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PresizeCollections.java
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PresizeCollections.java
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/*
* fb-contrib - Auxiliary detectors for Java programs
* Copyright (C) 2005-2017 Dave Brosius
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.mebigfatguy.fbcontrib.detect;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.bcel.Const;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.CodeException;
import org.apache.bcel.classfile.JavaClass;
import com.mebigfatguy.fbcontrib.utils.BugType;
import com.mebigfatguy.fbcontrib.utils.FQMethod;
import com.mebigfatguy.fbcontrib.utils.QMethod;
import com.mebigfatguy.fbcontrib.utils.SignatureBuilder;
import com.mebigfatguy.fbcontrib.utils.SignatureUtils;
import com.mebigfatguy.fbcontrib.utils.ToString;
import com.mebigfatguy.fbcontrib.utils.UnmodifiableSet;
import com.mebigfatguy.fbcontrib.utils.Values;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.OpcodeStack.CustomUserValue;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.XMethod;
/**
* finds methods that create and populate collections, and while knowing the end size of those collections, does not pre allocate the collection to be big
* enough. This just causes unneeded reallocations putting strain on the garbage collector.
*/
@CustomUserValue
public class PresizeCollections extends BytecodeScanningDetector {
private static final Set<String> PRESIZEABLE_COLLECTIONS = UnmodifiableSet.create("java/util/ArrayBlockingQueue", "java/util/ArrayDeque",
"java/util/ArrayList", "java/util/HashMap", "java/util/HashSet", "java/util/LinkedBlockingQueue", "java/util/LinkedHashMap",
"java/util/LinkedHashSet", "java/util/PriorityBlockingQueue", "java/util/PriorityQueue", "java/util/Vector");
private static final Set<FQMethod> STATIC_COLLECTION_FACTORIES = UnmodifiableSet.create(
// @formatter:off
new FQMethod("com/google/common/collect/Lists", "newArrayList", "()Ljava/util/ArrayList;"),
new FQMethod("com/google/common/collect/Sets", "newHashSet", "()Ljava/util/HashSet;"),
new FQMethod("com/google/common/collect/Maps", "newHashMap", "()Ljava/util/HashMap;")
// @formatter:on
);
private static final Set<FQMethod> UNSIZED_SOURCES = UnmodifiableSet.create(
// @formatter:off
new FQMethod("java/util/Enumeration", "hasMoreElements", "()Z"),
new FQMethod("java/util/StringTokenizer", "hasMoreElements", "()Z"),
new FQMethod("java/util/StringTokenizer", "hasMoreTokens", "()Z")
// @formatter:on
);
private static final FQMethod ITERATOR_HASNEXT = new FQMethod("java/util/Iterator", "hasNext", "()Z");
private static final QMethod ITERATOR_METHOD = new QMethod("iterator", "()Ljava/util/Iterator;");
private BugReporter bugReporter;
private JavaClass collectionClass;
private OpcodeStack stack;
private int nextAllocNumber;
private Map<Comparable<?>, PSCUserValue> storeToUserValue;
private Map<Integer, Integer> allocLocation;
private Map<Integer, List<Integer>> allocToAddPCs;
private List<CodeRange> optionalRanges;
public PresizeCollections(BugReporter bugReporter) {
this.bugReporter = bugReporter;
try {
collectionClass = Repository.lookupClass("java/util/Collection");
} catch (ClassNotFoundException e) {
bugReporter.reportMissingClass(e);
}
}
/**
* overrides the visitor to initialize the opcode stack
*
* @param classContext
* the context object that holds the JavaClass being parsed
*/
@Override
public void visitClassContext(ClassContext classContext) {
try {
stack = new OpcodeStack();
storeToUserValue = new HashMap<>();
allocLocation = new HashMap<>();
allocToAddPCs = new HashMap<>();
optionalRanges = new ArrayList<>();
super.visitClassContext(classContext);
} finally {
stack = null;
storeToUserValue = null;
allocLocation = null;
allocToAddPCs = null;
optionalRanges = null;
}
}
/**
* implements the visitor to reset the opcode stack
*
* @param obj
* the context object of the currently parsed code block
*/
@Override
public void visitCode(Code obj) {
stack.resetForMethodEntry(this);
nextAllocNumber = 1;
storeToUserValue.clear();
allocLocation.clear();
allocToAddPCs.clear();
optionalRanges.clear();
addExceptionRanges(obj);
super.visitCode(obj);
for (List<Integer> pcs : allocToAddPCs.values()) {
if (pcs.size() > 16) {
bugReporter.reportBug(new BugInstance(this, BugType.PSC_PRESIZE_COLLECTIONS.name(), NORMAL_PRIORITY).addClass(this).addMethod(this)
.addSourceLine(this, pcs.get(0).intValue()));
}
}
}
/**
* implements the visitor to look for creation of collections that are then populated with a known number of elements usually based on another collection,
* but the new collection is not presized.
*
* @param seen
* the opcode of the currently parsed instruction
*/
@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(value = "CLI_CONSTANT_LIST_INDEX", justification = "Constrained by FindBugs API")
@Override
public void sawOpcode(int seen) {
PSCUserValue userValue = null;
boolean sawAlloc = false;
try {
stack.precomputation(this);
switch (seen) {
case Const.INVOKESPECIAL:
String clsName = getClassConstantOperand();
if (PRESIZEABLE_COLLECTIONS.contains(clsName)) {
String methodName = getNameConstantOperand();
if (Values.CONSTRUCTOR.equals(methodName)) {
String signature = getSigConstantOperand();
if (SignatureBuilder.SIG_VOID_TO_VOID.equals(signature)) {
userValue = new PSCUserValue(Integer.valueOf(nextAllocNumber++));
sawAlloc = true;
}
}
}
break;
case Const.INVOKEINTERFACE:
String methodName = getNameConstantOperand();
if (ITERATOR_METHOD.equals(new QMethod(methodName, getSigConstantOperand()))) {
if (stack.getStackDepth() > 0) {
OpcodeStack.Item itm = stack.getStackItem(0);
userValue = isSizedSource(itm);
}
} else if (ITERATOR_HASNEXT.equals(new FQMethod(getClassConstantOperand(), methodName, getSigConstantOperand()))) {
if (stack.getStackDepth() > 0) {
OpcodeStack.Item itm = stack.getStackItem(0);
userValue = (PSCUserValue) itm.getUserValue();
}
} else if ("add".equals(methodName) || "addAll".equals(methodName)) {
String signature = getSigConstantOperand();
int numArguments = SignatureUtils.getNumParameters(signature);
if ((numArguments == 1) && (stack.getStackDepth() > 1)) {
OpcodeStack.Item item = stack.getStackItem(1);
PSCUserValue uv = (PSCUserValue) item.getUserValue();
if (uv != null) {
Integer allocNum = uv.getAllocationNumber();
if (allocNum != null) {
if ("addAll".equals(methodName)) {
allocToAddPCs.remove(allocNum);
} else {
List<Integer> lines = allocToAddPCs.get(allocNum);
if (lines == null) {
lines = new ArrayList<>();
allocToAddPCs.put(allocNum, lines);
}
lines.add(Integer.valueOf(getPC()));
}
}
}
}
} else if ("put".equals(methodName) || "putAll".equals(methodName)) {
String signature = getSigConstantOperand();
int numArguments = SignatureUtils.getNumParameters(signature);
if ((numArguments == 2) && (stack.getStackDepth() > 2)) {
OpcodeStack.Item item = stack.getStackItem(2);
PSCUserValue uv = (PSCUserValue) item.getUserValue();
if (uv != null) {
Integer allocNum = uv.getAllocationNumber();
if (allocNum != null) {
if ("putAll".equals(methodName)) {
allocToAddPCs.remove(allocNum);
} else {
List<Integer> lines = allocToAddPCs.get(allocNum);
if (lines == null) {
lines = new ArrayList<>();
allocToAddPCs.put(allocNum, lines);
}
lines.add(Integer.valueOf(getPC()));
}
}
}
}
}
break;
case Const.INVOKESTATIC:
FQMethod fqm = new FQMethod(getClassConstantOperand(), getNameConstantOperand(), getSigConstantOperand());
if (STATIC_COLLECTION_FACTORIES.contains(fqm)) {
userValue = new PSCUserValue(Integer.valueOf(nextAllocNumber++));
sawAlloc = true;
}
break;
case Const.LOOKUPSWITCH:
case Const.TABLESWITCH:
int[] offsets = getSwitchOffsets();
if (offsets.length >= 2) {
int pc = getPC();
int thisOffset = pc + offsets[0];
for (int o = 0; o < (offsets.length - 1); o++) {
int nextOffset = offsets[o + 1] + pc;
CodeRange db = new CodeRange(thisOffset, nextOffset);
optionalRanges.add(db);
thisOffset = nextOffset;
}
}
break;
case Const.IFEQ:
case Const.IFNE:
case Const.IFLT:
case Const.IFLE:
case Const.IF_ICMPEQ:
case Const.IF_ICMPNE:
case Const.IF_ICMPLT:
case Const.IF_ICMPGE:
case Const.IF_ICMPGT:
case Const.IF_ICMPLE:
case Const.IF_ACMPEQ:
case Const.IF_ACMPNE:
case Const.GOTO:
case Const.GOTO_W:
if (getBranchOffset() < 0) {
if (branchBasedOnUnsizedObject(seen)) {
break;
}
int target = getBranchTarget();
Iterator<Map.Entry<Integer, List<Integer>>> it = allocToAddPCs.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Integer, List<Integer>> entry = it.next();
Integer allocLoc = allocLocation.get(entry.getKey());
if ((allocLoc != null) && (allocLoc.intValue() < target)) {
List<Integer> pcs = entry.getValue();
for (int pc : pcs) {
if (pc > target) {
int numDownBranches = countDownBranches(allocLoc.intValue(), pc);
if (numDownBranches == 1) {
bugReporter.reportBug(new BugInstance(this, BugType.PSC_PRESIZE_COLLECTIONS.name(), NORMAL_PRIORITY).addClass(this)
.addMethod(this).addSourceLine(this, pc));
it.remove();
}
break;
}
}
}
}
} else {
CodeRange db = new CodeRange(getPC(), getBranchTarget());
optionalRanges.add(db);
}
break;
case Const.IFNULL:
case Const.IFNONNULL:
case Const.IFGE:
case Const.IFGT:
// null check and >, >= branches are hard to presize
if (getBranchOffset() > 0) {
CodeRange db = new CodeRange(getPC(), getBranchTarget());
optionalRanges.add(db);
}
break;
case Const.ASTORE:
case Const.ASTORE_0:
case Const.ASTORE_1:
case Const.ASTORE_2:
case Const.ASTORE_3: {
if (stack.getStackDepth() > 0) {
PSCUserValue uv = (PSCUserValue) stack.getStackItem(0).getUserValue();
if (uv != null) {
storeToUserValue.put(getRegisterOperand(), uv);
}
}
}
break;
case Const.ALOAD:
case Const.ALOAD_0:
case Const.ALOAD_1:
case Const.ALOAD_2:
case Const.ALOAD_3: {
userValue = storeToUserValue.get(getRegisterOperand());
}
break;
case Const.PUTFIELD: {
if (stack.getStackDepth() > 0) {
PSCUserValue uv = (PSCUserValue) stack.getStackItem(0).getUserValue();
if (uv != null) {
storeToUserValue.put(getNameConstantOperand(), uv);
}
}
}
break;
case Const.GETFIELD: {
userValue = storeToUserValue.get(getNameConstantOperand());
}
}
} finally {
stack.sawOpcode(this, seen);
if ((userValue != null) && (stack.getStackDepth() > 0)) {
OpcodeStack.Item item = stack.getStackItem(0);
item.setUserValue(userValue);
if (sawAlloc) {
allocLocation.put(userValue.getAllocationNumber(), Integer.valueOf(getPC()));
}
}
}
}
private int countDownBranches(int allocationPos, int addPC) {
int numDownBranches = 0;
for (CodeRange db : optionalRanges) {
if ((db.fromPC > allocationPos) && (db.fromPC < addPC) && (db.toPC > addPC)) {
numDownBranches++;
}
}
return numDownBranches;
}
/**
* adds optionalRanges for all try/catch blocks
*
* @param c
* the currently parsed code object
*/
private void addExceptionRanges(Code c) {
Map<CodeRange, List<Integer>> ranges = new HashMap<>();
CodeException[] ces = c.getExceptionTable();
if (ces != null) {
for (CodeException ce : ces) {
CodeRange range = new CodeRange(ce.getStartPC(), ce.getEndPC());
List<Integer> handlers = ranges.get(range);
if (handlers == null) {
handlers = new ArrayList<>(6);
ranges.put(range, handlers);
}
handlers.add(ce.getHandlerPC());
}
}
for (Map.Entry<CodeRange, List<Integer>> entry : ranges.entrySet()) {
optionalRanges.add(entry.getKey());
List<Integer> handlers = entry.getValue();
Collections.sort(handlers);
for (int h = 0; h < (handlers.size() - 1); h++) {
optionalRanges.add(new CodeRange(handlers.get(h), handlers.get(h + 1)));
}
}
}
/**
* returns if the conditional is based on a method call from an object that has no sizing to determine what presize should be. it's possible the correct
* implementation should just return true, if <code>if ((seen != IFNE) || (stack.getStackDepth() == 0))</code>
*
* @param seen
* the current visited opcode
* @return whether this conditional is based on a unsized object
*/
private boolean branchBasedOnUnsizedObject(int seen) {
if ((seen == Const.IF_ACMPEQ) || (seen == Const.IF_ACMPNE)) {
return true;
}
if ((seen != Const.IFNE) || (stack.getStackDepth() == 0)) {
return false;
}
OpcodeStack.Item itm = stack.getStackItem(0);
XMethod xm = itm.getReturnValueOf();
if (xm == null) {
return false;
}
FQMethod fqm = new FQMethod(xm.getClassName().replace('.', '/'), xm.getName(), xm.getSignature());
if (ITERATOR_HASNEXT.equals(fqm)) {
PSCUserValue uv = (PSCUserValue) itm.getUserValue();
if (uv == null) {
return true;
}
return !uv.hasSizedSource();
}
return UNSIZED_SOURCES.contains(fqm);
}
private PSCUserValue isSizedSource(OpcodeStack.Item itm) {
try {
String sig = itm.getSignature();
JavaClass cls = Repository.lookupClass(sig.substring(1, sig.length() - 1));
if (cls.instanceOf(collectionClass)) {
return new PSCUserValue(true);
}
} catch (ClassNotFoundException e) {
bugReporter.reportMissingClass(e);
}
return null;
}
static class CodeRange {
public int fromPC;
public int toPC;
CodeRange(int from, int to) {
fromPC = from;
toPC = to;
}
@Override
public int hashCode() {
return fromPC ^ toPC;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof CodeRange)) {
return false;
}
CodeRange that = (CodeRange) o;
return (fromPC == that.fromPC) && (toPC == that.toPC);
}
@Override
public String toString() {
return ToString.build(this);
}
}
class PSCUserValue {
private Integer allocationNumber;
private boolean hasSizedSource;
public PSCUserValue(Integer allocNumber) {
allocationNumber = allocNumber;
}
public PSCUserValue(boolean sizedSource) {
hasSizedSource = sizedSource;
}
public Integer getAllocationNumber() {
return allocationNumber;
}
public boolean hasSizedSource() {
return hasSizedSource;
}
@Override
public String toString() {
return ToString.build(this);
}
}
}