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package com.facebook.presto.jdbc.internal.jol.layouters;
import com.facebook.presto.jdbc.internal.jol.datamodel.DataModel;
import com.facebook.presto.jdbc.internal.jol.info.ClassData;
import com.facebook.presto.jdbc.internal.jol.info.ClassLayout;
import com.facebook.presto.jdbc.internal.jol.info.FieldData;
import com.facebook.presto.jdbc.internal.jol.info.FieldLayout;
import com.facebook.presto.jdbc.internal.jol.util.VMSupport;
import java.util.BitSet;
import java.util.Collection;
import java.util.List;
import java.util.SortedSet;
import java.util.TreeSet;
/**
* VM layout simulator.
*
* @author Aleksey Shipilev
*/
public class HotSpotLayouter implements Layouter {
private final DataModel model;
private final boolean takeHierarchyGaps;
private final boolean takeSuperGaps;
private final boolean autoAlign;
public HotSpotLayouter(DataModel model) {
this(model, false, false, false);
}
public HotSpotLayouter(DataModel model, boolean takeHierarchyGaps, boolean takeSuperGaps, boolean autoAlign) {
this.model = model;
this.takeHierarchyGaps = takeHierarchyGaps;
this.takeSuperGaps = takeSuperGaps;
this.autoAlign = autoAlign;
}
@Override
public ClassLayout layout(ClassData cd) {
SortedSet<FieldLayout> result = new TreeSet<FieldLayout>();
if (cd.isArray()) {
// special case for arrays
int base = model.headerSize() + model.sizeOf("int");
int scale = model.sizeOf(cd.arrayComponentType());
int instanceSize = base + cd.arrayLength() * scale;
instanceSize = VMSupport.align(instanceSize, autoAlign ? Math.max(4, scale) : 8);
base = VMSupport.align(base, Math.max(4, scale));
result.add(new FieldLayout(FieldData.create(cd.arrayClass(), "length", "int"), model.headerSize(), model.sizeOf("int")));
result.add(new FieldLayout(FieldData.create(cd.arrayClass(), "<elements>", cd.arrayComponentType()), base, scale * cd.arrayLength()));
return new ClassLayout(cd, result, model.headerSize(), instanceSize, false);
}
List<String> hierarchy = cd.classHierarchy();
BitSet claimed = new BitSet();
claimed.set(0, model.headerSize());
for (String k : hierarchy) {
Collection<FieldData> fields = cd.fieldsFor(k);
SortedSet<FieldLayout> current = new TreeSet<FieldLayout>();
for (int size : new int[]{8, 4, 2, 1}) {
for (FieldData f : fields) {
int fSize = model.sizeOf(f.typeClass());
if (fSize != size) continue;
for (int t = 0; t < Integer.MAX_VALUE; t++) {
if (claimed.get(t * size, (t + 1) * size).isEmpty()) {
claimed.set(t * size, (t + 1) * size);
current.add(new FieldLayout(f, t * size, size));
break;
}
}
}
}
result.addAll(current);
if (takeSuperGaps) {
// do nothing
} else if (takeHierarchyGaps) {
// claim only the class body up to the field
int lastSet = claimed.length() - 1;
claimed.set(0, lastSet);
} else {
// claim the entire class body, plus some alignment
int lastSet = claimed.length() - 1;
claimed.set(0, VMSupport.align(lastSet, 4));
}
}
int instanceSize;
if (autoAlign) {
int a = 4;
for (FieldLayout f : result) {
a = Math.max(a, model.sizeOf(f.typeClass()));
}
instanceSize = VMSupport.align(claimed.length(), a);
} else {
instanceSize = VMSupport.align(claimed.length());
}
return new ClassLayout(cd, result, model.headerSize(), instanceSize, true);
}
@Override
public String toString() {
return "VM Layout Simulation (" + model
+ (takeHierarchyGaps ? ", hierarchy gaps" : "")
+ (takeSuperGaps ? ", super gaps" : "")
+ (autoAlign ? ", autoalign" : "") + ")";
}
}