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package com.sun.org.apache.bcel.internal.classfile;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

import com.sun.org.apache.bcel.internal.Const;

Wrapper class that parses a given Java .class file. The method parse returns a JavaClass object on success. When an I/O error or an inconsistency occurs an appropiate exception is propagated back to the caller. The structure and the names comply, except for a few conveniences, exactly with the JVM specification 1.0. See this paper for further details about the structure of a bytecode file.
/** * Wrapper class that parses a given Java .class file. The method <A * href ="#parse">parse</A> returns a <A href ="JavaClass.html"> * JavaClass</A> object on success. When an I/O error or an * inconsistency occurs an appropiate exception is propagated back to * the caller. * * The structure and the names comply, except for a few conveniences, * exactly with the <A href="http://docs.oracle.com/javase/specs/"> * JVM specification 1.0</a>. See this paper for * further details about the structure of a bytecode file. * */
public final class ClassParser { private DataInputStream dataInputStream; private final boolean fileOwned; private final String file_name; private String zip_file; private int class_name_index; private int superclass_name_index; private int major; // Compiler version private int minor; // Compiler version private int access_flags; // Access rights of parsed class private int[] interfaces; // Names of implemented interfaces private ConstantPool constant_pool; // collection of constants private Field[] fields; // class fields, i.e., its variables private Method[] methods; // methods defined in the class private Attribute[] attributes; // attributes defined in the class private final boolean is_zip; // Loaded from zip file private static final int BUFSIZE = 8192;
Parses class from the given stream.
Params:
  • inputStream – Input stream
  • file_name – File name
/** * Parses class from the given stream. * * @param inputStream Input stream * @param file_name File name */
public ClassParser(final InputStream inputStream, final String file_name) { this.file_name = file_name; fileOwned = false; final String clazz = inputStream.getClass().getName(); // Not a very clean solution ... is_zip = clazz.startsWith("java.util.zip.") || clazz.startsWith("java.util.jar."); if (inputStream instanceof DataInputStream) { this.dataInputStream = (DataInputStream) inputStream; } else { this.dataInputStream = new DataInputStream(new BufferedInputStream(inputStream, BUFSIZE)); } }
Parses class from given .class file.
Params:
  • file_name – file name
/** Parses class from given .class file. * * @param file_name file name */
public ClassParser(final String file_name) { is_zip = false; this.file_name = file_name; fileOwned = true; }
Parses class from given .class file in a ZIP-archive
Params:
  • zip_file – zip file name
  • file_name – file name
/** Parses class from given .class file in a ZIP-archive * * @param zip_file zip file name * @param file_name file name */
public ClassParser(final String zip_file, final String file_name) { is_zip = true; fileOwned = true; this.zip_file = zip_file; this.file_name = file_name; }
Parses the given Java class file and return an object that represents the contained data, i.e., constants, methods, fields and commands. A ClassFormatException is raised, if the file is not a valid .class file. (This does not include verification of the byte code as it is performed by the java interpreter).
Throws:
Returns:Class object representing the parsed class file
/** * Parses the given Java class file and return an object that represents * the contained data, i.e., constants, methods, fields and commands. * A <em>ClassFormatException</em> is raised, if the file is not a valid * .class file. (This does not include verification of the byte code as it * is performed by the java interpreter). * * @return Class object representing the parsed class file * @throws IOException * @throws ClassFormatException */
public JavaClass parse() throws IOException, ClassFormatException { ZipFile zip = null; try { if (fileOwned) { if (is_zip) { zip = new ZipFile(zip_file); final ZipEntry entry = zip.getEntry(file_name); if (entry == null) { throw new IOException("File " + file_name + " not found"); } dataInputStream = new DataInputStream(new BufferedInputStream(zip.getInputStream(entry), BUFSIZE)); } else { dataInputStream = new DataInputStream(new BufferedInputStream(new FileInputStream( file_name), BUFSIZE)); } } /****************** Read headers ********************************/ // Check magic tag of class file readID(); // Get compiler version readVersion(); /****************** Read constant pool and related **************/ // Read constant pool entries readConstantPool(); // Get class information readClassInfo(); // Get interface information, i.e., implemented interfaces readInterfaces(); /****************** Read class fields and methods ***************/ // Read class fields, i.e., the variables of the class readFields(); // Read class methods, i.e., the functions in the class readMethods(); // Read class attributes readAttributes(); // Check for unknown variables //Unknown[] u = Unknown.getUnknownAttributes(); //for (int i=0; i < u.length; i++) // System.err.println("WARNING: " + u[i]); // Everything should have been read now // if(file.available() > 0) { // int bytes = file.available(); // byte[] buf = new byte[bytes]; // file.read(buf); // if(!(is_zip && (buf.length == 1))) { // System.err.println("WARNING: Trailing garbage at end of " + file_name); // System.err.println(bytes + " extra bytes: " + Utility.toHexString(buf)); // } // } } finally { // Read everything of interest, so close the file if (fileOwned) { try { if (dataInputStream != null) { dataInputStream.close(); } } catch (final IOException ioe) { //ignore close exceptions } } try { if (zip != null) { zip.close(); } } catch (final IOException ioe) { //ignore close exceptions } } // Return the information we have gathered in a new object return new JavaClass(class_name_index, superclass_name_index, file_name, major, minor, access_flags, constant_pool, interfaces, fields, methods, attributes, is_zip ? JavaClass.ZIP : JavaClass.FILE); }
Reads information about the attributes of the class.
Throws:
/** * Reads information about the attributes of the class. * @throws IOException * @throws ClassFormatException */
private void readAttributes() throws IOException, ClassFormatException { final int attributes_count = dataInputStream.readUnsignedShort(); attributes = new Attribute[attributes_count]; for (int i = 0; i < attributes_count; i++) { attributes[i] = Attribute.readAttribute(dataInputStream, constant_pool); } }
Reads information about the class and its super class.
Throws:
/** * Reads information about the class and its super class. * @throws IOException * @throws ClassFormatException */
private void readClassInfo() throws IOException, ClassFormatException { access_flags = dataInputStream.readUnsignedShort(); /* Interfaces are implicitely abstract, the flag should be set * according to the JVM specification. */ if ((access_flags & Const.ACC_INTERFACE) != 0) { access_flags |= Const.ACC_ABSTRACT; } if (((access_flags & Const.ACC_ABSTRACT) != 0) && ((access_flags & Const.ACC_FINAL) != 0)) { throw new ClassFormatException("Class " + file_name + " can't be both final and abstract"); } class_name_index = dataInputStream.readUnsignedShort(); superclass_name_index = dataInputStream.readUnsignedShort(); }
Reads constant pool entries.
Throws:
/** * Reads constant pool entries. * @throws IOException * @throws ClassFormatException */
private void readConstantPool() throws IOException, ClassFormatException { constant_pool = new ConstantPool(dataInputStream); }
Reads information about the fields of the class, i.e., its variables.
Throws:
/** * Reads information about the fields of the class, i.e., its variables. * @throws IOException * @throws ClassFormatException */
private void readFields() throws IOException, ClassFormatException { final int fields_count = dataInputStream.readUnsignedShort(); fields = new Field[fields_count]; for (int i = 0; i < fields_count; i++) { fields[i] = new Field(dataInputStream, constant_pool); } } /******************** Private utility methods **********************/
Checks whether the header of the file is ok. Of course, this has to be the first action on successive file reads.
Throws:
/** * Checks whether the header of the file is ok. * Of course, this has to be the first action on successive file reads. * @throws IOException * @throws ClassFormatException */
private void readID() throws IOException, ClassFormatException { if (dataInputStream.readInt() != Const.JVM_CLASSFILE_MAGIC) { throw new ClassFormatException(file_name + " is not a Java .class file"); } }
Reads information about the interfaces implemented by this class.
Throws:
/** * Reads information about the interfaces implemented by this class. * @throws IOException * @throws ClassFormatException */
private void readInterfaces() throws IOException, ClassFormatException { final int interfaces_count = dataInputStream.readUnsignedShort(); interfaces = new int[interfaces_count]; for (int i = 0; i < interfaces_count; i++) { interfaces[i] = dataInputStream.readUnsignedShort(); } }
Reads information about the methods of the class.
Throws:
/** * Reads information about the methods of the class. * @throws IOException * @throws ClassFormatException */
private void readMethods() throws IOException, ClassFormatException { final int methods_count = dataInputStream.readUnsignedShort(); methods = new Method[methods_count]; for (int i = 0; i < methods_count; i++) { methods[i] = new Method(dataInputStream, constant_pool); } }
Reads major and minor version of compiler which created the file.
Throws:
/** * Reads major and minor version of compiler which created the file. * @throws IOException * @throws ClassFormatException */
private void readVersion() throws IOException, ClassFormatException { minor = dataInputStream.readUnsignedShort(); major = dataInputStream.readUnsignedShort(); } }