src/main/java/com/google/devtools/build/lib/packages/CallStack.java - bazel - Git at Google

 // Copyright 2020 The Bazel Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package com.google.devtools.build.lib.packages;

 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;

 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Interner;
 import com.google.devtools.build.lib.concurrent.BlazeInterners;
 import com.google.devtools.build.lib.util.HashCodes;
 import com.google.devtools.build.lib.util.StringCanonicalizer;
 import com.google.protobuf.CodedInputStream;
 import com.google.protobuf.CodedOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.IdentityHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import javax.annotation.Nullable;
 import net.starlark.java.eval.StarlarkThread;
 import net.starlark.java.syntax.Location;

 /**
  * Compact representation of a Starlark call stack for rule instantiations.
  *
  * <p>Implementation is optimized for minimizing memory overhead by sharing {@link Node} instances
  * when two call stacks have a common tail. For example, two different BUILD files that call into
  * the same macro can share {@link Node} instances for every frame except the top-level call.
  *
  * <p>The sharing rate of interior nodes is expected to be high, so nodes are implemented as a
  * linked list to eliminate array cost.
  */
 public final class CallStack {

   /** Null instance, for use in testing or where content doesn't actually matter. */
   public static final CallStack EMPTY = new CallStack(/* size= */ 0, /* head= */ null);

   /** Number of frames in this stack. */
   private final int size;
   /** Top-level call in the call stack. */
   @Nullable final Node head;

   private CallStack(int size, @Nullable Node head) {
     this.size = size;
     this.head = head;
   }

   /** Returns the call stack as a list of frames, outermost call first. */
   public ImmutableList<StarlarkThread.CallStackEntry> toList() {
     StarlarkThread.CallStackEntry[] array = new StarlarkThread.CallStackEntry[size];
     int i = 0;
     for (Node n = head; n != null; n = n.next) {
       array[i++] = n.toCallStackEntry();
     }
     return ImmutableList.copyOf(array);
   }

   /** Returns a single frame, like {@code toList().get(i)} but more efficient. */
   StarlarkThread.CallStackEntry getFrame(int i) {
     for (Node n = head; n != null; n = n.next, i--) {
       if (i == 0) {
         return n.toCallStackEntry();
       }
     }
     throw new IndexOutOfBoundsException(); // !(0 <= i < size)
   }

   /** Returns the number of frames in the call stack. */
   public int size() {
     return size;
   }

   /** Compact representation of a call stack entry. */
   static final class Node {
     /** Function name. */
     private final String name;
     /** File name. */
     private final String file;

     private final int line;
     private final int col;
     @Nullable private final Node next;

     private Node(String name, String file, int line, int col, @Nullable Node next) {
       this.name = name;
       this.file = file;
       this.line = line;
       this.col = col;
       this.next = next;
     }

     private Location toLocation() {
       return Location.fromFileLineColumn(file, line, col);
     }

     private StarlarkThread.CallStackEntry toCallStackEntry() {
       return new StarlarkThread.CallStackEntry(name, toLocation());
     }

     @Nullable
     Node next() {
       return next;
     }

     @Override
     public boolean equals(Object o) {
       if (this == o) {
         return true;
       }
       if (!(o instanceof Node)) {
         return false;
       }
       Node node = (Node) o;
       return line == node.line
           && col == node.col
           && name.equals(node.name)
           && file.equals(node.file)
           && Objects.equals(next, node.next);
     }

     @Override
     public int hashCode() {
       int result = HashCodes.hashObjects(name, file, next);
       result = result * 31 + Integer.hashCode(line);
       result = result * 31 + Integer.hashCode(col);
       return result;
     }
   }

   private static final Interner<Node> nodeInterner = BlazeInterners.newWeakInterner();

   static CallStack createFrom(List<StarlarkThread.CallStackEntry> stack) {
     Node child = null;
     int n = stack.size();
     for (int i = n - 1; i >= 0; i--) {
       StarlarkThread.CallStackEntry entry = stack.get(i);

       String name = entry.name;
       String file = entry.location.file();
       int line = entry.location.line();
       int column = entry.location.column();

       child = new Node(name, file, line, column, child);
       if (i != 0) {
         // We don't intern top node, because it hardly ever repeats.
         child = nodeInterner.intern(child);
       }
     }

     // Use the same node for all empty stacks, to avoid allocations.
     return child != null ? new CallStack(n, child) : EMPTY;
   }

   /**
    * Efficient serializer for {@link CallStack}s. Before callstacks are serialized in a package
    * {@link #prepareCallStack(CallStack)} method must be called on them (to prepare a table of
    * strings).
    */
   static class Serializer {
     private static final int NULL_NODE_ID = 0;

     private final IdentityHashMap<Node, Integer> nodeTable = new IdentityHashMap<>();
     private final List<String> stringTable = new ArrayList<>();
     private boolean stringTableSerialized = false;

     private final Map<String, Integer> stringTableIndex = new HashMap<>();

     private int indexOf(String s) {
       int i = stringTableIndex.size();
       Integer prev = stringTableIndex.putIfAbsent(s, i);
       if (prev != null) {
         i = prev;
       } else {
         checkArgument(
             !stringTableSerialized, "Can only serialize CallStacks that were prepared before.");
         stringTable.add(s);
       }
       return i;
     }

     Serializer() {
       nodeTable.put(null, NULL_NODE_ID);
     }

     void serializeCallStack(CallStack callStack, CodedOutputStream codedOut) throws IOException {
       if (!stringTableSerialized) {
         codedOut.writeInt32NoTag(stringTable.size());
         for (String string : stringTable) {
           codedOut.writeStringNoTag(string);
         }
         stringTableSerialized = true;
       }

       codedOut.writeInt32NoTag(callStack.size);
       emitNode(callStack.head, codedOut);
     }

     private void emitNode(Node node, CodedOutputStream codedOut) throws IOException {
       Integer index = nodeTable.get(node);
       if (index != null) {
         codedOut.writeInt32NoTag(index);
         return;
       }

       if (node == null) {
         return;
       }

       int newIndex = nodeTable.size();
       codedOut.writeInt32NoTag(newIndex);
       nodeTable.put(node, newIndex);
       codedOut.writeInt32NoTag(indexOf(node.name));
       codedOut.writeInt32NoTag(indexOf(node.file));
       codedOut.writeInt32NoTag(node.line);
       codedOut.writeInt32NoTag(node.col);
       emitNode(node.next, codedOut);
     }

     void prepareCallStack(CallStack callStack) {
       for (Node n = callStack.head; n != null; n = n.next) {
         indexOf(n.name);
         indexOf(n.file);
       }
     }
   }

   /** Deserializes {@link CallStack}s as serialized by a {@link Serializer}. */
   static class Deserializer {
     private static final Node DUMMY_NODE = new Node("", "", -1, -1, null);

     private final List<Node> nodeTable = new ArrayList<>();
     @Nullable private List<String> stringTable;

     Deserializer() {
       // By convention index 0 = null.
       nodeTable.add(null);
     }

     CallStack deserializeCallStack(CodedInputStream codedIn) throws IOException {
       if (stringTable == null) {
         int length = codedIn.readInt32();
         stringTable = new ArrayList<>(length);
         for (int i = 0; i < length; i++) {
           // Avoid having a new set of strings per deserialized string table. Use common
           // canonicalizer based on assertion that most strings (function names, locations) were
           // already some degree of shared across packages.
           stringTable.add(StringCanonicalizer.intern(codedIn.readString()));
         }
       }

       int size = codedIn.readInt32();
       return new CallStack(size, readNode(codedIn));
     }

     @Nullable
     @SuppressWarnings("ReferenceEquality")
     private Node readNode(CodedInputStream codedIn) throws IOException {
       int index = codedIn.readInt32();
       if (index < nodeTable.size()) {
         Node result = nodeTable.get(index);
         checkState(result != DUMMY_NODE, "Loop detected at index %s", index);
         return result;
       }

       checkState(
           index == nodeTable.size(),
           "Unexpected next value index - read %s, expected %s",
           index,
           nodeTable.size());

       // Add dummy node to grow the table and save our spot in the table until we're done.
       nodeTable.add(DUMMY_NODE);
       int name = codedIn.readInt32();
       int file = codedIn.readInt32();
       int line = codedIn.readInt32();
       int col = codedIn.readInt32();
       Node child = readNode(codedIn);

       Node result = new Node(stringTable.get(name), stringTable.get(file), line, col, child);
       nodeTable.set(index, result);
       return result;
     }
   }
 }
	// Copyright 2020 The Bazel Authors. All rights reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package com.google.devtools.build.lib.packages;

	import static com.google.common.base.Preconditions.checkArgument;
	import static com.google.common.base.Preconditions.checkState;

	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.Interner;
	import com.google.devtools.build.lib.concurrent.BlazeInterners;
	import com.google.devtools.build.lib.util.HashCodes;
	import com.google.devtools.build.lib.util.StringCanonicalizer;
	import com.google.protobuf.CodedInputStream;
	import com.google.protobuf.CodedOutputStream;
	import java.io.IOException;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.IdentityHashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.Objects;
	import javax.annotation.Nullable;
	import net.starlark.java.eval.StarlarkThread;
	import net.starlark.java.syntax.Location;

	/**
	* Compact representation of a Starlark call stack for rule instantiations.
	*
	* <p>Implementation is optimized for minimizing memory overhead by sharing {@link Node} instances
	* when two call stacks have a common tail. For example, two different BUILD files that call into
	* the same macro can share {@link Node} instances for every frame except the top-level call.
	*
	* <p>The sharing rate of interior nodes is expected to be high, so nodes are implemented as a
	* linked list to eliminate array cost.
	*/
	public final class CallStack {

	/** Null instance, for use in testing or where content doesn't actually matter. */
	public static final CallStack EMPTY = new CallStack(/* size= / 0, / head= */ null);

	/** Number of frames in this stack. */
	private final int size;
	/** Top-level call in the call stack. */
	@Nullable final Node head;

	private CallStack(int size, @Nullable Node head) {
	this.size = size;
	this.head = head;
	}

	/** Returns the call stack as a list of frames, outermost call first. */
	public ImmutableList<StarlarkThread.CallStackEntry> toList() {
	StarlarkThread.CallStackEntry[] array = new StarlarkThread.CallStackEntry[size];
	int i = 0;
	for (Node n = head; n != null; n = n.next) {
	array[i++] = n.toCallStackEntry();
	}
	return ImmutableList.copyOf(array);
	}

	/** Returns a single frame, like {@code toList().get(i)} but more efficient. */
	StarlarkThread.CallStackEntry getFrame(int i) {
	for (Node n = head; n != null; n = n.next, i--) {
	if (i == 0) {
	return n.toCallStackEntry();
	}
	}
	throw new IndexOutOfBoundsException(); // !(0 <= i < size)
	}

	/** Returns the number of frames in the call stack. */
	public int size() {
	return size;
	}

	/** Compact representation of a call stack entry. */
	static final class Node {
	/** Function name. */
	private final String name;
	/** File name. */
	private final String file;

	private final int line;
	private final int col;
	@Nullable private final Node next;

	private Node(String name, String file, int line, int col, @Nullable Node next) {
	this.name = name;
	this.file = file;
	this.line = line;
	this.col = col;
	this.next = next;
	}

	private Location toLocation() {
	return Location.fromFileLineColumn(file, line, col);
	}

	private StarlarkThread.CallStackEntry toCallStackEntry() {
	return new StarlarkThread.CallStackEntry(name, toLocation());
	}

	@Nullable
	Node next() {
	return next;
	}

	@Override
	public boolean equals(Object o) {
	if (this == o) {
	return true;
	}
	if (!(o instanceof Node)) {
	return false;
	}
	Node node = (Node) o;
	return line == node.line
	&& col == node.col
	&& name.equals(node.name)
	&& file.equals(node.file)
	&& Objects.equals(next, node.next);
	}

	@Override
	public int hashCode() {
	int result = HashCodes.hashObjects(name, file, next);
	result = result * 31 + Integer.hashCode(line);
	result = result * 31 + Integer.hashCode(col);
	return result;
	}
	}

	private static final Interner<Node> nodeInterner = BlazeInterners.newWeakInterner();

	static CallStack createFrom(List<StarlarkThread.CallStackEntry> stack) {
	Node child = null;
	int n = stack.size();
	for (int i = n - 1; i >= 0; i--) {
	StarlarkThread.CallStackEntry entry = stack.get(i);

	String name = entry.name;
	String file = entry.location.file();
	int line = entry.location.line();
	int column = entry.location.column();

	child = new Node(name, file, line, column, child);
	if (i != 0) {
	// We don't intern top node, because it hardly ever repeats.
	child = nodeInterner.intern(child);
	}
	}

	// Use the same node for all empty stacks, to avoid allocations.
	return child != null ? new CallStack(n, child) : EMPTY;
	}

	/**
	* Efficient serializer for {@link CallStack}s. Before callstacks are serialized in a package
	* {@link #prepareCallStack(CallStack)} method must be called on them (to prepare a table of
	* strings).
	*/
	static class Serializer {
	private static final int NULL_NODE_ID = 0;

	private final IdentityHashMap<Node, Integer> nodeTable = new IdentityHashMap<>();
	private final List<String> stringTable = new ArrayList<>();
	private boolean stringTableSerialized = false;

	private final Map<String, Integer> stringTableIndex = new HashMap<>();

	private int indexOf(String s) {
	int i = stringTableIndex.size();
	Integer prev = stringTableIndex.putIfAbsent(s, i);
	if (prev != null) {
	i = prev;
	} else {
	checkArgument(
	!stringTableSerialized, "Can only serialize CallStacks that were prepared before.");
	stringTable.add(s);
	}
	return i;
	}

	Serializer() {
	nodeTable.put(null, NULL_NODE_ID);
	}

	void serializeCallStack(CallStack callStack, CodedOutputStream codedOut) throws IOException {
	if (!stringTableSerialized) {
	codedOut.writeInt32NoTag(stringTable.size());
	for (String string : stringTable) {
	codedOut.writeStringNoTag(string);
	}
	stringTableSerialized = true;
	}

	codedOut.writeInt32NoTag(callStack.size);
	emitNode(callStack.head, codedOut);
	}

	private void emitNode(Node node, CodedOutputStream codedOut) throws IOException {
	Integer index = nodeTable.get(node);
	if (index != null) {
	codedOut.writeInt32NoTag(index);
	return;
	}

	if (node == null) {
	return;
	}

	int newIndex = nodeTable.size();
	codedOut.writeInt32NoTag(newIndex);
	nodeTable.put(node, newIndex);
	codedOut.writeInt32NoTag(indexOf(node.name));
	codedOut.writeInt32NoTag(indexOf(node.file));
	codedOut.writeInt32NoTag(node.line);
	codedOut.writeInt32NoTag(node.col);
	emitNode(node.next, codedOut);
	}

	void prepareCallStack(CallStack callStack) {
	for (Node n = callStack.head; n != null; n = n.next) {
	indexOf(n.name);
	indexOf(n.file);
	}
	}
	}

	/** Deserializes {@link CallStack}s as serialized by a {@link Serializer}. */
	static class Deserializer {
	private static final Node DUMMY_NODE = new Node("", "", -1, -1, null);

	private final List<Node> nodeTable = new ArrayList<>();
	@Nullable private List<String> stringTable;

	Deserializer() {
	// By convention index 0 = null.
	nodeTable.add(null);
	}

	CallStack deserializeCallStack(CodedInputStream codedIn) throws IOException {
	if (stringTable == null) {
	int length = codedIn.readInt32();
	stringTable = new ArrayList<>(length);
	for (int i = 0; i < length; i++) {
	// Avoid having a new set of strings per deserialized string table. Use common
	// canonicalizer based on assertion that most strings (function names, locations) were
	// already some degree of shared across packages.
	stringTable.add(StringCanonicalizer.intern(codedIn.readString()));
	}
	}

	int size = codedIn.readInt32();
	return new CallStack(size, readNode(codedIn));
	}

	@Nullable
	@SuppressWarnings("ReferenceEquality")
	private Node readNode(CodedInputStream codedIn) throws IOException {
	int index = codedIn.readInt32();
	if (index < nodeTable.size()) {
	Node result = nodeTable.get(index);
	checkState(result != DUMMY_NODE, "Loop detected at index %s", index);
	return result;
	}

	checkState(
	index == nodeTable.size(),
	"Unexpected next value index - read %s, expected %s",
	index,
	nodeTable.size());

	// Add dummy node to grow the table and save our spot in the table until we're done.
	nodeTable.add(DUMMY_NODE);
	int name = codedIn.readInt32();
	int file = codedIn.readInt32();
	int line = codedIn.readInt32();
	int col = codedIn.readInt32();
	Node child = readNode(codedIn);

	Node result = new Node(stringTable.get(name), stringTable.get(file), line, col, child);
	nodeTable.set(index, result);
	return result;
	}
	}
	}