Improve entry crc32 computation

[controller.git] / atomix-storage / src / main / java / io / atomix / storage / journal / MappedJournalSegmentWriter.java

diff --git a/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
index 6ca6ab30dd72cce4a8952782375d83a2e17b3c67..bc74e8b0ef899f99a17120d34447b1be60f2dd11 100644 (file)
--- a/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
+++ b/atomix-storage/src/main/java/io/atomix/storage/journal/MappedJournalSegmentWriter.java
@@ -97,23 +97,25 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
         // Read the checksum of the entry.
         final long checksum = buffer.getInt() & 0xFFFFFFFFL;
 
+        // Slice off the entry's bytes
+        final ByteBuffer entryBytes = buffer.slice();
+        entryBytes.limit(length);
+
         // Compute the checksum for the entry bytes.
         final CRC32 crc32 = new CRC32();
-        ByteBuffer slice = buffer.slice();
-        slice.limit(length);
-        crc32.update(slice);
-
-        // If the stored checksum equals the computed checksum, return the entry.
-        if (checksum == crc32.getValue()) {
-          slice.rewind();
-          final E entry = namespace.deserialize(slice);
-          lastEntry = new Indexed<>(nextIndex, entry, length);
-          this.index.index(nextIndex, position);
-          nextIndex++;
-        } else {
+        crc32.update(entryBytes);
+
+        // If the stored checksum does not equal the computed checksum, do not proceed further
+        if (checksum != crc32.getValue()) {
           break;
         }
 
+        entryBytes.rewind();
+        final E entry = namespace.deserialize(entryBytes);
+        lastEntry = new Indexed<>(nextIndex, entry, length);
+        this.index.index(nextIndex, position);
+        nextIndex++;
+
         // Update the current position for indexing.
         position = buffer.position() + length;
         buffer.position(position);
@@ -233,20 +235,18 @@ class MappedJournalSegmentWriter<E> implements JournalWriter<E> {
     this.index.truncate(index);
 
     if (index < segment.index()) {
-      buffer.position(JournalSegmentDescriptor.BYTES);
-      buffer.putInt(0);
-      buffer.putInt(0);
+      // Reset the writer to the first entry.
       buffer.position(JournalSegmentDescriptor.BYTES);
     } else {
       // Reset the writer to the given index.
       reset(index);
-
-      // Zero entries after the given index.
-      int position = buffer.position();
-      buffer.putInt(0);
-      buffer.putInt(0);
-      buffer.position(position);
     }
+
+    // Zero the entry header at current buffer position.
+    int position = buffer.position();
+    // Note: we issue a single putLong() instead of two putInt()s.
+    buffer.putLong(0);
+    buffer.position(position);
   }
 
   @Override