Source for gnu.java.io.PlatformHelper

   1: /* PlatformHelper.java -- Isolate OS-specific IO helper methods and variables
   2:    Copyright (C) 1998, 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: package gnu.java.io;
  39: 
  40: import java.util.StringTokenizer;
  41: 
  42: /**
  43:  * We had many changes in File.java, URLStreamHandler.java etc. to handle
  44:  * path representations on different platforms (Windows/Unix-family).
  45:  * Finally we'd like to collect all these ad hoc codes into this utility class.
  46:  *       --Gansha
  47:  */
  48: public class PlatformHelper
  49: {
  50:   public static final boolean isWindows = System.getProperty("os.name").indexOf("Windows") >= 0;
  51:   public static final String separator = System.getProperty("file.separator");
  52:   public static final char separatorChar = separator.charAt(0);
  53:   public static final String pathSeparator = System.getProperty("path.separator");
  54:   public static final char pathSeparatorChar = pathSeparator.charAt(0);
  55: 
  56:   /**
  57:    * On most platforms 260 is equal or greater than a max path value, 
  58:    * so we can set the initial buffer size of StringBuffer to half of this value
  59:    * to improve performance.
  60:    */
  61:   public static final int INITIAL_MAX_PATH = 260/2;
  62: 
  63:   /**
  64:    * This routine checks the input param "path" whether it begins with root path
  65:    * prefix.
  66:    * if not, return 0;
  67:    * if yes, return the len of root path prefix;
  68:    *   --for Unix-family platform, root path begins with "/" and len is 1
  69:    *   --for Windows platform, root path begins with "drive:\\" and len is 3
  70:    */
  71:   public static final int beginWithRootPathPrefix(String path)
  72:   {
  73:     if (path.startsWith("/") || path.startsWith("\\"))
  74:       return 1;
  75: 
  76:     if (!isWindows)
  77:       return 0;
  78: 
  79:     if (path.length() > 2
  80:         && Character.isLetter(path.charAt(0))
  81:         && path.charAt(1) == ':'
  82:         && (path.charAt(2) == '/' || path.charAt(2) == '\\'))
  83:       return 3;
  84: 
  85:     return 0;
  86:   }
  87: 
  88:   /**
  89:    * This routine checks the input param "path" whether it's root directory.
  90:    *  --for Unix-family platform, root directory is "/"
  91:    *  --for Windows platform, root directory is "\\" or "drive:\\".
  92:    */
  93:   public static final boolean isRootDirectory(String path)
  94:   {
  95:     int len = path.length();
  96:     return len > 0 && beginWithRootPathPrefix(path) == len;
  97:   }
  98: 
  99:   /**
 100:    * This routine canonicalizes input param "path" to formal path representation
 101:    *  for current platform, including interpreting ".." and "." .
 102:    */
 103:   public static final String toCanonicalForm(String path)
 104:   {
 105:     /*??
 106:     if(path.indexOf('.') < 0 && path.indexOf("..") < 0)
 107:         return path; 
 108:     */
 109:     String tmppath = path.replace('/', separatorChar);
 110:     StringBuffer canonpath;
 111: 
 112:     int i;
 113: 
 114:     if ((i = beginWithRootPathPrefix(tmppath)) == 0 )
 115:       return path;
 116:     
 117:     /* The original 
 118:            "canonpath = new StringBuffer(tmppath.substring(0, i))"
 119:        isn't very efficient because StringBuffer's 
 120:        ensureCapacity_unsynchronized will fail definitely each time 
 121:        and will enlarge buffer and copy contents.       .
 122:     */
 123:     canonpath = new StringBuffer(INITIAL_MAX_PATH);
 124:     canonpath.append(tmppath.substring(0, i));
 125:     tmppath = tmppath.substring(i);
 126:     // pathdepth==0 indicates there're only root path in the buffer
 127:     int pathdepth = 0;
 128:     
 129:     StringTokenizer st = new StringTokenizer(tmppath, separator);
 130:     
 131:     // Traverse each element of the path, handling "." and ".."
 132:     // Should handle "~" too?
 133:     if (st.hasMoreTokens())
 134:       do
 135:         {
 136:           String s = st.nextToken();
 137:         
 138:           // Handle "." or an empty element.  
 139:           if (s.equals(".") || s.equals(""))
 140:             continue;
 141:         
 142:           // Handle ".." by deleting the last element from the path
 143:           if (s.equals(".."))
 144:             {
 145:               if (pathdepth == 0)
 146:                 continue;
 147: 
 148:               // Strip of trailing separator
 149:               canonpath.setLength(canonpath.length() - 1/*separator.length()*/);
 150:               String tmpstr = canonpath.toString();
 151:               int idx = tmpstr.lastIndexOf(separator); 
 152: 
 153:               if ((idx == -1) || ((idx + 1/*separator.length()*/) > tmpstr.length()))
 154:                 //throw new IOException("Can't happen error"); 
 155:                 return path; // Shouldn't happen 
 156:         
 157:               canonpath.setLength(idx + 1/*separator.length()*/);
 158:               pathdepth--;
 159:               continue;
 160:             }
 161:         
 162:           canonpath.append(s);
 163:           pathdepth++; //now it's more than root path
 164: 
 165:           if (st.hasMoreTokens())
 166:             canonpath.append(separator);
 167:         }
 168:       while (st.hasMoreTokens());
 169:     
 170:     if (endWithSeparator(path))
 171:       canonpath.append(separator);
 172:         
 173:     String tmpstr = canonpath.toString();
 174:     //if (pathdepth > 0 && endWithSeparator(tmpstr) )
 175:     //    tmpstr = tmpstr.substring(0, tmpstr.length() - 1/*separator.length()*/);
 176:     
 177:     return tmpstr;
 178:   }
 179: 
 180:   /**
 181:    * This routine canonicalizes input param "path" to formal path representation
 182:    *  for current platform, and normalize all separators to "sepchar".
 183:    */
 184:   public static final String toCanonicalForm(String path, char sepchar)
 185:   {
 186:     String tmpstr = toCanonicalForm(path);
 187:     tmpstr = tmpstr.replace(separatorChar, sepchar);
 188:     return tmpstr;
 189:   }
 190: 
 191:   /**
 192:    * This routine checks whether input param "path" ends with separator
 193:    */
 194:   public static final boolean endWithSeparator(String path)
 195:   {
 196:     if (path.endsWith("\\") || path.endsWith("/"))
 197:       return true;
 198: 
 199:     return false;
 200:   }
 201: 
 202:   /**
 203:    * This routine removes from input param "path" the tail separator if it exists, 
 204:    * and return the remain part.
 205:    */
 206:   public static final String removeTailSeparator(String path)
 207:   {
 208:     if (endWithSeparator(path) && !isRootDirectory(path))
 209:       return path.substring(0, path.length() - 1);
 210: 
 211:     return path;
 212:   }
 213: 
 214:   /**
 215:    * This routine returns last index of separator in input param "path", 
 216:    * and return it.
 217:    */
 218:   public static final int lastIndexOfSeparator(String path)
 219:   {
 220:     return Math.max(path.lastIndexOf("/"), path.lastIndexOf("\\"));
 221:   }
 222: 
 223: }