libjava/java/io/FilePermission.java

/* java.lang.FilePermission
   Copyright (C) 1998, 2000 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.io;

import java.security.*;


public final class FilePermission extends Permission implements Serializable {
  private static final String CURRENT_DIRECTORY = System.getProperty("user.dir");
  private boolean usingPerms = false;
  private boolean readPerm = false;
  private boolean writePerm = false;
  private boolean executePerm = false;
  private boolean deletePerm = false;
  private String actionsString;
  
  private void cachePerms() {
    // While race conditions could occur, they don't matter at all.
    
    String action;
    int i = actionsString.indexOf(',');
    int startI = 0;
    while(i != -1) {
      action = actionsString.substring(startI,i);
      if(action.equals("read"))
	readPerm = true;
      else if(action.equals("write"))
	writePerm = true;
      else if(action.equals("execute"))
	executePerm = true;
      else if(action.equals("delete"))
	deletePerm = true;
      
      startI = i+1;
      i = actionsString.indexOf(',',startI);
    }
    
    action = actionsString.substring(startI);
    if(action.equals("read"))
      readPerm = true;
    else if(action.equals("write"))
      writePerm = true;
    else if(action.equals("execute"))
      executePerm = true;
    else if(action.equals("delete"))
      deletePerm = true;
  }
  
  /** Create a new FilePermission.
   ** @param pathExpression an expression specifying the paths this
   **        permission represents.
   ** @param actionsString a comma-separated list of the actions this
   **        permission represents.
   ** @XXX what to do when the file string is malformed?
   **/
  public FilePermission(String pathExpression, String actionsString) 
    {
      super(pathExpression);
      this.actionsString = actionsString;
    }
  
  /** Get the actions this FilePermission supports.
   ** @return the String representing the actions this FilePermission supports.
   **/
  public String getActions() {
    return actionsString;
  }
  
  /** Get the hash code for this Object.<P>
   ** FilePermission's hash code is calculated as the exclusive or of the target
   ** String's hash code and the action String's hash code.
   ** @specnote Sun did not specify how to calculate the hash code; I made this up.
   ** @return the hash code for this Object.
   **/
  public int hashCode() {
    return getName().hashCode() ^ actionsString.hashCode();
  }
  
  /** Check two FilePermissions for semantic equality.
   ** Two FilePermissions are exactly equivalent if they have identical path
   ** expressions and have exactly the same access permissions.
   ** @param o the Object to compare to.
   ** @return whether the Objects are semantically equivalent.
   **/
  public boolean equals(Object o) {
    if(!(o instanceof FilePermission))
      return false;
    FilePermission p = (FilePermission)o;
    if(!usingPerms)
      cachePerms();
    if(!p.usingPerms)
      p.cachePerms();
    
    String f1 = getName();
    String f2 = p.getName();

    /* Compare names, taking into account if they refer to a
     * directory and one has a separator and the other does not.
     */
    if(f1.charAt(f1.length()) == File.separatorChar) {
      if(f2.charAt(f2.length()) == File.separatorChar) {
	if(!f2.equals(f1))
	  return false;
      } else {
	if(!f2.equals(f1.substring(0,f1.length()-1)))
	  return false;
      }
    } else {
      if(f2.charAt(f2.length()) == File.separatorChar) {
	if(!f1.equals(f2.substring(0,f2.length()-1)))
	  return false;
      } else {
	if(!f1.equals(f2))
	  return false;
      }
    }
    return readPerm == p.readPerm && writePerm == p.writePerm && executePerm == p.executePerm && deletePerm == p.deletePerm;
  }
  
  /** Check to see if this permission implies another.
   ** Permission A implies permission B if these things are all true:
   ** <OL>
   ** <LI>A and B are both FilePermissions.</LI>
   ** <LI>All possible files in B are included in A (possibly more are in A).</LI>
   ** <LI>All actions B supports, A also supports.</LI>
   ** </OL>
   ** @param p the Permission to compare against.
   ** @return whether this Permission implies p
   **/
  public boolean implies(Permission p) {
    FilePermission fp;
    if(!(p instanceof FilePermission))
      return false;
    fp = (FilePermission)p;
    
    String f1 = getName();
    String f2 = fp.getName();
    if(f1.charAt(0) != File.separatorChar) {
      f1 = CURRENT_DIRECTORY + f1;
    }
    if(f2.charAt(0) != File.separatorChar) {
      f2 = CURRENT_DIRECTORY + f2;
    }
    
    String sub1, sub2a, sub2b;
    switch(f1.charAt(f1.length() - 1)) {
    case '*':
      sub1 = f1.substring(0,f1.length() - 1); // chop off "*"
      if(f2.length() <= sub1.length()) {
	/* If it's smaller, there is no way it could be part of this directory.
	 * If it's the same (or length - 1), it could be the same directory but
	 * specifies access to the directory rather than the files in it.
	 */
	return false;
      } else if(f2.charAt(sub1.length() - 1) == File.separatorChar) {
	/* Make sure the part before the "/" is the same */
	if(!f2.substring(0,sub1.length()).equals(sub1))
	  return false;
	/* Make sure there are no subdirectories specified underneath this one */
	String sub2 = f2.substring(sub1.length()+1);
	if(f2.substring(sub1.length()+1).indexOf(File.separatorChar) != -1)
	  return false;
      } else {
	/* Obviously not equal: f2 is either not a directory or is not
	 * the same directory (its name continues further than we want)
	 */
	return false;
      }
      break;
    case '-':
      sub1 = f1.substring(0,f1.length() - 2); // chop off "/-"
      if(f2.length() < sub1.length()) {
	/* If it's smaller, there is no way it could be part of this directory. */
	return false;
      } else if(f2.length() > sub1.length() && f2.charAt(sub1.length()) != File.separatorChar) {
	return false;
      } else if(!f2.substring(0,sub1.length()).equals(sub1))
	return false;
      break;
/* Looks redundant with default case and won't compile anyway - arenn
    case File.separatorChar:
      if(f2.charAt(f2.length()) == File.separatorChar) {
	if(!f2.equals(f1))
	  return false;
      } else {
	if(!f2.equals(f1.substring(0,f1.length()-1)))
	  return false;
      }
      break;
*/
    default:
      if(f2.charAt(f2.length()) == File.separatorChar) {
	if(!f1.equals(f2.substring(0,f2.length()-1)))
	  return false;
      } else {
	if(!f1.equals(f2))
	  return false;
      }
      break;
    }
    
    if(!usingPerms)
      cachePerms();
    if(!fp.usingPerms)
      fp.cachePerms();
    
    if(readPerm && !fp.readPerm)
      return false;
    if(writePerm && !fp.writePerm)
      return false;
    if(executePerm && !fp.executePerm)
      return false;
    if(deletePerm && !fp.deletePerm)
      return false;
    
    return true;
  }
}