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package com.cybermkd.upload.multipart;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* A PartInputStream filters a ServletInputStream,
* providing access to a single MIME part contained with in which ends with
* the boundary specified. It uses buffering to provide maximum performance.
*
* Note the readLine method of ServletInputStream
* has the annoying habit of adding a \r\n to the end of the last line. Since
* we want a byte-for-byte transfer, we have to cut those chars. This means
* that we must always maintain at least 2 characters in our buffer to allow
* us to trim when necessary.
*
* @author Geoff Soutter
* @author Jason Hunter
* @version 1.0, 2000/10/27, initial revision
*/
public class PartInputStream extends FilterInputStream {
/**
* boundary which "ends" the stream
*/
private String boundary;
/**
* our buffer
*/
private byte[] buf = new byte[64 * 1024]; // 64k
/**
* number of bytes we've read into the buffer
*/
private int count;
/**
* current position in the buffer
*/
private int pos;
/**
* flag that indicates if we have encountered the boundary
*/
private boolean eof;
/**
* Creates a PartInputStream which stops at the specified
* boundary from a ServletInputStream.
*
* @param in a servlet input stream.
* @param boundary the MIME boundary to stop at.
*/
PartInputStream(InputStream in,
String boundary) throws IOException {
super(in);
this.boundary = boundary;
}
/**
* Fill up our buffer from the underlying input stream, and check for the
* boundary that signifies end-of-file. Users of this method must ensure
* that they leave exactly 2 characters in the buffer before calling this
* method (except the first time), so that we may only use these characters
* if a boundary is not found in the first line read.
*
* @throws IOException if an I/O error occurs.
*/
private void fill() throws IOException {
if (eof)
return;
// as long as we are not just starting up
if (count > 0) {
// if the caller left the requisite amount spare in the buffer
if (count - pos == 2) {
// copy it back to the start of the buffer
System.arraycopy(buf, pos, buf, 0, count - pos);
count -= pos;
pos = 0;
} else {
// should never happen, but just in case
throw new IllegalStateException("fill() detected illegal buffer state");
}
}
// Try and fill the entire buffer, starting at count, line by line
// but never read so close to the end that we might split a boundary
// Thanks to Tony Chu, [email protected], for the -2 suggestion.
int read = 0;
int boundaryLength = boundary.length();
int maxRead = buf.length - boundaryLength - 2; // -2 is for /r/n
while (count < maxRead) {
// read a line
read = ((ServletInputStream) in).readLine(buf, count, buf.length - count);
// check for eof and boundary
if (read == -1) {
throw new IOException("unexpected end of part");
} else {
if (read >= boundaryLength) {
eof = true;
for (int i = 0; i < boundaryLength; i++) {
if (boundary.charAt(i) != buf[count + i]) {
// Not the boundary!
eof = false;
break;
}
}
if (eof) {
break;
}
}
}
// success
count += read;
}
}
/**
* See the general contract of the read
* method of InputStream.
*
* Returns -1 (end of file) when the MIME
* boundary of this part is encountered.
*
* @return the next byte of data, or -1 if the end of the
* stream is reached.
* @throws IOException if an I/O error occurs.
*/
public int read() throws IOException {
if (count - pos <= 2) {
fill();
if (count - pos <= 2) {
return -1;
}
}
return buf[pos++] & 0xff;
}
/**
* See the general contract of the read
* method of InputStream.
*
* Returns -1 (end of file) when the MIME
* boundary of this part is encountered.
*
* @param b the buffer into which the data is read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end
* of the stream has been reached.
* @throws IOException if an I/O error occurs.
*/
public int read(byte b[]) throws IOException {
return read(b, 0, b.length);
}
/**
* See the general contract of the read
* method of InputStream.
*
* Returns -1 (end of file) when the MIME
* boundary of this part is encountered.
*
* @param b 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
* -1 if there is no more data because the end
* of the stream has been reached.
* @throws IOException if an I/O error occurs.
*/
public int read(byte b[], int off, int len) throws IOException {
int total = 0;
if (len == 0) {
return 0;
}
int avail = count - pos - 2;
if (avail <= 0) {
fill();
avail = count - pos - 2;
if (avail <= 0) {
return -1;
}
}
int copy = Math.min(len, avail);
System.arraycopy(buf, pos, b, off, copy);
pos += copy;
total += copy;
while (total < len) {
fill();
avail = count - pos - 2;
if (avail <= 0) {
return total;
}
copy = Math.min(len - total, avail);
System.arraycopy(buf, pos, b, off + total, copy);
pos += copy;
total += copy;
}
return total;
}
/**
* Returns the number of bytes that can be read from this input stream
* without blocking. This is a standard InputStream idiom
* to deal with buffering gracefully, and is not same as the length of the
* part arriving in this stream.
*
* @return the number of bytes that can be read from the input stream
* without blocking.
* @throws IOException if an I/O error occurs.
*/
public int available() throws IOException {
int avail = (count - pos - 2) + in.available();
// Never return a negative value
return (avail < 0 ? 0 : avail);
}
/**
* Closes this input stream and releases any system resources
* associated with the stream.
*
* This method will read any unread data in the MIME part so that the next
* part starts an an expected place in the parent InputStream.
* Note that if the client code forgets to call this method on error,
* MultipartParser will call it automatically if you call
* readNextPart().
*
* @throws IOException if an I/O error occurs.
*/
public void close() throws IOException {
if (!eof) {
while (read(buf, 0, buf.length) != -1)
; // do nothing
}
}
}
