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JSONTokener.java

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.sf.json.util;

import net.sf.json.JSONArray;
import net.sf.json.JSONException;
import net.sf.json.JSONNull;
import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.regexp.RegexpUtils;

/*
Copyright (c) 2002 JSON.org

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

The Software shall be used for Good, not Evil.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/**
 * A JSONTokener takes a source string and extracts characters and tokens from
 * it. It is used by the JSONObject and JSONArray constructors to parse JSON
 * source strings.
 *
 * @author JSON.org
 * @version 4
 */
00057 public class JSONTokener {
   /**
    * Get the hex value of a character (base16).
    *
    * @param c A character between '0' and '9' or between 'A' and 'F' or between
    *        'a' and 'f'.
    * @return An int between 0 and 15, or -1 if c was not a hex digit.
    */
00065    public static int dehexchar( char c ) {
      if( c >= '0' && c <= '9' ){
         return c - '0';
      }
      if( c >= 'A' && c <= 'F' ){
         return c - ('A' - 10);
      }
      if( c >= 'a' && c <= 'f' ){
         return c - ('a' - 10);
      }
      return -1;
   }

   /**
    * The index of the next character.
    */
00081    private int myIndex;

   /**
    * The source string being tokenized.
    */
00086    private String mySource;

   /**
    * Construct a JSONTokener from a string.
    *
    * @param s A source string.
    */
00093    public JSONTokener( String s ) {
      this.myIndex = 0;
      this.mySource = s;
   }

   /**
    * Back up one character. This provides a sort of lookahead capability, so
    * that you can test for a digit or letter before attempting to parse the
    * next number or identifier.
    */
00103    public void back() {
      if( this.myIndex > 0 ){
         this.myIndex -= 1;
      }
   }

   public int length() {
      if( this.mySource == null ){
         return 0;
      }
      return this.mySource.length();
   }

   public boolean matches( String pattern ) {
      String str = this.mySource.substring( this.myIndex );
      return RegexpUtils.getMatcher( pattern )
            .matches( str );
   }

   /**
    * Determine if the source string still contains characters that next() can
    * consume.
    *
    * @return true if not yet at the end of the source.
    */
00128    public boolean more() {
      return this.myIndex < this.mySource.length();
   }

   /**
    * Get the next character in the source string.
    *
    * @return The next character, or 0 if past the end of the source string.
    */
00137    public char next() {
      if( more() ){
         char c = this.mySource.charAt( this.myIndex );
         this.myIndex += 1;
         return c;
      }
      return 0;
   }

   /**
    * Consume the next character, and check that it matches a specified
    * character.
    *
    * @param c The character to match.
    * @return The character.
    * @throws JSONException if the character does not match.
    */
00154    public char next( char c ) {
      char n = next();
      if( n != c ){
         throw syntaxError( "Expected '" + c + "' and instead saw '" + n + "'." );
      }
      return n;
   }

   /**
    * Get the next n characters.
    *
    * @param n The number of characters to take.
    * @return A string of n characters.
    * @throws JSONException Substring bounds error if there are not n characters
    *         remaining in the source string.
    */
00170    public String next( int n ) {
      int i = this.myIndex;
      int j = i + n;
      if( j >= this.mySource.length() ){
         throw syntaxError( "Substring bounds error" );
      }
      this.myIndex += n;
      return this.mySource.substring( i, j );
   }

   /**
    * Get the next char in the string, skipping whitespace and comments
    * (slashslash, slashstar, and hash).
    *
    * @throws JSONException
    * @return A character, or 0 if there are no more characters.
    */
00187    public char nextClean() {
      for( ;; ){
         char c = next();
         if( c == '/' ){
            switch( next() ){
               case '/':
                  do{
                     c = next();
                  }while( c != '\n' && c != '\r' && c != 0 );
                  break;
               case '*':
                  for( ;; ){
                     c = next();
                     if( c == 0 ){
                        throw syntaxError( "Unclosed comment." );
                     }
                     if( c == '*' ){
                        if( next() == '/' ){
                           break;
                        }
                        back();
                     }
                  }
                  break;
               default:
                  back();
                  return '/';
            }
         }else if( c == '#' ){
            do{
               c = next();
            }while( c != '\n' && c != '\r' && c != 0 );
         }else if( c == 0 || c > ' ' ){
            return c;
         }
      }
   }

   /**
    * Return the characters up to the next close quote character. Backslash
    * processing is done. The formal JSON format does not allow strings in
    * single quotes, but an implementation is allowed to accept them.
    *
    * @param quote The quoting character, either <code>"</code>&nbsp;<small>(double
    *        quote)</small> or <code>'</code>&nbsp;<small>(single quote)</small>.
    * @return A String.
    * @throws JSONException Unterminated string.
    */
00235    public String nextString( char quote ) {
      char c;
      StringBuffer sb = new StringBuffer();
      for( ;; ){
         c = next();
         switch( c ){
            case 0:
            case '\n':
            case '\r':
               throw syntaxError( "Unterminated string" );
            case '\\':
               c = next();
               switch( c ){
                  case 'b':
                     sb.append( '\b' );
                     break;
                  case 't':
                     sb.append( '\t' );
                     break;
                  case 'n':
                     sb.append( '\n' );
                     break;
                  case 'f':
                     sb.append( '\f' );
                     break;
                  case 'r':
                     sb.append( '\r' );
                     break;
                  case 'u':
                     sb.append( (char) Integer.parseInt( next( 4 ), 16 ) );
                     break;
                  case 'x':
                     sb.append( (char) Integer.parseInt( next( 2 ), 16 ) );
                     break;
                  default:
                     sb.append( c );
               }
               break;
            default:
               if( c == quote ){
                  return sb.toString();
               }
               sb.append( c );
         }
      }
   }

   /**
    * Get the text up but not including the specified character or the end of
    * line, whichever comes first.
    *
    * @param d A delimiter character.
    * @return A string.
    */
00289    public String nextTo( char d ) {
      StringBuffer sb = new StringBuffer();
      for( ;; ){
         char c = next();
         if( c == d || c == 0 || c == '\n' || c == '\r' ){
            if( c != 0 ){
               back();
            }
            return sb.toString()
                  .trim();
         }
         sb.append( c );
      }
   }

   /**
    * Get the text up but not including one of the specified delimeter
    * characters or the end of line, whichever comes first.
    *
    * @param delimiters A set of delimiter characters.
    * @return A string, trimmed.
    */
00311    public String nextTo( String delimiters ) {
      char c;
      StringBuffer sb = new StringBuffer();
      for( ;; ){
         c = next();
         if( delimiters.indexOf( c ) >= 0 || c == 0 || c == '\n' || c == '\r' ){
            if( c != 0 ){
               back();
            }
            return sb.toString()
                  .trim();
         }
         sb.append( c );
      }
   }

   /**
    * Get the next value. The value can be a Boolean, Double, Integer,
    * JSONArray, JSONObject, Long, or String, or the JSONObject.NULL object.
    *
    * @throws JSONException If syntax error.
    * @return An object.
    */
00334    public Object nextValue() {
      return nextValue( new JsonConfig() );
   }

   /**
    * Get the next value. The value can be a Boolean, Double, Integer,
    * JSONArray, JSONObject, Long, or String, or the JSONObject.NULL object.
    *
    * @throws JSONException If syntax error.
    * @return An object.
    */
00345    public Object nextValue( JsonConfig jsonConfig ) {
      char c = nextClean();
      String s;

      switch( c ){
         case '"':
         case '\'':
            return nextString( c );
         case '{':
            back();
            return JSONObject.fromObject( this, jsonConfig );
         case '[':
            back();
            return JSONArray.fromObject( this, jsonConfig );
         default:
            // empty
      }

      /*
       * Handle unquoted text. This could be the values true, false, or null, or
       * it can be a number. An implementation (such as this one) is allowed to
       * also accept non-standard forms. Accumulate characters until we reach
       * the end of the text or a formatting character.
       */

      StringBuffer sb = new StringBuffer();
      char b = c;
      while( c >= ' ' && ",:]}/\\\"[{;=#".indexOf( c ) < 0 ){
         sb.append( c );
         c = next();
      }
      back();

      /*
       * If it is true, false, or null, return the proper value.
       */

      s = sb.toString()
            .trim();
      if( s.equals( "" ) ){
         throw syntaxError( "Missing value." );
      }
      if( s.equalsIgnoreCase( "true" ) ){
         return Boolean.TRUE;
      }
      if( s.equalsIgnoreCase( "false" ) ){
         return Boolean.FALSE;
      }
      if( s.equals( "null" ) ){
         return JSONNull.getInstance();
      }

      /*
       * If it might be a number, try converting it. We support the 0- and 0x-
       * conventions. If a number cannot be produced, then the value will just
       * be a string. Note that the 0-, 0x-, plus, and implied string
       * conventions are non-standard. A JSON parser is free to accept non-JSON
       * forms as long as it accepts all correct JSON forms.
       */

      if( (b >= '0' && b <= '9') || b == '.' || b == '-' || b == '+' ){
         if( b == '0' ){
            if( s.length() > 2 && (s.charAt( 1 ) == 'x' || s.charAt( 1 ) == 'X') ){
               try{
                  return new Integer( Integer.parseInt( s.substring( 2 ), 16 ) );
               }catch( Exception e ){
                  /* Ignore the error */
               }
            }else{
               try{
                  return new Integer( Integer.parseInt( s, 8 ) );
               }catch( Exception e ){
                  /* Ignore the error */
               }
            }
         }
         try{
            return new Integer( s );
         }catch( Exception e ){
            try{
               return new Long( s );
            }catch( Exception f ){
               try{
                  return new Double( s );
               }catch( Exception g ){
                  return s;
               }
            }
         }
      }

      if( JSONUtils.isFunctionHeader( s ) || JSONUtils.isFunction( s ) ){
         return s;
      }
      switch( peek() ){
         case ',':
         case '}':
         case '{':
         case '[':
         case ']':
            throw new JSONException( "Unquotted string '" + s + "'" );
      }

      return s;
   }

   /**
    * Look at the next character in the source string.
    *
    * @return The next character, or 0 if past the end of the source string.
    */
00456    public char peek() {
      if( more() ){
         char c = this.mySource.charAt( this.myIndex );
         return c;
      }
      return 0;
   }

   public void reset() {
      this.myIndex = 0;
   }

   /**
    * Skip characters until past the requested string. If it is not found, we
    * are left at the end of the source.
    *
    * @param to A string to skip past.
    */
00474    public void skipPast( String to ) {
      this.myIndex = this.mySource.indexOf( to, this.myIndex );
      if( this.myIndex < 0 ){
         this.myIndex = this.mySource.length();
      }else{
         this.myIndex += to.length();
      }
   }

   /**
    * Skip characters until the next character is the requested character. If
    * the requested character is not found, no characters are skipped.
    *
    * @param to A character to skip to.
    * @return The requested character, or zero if the requested character is not
    *         found.
    */
00491    public char skipTo( char to ) {
      char c;
      int index = this.myIndex;
      do{
         c = next();
         if( c == 0 ){
            this.myIndex = index;
            return c;
         }
      }while( c != to );
      back();
      return c;
   }

   /**
    * Make a JSONException to signal a syntax error.
    *
    * @param message The error message.
    * @return A JSONException object, suitable for throwing
    */
00511    public JSONException syntaxError( String message ) {
      return new JSONException( message + toString() );
   }

   /**
    * Make a printable string of this JSONTokener.
    *
    * @return " at character [this.myIndex] of [this.mySource]"
    */
00520    public String toString() {
      return " at character " + this.myIndex + " of " + this.mySource;
   }
}

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