Introduce a crude implementation of a segment tree
The SourceDebugExtensionRewriter needs to lookup points for intervals
to find the correct starting positions. The segment tree is a perfect
candidate for that.
The segment tree do not support removals at this moment, but that is
fine for now.
Bug: 141817471
Change-Id: I8bac225b9a8782568631d1e10fc06e86ffe53250
diff --git a/src/main/java/com/android/tools/r8/utils/SegmentTree.java b/src/main/java/com/android/tools/r8/utils/SegmentTree.java
new file mode 100644
index 0000000..1fc95b0
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/utils/SegmentTree.java
@@ -0,0 +1,82 @@
+// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.utils;
+
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * Implementation of a discrete segment tree where intervals are specified by their start end and
+ * point. Both points are considered part of the interval.
+ */
+public class SegmentTree<V> {
+
+ private final TreeMap<Integer, V> internalTree = new TreeMap<>();
+ private final boolean allowIntervalOverwrites;
+
+ private int size = 0;
+
+ public SegmentTree(boolean allowIntervalOverwrites) {
+ this.allowIntervalOverwrites = allowIntervalOverwrites;
+ }
+
+ public V find(int point) {
+ Map.Entry<Integer, V> entry = findEntry(point);
+ return entry != null ? entry.getValue() : null;
+ }
+
+ public Map.Entry<Integer, V> findEntry(Integer point) {
+ Map.Entry<Integer, V> kvEntry = internalTree.floorEntry(point);
+ return (kvEntry == null || kvEntry.getValue() == null) ? null : kvEntry;
+ }
+
+ public SegmentTree<V> add(int start, int end, V value) {
+ Map.Entry<Integer, V> existingEndRange = findEntry(end);
+ Box<Integer> removedIntervals = new Box<>(0);
+ boolean removedKeys =
+ internalTree
+ .navigableKeySet()
+ .removeIf(
+ key -> {
+ if (start < key && key <= end) {
+ assert allowIntervalOverwrites;
+ if (internalTree.get(key) != null) {
+ removedIntervals.set(removedIntervals.get() + 1);
+ }
+ return true;
+ }
+ return false;
+ });
+ if (existingEndRange != null) {
+ assert allowIntervalOverwrites;
+ if (removedKeys) {
+ // We have counted a removed interval where it was actually just shortened:
+ // I1 |----------------------------------|
+ // I2 |--------|
+ // R |--------||---------------------------|
+ // I1.start has been removed and counted, but it is actually just moved, so we decrease the
+ // removed counter by 1.
+ removedIntervals.set(removedIntervals.get() - 1);
+ }
+ }
+ internalTree.put(start, value);
+ if (!internalTree.containsKey(end + 1)) {
+ internalTree.put(end + 1, existingEndRange == null ? null : existingEndRange.getValue());
+ }
+ // We only count unique intervals, thus the following is two and not three intervals when
+ // adding I2:
+ // I1 |-------------------------------|
+ // I2 |------------|
+ // R |------||------------||---------|
+ // However, if the order was reversed, we should remove one from the size count since I1
+ // completely shadows I2.
+ size = (size - removedIntervals.get()) + 1;
+ return this;
+ }
+
+ public int size() {
+ return size;
+ }
+}
diff --git a/src/test/java/com/android/tools/r8/utils/SegmentTreeTests.java b/src/test/java/com/android/tools/r8/utils/SegmentTreeTests.java
new file mode 100644
index 0000000..bb2ea17
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/utils/SegmentTreeTests.java
@@ -0,0 +1,106 @@
+// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.utils;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import java.util.Map;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+
+@RunWith(Parameterized.class)
+public class SegmentTreeTests extends TestBase {
+
+ private final TestParameters parameters;
+
+ @Parameters(name = "{0}")
+ public static TestParametersCollection data() {
+ return getTestParameters().withNoneRuntime().build();
+ }
+
+ public SegmentTreeTests(TestParameters parameters) {
+ this.parameters = parameters;
+ }
+
+ private SegmentTree<Integer> tree(boolean allowOverrides) {
+ return new SegmentTree<>(allowOverrides);
+ }
+
+ @Test
+ public void testInsertSimpleRange() {
+ SegmentTree<Integer> tree = tree(false).add(1, 100, 3);
+ Map.Entry<Integer, Integer> entry = tree.findEntry(50);
+ assertEntry(tree, 50, 1, 3);
+ assertNull(tree.find(0));
+ assertNull(tree.find(101));
+ }
+
+ @Test
+ public void testInsertMultipleRanges() {
+ SegmentTree<Integer> tree = tree(false).add(1, 10, 3).add(20, 30, 7).add(31, 100, 9);
+ assertEntry(tree, 10, 1, 3);
+ assertNull(tree.findEntry(11));
+ assertEntry(tree, 20, 20, 7);
+ assertEquals(tree.findEntry(31), tree.findEntry(100));
+ assertNull(tree.find(101));
+ }
+
+ @Test(expected = AssertionError.class)
+ public void testAssertingNoOverrides() {
+ tree(false).add(1, 10, 3).add(7, 2, 4);
+ }
+
+ @Test
+ public void testOverrideLeft() {
+ SegmentTree<Integer> tree = tree(true).add(7, 9, 2).add(6, 7, 1);
+ assertNull(tree.findEntry(5));
+ assertEntry(tree, 7, 6, 1);
+ assertEntry(tree, 9, 8, 2);
+ assertNull(tree.findEntry(10));
+ assertEquals(2, tree.size());
+ }
+
+ @Test
+ public void testOverrideRight() {
+ SegmentTree<Integer> tree = tree(true).add(6, 7, 1).add(7, 9, 2);
+ assertNull(tree.findEntry(5));
+ assertEntry(tree, 6, 6, 1);
+ assertEntry(tree, 8, 7, 2);
+ assertNull(tree.findEntry(10));
+ assertEquals(2, tree.size());
+ }
+
+ @Test
+ public void testOverrideContained() {
+ SegmentTree<Integer> tree = tree(true).add(0, 100, 1).add(25, 75, 2);
+ assertEntry(tree, 24, 0, 1);
+ assertEntry(tree, 75, 25, 2);
+ assertEntry(tree, 100, 76, 1);
+ assertNull(tree.findEntry(101));
+ assertEquals(2, tree.size());
+ }
+
+ @Test
+ public void testOverrideContainer() {
+ SegmentTree<Integer> tree = tree(true).add(25, 75, 2).add(0, 100, 1);
+ assertEntry(tree, 24, 0, 1);
+ assertEntry(tree, 75, 0, 1);
+ assertEntry(tree, 100, 0, 1);
+ assertNull(tree.findEntry(101));
+ assertEquals(1, tree.size());
+ }
+
+ private void assertEntry(
+ SegmentTree<Integer> tree, int index, int expectedStart, int expectedValue) {
+ assertEquals(expectedStart, (int) tree.findEntry(index).getKey());
+ assertEquals(expectedValue, (int) tree.findEntry(index).getValue());
+ }
+}
