File	Doc	Category	Size	Date	Package
ConstantPool.java	API Doc	Java SE 5 API	11977	Fri Aug 26 14:55:16 BST 2005	com.sun.org.apache.bcel.internal.classfile

ConstantPool

• java.lang.Object

Fields Summary
private int	constant_pool_count
private Constant[]	constant_pool

Constructors Summary
public ConstantPool(Constant[] constant_pool) param constant_pool Array of constants setConstantPool(constant_pool);
ConstantPool(DataInputStream file) Read constants from given file stream. param file Input stream throw IOException throw ClassFormatError byte tag; constant_pool_count = file.readUnsignedShort(); constant_pool = new Constant[constant_pool_count]; /* constant_pool[0] is unused by the compiler and may be used freely * by the implementation. */ for(int i=1; i < constant_pool_count; i++) { constant_pool[i] = Constant.readConstant(file); /* Quote from the JVM specification: * "All eight byte constants take up two spots in the constant pool. * If this is the n'th byte in the constant pool, then the next item * will be numbered n+2" * * Thus we have to increment the index counter. */ tag = constant_pool[i].getTag(); if((tag == Constants.CONSTANT_Double) || (tag == Constants.CONSTANT_Long)) i++; }

Methods Summary
public void	accept(com.sun.org.apache.bcel.internal.classfile.Visitor v) Called by objects that are traversing the nodes of the tree implicitely defined by the contents of a Java class. I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects. param v Visitor object v.visitConstantPool(this);
public java.lang.String	constantToString(com.sun.org.apache.bcel.internal.classfile.Constant c) Resolve constant to a string representation. param constant Constant to be printed return String representation String str; int i; byte tag = c.getTag(); switch(tag) { case Constants.CONSTANT_Class: i = ((ConstantClass)c).getNameIndex(); c = getConstant(i, Constants.CONSTANT_Utf8); str = Utility.compactClassName(((ConstantUtf8)c).getBytes(), false); break; case Constants.CONSTANT_String: i = ((ConstantString)c).getStringIndex(); c = getConstant(i, Constants.CONSTANT_Utf8); str = "\"" + escape(((ConstantUtf8)c).getBytes()) + "\""; break; case Constants.CONSTANT_Utf8: str = ((ConstantUtf8)c).getBytes(); break; case Constants.CONSTANT_Double: str = "" + ((ConstantDouble)c).getBytes(); break; case Constants.CONSTANT_Float: str = "" + ((ConstantFloat)c).getBytes(); break; case Constants.CONSTANT_Long: str = "" + ((ConstantLong)c).getBytes(); break; case Constants.CONSTANT_Integer: str = "" + ((ConstantInteger)c).getBytes(); break; case Constants.CONSTANT_NameAndType: str = (constantToString(((ConstantNameAndType)c).getNameIndex(), Constants.CONSTANT_Utf8) + " " + constantToString(((ConstantNameAndType)c).getSignatureIndex(), Constants.CONSTANT_Utf8)); break; case Constants.CONSTANT_InterfaceMethodref: case Constants.CONSTANT_Methodref: case Constants.CONSTANT_Fieldref: str = (constantToString(((ConstantCP)c).getClassIndex(), Constants.CONSTANT_Class) + "." + constantToString(((ConstantCP)c).getNameAndTypeIndex(), Constants.CONSTANT_NameAndType)); break; default: // Never reached throw new RuntimeException("Unknown constant type " + tag); } return str;
public java.lang.String	constantToString(int index, byte tag) Retrieve constant at `index' from constant pool and resolve it to a string representation. param index of constant in constant pool param tag expected type return String representation Constant c = getConstant(index, tag); return constantToString(c);
public com.sun.org.apache.bcel.internal.classfile.ConstantPool	copy() return deep copy of this constant pool ConstantPool c = null; try { c = (ConstantPool)clone(); } catch(CloneNotSupportedException e) {} c.constant_pool = new Constant[constant_pool_count]; for(int i=1; i < constant_pool_count; i++) { if(constant_pool[i] != null) c.constant_pool[i] = constant_pool[i].copy(); } return c;
public void	dump(java.io.DataOutputStream file) Dump constant pool to file stream in binary format. param file Output file stream throw IOException file.writeShort(constant_pool_count); for(int i=1; i < constant_pool_count; i++) if(constant_pool[i] != null) constant_pool[i].dump(file);
private static final java.lang.String	escape(java.lang.String str) int len = str.length(); StringBuffer buf = new StringBuffer(len + 5); char[] ch = str.toCharArray(); for(int i=0; i < len; i++) { switch(ch[i]) { case '\n" : buf.append("\\n"); break; case '\r" : buf.append("\\r"); break; case '\t" : buf.append("\\t"); break; case '\b" : buf.append("\\b"); break; case '"" : buf.append("\\\""); break; default: buf.append(ch[i]); } } return buf.toString();
public com.sun.org.apache.bcel.internal.classfile.Constant	getConstant(int index) Get constant from constant pool. param index Index in constant pool return Constant value see Constant if (index >= constant_pool.length || index < 0) throw new ClassFormatError("Invalid constant pool reference: " + index + ". Constant pool size is: " + constant_pool.length); return constant_pool[index];
public com.sun.org.apache.bcel.internal.classfile.Constant	getConstant(int index, byte tag) Get constant from constant pool and check whether it has the expected type. param index Index in constant pool param tag Tag of expected constant, i.e., its type return Constant value see Constant throw ClassFormatError Constant c; c = getConstant(index); if(c == null) throw new ClassFormatError("Constant pool at index " + index + " is null."); if(c.getTag() == tag) return c; else throw new ClassFormatError("Expected class `" + Constants.CONSTANT_NAMES[tag] + "' at index " + index + " and got " + c);
public com.sun.org.apache.bcel.internal.classfile.Constant[]	getConstantPool() return Array of constants. see Constant return constant_pool;
public java.lang.String	getConstantString(int index, byte tag) Get string from constant pool and bypass the indirection of `ConstantClass' and `ConstantString' objects. I.e. these classes have an index field that points to another entry of the constant pool of type `ConstantUtf8' which contains the real data. param index Index in constant pool param tag Tag of expected constant, either ConstantClass or ConstantString return Contents of string reference see ConstantClass see ConstantString throw ClassFormatError Constant c; int i; String s; c = getConstant(index, tag); /* This switch() is not that elegant, since the two classes have the * same contents, they just differ in the name of the index * field variable. * But we want to stick to the JVM naming conventions closely though * we could have solved these more elegantly by using the same * variable name or by subclassing. */ switch(tag) { case Constants.CONSTANT_Class: i = ((ConstantClass)c).getNameIndex(); break; case Constants.CONSTANT_String: i = ((ConstantString)c).getStringIndex(); break; default: throw new RuntimeException("getConstantString called with illegal tag " + tag); } // Finally get the string from the constant pool c = getConstant(i, Constants.CONSTANT_Utf8); return ((ConstantUtf8)c).getBytes();
public int	getLength() return Length of constant pool. return constant_pool_count;
public void	setConstant(int index, com.sun.org.apache.bcel.internal.classfile.Constant constant) param constant Constant to set constant_pool[index] = constant;
public void	setConstantPool(com.sun.org.apache.bcel.internal.classfile.Constant[] constant_pool) param constant_pool this.constant_pool = constant_pool; constant_pool_count = (constant_pool == null)? 0 : constant_pool.length;
public java.lang.String	toString() return String representation. StringBuffer buf = new StringBuffer(); for(int i=1; i < constant_pool_count; i++) buf.append(i + ")" + constant_pool[i] + "\n"); return buf.toString();