File	Doc	Category	Size	Date	Package
Base64.java	API Doc	phoneME MR2 API (J2ME)	9057	Wed May 02 18:00:40 BST 2007	dummyCA

Base64

• java.lang.Object

String encodedData;
byte binaryData[];

binaryData = Base64.decode(encodedData);

"Base64 string not a mulitple of 4"
"Invalid character in Base64 string"

Fields Summary
private static final char[]	ALPHABET This character array provides the alphabet map from RFC1521.
private static int[]	valueDecoding Decodes a 7 bit Base64 character into its binary value.

Constructors Summary
private Base64() prevents anyone from instantiating this class

Methods Summary
public static byte[]	decode(java.lang.String encoded) Converts a Base64 encoded string to a byte array. param encoded Base64 encoded data return decode binary data; 3 bytes for every 4 chars - minus padding exception java.io.IOException is thrown, if an I/O error occurs reading the data return decode(encoded, 0, encoded.length());
public static byte[]	decode(java.lang.String encoded, int offset, int length) Converts an embedded Base64 encoded string to a byte array. param encoded a String with Base64 data embedded in it param offset which char of the String to start at param length how many chars to decode; must be a multiple of 4 return decode binary data; 3 bytes for every 4 chars - minus padding exception java.io.IOException is thrown, if an I/O error occurs reading the data int i; int decodedLen; byte[] decoded; // the input must be a multiple of 4 if (length % 4 != 0) { throw new IOException( "Base64 string length is not multiple of 4"); } // 4 chars for 3 bytes, but there may have been pad bytes decodedLen = length / 4 * 3; if (encoded.charAt(offset + length - 1) == '=") { decodedLen--; if (encoded.charAt(offset + length - 2) == '=") { decodedLen--; } } decoded = new byte [decodedLen]; for (i = 0, decodedLen = 0; i < length; i += 4, decodedLen += 3) { decodeQuantum(encoded.charAt(offset + i), encoded.charAt(offset + i + 1), encoded.charAt(offset + i + 2), encoded.charAt(offset + i + 3), decoded, decodedLen); } return decoded;
private static void	decodeQuantum(char in1, char in2, char in3, char in4, byte[] out, int outOffset) Decode 4 Base64 chars as 1, 2, or 3 bytes of data. param in1 first char of quantum to decode param in2 second char of quantum to decode param in3 third char of quantum to decode param in4 forth char of quantum to decode param out buffer to put the output in param outOffset where in the output buffer to put the bytes int a = 0, b = 0, c = 0, d = 0; int pad = 0; a = valueDecoding[in1 & 127]; b = valueDecoding[in2 & 127]; if (in4 == '=") { pad++; if (in3 == '=") { pad++; } else { c = valueDecoding[in3 & 127]; } } else { c = valueDecoding[in3 & 127]; d = valueDecoding[in4 & 127]; } if (a < 0 || b < 0 || c < 0 || d < 0) { throw new IOException("Invalid character in Base64 string"); } // the first byte is the 6 bits of a and 2 bits of b out[outOffset] = (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3)); if (pad < 2) { // the second byte is 4 bits of b and 4 bits of c out[outOffset + 1] = (byte)(((b << 4) & 0xf0) | ((c >>> 2) & 0xf)); if (pad < 1) { // the third byte is 2 bits of c and 4 bits of d out[outOffset + 2] = (byte)(((c << 6) & 0xc0) | (d & 0x3f)); } }
public static java.lang.String	encode(byte[] data, int offset, int length) Converts a byte array into a Base64 encoded string. param data bytes to encode param offset which byte to start at param length how many bytes to encode; padding will be added if needed return base64 encoding of data; 4 chars for every 3 bytes for (int i = 0; i < valueDecoding.length; i++) { valueDecoding[i] = -1; } for (int i = 0; i < ALPHABET.length; i++) { valueDecoding[ALPHABET[i]] = i; } int i; int encodedLen; char[] encoded; // 4 chars for 3 bytes, run input up to a multiple of 3 encodedLen = (length + 2) / 3 * 4; encoded = new char [encodedLen]; for (i = 0, encodedLen = 0; encodedLen < encoded.length; i += 3, encodedLen += 4) { encodeQuantum(data, offset + i, length - i, encoded, encodedLen); } return new String(encoded);
private static void	encodeQuantum(byte[] in, int inOffset, int len, char[] out, int outOffset) Encodes 1, 2, or 3 bytes of data as 4 Base64 chars. param in buffer of bytes to encode param inOffset where the first byte to encode is param len how many bytes to encode param out buffer to put the output in param outOffset where in the output buffer to put the chars byte a = 0, b = 0, c = 0; a = in[inOffset]; out[outOffset] = ALPHABET[(a >>> 2) & 0x3F]; if (len > 2) { b = in[inOffset + 1]; c = in[inOffset + 2]; out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]; out[outOffset + 2] = ALPHABET[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]; out[outOffset + 3] = ALPHABET[c & 0x3F]; } else if (len > 1) { b = in[inOffset + 1]; out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]; out[outOffset + 2] = ALPHABET[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]; out[outOffset + 3] = '="; } else { out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]; out[outOffset + 2] = '="; out[outOffset + 3] = '="; }