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* ASM: a very small and fast Java bytecode manipulation framework
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package jdk.internal.org.objectweb.asm.signature;
A parser for signature literals, as defined in the Java Virtual Machine Specification (JVMS), to
visit them with a SignatureVisitor.
Author: Thomas Hallgren, Eric Bruneton See Also:
/**
* A parser for signature literals, as defined in the Java Virtual Machine Specification (JVMS), to
* visit them with a SignatureVisitor.
*
* @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.9.1">JVMS
* 4.7.9.1</a>
* @author Thomas Hallgren
* @author Eric Bruneton
*/
public class SignatureReader {
The JVMS signature to be read. /** The JVMS signature to be read. */
private final String signatureValue;
Constructs a SignatureReader for the given signature. Params: - signature – A JavaTypeSignature, ClassSignature or MethodSignature.
/**
* Constructs a {@link SignatureReader} for the given signature.
*
* @param signature A <i>JavaTypeSignature</i>, <i>ClassSignature</i> or <i>MethodSignature</i>.
*/
public SignatureReader(final String signature) {
this.signatureValue = signature;
}
Makes the given visitor visit the signature of this SignatureReader. This signature is the one specified in the constructor (see SignatureReader). This method is intended to be called on a SignatureReader that was created using a ClassSignature (such as
the signature parameter of the ClassVisitor.visit method) or a MethodSignature (such as the signature parameter of the ClassVisitor.visitMethod method). Params: - signatureVistor – the visitor that must visit this signature.
/**
* Makes the given visitor visit the signature of this {@link SignatureReader}. This signature is
* the one specified in the constructor (see {@link #SignatureReader}). This method is intended to
* be called on a {@link SignatureReader} that was created using a <i>ClassSignature</i> (such as
* the <code>signature</code> parameter of the {@link jdk.internal.org.objectweb.asm.ClassVisitor#visit}
* method) or a <i>MethodSignature</i> (such as the <code>signature</code> parameter of the {@link
* jdk.internal.org.objectweb.asm.ClassVisitor#visitMethod} method).
*
* @param signatureVistor the visitor that must visit this signature.
*/
public void accept(final SignatureVisitor signatureVistor) {
String signature = this.signatureValue;
int length = signature.length();
int offset; // Current offset in the parsed signature (parsed from left to right).
char currentChar; // The signature character at 'offset', or just before.
// If the signature starts with '<', it starts with TypeParameters, i.e. a formal type parameter
// identifier, followed by one or more pair ':',ReferenceTypeSignature (for its class bound and
// interface bounds).
if (signature.charAt(0) == '<') {
// Invariant: offset points to the second character of a formal type parameter name at the
// beginning of each iteration of the loop below.
offset = 2;
do {
// The formal type parameter name is everything between offset - 1 and the first ':'.
int classBoundStartOffset = signature.indexOf(':', offset);
signatureVistor.visitFormalTypeParameter(
signature.substring(offset - 1, classBoundStartOffset));
// If the character after the ':' class bound marker is not the start of a
// ReferenceTypeSignature, it means the class bound is empty (which is a valid case).
offset = classBoundStartOffset + 1;
currentChar = signature.charAt(offset);
if (currentChar == 'L' || currentChar == '[' || currentChar == 'T') {
offset = parseType(signature, offset, signatureVistor.visitClassBound());
}
// While the character after the class bound or after the last parsed interface bound
// is ':', we need to parse another interface bound.
while ((currentChar = signature.charAt(offset++)) == ':') {
offset = parseType(signature, offset, signatureVistor.visitInterfaceBound());
}
// At this point a TypeParameter has been fully parsed, and we need to parse the next one
// (note that currentChar is now the first character of the next TypeParameter, and that
// offset points to the second character), unless the character just after this
// TypeParameter signals the end of the TypeParameters.
} while (currentChar != '>');
} else {
offset = 0;
}
// If the (optional) TypeParameters is followed by '(' this means we are parsing a
// MethodSignature, which has JavaTypeSignature type inside parentheses, followed by a Result
// type and optional ThrowsSignature types.
if (signature.charAt(offset) == '(') {
offset++;
while (signature.charAt(offset) != ')') {
offset = parseType(signature, offset, signatureVistor.visitParameterType());
}
// Use offset + 1 to skip ')'.
offset = parseType(signature, offset + 1, signatureVistor.visitReturnType());
while (offset < length) {
// Use offset + 1 to skip the first character of a ThrowsSignature, i.e. '^'.
offset = parseType(signature, offset + 1, signatureVistor.visitExceptionType());
}
} else {
// Otherwise we are parsing a ClassSignature (by hypothesis on the method input), which has
// one or more ClassTypeSignature for the super class and the implemented interfaces.
offset = parseType(signature, offset, signatureVistor.visitSuperclass());
while (offset < length) {
offset = parseType(signature, offset, signatureVistor.visitInterface());
}
}
}
Makes the given visitor visit the signature of this SignatureReader. This signature is the one specified in the constructor (see SignatureReader). This method is intended to be called on a SignatureReader that was created using a JavaTypeSignature, such
as the signature parameter of the ClassVisitor.visitField or MethodVisitor.visitLocalVariable methods. Params: - signatureVisitor – the visitor that must visit this signature.
/**
* Makes the given visitor visit the signature of this {@link SignatureReader}. This signature is
* the one specified in the constructor (see {@link #SignatureReader}). This method is intended to
* be called on a {@link SignatureReader} that was created using a <i>JavaTypeSignature</i>, such
* as the <code>signature</code> parameter of the {@link
* jdk.internal.org.objectweb.asm.ClassVisitor#visitField} or {@link
* jdk.internal.org.objectweb.asm.MethodVisitor#visitLocalVariable} methods.
*
* @param signatureVisitor the visitor that must visit this signature.
*/
public void acceptType(final SignatureVisitor signatureVisitor) {
parseType(signatureValue, 0, signatureVisitor);
}
Parses a JavaTypeSignature and makes the given visitor visit it.
Params: - signature – a string containing the signature that must be parsed.
- startOffset – index of the first character of the signature to parsed.
- signatureVisitor – the visitor that must visit this signature.
Returns: the index of the first character after the parsed signature.
/**
* Parses a JavaTypeSignature and makes the given visitor visit it.
*
* @param signature a string containing the signature that must be parsed.
* @param startOffset index of the first character of the signature to parsed.
* @param signatureVisitor the visitor that must visit this signature.
* @return the index of the first character after the parsed signature.
*/
private static int parseType(
final String signature, final int startOffset, final SignatureVisitor signatureVisitor) {
int offset = startOffset; // Current offset in the parsed signature.
char currentChar = signature.charAt(offset++); // The signature character at 'offset'.
// Switch based on the first character of the JavaTypeSignature, which indicates its kind.
switch (currentChar) {
case 'Z':
case 'C':
case 'B':
case 'S':
case 'I':
case 'F':
case 'J':
case 'D':
case 'V':
// Case of a BaseType or a VoidDescriptor.
signatureVisitor.visitBaseType(currentChar);
return offset;
case '[':
// Case of an ArrayTypeSignature, a '[' followed by a JavaTypeSignature.
return parseType(signature, offset, signatureVisitor.visitArrayType());
case 'T':
// Case of TypeVariableSignature, an identifier between 'T' and ';'.
int endOffset = signature.indexOf(';', offset);
signatureVisitor.visitTypeVariable(signature.substring(offset, endOffset));
return endOffset + 1;
case 'L':
// Case of a ClassTypeSignature, which ends with ';'.
// These signatures have a main class type followed by zero or more inner class types
// (separated by '.'). Each can have type arguments, inside '<' and '>'.
int start = offset; // The start offset of the currently parsed main or inner class name.
boolean visited = false; // Whether the currently parsed class name has been visited.
boolean inner = false; // Whether we are currently parsing an inner class type.
// Parses the signature, one character at a time.
while (true) {
currentChar = signature.charAt(offset++);
if (currentChar == '.' || currentChar == ';') {
// If a '.' or ';' is encountered, this means we have fully parsed the main class name
// or an inner class name. This name may already have been visited it is was followed by
// type arguments between '<' and '>'. If not, we need to visit it here.
if (!visited) {
String name = signature.substring(start, offset - 1);
if (inner) {
signatureVisitor.visitInnerClassType(name);
} else {
signatureVisitor.visitClassType(name);
}
}
// If we reached the end of the ClassTypeSignature return, otherwise start the parsing
// of a new class name, which is necessarily an inner class name.
if (currentChar == ';') {
signatureVisitor.visitEnd();
break;
}
start = offset;
visited = false;
inner = true;
} else if (currentChar == '<') {
// If a '<' is encountered, this means we have fully parsed the main class name or an
// inner class name, and that we now need to parse TypeArguments. First, we need to
// visit the parsed class name.
String name = signature.substring(start, offset - 1);
if (inner) {
signatureVisitor.visitInnerClassType(name);
} else {
signatureVisitor.visitClassType(name);
}
visited = true;
// Now, parse the TypeArgument(s), one at a time.
while ((currentChar = signature.charAt(offset)) != '>') {
switch (currentChar) {
case '*':
// Unbounded TypeArgument.
++offset;
signatureVisitor.visitTypeArgument();
break;
case '+':
case '-':
// Extends or Super TypeArgument. Use offset + 1 to skip the '+' or '-'.
offset =
parseType(
signature, offset + 1, signatureVisitor.visitTypeArgument(currentChar));
break;
default:
// Instanceof TypeArgument. The '=' is implicit.
offset = parseType(signature, offset, signatureVisitor.visitTypeArgument('='));
break;
}
}
}
}
return offset;
default:
throw new IllegalArgumentException();
}
}
}