File	Doc	Category	Size	Date	Package
Base64Decoder.java	API Doc	Example	6376	Wed Nov 03 11:59:12 GMT 2004	com.oreilly.servlet

Base64Decoder

• java.lang.Object
  • java.io.InputStream
    • java.io.FilterInputStream

Fields Summary
private static final char[]	chars
private static final int[]	ints
private int	charCount
private int	carryOver

Constructors Summary
public Base64Decoder(InputStream in) Constructs a new Base64 decoder that reads input from the given InputStream. param in the input stream super(in);

Methods Summary
public static java.lang.String	decode(java.lang.String encoded) Returns the decoded form of the given encoded string, as a String. Note that not all binary data can be represented as a String, so this method should only be used for encoded String data. Use decodeToBytes() otherwise. param encoded the string to decode return the decoded form of the encoded string return new String(decodeToBytes(encoded));
public static byte[]	decodeToBytes(java.lang.String encoded) Returns the decoded form of the given encoded string, as bytes. param encoded the string to decode return the decoded form of the encoded string byte[] bytes = null; try { bytes = encoded.getBytes("8859_1"); } catch (UnsupportedEncodingException ignored) { } Base64Decoder in = new Base64Decoder( new ByteArrayInputStream(bytes)); ByteArrayOutputStream out = new ByteArrayOutputStream((int) (bytes.length * 0.67)); try { byte[] buf = new byte[4 * 1024]; // 4K buffer int bytesRead; while ((bytesRead = in.read(buf)) != -1) { out.write(buf, 0, bytesRead); } out.close(); return out.toByteArray(); } catch (IOException ignored) { return null; }
public static void	main(java.lang.String[] args) if (args.length != 1) { System.err.println("Usage: java Base64Decoder fileToDecode"); return; } Base64Decoder decoder = null; try { decoder = new Base64Decoder( new BufferedInputStream( new FileInputStream(args[0]))); byte[] buf = new byte[4 * 1024]; // 4K buffer int bytesRead; while ((bytesRead = decoder.read(buf)) != -1) { System.out.write(buf, 0, bytesRead); } } finally { if (decoder != null) decoder.close(); }
public int	read() Returns the next decoded character from the stream, or -1 if end of stream was reached. return the decoded character, or -1 if the end of the input stream is reached exception IOException if an I/O error occurs // Read the next non-whitespace character int x; do { x = in.read(); if (x == -1) { return -1; } } while (Character.isWhitespace((char)x)); charCount++; // The '=' sign is just padding if (x == '=") { return -1; // effective end of stream } // Convert from raw form to 6-bit form x = ints[x]; // Calculate which character we're decoding now int mode = (charCount - 1) % 4; // First char save all six bits, go for another if (mode == 0) { carryOver = x & 63; return read(); } // Second char use previous six bits and first two new bits, // save last four bits else if (mode == 1) { int decoded = ((carryOver << 2) + (x >> 4)) & 255; carryOver = x & 15; return decoded; } // Third char use previous four bits and first four new bits, // save last two bits else if (mode == 2) { int decoded = ((carryOver << 4) + (x >> 2)) & 255; carryOver = x & 3; return decoded; } // Fourth char use previous two bits and all six new bits else if (mode == 3) { int decoded = ((carryOver << 6) + x) & 255; return decoded; } return -1; // can't actually reach this line
public int	read(byte[] buf, int off, int len) Reads decoded data into an array of bytes and returns the actual number of bytes read, or -1 if end of stream was reached. param buf the buffer into which the data is read param off the start offset of the data param len the maximum number of bytes to read return the actual number of bytes read, or -1 if the end of the input stream is reached exception IOException if an I/O error occurs if (buf.length < (len + off - 1)) { throw new IOException("The input buffer is too small: " + len + " bytes requested starting at offset " + off + " while the buffer " + " is only " + buf.length + " bytes long."); } // This could of course be optimized int i; for (i = 0; i < len; i++) { int x = read(); if (x == -1 && i == 0) { // an immediate -1 returns -1 return -1; } else if (x == -1) { // a later -1 returns the chars read so far break; } buf[off + i] = (byte) x; } return i;