org.springframework.expression.spel.CodeFlow Maven / Gradle / Ivy
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/*
* Copyright 2002-2021 the original author or authors.
*
* 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
*
* https://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 org.springframework.expression.spel;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import org.springframework.asm.ClassWriter;
import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Opcodes;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
/**
* Manages the class being generated by the compilation process.
*
* Records intermediate compilation state as the bytecode is generated.
* Also includes various bytecode generation helper functions.
*
* @author Andy Clement
* @author Juergen Hoeller
* @since 4.1
*/
public class CodeFlow implements Opcodes {
/**
* Name of the class being generated. Typically used when generating code
* that accesses freshly generated fields on the generated type.
*/
private final String className;
/**
* The current class being generated.
*/
private final ClassWriter classWriter;
/**
* Record the type of what is on top of the bytecode stack (i.e. the type of the
* output from the previous expression component). New scopes are used to evaluate
* sub-expressions like the expressions for the argument values in a method invocation
* expression.
*/
private final Deque> compilationScopes;
/**
* As SpEL ast nodes are called to generate code for the main evaluation method
* they can register to add a field to this class. Any registered FieldAdders
* will be called after the main evaluation function has finished being generated.
*/
@Nullable
private List fieldAdders;
/**
* As SpEL ast nodes are called to generate code for the main evaluation method
* they can register to add code to a static initializer in the class. Any
* registered ClinitAdders will be called after the main evaluation function
* has finished being generated.
*/
@Nullable
private List clinitAdders;
/**
* When code generation requires holding a value in a class level field, this
* is used to track the next available field id (used as a name suffix).
*/
private int nextFieldId = 1;
/**
* When code generation requires an intermediate variable within a method,
* this method records the next available variable (variable 0 is 'this').
*/
private int nextFreeVariableId = 1;
/**
* Construct a new {@code CodeFlow} for the given class.
* @param className the name of the class
* @param classWriter the corresponding ASM {@code ClassWriter}
*/
public CodeFlow(String className, ClassWriter classWriter) {
this.className = className;
this.classWriter = classWriter;
this.compilationScopes = new ArrayDeque<>();
this.compilationScopes.add(new ArrayList());
}
/**
* Push the byte code to load the target (i.e. what was passed as the first argument
* to CompiledExpression.getValue(target, context))
* @param mv the visitor into which the load instruction should be inserted
*/
public void loadTarget(MethodVisitor mv) {
mv.visitVarInsn(ALOAD, 1);
}
/**
* Push the bytecode to load the EvaluationContext (the second parameter passed to
* the compiled expression method).
* @param mv the visitor into which the load instruction should be inserted
* @since 4.3.4
*/
public void loadEvaluationContext(MethodVisitor mv) {
mv.visitVarInsn(ALOAD, 2);
}
/**
* Record the descriptor for the most recently evaluated expression element.
* @param descriptor type descriptor for most recently evaluated element
*/
public void pushDescriptor(@Nullable String descriptor) {
if (descriptor != null) {
this.compilationScopes.element().add(descriptor);
}
}
/**
* Enter a new compilation scope, usually due to nested expression evaluation. For
* example when the arguments for a method invocation expression are being evaluated,
* each argument will be evaluated in a new scope.
*/
public void enterCompilationScope() {
this.compilationScopes.push(new ArrayList<>());
}
/**
* Exit a compilation scope, usually after a nested expression has been evaluated. For
* example after an argument for a method invocation has been evaluated this method
* returns us to the previous (outer) scope.
*/
public void exitCompilationScope() {
this.compilationScopes.pop();
}
/**
* Return the descriptor for the item currently on top of the stack (in the current scope).
*/
@Nullable
public String lastDescriptor() {
return CollectionUtils.lastElement(this.compilationScopes.peek());
}
/**
* If the codeflow shows the last expression evaluated to java.lang.Boolean then
* insert the necessary instructions to unbox that to a boolean primitive.
* @param mv the visitor into which new instructions should be inserted
*/
public void unboxBooleanIfNecessary(MethodVisitor mv) {
if ("Ljava/lang/Boolean".equals(lastDescriptor())) {
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Boolean", "booleanValue", "()Z", false);
}
}
/**
* Called after the main expression evaluation method has been generated, this
* method will call back any registered FieldAdders or ClinitAdders to add any
* extra information to the class representing the compiled expression.
*/
public void finish() {
if (this.fieldAdders != null) {
for (FieldAdder fieldAdder : this.fieldAdders) {
fieldAdder.generateField(this.classWriter, this);
}
}
if (this.clinitAdders != null) {
MethodVisitor mv = this.classWriter.visitMethod(ACC_PUBLIC | ACC_STATIC, "", "()V", null, null);
mv.visitCode();
this.nextFreeVariableId = 0; // to 0 because there is no 'this' in a clinit
for (ClinitAdder clinitAdder : this.clinitAdders) {
clinitAdder.generateCode(mv, this);
}
mv.visitInsn(RETURN);
mv.visitMaxs(0,0); // not supplied due to COMPUTE_MAXS
mv.visitEnd();
}
}
/**
* Register a FieldAdder which will add a new field to the generated
* class to support the code produced by an ast nodes primary
* generateCode() method.
*/
public void registerNewField(FieldAdder fieldAdder) {
if (this.fieldAdders == null) {
this.fieldAdders = new ArrayList<>();
}
this.fieldAdders.add(fieldAdder);
}
/**
* Register a ClinitAdder which will add code to the static
* initializer in the generated class to support the code
* produced by an ast nodes primary generateCode() method.
*/
public void registerNewClinit(ClinitAdder clinitAdder) {
if (this.clinitAdders == null) {
this.clinitAdders = new ArrayList<>();
}
this.clinitAdders.add(clinitAdder);
}
public int nextFieldId() {
return this.nextFieldId++;
}
public int nextFreeVariableId() {
return this.nextFreeVariableId++;
}
public String getClassName() {
return this.className;
}
/**
* Insert any necessary cast and value call to convert from a boxed type to a
* primitive value.
* @param mv the method visitor into which instructions should be inserted
* @param ch the primitive type desired as output
* @param stackDescriptor the descriptor of the type on top of the stack
*/
public static void insertUnboxInsns(MethodVisitor mv, char ch, @Nullable String stackDescriptor) {
if (stackDescriptor == null) {
return;
}
switch (ch) {
case 'Z':
if (!stackDescriptor.equals("Ljava/lang/Boolean")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Boolean");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Boolean", "booleanValue", "()Z", false);
break;
case 'B':
if (!stackDescriptor.equals("Ljava/lang/Byte")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Byte");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Byte", "byteValue", "()B", false);
break;
case 'C':
if (!stackDescriptor.equals("Ljava/lang/Character")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Character");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Character", "charValue", "()C", false);
break;
case 'D':
if (!stackDescriptor.equals("Ljava/lang/Double")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Double");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Double", "doubleValue", "()D", false);
break;
case 'F':
if (!stackDescriptor.equals("Ljava/lang/Float")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Float");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Float", "floatValue", "()F", false);
break;
case 'I':
if (!stackDescriptor.equals("Ljava/lang/Integer")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Integer");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Integer", "intValue", "()I", false);
break;
case 'J':
if (!stackDescriptor.equals("Ljava/lang/Long")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Long");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Long", "longValue", "()J", false);
break;
case 'S':
if (!stackDescriptor.equals("Ljava/lang/Short")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Short");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Short", "shortValue", "()S", false);
break;
default:
throw new IllegalArgumentException("Unboxing should not be attempted for descriptor '" + ch + "'");
}
}
/**
* For numbers, use the appropriate method on the number to convert it to the primitive type requested.
* @param mv the method visitor into which instructions should be inserted
* @param targetDescriptor the primitive type desired as output
* @param stackDescriptor the descriptor of the type on top of the stack
*/
public static void insertUnboxNumberInsns(
MethodVisitor mv, char targetDescriptor, @Nullable String stackDescriptor) {
if (stackDescriptor == null) {
return;
}
switch (targetDescriptor) {
case 'D':
if (stackDescriptor.equals("Ljava/lang/Object")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Number");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Number", "doubleValue", "()D", false);
break;
case 'F':
if (stackDescriptor.equals("Ljava/lang/Object")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Number");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Number", "floatValue", "()F", false);
break;
case 'J':
if (stackDescriptor.equals("Ljava/lang/Object")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Number");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Number", "longValue", "()J", false);
break;
case 'I':
if (stackDescriptor.equals("Ljava/lang/Object")) {
mv.visitTypeInsn(CHECKCAST, "java/lang/Number");
}
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Number", "intValue", "()I", false);
break;
// does not handle Z, B, C, S
default:
throw new IllegalArgumentException("Unboxing should not be attempted for descriptor '" + targetDescriptor + "'");
}
}
/**
* Insert any necessary numeric conversion bytecodes based upon what is on the stack and the desired target type.
* @param mv the method visitor into which instructions should be placed
* @param targetDescriptor the (primitive) descriptor of the target type
* @param stackDescriptor the descriptor of the operand on top of the stack
*/
public static void insertAnyNecessaryTypeConversionBytecodes(MethodVisitor mv, char targetDescriptor, String stackDescriptor) {
if (CodeFlow.isPrimitive(stackDescriptor)) {
char stackTop = stackDescriptor.charAt(0);
if (stackTop == 'I' || stackTop == 'B' || stackTop == 'S' || stackTop == 'C') {
if (targetDescriptor == 'D') {
mv.visitInsn(I2D);
}
else if (targetDescriptor == 'F') {
mv.visitInsn(I2F);
}
else if (targetDescriptor == 'J') {
mv.visitInsn(I2L);
}
else if (targetDescriptor == 'I') {
// nop
}
else {
throw new IllegalStateException("Cannot get from " + stackTop + " to " + targetDescriptor);
}
}
else if (stackTop == 'J') {
if (targetDescriptor == 'D') {
mv.visitInsn(L2D);
}
else if (targetDescriptor == 'F') {
mv.visitInsn(L2F);
}
else if (targetDescriptor == 'J') {
// nop
}
else if (targetDescriptor == 'I') {
mv.visitInsn(L2I);
}
else {
throw new IllegalStateException("Cannot get from " + stackTop + " to " + targetDescriptor);
}
}
else if (stackTop == 'F') {
if (targetDescriptor == 'D') {
mv.visitInsn(F2D);
}
else if (targetDescriptor == 'F') {
// nop
}
else if (targetDescriptor == 'J') {
mv.visitInsn(F2L);
}
else if (targetDescriptor == 'I') {
mv.visitInsn(F2I);
}
else {
throw new IllegalStateException("Cannot get from " + stackTop + " to " + targetDescriptor);
}
}
else if (stackTop == 'D') {
if (targetDescriptor == 'D') {
// nop
}
else if (targetDescriptor == 'F') {
mv.visitInsn(D2F);
}
else if (targetDescriptor == 'J') {
mv.visitInsn(D2L);
}
else if (targetDescriptor == 'I') {
mv.visitInsn(D2I);
}
else {
throw new IllegalStateException("Cannot get from " + stackDescriptor + " to " + targetDescriptor);
}
}
}
}
/**
* Create the JVM signature descriptor for a method. This consists of the descriptors
* for the method parameters surrounded with parentheses, followed by the
* descriptor for the return type. Note the descriptors here are JVM descriptors,
* unlike the other descriptor forms the compiler is using which do not include the
* trailing semicolon.
* @param method the method
* @return a String signature descriptor (e.g. "(ILjava/lang/String;)V")
*/
public static String createSignatureDescriptor(Method method) {
Class[] params = method.getParameterTypes();
StringBuilder sb = new StringBuilder();
sb.append('(');
for (Class param : params) {
sb.append(toJvmDescriptor(param));
}
sb.append(')');
sb.append(toJvmDescriptor(method.getReturnType()));
return sb.toString();
}
/**
* Create the JVM signature descriptor for a constructor. This consists of the
* descriptors for the constructor parameters surrounded with parentheses, followed by
* the descriptor for the return type, which is always "V". Note the
* descriptors here are JVM descriptors, unlike the other descriptor forms the
* compiler is using which do not include the trailing semicolon.
* @param ctor the constructor
* @return a String signature descriptor (e.g. "(ILjava/lang/String;)V")
*/
public static String createSignatureDescriptor(Constructor ctor) {
Class[] params = ctor.getParameterTypes();
StringBuilder sb = new StringBuilder();
sb.append('(');
for (Class param : params) {
sb.append(toJvmDescriptor(param));
}
sb.append(")V");
return sb.toString();
}
/**
* Determine the JVM descriptor for a specified class. Unlike the other descriptors
* used in the compilation process, this is the one the JVM wants, so this one
* includes any necessary trailing semicolon (e.g. Ljava/lang/String; rather than
* Ljava/lang/String)
* @param clazz a class
* @return the JVM descriptor for the class
*/
public static String toJvmDescriptor(Class clazz) {
StringBuilder sb = new StringBuilder();
if (clazz.isArray()) {
while (clazz.isArray()) {
sb.append('[');
clazz = clazz.getComponentType();
}
}
if (clazz.isPrimitive()) {
if (clazz == Boolean.TYPE) {
sb.append('Z');
}
else if (clazz == Byte.TYPE) {
sb.append('B');
}
else if (clazz == Character.TYPE) {
sb.append('C');
}
else if (clazz == Double.TYPE) {
sb.append('D');
}
else if (clazz == Float.TYPE) {
sb.append('F');
}
else if (clazz == Integer.TYPE) {
sb.append('I');
}
else if (clazz == Long.TYPE) {
sb.append('J');
}
else if (clazz == Short.TYPE) {
sb.append('S');
}
else if (clazz == Void.TYPE) {
sb.append('V');
}
}
else {
sb.append('L');
sb.append(clazz.getName().replace('.', '/'));
sb.append(';');
}
return sb.toString();
}
/**
* Determine the descriptor for an object instance (or {@code null}).
* @param value an object (possibly {@code null})
* @return the type descriptor for the object
* (descriptor is "Ljava/lang/Object" for {@code null} value)
*/
public static String toDescriptorFromObject(@Nullable Object value) {
if (value == null) {
return "Ljava/lang/Object";
}
else {
return toDescriptor(value.getClass());
}
}
/**
* Determine whether the descriptor is for a boolean primitive or boolean reference type.
* @param descriptor type descriptor
* @return {@code true} if the descriptor is boolean compatible
*/
public static boolean isBooleanCompatible(@Nullable String descriptor) {
return (descriptor != null && (descriptor.equals("Z") || descriptor.equals("Ljava/lang/Boolean")));
}
/**
* Determine whether the descriptor is for a primitive type.
* @param descriptor type descriptor
* @return {@code true} if a primitive type
*/
public static boolean isPrimitive(@Nullable String descriptor) {
return (descriptor != null && descriptor.length() == 1);
}
/**
* Determine whether the descriptor is for a primitive array (e.g. "[[I").
* @param descriptor the descriptor for a possible primitive array
* @return {@code true} if the descriptor a primitive array
*/
public static boolean isPrimitiveArray(@Nullable String descriptor) {
if (descriptor == null) {
return false;
}
boolean primitive = true;
for (int i = 0, max = descriptor.length(); i < max; i++) {
char ch = descriptor.charAt(i);
if (ch == '[') {
continue;
}
primitive = (ch != 'L');
break;
}
return primitive;
}
/**
* Determine whether boxing/unboxing can get from one type to the other.
* Assumes at least one of the types is in boxed form (i.e. single char descriptor).
* @return {@code true} if it is possible to get (via boxing) from one descriptor to the other
*/
public static boolean areBoxingCompatible(String desc1, String desc2) {
if (desc1.equals(desc2)) {
return true;
}
if (desc1.length() == 1) {
if (desc1.equals("Z")) {
return desc2.equals("Ljava/lang/Boolean");
}
else if (desc1.equals("D")) {
return desc2.equals("Ljava/lang/Double");
}
else if (desc1.equals("F")) {
return desc2.equals("Ljava/lang/Float");
}
else if (desc1.equals("I")) {
return desc2.equals("Ljava/lang/Integer");
}
else if (desc1.equals("J")) {
return desc2.equals("Ljava/lang/Long");
}
}
else if (desc2.length() == 1) {
if (desc2.equals("Z")) {
return desc1.equals("Ljava/lang/Boolean");
}
else if (desc2.equals("D")) {
return desc1.equals("Ljava/lang/Double");
}
else if (desc2.equals("F")) {
return desc1.equals("Ljava/lang/Float");
}
else if (desc2.equals("I")) {
return desc1.equals("Ljava/lang/Integer");
}
else if (desc2.equals("J")) {
return desc1.equals("Ljava/lang/Long");
}
}
return false;
}
/**
* Determine if the supplied descriptor is for a supported number type or boolean. The
* compilation process only (currently) supports certain number types. These are
* double, float, long and int.
* @param descriptor the descriptor for a type
* @return {@code true} if the descriptor is for a supported numeric type or boolean
*/
public static boolean isPrimitiveOrUnboxableSupportedNumberOrBoolean(@Nullable String descriptor) {
if (descriptor == null) {
return false;
}
if (isPrimitiveOrUnboxableSupportedNumber(descriptor)) {
return true;
}
return ("Z".equals(descriptor) || descriptor.equals("Ljava/lang/Boolean"));
}
/**
* Determine if the supplied descriptor is for a supported number. The compilation
* process only (currently) supports certain number types. These are double, float,
* long and int.
* @param descriptor the descriptor for a type
* @return {@code true} if the descriptor is for a supported numeric type
*/
public static boolean isPrimitiveOrUnboxableSupportedNumber(@Nullable String descriptor) {
if (descriptor == null) {
return false;
}
if (descriptor.length() == 1) {
return "DFIJ".contains(descriptor);
}
if (descriptor.startsWith("Ljava/lang/")) {
String name = descriptor.substring("Ljava/lang/".length());
if (name.equals("Double") || name.equals("Float") || name.equals("Integer") || name.equals("Long")) {
return true;
}
}
return false;
}
/**
* Determine whether the given number is to be considered as an integer
* for the purposes of a numeric operation at the bytecode level.
* @param number the number to check
* @return {@code true} if it is an {@link Integer}, {@link Short} or {@link Byte}
*/
public static boolean isIntegerForNumericOp(Number number) {
return (number instanceof Integer || number instanceof Short || number instanceof Byte);
}
/**
* Convert a type descriptor to the single character primitive descriptor.
* @param descriptor a descriptor for a type that should have a primitive representation
* @return the single character descriptor for a primitive input descriptor
*/
public static char toPrimitiveTargetDesc(String descriptor) {
if (descriptor.length() == 1) {
return descriptor.charAt(0);
}
else if (descriptor.equals("Ljava/lang/Boolean")) {
return 'Z';
}
else if (descriptor.equals("Ljava/lang/Byte")) {
return 'B';
}
else if (descriptor.equals("Ljava/lang/Character")) {
return 'C';
}
else if (descriptor.equals("Ljava/lang/Double")) {
return 'D';
}
else if (descriptor.equals("Ljava/lang/Float")) {
return 'F';
}
else if (descriptor.equals("Ljava/lang/Integer")) {
return 'I';
}
else if (descriptor.equals("Ljava/lang/Long")) {
return 'J';
}
else if (descriptor.equals("Ljava/lang/Short")) {
return 'S';
}
else {
throw new IllegalStateException("No primitive for '" + descriptor + "'");
}
}
/**
* Insert the appropriate CHECKCAST instruction for the supplied descriptor.
* @param mv the target visitor into which the instruction should be inserted
* @param descriptor the descriptor of the type to cast to
*/
public static void insertCheckCast(MethodVisitor mv, @Nullable String descriptor) {
if (descriptor != null && descriptor.length() != 1) {
if (descriptor.charAt(0) == '[') {
if (isPrimitiveArray(descriptor)) {
mv.visitTypeInsn(CHECKCAST, descriptor);
}
else {
mv.visitTypeInsn(CHECKCAST, descriptor + ";");
}
}
else {
if (!descriptor.equals("Ljava/lang/Object")) {
// This is chopping off the 'L' to leave us with "java/lang/String"
mv.visitTypeInsn(CHECKCAST, descriptor.substring(1));
}
}
}
}
/**
* Determine the appropriate boxing instruction for a specific type (if it needs
* boxing) and insert the instruction into the supplied visitor.
* @param mv the target visitor for the new instructions
* @param descriptor the descriptor of a type that may or may not need boxing
*/
public static void insertBoxIfNecessary(MethodVisitor mv, @Nullable String descriptor) {
if (descriptor != null && descriptor.length() == 1) {
insertBoxIfNecessary(mv, descriptor.charAt(0));
}
}
/**
* Determine the appropriate boxing instruction for a specific type (if it needs
* boxing) and insert the instruction into the supplied visitor.
* @param mv the target visitor for the new instructions
* @param ch the descriptor of the type that might need boxing
*/
public static void insertBoxIfNecessary(MethodVisitor mv, char ch) {
switch (ch) {
case 'Z':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Boolean", "valueOf", "(Z)Ljava/lang/Boolean;", false);
break;
case 'B':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Byte", "valueOf", "(B)Ljava/lang/Byte;", false);
break;
case 'C':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Character", "valueOf", "(C)Ljava/lang/Character;", false);
break;
case 'D':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Double", "valueOf", "(D)Ljava/lang/Double;", false);
break;
case 'F':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Float", "valueOf", "(F)Ljava/lang/Float;", false);
break;
case 'I':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Integer", "valueOf", "(I)Ljava/lang/Integer;", false);
break;
case 'J':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;", false);
break;
case 'S':
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Short", "valueOf", "(S)Ljava/lang/Short;", false);
break;
case 'L':
case 'V':
case '[':
// no box needed
break;
default:
throw new IllegalArgumentException("Boxing should not be attempted for descriptor '" + ch + "'");
}
}
/**
* Deduce the descriptor for a type. Descriptors are like JVM type names but missing the
* trailing ';' so for Object the descriptor is "Ljava/lang/Object" for int it is "I".
* @param type the type (may be primitive) for which to determine the descriptor
* @return the descriptor
*/
public static String toDescriptor(Class type) {
String name = type.getName();
if (type.isPrimitive()) {
switch (name.length()) {
case 3:
return "I";
case 4:
if (name.equals("byte")) {
return "B";
}
else if (name.equals("char")) {
return "C";
}
else if (name.equals("long")) {
return "J";
}
else if (name.equals("void")) {
return "V";
}
break;
case 5:
if (name.equals("float")) {
return "F";
}
else if (name.equals("short")) {
return "S";
}
break;
case 6:
if (name.equals("double")) {
return "D";
}
break;
case 7:
if (name.equals("boolean")) {
return "Z";
}
break;
}
}
else {
if (name.charAt(0) != '[') {
return "L" + type.getName().replace('.', '/');
}
else {
if (name.endsWith(";")) {
return name.substring(0, name.length() - 1).replace('.', '/');
}
else {
return name; // array has primitive component type
}
}
}
return "";
}
/**
* Create an array of descriptors representing the parameter types for the supplied
* method. Returns a zero sized array if there are no parameters.
* @param method a Method
* @return a String array of descriptors, one entry for each method parameter
*/
public static String[] toParamDescriptors(Method method) {
return toDescriptors(method.getParameterTypes());
}
/**
* Create an array of descriptors representing the parameter types for the supplied
* constructor. Returns a zero sized array if there are no parameters.
* @param ctor a Constructor
* @return a String array of descriptors, one entry for each constructor parameter
*/
public static String[] toParamDescriptors(Constructor ctor) {
return toDescriptors(ctor.getParameterTypes());
}
/**
* Create an array of descriptors from an array of classes.
* @param types the input array of classes
* @return an array of descriptors
*/
public static String[] toDescriptors(Class[] types) {
int typesCount = types.length;
String[] descriptors = new String[typesCount];
for (int p = 0; p < typesCount; p++) {
descriptors[p] = toDescriptor(types[p]);
}
return descriptors;
}
/**
* Create the optimal instruction for loading a number on the stack.
* @param mv where to insert the bytecode
* @param value the value to be loaded
*/
public static void insertOptimalLoad(MethodVisitor mv, int value) {
if (value < 6) {
mv.visitInsn(ICONST_0+value);
}
else if (value < Byte.MAX_VALUE) {
mv.visitIntInsn(BIPUSH, value);
}
else if (value < Short.MAX_VALUE) {
mv.visitIntInsn(SIPUSH, value);
}
else {
mv.visitLdcInsn(value);
}
}
/**
* Produce appropriate bytecode to store a stack item in an array. The
* instruction to use varies depending on whether the type
* is a primitive or reference type.
* @param mv where to insert the bytecode
* @param arrayElementType the type of the array elements
*/
public static void insertArrayStore(MethodVisitor mv, String arrayElementType) {
if (arrayElementType.length()==1) {
switch (arrayElementType.charAt(0)) {
case 'I':
mv.visitInsn(IASTORE);
break;
case 'J':
mv.visitInsn(LASTORE);
break;
case 'F':
mv.visitInsn(FASTORE);
break;
case 'D':
mv.visitInsn(DASTORE);
break;
case 'B':
mv.visitInsn(BASTORE);
break;
case 'C':
mv.visitInsn(CASTORE);
break;
case 'S':
mv.visitInsn(SASTORE);
break;
case 'Z':
mv.visitInsn(BASTORE);
break;
default:
throw new IllegalArgumentException(
"Unexpected arraytype " + arrayElementType.charAt(0));
}
}
else {
mv.visitInsn(AASTORE);
}
}
/**
* Determine the appropriate T tag to use for the NEWARRAY bytecode.
* @param arraytype the array primitive component type
* @return the T tag to use for NEWARRAY
*/
public static int arrayCodeFor(String arraytype) {
switch (arraytype.charAt(0)) {
case 'I': return T_INT;
case 'J': return T_LONG;
case 'F': return T_FLOAT;
case 'D': return T_DOUBLE;
case 'B': return T_BYTE;
case 'C': return T_CHAR;
case 'S': return T_SHORT;
case 'Z': return T_BOOLEAN;
default:
throw new IllegalArgumentException("Unexpected arraytype " + arraytype.charAt(0));
}
}
/**
* Return if the supplied array type has a core component reference type.
*/
public static boolean isReferenceTypeArray(String arraytype) {
int length = arraytype.length();
for (int i = 0; i < length; i++) {
char ch = arraytype.charAt(i);
if (ch == '[') {
continue;
}
return (ch == 'L');
}
return false;
}
/**
* Produce the correct bytecode to build an array. The opcode to use and the
* signature to pass along with the opcode can vary depending on the signature
* of the array type.
* @param mv the methodvisitor into which code should be inserted
* @param size the size of the array
* @param arraytype the type of the array
*/
public static void insertNewArrayCode(MethodVisitor mv, int size, String arraytype) {
insertOptimalLoad(mv, size);
if (arraytype.length() == 1) {
mv.visitIntInsn(NEWARRAY, CodeFlow.arrayCodeFor(arraytype));
}
else {
if (arraytype.charAt(0) == '[') {
// Handling the nested array case here.
// If vararg is [[I then we want [I and not [I;
if (CodeFlow.isReferenceTypeArray(arraytype)) {
mv.visitTypeInsn(ANEWARRAY, arraytype + ";");
}
else {
mv.visitTypeInsn(ANEWARRAY, arraytype);
}
}
else {
mv.visitTypeInsn(ANEWARRAY, arraytype.substring(1));
}
}
}
/**
* For use in mathematical operators, handles converting from a (possibly boxed)
* number on the stack to a primitive numeric type.
* For example, from an Integer to a double, just need to call 'Number.doubleValue()'
* but from an int to a double, need to use the bytecode 'i2d'.
* @param mv the method visitor when instructions should be appended
* @param stackDescriptor a descriptor of the operand on the stack
* @param targetDescriptor a primitive type descriptor
*/
public static void insertNumericUnboxOrPrimitiveTypeCoercion(
MethodVisitor mv, @Nullable String stackDescriptor, char targetDescriptor) {
if (!CodeFlow.isPrimitive(stackDescriptor)) {
CodeFlow.insertUnboxNumberInsns(mv, targetDescriptor, stackDescriptor);
}
else {
CodeFlow.insertAnyNecessaryTypeConversionBytecodes(mv, targetDescriptor, stackDescriptor);
}
}
public static String toBoxedDescriptor(String primitiveDescriptor) {
switch (primitiveDescriptor.charAt(0)) {
case 'I': return "Ljava/lang/Integer";
case 'J': return "Ljava/lang/Long";
case 'F': return "Ljava/lang/Float";
case 'D': return "Ljava/lang/Double";
case 'B': return "Ljava/lang/Byte";
case 'C': return "Ljava/lang/Character";
case 'S': return "Ljava/lang/Short";
case 'Z': return "Ljava/lang/Boolean";
default:
throw new IllegalArgumentException("Unexpected non primitive descriptor " + primitiveDescriptor);
}
}
/**
* Interface used to generate fields.
*/
@FunctionalInterface
public interface FieldAdder {
void generateField(ClassWriter cw, CodeFlow codeflow);
}
/**
* Interface used to generate {@code clinit} static initializer blocks.
*/
@FunctionalInterface
public interface ClinitAdder {
void generateCode(MethodVisitor mv, CodeFlow codeflow);
}
}