Simplify the SwapperSet interface

community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/SwapperSet.java

@@ -19,7 +19,6 @@
  */
 package org.neo4j.io.pagecache.impl.muninn;
 
-import java.io.IOException;
 import java.util.Arrays;
 import java.util.function.IntConsumer;
 
@@ -36,7 +35,7 @@ final class SwapperSet
     private final PrimitiveIntSet free = Primitive.intSet();
     private final Object vacuumLock = new Object();
 
-    private static final class Allocation
+    public static final class Allocation
     {
         public final int id;
         public final int filePageSize;
@@ -50,28 +49,15 @@ private Allocation( int id, int filePageSize, PageSwapper swapper )
         }
     }
 
-    public interface ApplyCall
-    {
-        void apply( PageSwapper swapper, int filePageSize ) throws IOException;
-    }
-
-    public PageSwapper getSwapper( int id )
-    {
-        checkId( id );
-        return allocations[id].swapper;
-    }
-
-    public int getFilePageSize( int id )
-    {
-        checkId( id );
-        return allocations[id].filePageSize;
-    }
-
-    public void apply( int id, ApplyCall call ) throws IOException
+    public Allocation getAllocation( int id )
     {
         checkId( id );
         Allocation allocation = allocations[id];
-        call.apply( allocation.swapper, allocation.filePageSize );
+        if ( allocation == null )
+        {
+            throw noSuchId( id );
+        }
+        return allocation;
     }
 
     private void checkId( int id )
@@ -82,6 +68,11 @@ private void checkId( int id )
         }
     }
 
+    private NullPointerException noSuchId( int id )
+    {
+        return new NullPointerException( "Swapper allocation by id " + id + " does not exist; it might have been freed" );
+    }
+
     public synchronized int allocate( PageSwapper swapper, int filePageSize )
     {
         Allocation[] allocations = this.allocations;

community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/SwapperSetTest.java

@@ -25,9 +25,6 @@
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicReference;
-
 import org.neo4j.collection.primitive.Primitive;
 import org.neo4j.collection.primitive.PrimitiveIntSet;
 import org.neo4j.io.pagecache.PageSwapper;
@@ -36,7 +33,6 @@
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
-import static org.hamcrest.Matchers.sameInstance;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.fail;
 
@@ -54,34 +50,27 @@ public void setUp()
     }
 
     @Test
-    public void mustReturnAllocatedSwapperAndFilePageSize() throws Exception
+    public void mustReturnAllocationWithSwapperAndFilePageSize() throws Exception
     {
         DummyPageSwapper a = new DummyPageSwapper( "a" );
         DummyPageSwapper b = new DummyPageSwapper( "b" );
         int idA = set.allocate( a, 42 );
         int idB = set.allocate( b, 43 );
-        assertThat( set.getSwapper( idA ), is( a ) );
-        assertThat( set.getFilePageSize( idA ), is( 42 ) );
-        assertThat( set.getSwapper( idB ), is( b ) );
-        assertThat( set.getFilePageSize( idB ), is( 43 ) );
-    }
-
-    @Test
-    public void accessingPageSwapperOfFreedAllocationMustThrow() throws Exception
-    {
-        int id = set.allocate( new DummyPageSwapper( "a" ), 42 );
-        set.free( id );
-        exception.expect( NullPointerException.class );
-        set.getSwapper( id );
+        SwapperSet.Allocation allocA = set.getAllocation( idA );
+        SwapperSet.Allocation allocB = set.getAllocation( idB );
+        assertThat( allocA.swapper, is( a ) );
+        assertThat( allocA.filePageSize, is( 42 ) );
+        assertThat( allocB.swapper, is( b ) );
+        assertThat( allocB.filePageSize, is( 43 ) );
     }
 
     @Test
-    public void accessingFilePageSizeOfFreedAllocationMustThrow() throws Exception
+    public void accessingFreedAllocationMustThrow() throws Exception
     {
         int id = set.allocate( new DummyPageSwapper( "a" ), 42 );
         set.free( id );
         exception.expect( NullPointerException.class );
-        set.getSwapper( id );
+        set.getAllocation( id );
     }
 
     @Test
@@ -176,42 +165,16 @@ public void mustNotUseZeroAsSwapperId() throws Exception
     }
 
     @Test
-    public void freeOfIdZeroMustThrow() throws Exception
+    public void gettingAllocationZeroMustThrow() throws Exception
     {
         exception.expect( IllegalArgumentException.class );
-        set.free( 0 );
+        set.getAllocation( 0 );
     }
 
     @Test
-    public void gettingSwapperOfIdZeroMustThrow() throws Exception
-    {
-        exception.expect( IllegalArgumentException.class );
-        set.getSwapper( 0 );
-    }
-
-    @Test
-    public void gettingFilePageSizeOfIdZeroMustThrow() throws Exception
-    {
-        exception.expect( IllegalArgumentException.class );
-        set.getFilePageSize( 0 );
-    }
-
-    @Test
-    public void applyMustThrowForIdZero() throws Exception
+    public void freeOfIdZeroMustThrow() throws Exception
     {
         exception.expect( IllegalArgumentException.class );
-        set.apply( 0, (swapper,size) -> fail( "should not have been called" ) );
-    }
-
-    @Test
-    public void applyMustReceiveArguments() throws Exception
-    {
-        AtomicReference<PageSwapper> gotSwapper = new AtomicReference<>();
-        AtomicInteger gotFilePageSize = new AtomicInteger();
-        PageSwapper swapper = new DummyPageSwapper( "a" );
-        int id = set.allocate( swapper, 3113 );
-        set.apply( id, (s,size) -> { gotSwapper.set( s ); gotFilePageSize.set( size ); } );
-        assertThat( gotSwapper.get(), is( sameInstance( swapper ) ) );
-        assertThat( gotFilePageSize.get(), is( 3113 ) );
+        set.free( 0 );
     }
 }