Trace InputStream
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/*
* @(#)TraceInputStream.java 1.8 07/05/04
*/
import java.io.*;
/**
* This class is a FilterInputStream that writes the bytes
* being read from the given input stream into the given output
* stream. This class is typically used to provide a trace of
* the data that is being retrieved from an input stream.
*
* @author John Mani
*/
public class TraceInputStream extends FilterInputStream {
private boolean trace = false;
private boolean quote = false;
private OutputStream traceOut;
/**
* Creates an input stream filter built on top of the specified
* input stream.
*
* @param in the underlying input stream.
* @param out the trace stream
*/
public TraceInputStream(InputStream in, OutputStream traceOut) {
super(in);
this.traceOut = traceOut;
}
/**
* Set trace mode.
* @param trace the trace mode
*/
public void setTrace(boolean trace) {
this.trace = trace;
}
/**
* Set quote mode.
* @param quote the quote mode
*/
public void setQuote(boolean quote) {
this.quote = quote;
}
/**
* Reads the next byte of data from this input stream. Returns
* <code>-1</code> if no data is available. Writes out the read
* byte into the trace stream, if trace mode is <code>true</code>
*/
public int read() throws IOException {
int b = in.read();
if (trace && b != -1) {
if (quote)
writeByte(b);
else
traceOut.write(b);
}
return b;
}
/**
* Reads up to <code>len</code> bytes of data from this input stream
* into an array of bytes. Returns <code>-1</code> if no more data
* is available. Writes out the read bytes into the trace stream, if
* trace mode is <code>true</code>
*/
public int read(byte b[], int off, int len) throws IOException {
int count = in.read(b, off, len);
if (trace && count != -1) {
if (quote) {
for (int i = 0; i < count; i++)
writeByte(b[off + i]);
} else
traceOut.write(b, off, count);
}
return count;
}
/**
* Write a byte in a way that every byte value is printable ASCII.
*/
private final void writeByte(int b) throws IOException {
b &= 0xff;
if (b > 0x7f) {
traceOut.write('M');
traceOut.write('-');
b &= 0x7f;
}
if (b == '\r') {
traceOut.write('\\');
traceOut.write('r');
} else if (b == '\n') {
traceOut.write('\\');
traceOut.write('n');
traceOut.write('\n');
} else if (b == '\t') {
traceOut.write('\\');
traceOut.write('t');
} else if (b < ' ') {
traceOut.write('^');
traceOut.write('@' + b);
} else {
traceOut.write(b);
}
}
}
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