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package com.sun.mail.util;
import java.io.*;
/**
* This class implements a QP Decoder. It is implemented as
* a FilterInputStream, so one can just wrap this class around
* any input stream and read bytes from this filter. The decoding
* is done as the bytes are read out.
*
* @author John Mani
*/
public class QPDecoderStream extends FilterInputStream {
protected byte[] ba = new byte[2];
protected int spaces = 0;
/**
* Create a Quoted Printable decoder that decodes the specified
* input stream.
* @param in the input stream
*/
public QPDecoderStream(InputStream in) {
super(new PushbackInputStream(in, 2)); // pushback of size=2
}
/**
* Read the next decoded byte from this input stream. The byte
* is returned as an <code>int</code> in the range <code>0</code>
* to <code>255</code>. If no byte is available because the end of
* the stream has been reached, the value <code>-1</code> is returned.
* This method blocks until input data is available, the end of the
* stream is detected, or an exception is thrown.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
*/
public int read() throws IOException {
if (spaces > 0) {
// We have cached space characters, return one
spaces--;
return ' ';
}
int c = in.read();
if (c == ' ') {
// Got space, keep reading till we get a non-space char
while ((c = in.read()) == ' ')
spaces++;
if (c == '\r' || c == '\n' || c == -1)
// If the non-space char is CR/LF/EOF, the spaces we got
// so far is junk introduced during transport. Junk 'em.
spaces = 0;
else {
// The non-space char is NOT CR/LF, the spaces are valid.
((PushbackInputStream)in).unread(c);
c = ' ';
}
return c; // return either <SPACE> or <CR/LF>
}
else if (c == '=') {
// QP Encoded atom. Decode the next two bytes
int a = in.read();
if (a == '\n') {
/* Hmm ... not really confirming QP encoding, but lets
* allow this as a LF terminated encoded line .. and
* consider this a soft linebreak and recurse to fetch
* the next char.
*/
return read();
} else if (a == '\r') {
// Expecting LF. This forms a soft linebreak to be ignored.
int b = in.read();
if (b != '\n')
/* Not really confirming QP encoding, but
* lets allow this as well.
*/
((PushbackInputStream)in).unread(b);
return read();
} else if (a == -1) {
// Not valid QP encoding, but we be nice and tolerant here !
return -1;
} else {
ba[0] = (byte)a;
ba[1] = (byte)in.read();
try {
return ASCIIUtility.parseInt(ba, 0, 2, 16);
} catch (NumberFormatException nex) {
/*
System.err.println(
"Illegal characters in QP encoded stream: " +
ASCIIUtility.toString(ba, 0, 2)
);
*/
((PushbackInputStream)in).unread(ba);
return c;
}
}
}
return c;
}
/**
* Reads up to <code>len</code> decoded bytes of data from this input stream
* into an array of bytes. This method blocks until some input is
* available.
* <p>
*
* @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 read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* the stream has been reached.
* @exception IOException if an I/O error occurs.
*/
public int read(byte[] buf, int off, int len) throws IOException {
int i, c;
for (i = 0; i < len; i++) {
if ((c = read()) == -1) {
if (i == 0) // At end of stream, so we should
i = -1; // return -1 , NOT 0.
break;
}
buf[off+i] = (byte)c;
}
return i;
}
/**
* Skips over and discards n bytes of data from this stream.
*/
public long skip(long n) throws IOException {
long skipped = 0;
while (n-- > 0 && read() >= 0)
skipped++;
return skipped;
}
/**
* Tests if this input stream supports marks. Currently this class
* does not support marks
*/
public boolean markSupported() {
return false;
}
/**
* Returns the number of bytes that can be read from this input
* stream without blocking. The QP algorithm does not permit
* a priori knowledge of the number of bytes after decoding, so
* this method just invokes the <code>available</code> method
* of the original input stream.
*/
public int available() throws IOException {
// This is bogus ! We don't really know how much
// bytes are available *after* decoding
return in.available();
}
/**** begin TEST program
public static void main(String argv[]) throws Exception {
FileInputStream infile = new FileInputStream(argv[0]);
QPDecoderStream decoder = new QPDecoderStream(infile);
int c;
while ((c = decoder.read()) != -1)
System.out.print((char)c);
System.out.println();
}
*** end TEST program ****/
}