Extract method DataUtils.parseChecksummedMap()

h2/src/main/org/h2/mvstore/DataUtils.java

@@ -10,6 +10,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
 import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -672,6 +673,26 @@ public final class DataUtils {
         return map;
     }
 
+    /**
+     * Parse a key-value pair list and checks its checksum.
+     *
+     * @param s the list
+     * @return the map without mapping for {@code "fletcher"}, or {@code null} if checksum is wrong
+     * @throws IllegalStateException if parsing failed
+     */
+    public static HashMap<String, String> parseChecksummedMap(String s) {
+        HashMap<String, String> m = DataUtils.parseMap(s);
+        int check = DataUtils.readHexInt(m, "fletcher", 0);
+        m.remove("fletcher");
+        s = s.substring(0, s.lastIndexOf("fletcher") - 1);
+        byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
+        int checksum = DataUtils.getFletcher32(bytes, bytes.length);
+        if (check == checksum) {
+            return m;
+        }
+        return null;
+    }
+
     /**
      * Parse a name from key-value pair list.
      *

h2/src/main/org/h2/mvstore/MVStore.java

@@ -577,7 +577,9 @@ public final class MVStore {
             try {
                 String s = new String(buff, 0, BLOCK_SIZE,
                         StandardCharsets.ISO_8859_1).trim();
-                HashMap<String, String> m = DataUtils.parseMap(s);
+                HashMap<String, String> m = DataUtils.parseChecksummedMap(s);
+                if (m == null)
+                    continue;
                 int blockSize = DataUtils.readHexInt(
                         m, "blockSize", BLOCK_SIZE);
                 if (blockSize != BLOCK_SIZE) {
@@ -586,15 +588,6 @@ public final class MVStore {
                             "Block size {0} is currently not supported",
                             blockSize);
                 }
-                int check = DataUtils.readHexInt(m, "fletcher", 0);
-                m.remove("fletcher");
-                s = s.substring(0, s.lastIndexOf("fletcher") - 1);
-                byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
-                int checksum = DataUtils.getFletcher32(bytes,
-                        bytes.length);
-                if (check != checksum) {
-                    continue;
-                }
                 long version = DataUtils.readHexLong(m, "version", 0);
                 if (newest == null || version > newest.version) {
                     validStoreHeader = true;
@@ -805,13 +798,8 @@ public final class MVStore {
             byte[] buff = new byte[Chunk.FOOTER_LENGTH];
             lastBlock.get(buff);
             String s = new String(buff, StandardCharsets.ISO_8859_1).trim();
-            HashMap<String, String> m = DataUtils.parseMap(s);
-            int check = DataUtils.readHexInt(m, "fletcher", 0);
-            m.remove("fletcher");
-            s = s.substring(0, s.lastIndexOf("fletcher") - 1);
-            byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
-            int checksum = DataUtils.getFletcher32(bytes, bytes.length);
-            if (check == checksum) {
+            HashMap<String, String> m = DataUtils.parseChecksummedMap(s);
+            if (m != null) {
                 int chunk = DataUtils.readHexInt(m, "chunk", 0);
                 Chunk c = new Chunk(chunk);
                 c.version = DataUtils.readHexLong(m, "version", 0);