codec.java

来自「J2ME MIDP_Example_Applications」· Java 代码 · 共 196 行

// Copyright 2003 Nokia Corporation.
//
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER,
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE
// OR TRADE PRACTICE, RELATING TO THE SOURCE CODE OR ANY WARRANTY OTHERWISE
// ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE AND WITH NO
// OBLIGATION OF NOKIA TO PROVIDE THE LICENSEE WITH ANY MAINTENANCE OR
// SUPPORT. FURTHERMORE, NOKIA MAKES NO WARRANTY THAT EXERCISE OF THE
// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT
// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED
// BY THIRD PARTIES
//
// Furthermore, information provided in this source code is preliminary,
// and may be changed substantially prior to final release. Nokia Corporation
// retains the right to make changes to this source code at
// any time, without notice. This source code is provided for informational
// purposes only.
//
// Nokia and Nokia Connecting People are registered trademarks of Nokia
// Corporation.
// Java and all Java-based marks are trademarks or registered trademarks of
// Sun Microsystems, Inc.
// Other product and company names mentioned herein may be trademarks or
// trade names of their respective owners.
//
// A non-exclusive, non-transferable, worldwide, limited license is hereby
// granted to the Licensee to download, print, reproduce and modify the
// source code. The licensee has the right to market, sell, distribute and
// make available the source code in original or modified form only when
// incorporated into the programs developed by the Licensee. No other
// license, express or implied, by estoppel or otherwise, to any other
// intellectual property rights is granted herein.
package example.mesql;

import java.io.*;

public class Codec
{
  private final static char[] hexdigits = new char[16];

  static
  {
    // fill hexdigits with {0123456789ABCDEF}
    for (int c = '0', i = 0; c <= '9'; c++, i++)
    {
      hexdigits[i] = (char) c;
    }
    for (int c = 'A', i = 10; c <= 'F'; c++, i++)
    {
      hexdigits[i] = (char) c;
    }
  }


  private Codec()
  {
  }


  // encodes the string in URL format as indicated in RFC 1738
  static String encode(String url)
  {
    if (url == null)
    {
      return "%0";
    }
    int maxBytesPerChar = 10;
    StringBuffer result = new StringBuffer();
    ByteArrayOutputStream buffer = 
      new ByteArrayOutputStream(maxBytesPerChar);
    OutputStreamWriter writer = null;
    // UTF-8 encoding is recommended by W3C
    try
    {
      writer = new OutputStreamWriter(buffer, "UTF-8");
    }
    catch (UnsupportedEncodingException e)
    {
      // use default encoding then
      writer = new OutputStreamWriter(buffer);
    }
    int size = url.length();

    for (int i = 0; i < size; i++)
    {
      int current = (int) url.charAt(i);
      // print non changed chars as normal
      if ((current >= 'a' && current <= 'z')
         || (current >= 'A' && current <= 'Z')
         || (current >= '0' && current <= '9')
         || current == '.' || current == '_'
         || current == '-' || current == '*')
      {
        result.append((char) current);
      }
      else if (current == ' ')
      {
        // space is a special case
        result.append('+');
      }
      else
      {
        // try to write to the ByteArrayStream
        try
        {
          writer.write(current);
          writer.flush();
        }
        catch (IOException e)
        {
          buffer.reset();
          continue;
        }
        byte[] array = buffer.toByteArray();
        for (int j = 0; j < array.length; j++)
        {
          byte currentByte = array[j];
          int low = (int) (currentByte & 0x0F);
          int high = (int) ((currentByte & 0xF0) >> 4);

          result.append('%');
          result.append(hexdigits[high]);
          result.append(hexdigits[low]);
        }
        buffer.reset();
      }
    }
    return result.toString();
  }


  // decodes the string in URL format
  // as indicated in RFC 1738
  public static String decode(String text)
  {
    StringBuffer result = new StringBuffer();
    int size = text.length();
    if ("%0".equals(text))
    {
      return null;
    }
    for (int i = 0; i < size; i++)
    {
      int current = (int) text.charAt(i);
      // space is a special case
      if (current == '+')
      {
        result.append(" ");
      }
      else if (current != '%')
      {
        // general character
        result.append((char) current);
      }
      else
      {
        // let's assume 4 bytes max.
        // Will expand if necessary
        byte[] buffer = new byte[4];
        int k = 0;
        while (current == '%' && i < (size - 2))
        {
          String chars = text.substring(i + 1, i + 3);
          buffer[k++] = (byte) Integer.parseInt(chars, 16);
          i += 3;
          if (i < (size - 2))
          {
            current = (int) text.charAt(i);
          }
          if (k == buffer.length)
          {
            // expand by 4
            byte[] tmp = new byte[buffer.length + 4];
            System.arraycopy(buffer, 0, tmp, 0,
              buffer.length);
            buffer = tmp;
          }
        }
        // need to go back one
        i--;
        try
        {
          result.append(new String(buffer, 0, k, "UTF-8"));
        }
        catch (UnsupportedEncodingException e)
        {
          // Shouldn't happen UTF-8 is mandatory in MIDP
        }
      }
    }
    return result.toString();
  }
}