001    package com.thaiopensource.util;
002    
003    import java.net.URL;
004    import java.net.MalformedURLException;
005    import java.io.UnsupportedEncodingException;
006    
007    public class Uri {
008      private static String utf8 = "UTF-8";
009    
010      public static boolean isValid(String s) {
011        return isValidPercent(s) && isValidFragment(s) && isValidScheme(s);
012      }
013    
014      private static final String HEX_DIGITS = "0123456789abcdef";
015    
016      public static String escapeDisallowedChars(String s) {
017        StringBuffer buf = null;
018        int len = s.length();
019        int done = 0;
020        for (;;) {
021          int i = done;
022          for (;;) {
023            if (i == len) {
024              if (done == 0)
025                return s;
026              break;
027            }
028            if (isExcluded(s.charAt(i)))
029              break;
030            i++;
031          }
032          if (buf == null)
033            buf = new StringBuffer();
034          if (i > done) {
035            buf.append(s.substring(done, i));
036            done = i;
037          }
038          if (i == len)
039            break;
040          for (i++; i < len && isExcluded(s.charAt(i)); i++)
041            ;
042          String tem = s.substring(done, i);
043          byte[] bytes;
044          try {
045            bytes = tem.getBytes(utf8);
046          }
047          catch (UnsupportedEncodingException e) {
048            utf8 = "UTF8";
049            try {
050              bytes = tem.getBytes(utf8);
051            }
052            catch (UnsupportedEncodingException e2) {
053              // Give up
054              return s;
055            }
056          }
057          for (int j = 0; j < bytes.length; j++) {
058            buf.append('%');
059            buf.append(HEX_DIGITS.charAt((bytes[j] & 0xFF) >> 4));
060            buf.append(HEX_DIGITS.charAt(bytes[j] & 0xF));
061          }
062          done = i;
063        }
064        return buf.toString();
065      }
066    
067      private static final String excluded = "<>\"{}|\\^`";
068    
069      private static boolean isExcluded(char c) {
070        return c <= 0x20 || c >= 0x7F || excluded.indexOf(c) >= 0;
071      }
072    
073      private static boolean isAlpha(char c) {
074        return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
075      }
076    
077      private static boolean isHexDigit(char c) {
078        return ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F') || isDigit(c);
079      }
080    
081      private static boolean isDigit(char c) {
082        return '0' <= c && c <= '9';
083      }
084      
085      private static boolean isSchemeChar(char c) {
086        return isAlpha(c) || isDigit(c) || c == '+' || c == '-' || c =='.';
087      }
088    
089      private static boolean isValidPercent(String s) {
090        int len = s.length();
091        for (int i = 0; i < len; i++)
092          if (s.charAt(i) == '%') {
093            if (i + 2 >= len)
094              return false;
095            else if (!isHexDigit(s.charAt(i + 1))
096                     || !isHexDigit(s.charAt(i + 2)))
097              return false;
098          }
099        return true;
100      }
101    
102      private static boolean isValidFragment(String s) {
103        int i = s.indexOf('#');
104        return i < 0 || s.indexOf('#', i + 1) < 0;
105      }
106    
107      private static boolean isValidScheme(String s) {
108        if (!isAbsolute(s))
109          return true;
110        int i = s.indexOf(':');
111        if (i == 0
112            || i + 1 == s.length()
113            || !isAlpha(s.charAt(0)))
114          return false;
115        while (--i > 0)
116          if (!isSchemeChar(s.charAt(i)))
117            return false;
118        return true;
119      }
120    
121      public static String resolve(String baseUri, String uriReference) {
122        if (!isAbsolute(uriReference) && baseUri != null && isAbsolute(baseUri)) {
123          try {
124            return new URL(new URL(baseUri), uriReference).toString();
125          }
126          catch (MalformedURLException e) { }
127        }
128        return uriReference;
129      }
130    
131      public static boolean hasFragmentId(String uri) {
132        return uri.indexOf('#') >= 0;
133      }
134    
135      public static boolean isAbsolute(String uri) {
136        int i = uri.indexOf(':');
137        if (i < 0)
138          return false;
139        while (--i >= 0) {
140          switch (uri.charAt(i)) {
141          case '#':
142          case '/':
143          case '?':
144            return false;
145          }
146        }
147        return true;
148      }
149    }