198,9 @@ public static long copy(InputStream in, OutputStream out, long length)
      * @return the number of bytes copied
      * @throws IOException on failure
      */
-    public static long copy(FileChannel in, OutputStream out)
+    public static long copy(FileChannel in, long startAt, OutputStream out)
             throws IOException {
-        return copy(in, out, Long.MAX_VALUE);
+        return copy(in, out, startAt, Long.MAX_VALUE);
     }
 
     /**
@@ -213,10 +213,10 @@ public static long copy(FileChannel in, OutputStream out)
      * @return the number of bytes copied
      * @throws IOException on failure
      */
-    public static long copy(FileChannel in, OutputStream out, long length)
+    public static long copy(FileChannel in, OutputStream out, long startAt, long length)
             throws IOException {
         try {
-            long copied = 0;
+            long copied = startAt;
             byte[] buffer = new byte[(int) Math.min(length, Constants.IO_BUFFER_SIZE)];
             ByteBuffer wrap = ByteBuffer.wrap(buffer);
             while (length > 0) {
@@ -234,7 +234,7 @@ public static long copy(FileChannel in, OutputStream out, long length)
                     wrap.limit((int)length);
                 }
             }
-            return copied;
+            return copied - startAt;
         } catch (Exception e) {
             throw DataUtils.convertToIOException(e);
         }