Source for gnu.java.lang.reflect.TypeSignature

   1: /* TypeSignature.java -- Class used to compute type signatures
   2:    Copyright (C) 1998, 2000, 2002 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.lang.reflect;
  40: 
  41: import gnu.java.lang.CPStringBuilder;
  42: 
  43: import java.lang.reflect.Constructor;
  44: import java.lang.reflect.Field;
  45: import java.lang.reflect.Member;
  46: import java.lang.reflect.Method;
  47: 
  48: /**
  49:  * This class provides static methods that can be used to compute
  50:  * type-signatures of <code>Class</code>s or <code>Member</code>s.
  51:  * More specific methods are also provided for computing the
  52:  * type-signature of <code>Constructor</code>s and
  53:  * <code>Method</code>s.  Methods are also provided to go in the
  54:  * reverse direction.
  55:  *
  56:  * @author Eric Blake (ebb9@email.byu.edu)
  57:  */
  58: public class TypeSignature
  59: {
  60:   /**
  61:    * Returns a <code>String</code> representing the type-encoding of a class.
  62:    * The .class file format has different encodings for classes, depending
  63:    * on whether it must be disambiguated from primitive types or not; hence
  64:    * the descriptor parameter to choose between them. If you are planning
  65:    * on decoding primitive types along with classes, then descriptor should
  66:    * be true for correct results. Type-encodings are computed as follows:
  67:    *
  68:    * <pre>
  69:    * boolean -> "Z"
  70:    * byte    -> "B"
  71:    * char    -> "C"
  72:    * double  -> "D"
  73:    * float   -> "F"
  74:    * int     -> "I"
  75:    * long    -> "J"
  76:    * short   -> "S"
  77:    * void    -> "V"
  78:    * arrays  -> "[" + descriptor format of component type
  79:    * object  -> class format: fully qualified name with '.' replaced by '/'
  80:    *            descriptor format: "L" + class format + ";"
  81:    * </pre>
  82:    *
  83:    * @param type the class name to encode
  84:    * @param descriptor true to return objects in descriptor format
  85:    * @return the class name, as it appears in bytecode constant pools
  86:    * @see #getClassForEncoding(String)
  87:    */
  88:   public static String getEncodingOfClass(String type, boolean descriptor)
  89:   {
  90:     if (! descriptor || type.charAt(0) == '[')
  91:       return type.replace('.', '/');
  92:     if (type.equals("boolean"))
  93:       return "Z";
  94:     if (type.equals("byte"))
  95:       return "B";
  96:     if (type.equals("short"))
  97:       return "S";
  98:     if (type.equals("char"))
  99:       return "C";
 100:     if (type.equals("int"))
 101:       return "I";
 102:     if (type.equals("long"))
 103:       return "J";
 104:     if (type.equals("float"))
 105:       return "F";
 106:     if (type.equals("double"))
 107:       return "D";
 108:     if (type.equals("void"))
 109:       return "V";
 110:     return 'L' + type.replace('.', '/') + ';';
 111:   }
 112: 
 113:   /**
 114:    * Gets the descriptor encoding for a class.
 115:    *
 116:    * @param clazz the class to encode
 117:    * @param descriptor true to return objects in descriptor format
 118:    * @return the class name, as it appears in bytecode constant pools
 119:    * @see #getEncodingOfClass(String, boolean)
 120:    */
 121:   public static String getEncodingOfClass(Class clazz, boolean descriptor)
 122:   {
 123:     return getEncodingOfClass(clazz.getName(), descriptor);
 124:   }
 125: 
 126:   /**
 127:    * Gets the descriptor encoding for a class.
 128:    *
 129:    * @param clazz the class to encode
 130:    * @return the class name, as it appears in bytecode constant pools
 131:    * @see #getEncodingOfClass(String, boolean)
 132:    */
 133:   public static String getEncodingOfClass(Class clazz)
 134:   {
 135:     return getEncodingOfClass(clazz.getName(), true);
 136:   }
 137: 
 138: 
 139:   /**
 140:    * This function is the inverse of <code>getEncodingOfClass</code>. This
 141:    * accepts both object and descriptor formats, but must know which style
 142:    * of string is being passed in (usually, descriptor should be true). In
 143:    * descriptor format, "I" is treated as int.class, in object format, it
 144:    * is treated as a class named I in the unnamed package. This method is
 145:    * strictly equivalent to {@link #getClassForEncoding(java.lang.String, boolean, java.lang.ClassLoader)}
 146:    * with a class loader equal to <code>null</code>. In that case, it
 147:    * uses the default class loader on the calling stack.
 148:    *
 149:    * @param type_code the class name to decode
 150:    * @param descriptor if the string is in descriptor format
 151:    * @return the corresponding Class object
 152:    * @throws ClassNotFoundException if the class cannot be located
 153:    * @see #getEncodingOfClass(Class, boolean)
 154:    */
 155:   public static Class getClassForEncoding(String type_code, boolean descriptor)
 156:     throws ClassNotFoundException
 157:   {
 158:     return getClassForEncoding(type_code, descriptor, null);
 159:   }
 160: 
 161:   /**
 162:    * This function is the inverse of <code>getEncodingOfClass</code>. This
 163:    * accepts both object and descriptor formats, but must know which style
 164:    * of string is being passed in (usually, descriptor should be true). In
 165:    * descriptor format, "I" is treated as int.class, in object format, it
 166:    * is treated as a class named I in the unnamed package.
 167:    *
 168:    * @param type_code The class name to decode.
 169:    * @param descriptor If the string is in descriptor format.
 170:    * @param loader The class loader when resolving generic object name. If
 171:    * <code>loader</code> is null then it uses the default class loader on the
 172:    * calling stack.
 173:    * @return the corresponding Class object.
 174:    * @throws ClassNotFoundException if the class cannot be located.
 175:    * @see #getEncodingOfClass(Class, boolean)
 176:    * @see #getClassForEncoding(String, boolean)
 177:    */
 178:   public static Class getClassForEncoding(String type_code, boolean descriptor,
 179:                                           ClassLoader loader)
 180:     throws ClassNotFoundException
 181:   {
 182:     if (descriptor)
 183:       {
 184:         switch (type_code.charAt(0))
 185:           {
 186:           case 'B':
 187:             return byte.class;
 188:           case 'C':
 189:             return char.class;
 190:           case 'D':
 191:             return double.class;
 192:           case 'F':
 193:             return float.class;
 194:           case 'I':
 195:             return int.class;
 196:           case 'J':
 197:             return long.class;
 198:           case 'S':
 199:             return short.class;
 200:           case 'V':
 201:             return void.class;
 202:           case 'Z':
 203:             return boolean.class;
 204:           default:
 205:             throw new ClassNotFoundException("Invalid class name: "
 206:                                              + type_code);
 207:           case 'L':
 208:             type_code = type_code.substring(1, type_code.length() - 1);
 209:             // Fallthrough.
 210:           case '[':
 211:           }
 212:       }
 213:     return Class.forName(type_code.replace('/', '.'), true, loader);
 214:   }
 215: 
 216:   /**
 217:    * Gets the Class object for a type name.
 218:    *
 219:    * @param type_code the class name to decode
 220:    * @return the corresponding Class object
 221:    * @throws ClassNotFoundException if the class cannot be located
 222:    * @see #getClassForEncoding(String, boolean)
 223:    */
 224:   public static Class getClassForEncoding(String type_code)
 225:     throws ClassNotFoundException
 226:   {
 227:     return getClassForEncoding(type_code, true);
 228:   }
 229: 
 230:   /**
 231:    * Returns a <code>String</code> representing the type-encoding of a
 232:    * method.  The type-encoding of a method is:
 233:    *
 234:    * "(" + parameter type descriptors + ")" + return type descriptor
 235:    *
 236:    * XXX This could be faster if it were implemented natively.
 237:    *
 238:    * @param m the method to encode
 239:    * @return the encoding
 240:    */
 241:   public static String getEncodingOfMethod(Method m)
 242:   {
 243:     Class[] paramTypes = m.getParameterTypes();
 244:     CPStringBuilder buf = new CPStringBuilder("(");
 245:     for (int i = 0; i < paramTypes.length; i++)
 246:       buf.append(getEncodingOfClass(paramTypes[i].getName(), true));
 247:     buf.append(')').append(getEncodingOfClass(m.getReturnType().getName(),
 248:                                               true));
 249:     return buf.toString();
 250:   }
 251: 
 252:   /**
 253:    * Returns a <code>String</code> representing the type-encoding of a
 254:    * constructor. The type-encoding of a method is:
 255:    *
 256:    * "(" + parameter type descriptors + ")V"
 257:    *
 258:    * XXX This could be faster if it were implemented natively.
 259:    *
 260:    * @param c the constructor to encode
 261:    * @return the encoding
 262:    */
 263:   public static String getEncodingOfConstructor(Constructor c)
 264:   {
 265:     Class[] paramTypes = c.getParameterTypes();
 266:     CPStringBuilder buf = new CPStringBuilder("(");
 267:     for (int i = 0; i < paramTypes.length; i++)
 268:       buf.append(getEncodingOfClass(paramTypes[i].getName(), true));
 269:     buf.append(")V");
 270:     return buf.toString();
 271:   }
 272: 
 273:   /**
 274:    * Returns a <code>String</code> representing the type-encoding of a
 275:    * class member. This appropriately handles Constructors, Methods, and
 276:    * Fields.
 277:    *
 278:    * @param mem the member to encode
 279:    * @return the encoding
 280:    */
 281:   public static String getEncodingOfMember(Member mem)
 282:   {
 283:     if (mem instanceof Constructor)
 284:       return getEncodingOfConstructor((Constructor) mem);
 285:     if (mem instanceof Method)
 286:       return getEncodingOfMethod((Method) mem);
 287:     else // Field
 288:       return getEncodingOfClass(((Field) mem).getType().getName(), true);
 289:   }
 290: } // class TypeSignature