Java example source code file (ConstantPoolParser.java)
The ConstantPoolParser.java Java example source code
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package sun.invoke.anon;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import static sun.invoke.anon.ConstantPoolVisitor.*;
/** A constant pool parser.
*/
public class ConstantPoolParser {
final byte[] classFile;
final byte[] tags;
final char[] firstHeader; // maghi, maglo, minor, major, cplen
// these are filled in on first parse:
int endOffset;
char[] secondHeader; // flags, this_class, super_class, intlen
// used to decode UTF8 array
private char[] charArray = new char[80];
/** Creates a constant pool parser.
* @param classFile an array of bytes containing a class.
* @throws InvalidConstantPoolFormatException if the header of the class has errors.
*/
public ConstantPoolParser(byte[] classFile) throws InvalidConstantPoolFormatException {
this.classFile = classFile;
this.firstHeader = parseHeader(classFile);
this.tags = new byte[firstHeader[4]];
}
/** Create a constant pool parser by loading the bytecodes of the
* class taken as argument.
*
* @param templateClass the class to parse.
*
* @throws IOException raised if an I/O occurs when loading
* the bytecode of the template class.
* @throws InvalidConstantPoolFormatException if the header of the class has errors.
*
* @see #ConstantPoolParser(byte[])
* @see AnonymousClassLoader#readClassFile(Class)
*/
public ConstantPoolParser(Class<?> templateClass) throws IOException, InvalidConstantPoolFormatException {
this(AnonymousClassLoader.readClassFile(templateClass));
}
/** Creates an empty patch to patch the class file
* used by the current parser.
* @return a new class patch.
*/
public ConstantPoolPatch createPatch() {
return new ConstantPoolPatch(this);
}
/** Report the tag of the indicated CP entry.
* @param index
* @return one of {@link ConstantPoolVisitor#CONSTANT_Utf8}, etc.
*/
public byte getTag(int index) {
getEndOffset(); // trigger an exception if we haven't parsed yet
return tags[index];
}
/** Report the length of the constant pool. */
public int getLength() {
return firstHeader[4];
}
/** Report the offset, within the class file, of the start of the constant pool. */
public int getStartOffset() {
return firstHeader.length * 2;
}
/** Report the offset, within the class file, of the end of the constant pool. */
public int getEndOffset() {
if (endOffset == 0)
throw new IllegalStateException("class file has not yet been parsed");
return endOffset;
}
/** Report the CP index of this class's own name. */
public int getThisClassIndex() {
getEndOffset(); // provoke exception if not yet parsed
return secondHeader[1];
}
/** Report the total size of the class file. */
public int getTailLength() {
return classFile.length - getEndOffset();
}
/** Write the head (header plus constant pool)
* of the class file to the indicated stream.
*/
public void writeHead(OutputStream out) throws IOException {
out.write(classFile, 0, getEndOffset());
}
/** Write the head (header plus constant pool)
* of the class file to the indicated stream,
* incorporating the non-null entries of the given array
* as patches.
*/
void writePatchedHead(OutputStream out, Object[] patchArray) {
// this will be useful to partially emulate the class loader on old JVMs
throw new UnsupportedOperationException("Not yet implemented");
}
/** Write the tail (everything after the constant pool)
* of the class file to the indicated stream.
*/
public void writeTail(OutputStream out) throws IOException {
out.write(classFile, getEndOffset(), getTailLength());
}
private static char[] parseHeader(byte[] classFile) throws InvalidConstantPoolFormatException {
char[] result = new char[5];
ByteBuffer buffer = ByteBuffer.wrap(classFile);
for (int i = 0; i < result.length; i++)
result[i] = (char) getUnsignedShort(buffer);
int magic = result[0] << 16 | result[1] << 0;
if (magic != 0xCAFEBABE)
throw new InvalidConstantPoolFormatException("invalid magic number "+magic);
// skip major, minor version
int len = result[4];
if (len < 1)
throw new InvalidConstantPoolFormatException("constant pool length < 1");
return result;
}
/** Parse the constant pool of the class
* calling a method visit* each time a constant pool entry is parsed.
*
* The order of the calls to visit* is not guaranteed to be the same
* than the order of the constant pool entry in the bytecode array.
*
* @param visitor
* @throws InvalidConstantPoolFormatException
*/
public void parse(ConstantPoolVisitor visitor) throws InvalidConstantPoolFormatException {
ByteBuffer buffer = ByteBuffer.wrap(classFile);
buffer.position(getStartOffset()); //skip header
Object[] values = new Object[getLength()];
try {
parseConstantPool(buffer, values, visitor);
} catch(BufferUnderflowException e) {
throw new InvalidConstantPoolFormatException(e);
}
if (endOffset == 0) {
endOffset = buffer.position();
secondHeader = new char[4];
for (int i = 0; i < secondHeader.length; i++) {
secondHeader[i] = (char) getUnsignedShort(buffer);
}
}
resolveConstantPool(values, visitor);
}
private char[] getCharArray(int utfLength) {
if (utfLength <= charArray.length)
return charArray;
return charArray = new char[utfLength];
}
private void parseConstantPool(ByteBuffer buffer, Object[] values, ConstantPoolVisitor visitor) throws InvalidConstantPoolFormatException {
for (int i = 1; i < tags.length; ) {
byte tag = (byte) getUnsignedByte(buffer);
assert(tags[i] == 0 || tags[i] == tag);
tags[i] = tag;
switch (tag) {
case CONSTANT_Utf8:
int utfLen = getUnsignedShort(buffer);
String value = getUTF8(buffer, utfLen, getCharArray(utfLen));
visitor.visitUTF8(i, CONSTANT_Utf8, value);
tags[i] = tag;
values[i++] = value;
break;
case CONSTANT_Integer:
visitor.visitConstantValue(i, tag, buffer.getInt());
i++;
break;
case CONSTANT_Float:
visitor.visitConstantValue(i, tag, buffer.getFloat());
i++;
break;
case CONSTANT_Long:
visitor.visitConstantValue(i, tag, buffer.getLong());
i+=2;
break;
case CONSTANT_Double:
visitor.visitConstantValue(i, tag, buffer.getDouble());
i+=2;
break;
case CONSTANT_Class: // fall through:
case CONSTANT_String:
tags[i] = tag;
values[i++] = new int[] { getUnsignedShort(buffer) };
break;
case CONSTANT_Fieldref: // fall through:
case CONSTANT_Methodref: // fall through:
case CONSTANT_InterfaceMethodref: // fall through:
case CONSTANT_NameAndType:
tags[i] = tag;
values[i++] = new int[] { getUnsignedShort(buffer), getUnsignedShort(buffer) };
break;
default:
throw new AssertionError("invalid constant "+tag);
}
}
}
private void resolveConstantPool(Object[] values, ConstantPoolVisitor visitor) {
// clean out the int[] values, which are temporary
for (int beg = 1, end = values.length-1, beg2, end2;
beg <= end;
beg = beg2, end = end2) {
beg2 = end; end2 = beg-1;
//System.out.println("CP resolve pass: "+beg+".."+end);
for (int i = beg; i <= end; i++) {
Object value = values[i];
if (!(value instanceof int[]))
continue;
int[] array = (int[]) value;
byte tag = tags[i];
switch (tag) {
case CONSTANT_String:
String stringBody = (String) values[array[0]];
visitor.visitConstantString(i, tag, stringBody, array[0]);
values[i] = null;
break;
case CONSTANT_Class: {
String className = (String) values[array[0]];
// use the external form favored by Class.forName:
className = className.replace('/', '.');
visitor.visitConstantString(i, tag, className, array[0]);
values[i] = className;
break;
}
case CONSTANT_NameAndType: {
String memberName = (String) values[array[0]];
String signature = (String) values[array[1]];
visitor.visitDescriptor(i, tag, memberName, signature,
array[0], array[1]);
values[i] = new String[] {memberName, signature};
break;
}
case CONSTANT_Fieldref: // fall through:
case CONSTANT_Methodref: // fall through:
case CONSTANT_InterfaceMethodref: {
Object className = values[array[0]];
Object nameAndType = values[array[1]];
if (!(className instanceof String) ||
!(nameAndType instanceof String[])) {
// one more pass is needed
if (beg2 > i) beg2 = i;
if (end2 < i) end2 = i;
continue;
}
String[] nameAndTypeArray = (String[]) nameAndType;
visitor.visitMemberRef(i, tag,
(String)className,
nameAndTypeArray[0],
nameAndTypeArray[1],
array[0], array[1]);
values[i] = null;
}
break;
default:
continue;
}
}
}
}
private static int getUnsignedByte(ByteBuffer buffer) {
return buffer.get() & 0xFF;
}
private static int getUnsignedShort(ByteBuffer buffer) {
int b1 = getUnsignedByte(buffer);
int b2 = getUnsignedByte(buffer);
return (b1 << 8) + (b2 << 0);
}
private static String getUTF8(ByteBuffer buffer, int utfLen, char[] charArray) throws InvalidConstantPoolFormatException {
int utfLimit = buffer.position() + utfLen;
int index = 0;
while (buffer.position() < utfLimit) {
int c = buffer.get() & 0xff;
if (c > 127) {
buffer.position(buffer.position() - 1);
return getUTF8Extended(buffer, utfLimit, charArray, index);
}
charArray[index++] = (char)c;
}
return new String(charArray, 0, index);
}
private static String getUTF8Extended(ByteBuffer buffer, int utfLimit, char[] charArray, int index) throws InvalidConstantPoolFormatException {
int c, c2, c3;
while (buffer.position() < utfLimit) {
c = buffer.get() & 0xff;
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
/* 0xxxxxxx*/
charArray[index++] = (char)c;
break;
case 12: case 13:
/* 110x xxxx 10xx xxxx*/
c2 = buffer.get();
if ((c2 & 0xC0) != 0x80)
throw new InvalidConstantPoolFormatException(
"malformed input around byte " + buffer.position());
charArray[index++] = (char)(((c & 0x1F) << 6) |
(c2 & 0x3F));
break;
case 14:
/* 1110 xxxx 10xx xxxx 10xx xxxx */
c2 = buffer.get();
c3 = buffer.get();
if (((c2 & 0xC0) != 0x80) || ((c3 & 0xC0) != 0x80))
throw new InvalidConstantPoolFormatException(
"malformed input around byte " + (buffer.position()));
charArray[index++] = (char)(((c & 0x0F) << 12) |
((c2 & 0x3F) << 6) |
((c3 & 0x3F) << 0));
break;
default:
/* 10xx xxxx, 1111 xxxx */
throw new InvalidConstantPoolFormatException(
"malformed input around byte " + buffer.position());
}
}
// The number of chars produced may be less than utflen
return new String(charArray, 0, index);
}
}
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