Extract a few constants in PageList.

neo4j · May 7, 2018 · 3ed9e88 · 3ed9e88
1 parent c715dec
commit 3ed9e88
Showing 1 changed file with 17 additions and 11 deletions.
diff --git a/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/PageList.java b/community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/PageList.java
@@ -66,6 +66,12 @@ class PageList
     private static final int OFFSET_SWAPPER_ID = 29; // 2 bytes, plus the 5 high-bits from usage counter
     @SuppressWarnings( "unused" )
     private static final int OFFSET_USAGE_COUNTER = 31; // 1 byte, but only the 3 low bits.
+    private static final int MASK_USAGE_COUNT = 0x07;
+    private static final long MASK_NOT_USAGE_COUNT = 0xFFFFFFFF_FFFFFFF8L;
+    private static final int SHIFT_FILE_PAGE_ID = 24;
+    private static final int MASK_NOT_FILE_PAGE_ID = 0xFFFFFF;
+    private static final int SHIFT_SWAPPER_ID = 3;
+    private static final int MASK_SHIFTED_SWAPPER_ID = 0b1_11111_11111_11111_11111;
 
     // todo we can alternatively also make use of the lower 12 bits of the address field, because
     // todo the addresses are page aligned, and we can assume them to be at least 4096 bytes in size.
@@ -313,7 +319,7 @@ public void initBuffer( long pageRef )
 
     private byte getUsageCounter( long pageRef )
     {
-        return (byte) (UnsafeUtil.getLongVolatile( offFilePageId( pageRef ) ) & 0x07);
+        return (byte) (UnsafeUtil.getLongVolatile( offFilePageId( pageRef ) ) & MASK_USAGE_COUNT);
     }
 
     /**
@@ -324,7 +330,7 @@ public void incrementUsage( long pageRef )
         // This is intentionally left benignly racy for performance.
         long address = offFilePageId( pageRef );
         long v = UnsafeUtil.getLongVolatile( address );
-        long usage = v & 0x07;
+        long usage = v & MASK_USAGE_COUNT;
         if ( usage < 4 ) // avoid cache sloshing by not doing a write if counter is already maxed out
         {
             usage++;
@@ -333,7 +339,7 @@ public void incrementUsage( long pageRef )
             // Those fields are updated under guard of the exclusive lock, but we *might* race with
             // that here, and in that case we would never want a usage counter update to clobber a page
             // binding update.
-            UnsafeUtil.compareAndSwapLong( null, address, v, (v & 0xFFFFFFFF_FFFFFFF8L) + usage );
+            UnsafeUtil.compareAndSwapLong( null, address, v, (v & MASK_NOT_USAGE_COUNT) + usage );
         }
     }
 
@@ -345,19 +351,19 @@ public boolean decrementUsage( long pageRef )
         // This is intentionally left benignly racy for performance.
         long address = offFilePageId( pageRef );
         long v = UnsafeUtil.getLongVolatile( address );
-        long usage = v & 0x07;
+        long usage = v & MASK_USAGE_COUNT;
         if ( usage > 0 )
         {
             usage--;
             // See `incrementUsage` about why we use `compareAndSwapLong`.
-            UnsafeUtil.compareAndSwapLong( null, address, v, (v & 0xFFFFFFFF_FFFFFFF8L) + usage );
+            UnsafeUtil.compareAndSwapLong( null, address, v, (v & MASK_NOT_USAGE_COUNT) + usage );
         }
         return usage == 0;
     }
 
     public long getFilePageId( long pageRef )
     {
-        long filePageId = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> 24;
+        long filePageId = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> SHIFT_FILE_PAGE_ID;
         return filePageId == MAX_FILE_PAGE_ID ? PageCursor.UNBOUND_PAGE_ID : filePageId;
     }
 
@@ -370,7 +376,7 @@ private void setFilePageId( long pageRef, long filePageId )
         }
         long address = offFilePageId( pageRef );
         long v = UnsafeUtil.getLong( address );
-        filePageId = (filePageId << 24) + (v & 0xFFFFFF);
+        filePageId = (filePageId << SHIFT_FILE_PAGE_ID) + (v & MASK_NOT_FILE_PAGE_ID);
         UnsafeUtil.putLong( address, filePageId );
     }
 
@@ -394,15 +400,15 @@ void setLastModifiedTxId( long pageRef, long modifierTxId )
 
     public int getSwapperId( long pageRef )
     {
-        long v = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> 3;
-        return (int) (v & 0b1_11111_11111_11111_11111); // 21 bits.
+        long v = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> SHIFT_SWAPPER_ID;
+        return (int) (v & MASK_SHIFTED_SWAPPER_ID); // 21 bits.
     }
 
     private void setSwapperId( long pageRef, int swapperId )
     {
-        swapperId = swapperId << 3;
+        swapperId = swapperId << SHIFT_SWAPPER_ID;
         long address = offFilePageId( pageRef );
-        long v = UnsafeUtil.getLong( address ) & (~(0b1_11111_11111_11111_11111 << 3));
+        long v = UnsafeUtil.getLong( address ) & (~(MASK_SHIFTED_SWAPPER_ID << SHIFT_SWAPPER_ID));
         UnsafeUtil.putLong( address, v + swapperId );
     }