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package sun.misc;

import java.io.PushbackInputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.IOException;

This class implements a Berkeley uu character decoder. This decoder was made famous by the uudecode program. The basic character coding is algorithmic, taking 6 bits of binary data and adding it to an ASCII ' ' (space) character. This converts these six bits into a printable representation. Note that it depends on the ASCII character encoding standard for english. Groups of three bytes are converted into 4 characters by treating the three bytes a four 6 bit groups, group 1 is byte 1's most significant six bits, group 2 is byte 1's least significant two bits plus byte 2's four most significant bits. etc. In this encoding, the buffer prefix is:
    begin [mode] [filename]
This is followed by one or more lines of the form:
     (len)(data)(data)(data) ...
where (len) is the number of bytes on this line. Note that groupings are always four characters, even if length is not a multiple of three bytes. When less than three characters are encoded, the values of the last remaining bytes is undefined and should be ignored. The last line of data in a uuencoded buffer is represented by a single space character. This is translated by the decoding engine to a line length of zero. This is immediately followed by a line which contains the word 'end[newline]' If an error is encountered during decoding this class throws a CEFormatException. The specific detail messages are:
     "UUDecoder: No begin line."
     "UUDecoder: Malformed begin line."
     "UUDecoder: Short Buffer."
     "UUDecoder: Bad Line Length."
     "UUDecoder: Missing 'end' line."
Author: Chuck McManis
See Also:
/** * This class implements a Berkeley uu character decoder. This decoder * was made famous by the uudecode program. * * The basic character coding is algorithmic, taking 6 bits of binary * data and adding it to an ASCII ' ' (space) character. This converts * these six bits into a printable representation. Note that it depends * on the ASCII character encoding standard for english. Groups of three * bytes are converted into 4 characters by treating the three bytes * a four 6 bit groups, group 1 is byte 1's most significant six bits, * group 2 is byte 1's least significant two bits plus byte 2's four * most significant bits. etc. * * In this encoding, the buffer prefix is: * <pre> * begin [mode] [filename] * </pre> * * This is followed by one or more lines of the form: * <pre> * (len)(data)(data)(data) ... * </pre> * where (len) is the number of bytes on this line. Note that groupings * are always four characters, even if length is not a multiple of three * bytes. When less than three characters are encoded, the values of the * last remaining bytes is undefined and should be ignored. * * The last line of data in a uuencoded buffer is represented by a single * space character. This is translated by the decoding engine to a line * length of zero. This is immediately followed by a line which contains * the word 'end[newline]' * * If an error is encountered during decoding this class throws a * CEFormatException. The specific detail messages are: * * <pre> * "UUDecoder: No begin line." * "UUDecoder: Malformed begin line." * "UUDecoder: Short Buffer." * "UUDecoder: Bad Line Length." * "UUDecoder: Missing 'end' line." * </pre> * * @author Chuck McManis * @see CharacterDecoder * @see UUEncoder */
public class UUDecoder extends CharacterDecoder {
This string contains the name that was in the buffer being decoded.
/** * This string contains the name that was in the buffer being decoded. */
public String bufferName;
Represents UNIX(tm) mode bits. Generally three octal digits representing read, write, and execute permission of the owner, group owner, and others. They should be interpreted as the bit groups:
(owner) (group) (others)
 rwx      rwx     rwx    (r = read, w = write, x = execute)
/** * Represents UNIX(tm) mode bits. Generally three octal digits * representing read, write, and execute permission of the owner, * group owner, and others. They should be interpreted as the bit groups: * <pre> * (owner) (group) (others) * rwx rwx rwx (r = read, w = write, x = execute) *</pre> * */
public int mode;
UU encoding specifies 3 bytes per atom.
/** * UU encoding specifies 3 bytes per atom. */
protected int bytesPerAtom() { return (3); }
All UU lines have 45 bytes on them, for line length of 15*4+1 or 61 characters per line.
/** * All UU lines have 45 bytes on them, for line length of 15*4+1 or 61 * characters per line. */
protected int bytesPerLine() { return (45); }
This is used to decode the atoms
/** This is used to decode the atoms */
private byte decoderBuffer[] = new byte[4];
Decode a UU atom. Note that if l is less than 3 we don't write the extra bits, however the encoder always encodes 4 character groups even when they are not needed.
/** * Decode a UU atom. Note that if l is less than 3 we don't write * the extra bits, however the encoder always encodes 4 character * groups even when they are not needed. */
protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int l) throws IOException { int i, c1, c2, c3, c4; int a, b, c; StringBuffer x = new StringBuffer(); for (i = 0; i < 4; i++) { c1 = inStream.read(); if (c1 == -1) { throw new CEStreamExhausted(); } x.append((char)c1); decoderBuffer[i] = (byte) ((c1 - ' ') & 0x3f); } a = ((decoderBuffer[0] << 2) & 0xfc) | ((decoderBuffer[1] >>> 4) & 3); b = ((decoderBuffer[1] << 4) & 0xf0) | ((decoderBuffer[2] >>> 2) & 0xf); c = ((decoderBuffer[2] << 6) & 0xc0) | (decoderBuffer[3] & 0x3f); outStream.write((byte)(a & 0xff)); if (l > 1) { outStream.write((byte)( b & 0xff)); } if (l > 2) { outStream.write((byte)(c&0xff)); } }
For uuencoded buffers, the data begins with a line of the form: begin MODE FILENAME This line always starts in column 1.
/** * For uuencoded buffers, the data begins with a line of the form: * begin MODE FILENAME * This line always starts in column 1. */
protected void decodeBufferPrefix(PushbackInputStream inStream, OutputStream outStream) throws IOException { int c; StringBuffer q = new StringBuffer(32); String r; boolean sawNewLine; /* * This works by ripping through the buffer until it finds a 'begin' * line or the end of the buffer. */ sawNewLine = true; while (true) { c = inStream.read(); if (c == -1) { throw new CEFormatException("UUDecoder: No begin line."); } if ((c == 'b') && sawNewLine){ c = inStream.read(); if (c == 'e') { break; } } sawNewLine = (c == '\n') || (c == '\r'); } /* * Now we think its begin, (we've seen ^be) so verify it here. */ while ((c != '\n') && (c != '\r')) { c = inStream.read(); if (c == -1) { throw new CEFormatException("UUDecoder: No begin line."); } if ((c != '\n') && (c != '\r')) { q.append((char)c); } } r = q.toString(); if (r.indexOf(' ') != 3) { throw new CEFormatException("UUDecoder: Malformed begin line."); } mode = Integer.parseInt(r.substring(4,7)); bufferName = r.substring(r.indexOf(' ',6)+1); /* * Check for \n after \r */ if (c == '\r') { c = inStream.read (); if ((c != '\n') && (c != -1)) inStream.unread (c); } }
In uuencoded buffers, encoded lines start with a character that represents the number of bytes encoded in this line. The last line of input is always a line that starts with a single space character, which would be a zero length line.
/** * In uuencoded buffers, encoded lines start with a character that * represents the number of bytes encoded in this line. The last * line of input is always a line that starts with a single space * character, which would be a zero length line. */
protected int decodeLinePrefix(PushbackInputStream inStream, OutputStream outStream) throws IOException { int c; c = inStream.read(); if (c == ' ') { c = inStream.read(); /* discard the (first)trailing CR or LF */ c = inStream.read(); /* check for a second one */ if ((c != '\n') && (c != -1)) inStream.unread (c); throw new CEStreamExhausted(); } else if (c == -1) { throw new CEFormatException("UUDecoder: Short Buffer."); } c = (c - ' ') & 0x3f; if (c > bytesPerLine()) { throw new CEFormatException("UUDecoder: Bad Line Length."); } return (c); }
Find the end of the line for the next operation. The following sequences are recognized as end-of-line CR, CR LF, or LF
/** * Find the end of the line for the next operation. * The following sequences are recognized as end-of-line * CR, CR LF, or LF */
protected void decodeLineSuffix(PushbackInputStream inStream, OutputStream outStream) throws IOException { int c; while (true) { c = inStream.read(); if (c == -1) { throw new CEStreamExhausted(); } if (c == '\n') { break; } if (c == '\r') { c = inStream.read(); if ((c != '\n') && (c != -1)) { inStream.unread (c); } break; } } }
UUencoded files have a buffer suffix which consists of the word end. This line should immediately follow the line with a single space in it.
/** * UUencoded files have a buffer suffix which consists of the word * end. This line should immediately follow the line with a single * space in it. */
protected void decodeBufferSuffix(PushbackInputStream inStream, OutputStream outStream) throws IOException { int c; c = inStream.read(decoderBuffer); if ((decoderBuffer[0] != 'e') || (decoderBuffer[1] != 'n') || (decoderBuffer[2] != 'd')) { throw new CEFormatException("UUDecoder: Missing 'end' line."); } } }