对类的植入锁定进行判断

几个可以对覆盖率跟踪的Java类定义进行instrument的API

public byte[] instrument(final ClassReader reader) {final ClassWriter writer = new ClassWriter(reader, 0) {@Overrideprotected String getCommonSuperClass(final String type1,final String type2) {throw new IllegalStateException();}};final IProbeArrayStrategy strategy = ProbeArrayStrategyFactory.createFor(reader, accessorGenerator);final ClassVisitor visitor = new ClassProbesAdapter(new ClassInstrumenter(strategy, writer), true);reader.accept(visitor, ClassReader.EXPAND_FRAMES);return writer.toByteArray();}public byte[] instrument(final byte[] buffer, final String name)throws IOException {try {return instrument(new ClassReader(buffer));} catch (final RuntimeException e) {throw instrumentError(name, e);}}public byte[] instrument(final InputStream input, final String name)throws IOException {final byte[] bytes;try {bytes = InputStreams.readFully(input);} catch (final IOException e) {throw instrumentError(name, e);}return instrument(bytes, name);}public void instrument(final InputStream input, final OutputStream output,final String name) throws IOException {output.write(instrument(input, name));}private IOException instrumentError(final String name,final Exception cause) {final IOException ex = new IOException(String.format("Error while instrumenting %s.", name));ex.initCause(cause);return ex;}

执行流程图:

所以最终的出口在于最下面的instrument(input,output,string)，下面是剩余部分代码：

public int instrumentAll(final InputStream input, final OutputStream output,final String name) throws IOException {final ContentTypeDetector detector;try {detector = new ContentTypeDetector(input);} catch (final IOException e) {throw instrumentError(name, e);}switch (detector.getType()) {case ContentTypeDetector.CLASSFILE:instrument(detector.getInputStream(), output, name);return 1;case ContentTypeDetector.ZIPFILE:return instrumentZip(detector.getInputStream(), output, name);case ContentTypeDetector.GZFILE:return instrumentGzip(detector.getInputStream(), output, name);case ContentTypeDetector.PACK200FILE:return instrumentPack200(detector.getInputStream(), output, name);default:copy(detector.getInputStream(), output, name);return 0;}}private int instrumentZip(final InputStream input,final OutputStream output, final String name) throws IOException {final ZipInputStream zipin = new ZipInputStream(input);final ZipOutputStream zipout = new ZipOutputStream(output);ZipEntry entry;int count = 0;while ((entry = nextEntry(zipin, name)) != null) {final String entryName = entry.getName();if (signatureRemover.removeEntry(entryName)) {continue;}zipout.putNextEntry(new ZipEntry(entryName));if (!signatureRemover.filterEntry(entryName, zipin, zipout)) {count += instrumentAll(zipin, zipout, name + "@" + entryName);}zipout.closeEntry();}zipout.finish();return count;}private ZipEntry nextEntry(final ZipInputStream input,final String location) throws IOException {try {return input.getNextEntry();} catch (final IOException e) {throw instrumentError(location, e);}}private int instrumentGzip(final InputStream input,final OutputStream output, final String name) throws IOException {final GZIPInputStream gzipInputStream;try {gzipInputStream = new GZIPInputStream(input);} catch (final IOException e) {throw instrumentError(name, e);}final GZIPOutputStream gzout = new GZIPOutputStream(output);final int count = instrumentAll(gzipInputStream, gzout, name);gzout.finish();return count;}private int instrumentPack200(final InputStream input,final OutputStream output, final String name) throws IOException {final InputStream unpackedInput;try {unpackedInput = Pack200Streams.unpack(input);} catch (final IOException e) {throw instrumentError(name, e);}final ByteArrayOutputStream buffer = new ByteArrayOutputStream();final int count = instrumentAll(unpackedInput, buffer, name);Pack200Streams.pack(buffer.toByteArray(), output);return count;}private void copy(final InputStream input, final OutputStream output,final String name) throws IOException {final byte[] buffer = new byte[1024];int len;while ((len = read(input, buffer, name)) != -1) {output.write(buffer, 0, len);}}private int read(final InputStream input, final byte[] buffer,final String name) throws IOException {try {return input.read(buffer);} catch (final IOException e) {throw instrumentError(name, e);}}

核心关键是instrumentAll这个方法，根据文件包是class还是zip，或者gz等，不同的加载方式。

ClassInstrumenter 类

适配器为了类覆盖率跟踪。

import org.jacoco.core.internal.flow.ClassProbesVisitor;
import org.jacoco.core.internal.flow.MethodProbesVisitor;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;/*** Adapter that instruments a class for coverage tracing.*/
public class ClassInstrumenter extends ClassProbesVisitor {private final IProbeArrayStrategy probeArrayStrategy;private String className;/*** Emits a instrumented version of this class to the given class visitor.* 向给定的class 访问者发出此类的instrumented版本** @param probeArrayStrategy*            该策略将用于访问探针数组* @param cv*            访问链中的下一位 delegate 将获得 instrumente 类*/public ClassInstrumenter(final IProbeArrayStrategy probeArrayStrategy,final ClassVisitor cv) {super(cv);this.probeArrayStrategy = probeArrayStrategy;}@Overridepublic void visit(final int version, final int access, final String name,final String signature, final String superName,final String[] interfaces) {this.className = name;super.visit(version, access, name, signature, superName, interfaces);}@Overridepublic FieldVisitor visitField(final int access, final String name,final String desc, final String signature, final Object value) {InstrSupport.assertNotInstrumented(name, className);return super.visitField(access, name, desc, signature, value);}@Overridepublic MethodProbesVisitor visitMethod(final int access, final String name,final String desc, final String signature,final String[] exceptions) {InstrSupport.assertNotInstrumented(name, className);final MethodVisitor mv = cv.visitMethod(access, name, desc, signature,exceptions);if (mv == null) {return null;}final MethodVisitor frameEliminator = new DuplicateFrameEliminator(mv);final ProbeInserter probeVariableInserter = new ProbeInserter(access,name, desc, frameEliminator, probeArrayStrategy);return new MethodInstrumenter(probeVariableInserter,probeVariableInserter);}@Overridepublic void visitTotalProbeCount(final int count) {probeArrayStrategy.addMembers(cv, count);}}

DuplicateFrameEliminator

消除了导致ASM创建无效类文件的连续 stackmap frames 定义。当原始类文件在意外偏移处包含其他 stackmap frames 时，就会发生这种情况，某些使用ECJ编译的类文件就是这种情况。

ProbeInserter - 探针植入类

内部实用程序，用于将探针添加到方法的控制流中。

探针的代码只是将布尔数组的某个插槽设置为true。
另外，必须在方法开始时检索探针数组并将其存储在局部变量中。

构造方法

创建一个新的ProbeInserter

 /**** @param access*            access flags of the adapted method* @param name*            the method's name* @param desc*            the method's descriptor* @param mv*            the method visitor to which this adapter delegates calls* @param arrayStrategy*            callback to create the code that retrieves the reference to*            the probe array*/

visitmax

探针代码的最大堆栈大小为3，这可以增加到原始堆栈大小，具体取决于探针位置。访问者堆栈大小是绝对最大值，因为当堆栈大小为空时，访问者代码会在每种方法的开头插入。

 @Overridepublic void visitMaxs(final int maxStack, final int maxLocals) {final int increasedStack = Math.max(maxStack + 3, accessorStackSize);mv.visitMaxs(increasedStack, maxLocals + 1);}

insertProbe - 插入具有给定id的探针

visitIincInsn - 访问 IINC 指令

visitLocalVariable - 访问局部变量声明

Visits a local variable declaration.

    private void visitInsn() {final Instruction insn = newInstruction(currentNode, currentLine);nodeToInstruction.put(currentNode,insn);instructions.add(insn);if (lastInsn != null) {insn.setPredecessor(lastInsn, 0);}final int labelCount =currentLabel.size();if (labelCount > 0) {for (int i = labelCount; --i >=0;) {LabelInfo.setInstruction(currentLabel.get(i),insn);}currentLabel.clear();}lastInsn = insn;}

大致就是，在对应字节码的执行入口和跳转入口处，置放 probe，是一个数值（该数值和probe id有关）,入栈后加1，则记录一次执行

所有放入的探针对应一个boolean[]
探针入栈之后，那么boolean[] 对应的位置变成true，记录执行了。

InstrSupport 类原理

Constants and utilities for byte code instrumentation
字节码检测的常量和实用程序。

属性

public static final int ASM_API_VERSION = Opcodes.ASM7;

接口初始化方法的名称。

static final String CLINIT_NAME = "<clinit>";

存储类的boolean[]数组的coverage信息的字段的数据类型

public static final String DATAFIELD_DESC = "[Z";

初始化方法的名称。

public static final String INITMETHOD_NAME = "$jacocoInit";

初始化方法的描述符。

public static final String INITMETHOD_DESC = "()[Z";

 /*** Access modifiers of the initialization method.*/public static final int INITMETHOD_ACC = Opcodes.ACC_SYNTHETIC| Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC;

needsFrames

 /*** 确定给定的 class 文件版本是否需要 stackmap frames.** @param version*            class file version* @return <code>true</code> if frames are required*/public static boolean needsFrames(final int version) {// consider major version only (due to 1.1 anomaly)return (version & 0xFFFF) >= Opcodes.V1_6;}

classReaderFor

 /*** Creates a {@link ClassReader} instance for given bytes of class even if* its version not yet supported by ASM.** @param b*            bytes of class* @return {@link ClassReader}*/public static ClassReader classReaderFor(final byte[] b) {final int originalVersion = getMajorVersion(b);if (originalVersion == Opcodes.V14 + 1) {// temporarily downgrade version to bypass check in ASMsetMajorVersion(Opcodes.V14, b);}final ClassReader classReader = new ClassReader(b);setMajorVersion(originalVersion, b);return classReader;}

assertNotInstrumented

Ensures that the given member does not correspond to a internal member created by the instrumentation process. This would mean that the class is already instrumented.
确保给定成员与 instrumentation 过程创建的内部成员不对应。这意味着该类已经被检测。

push

Generates the instruction to push the given int value on the stack.

Implementation taken from org.objectweb.asm.commons.GeneratorAdapter#push(int)

生成指令以将给定的int值压入堆栈。

取自org.objectweb.asm.commons.GeneratorAdapter＃push（int）的实现

Push是用来对于不同的变量值入栈的不同方式，当int取值

-1 ~ 5，JVM采用iconst指令将常量压入栈中
-128 ~ 127，bipush
-32768 ~ 32767，sipush
-2147483648~2147483647，ldc

主要作为单例的使用，ClassInstrumenter， ClassAnalyzer调用InstrSupport

ClassAnalyzer 类调用如下：

public static final String DATAFIELD_DESC = "[Z";// === Init Method ===/*** Name of the initialization method.*/public static final String INITMETHOD_NAME = "$jacocoInit";/*** Descriptor of the initialization method.*/public static final String INITMETHOD_DESC = "()[Z";public static void assertNotInstrumented(final String member,final String owner) throws IllegalStateException {if (member.equals(DATAFIELD_NAME) || member.equals(INITMETHOD_NAME)) {throw new IllegalStateException(format("Class %s is already instrumented.", owner));}}

IProbeArrayStrategy

检索类型内每个方法的探针数组实例的策略。这种抽象是必需的，因为我们需要根据所检测的类型是类还是接口来遵循不同的策略。

storeInstance

 /*** Creates code that stores the probe array instance in the given variable.** @param mv*            visitor to create code* @param clinit*            true in case of {@code <clinit>} method* @param variable*            variable index to store probe array to* @return maximum stack size required by the generated code*/int storeInstance(MethodVisitor mv, boolean clinit, int variable);

创建将探针数组实例存储在给定变量中的代码。

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