001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.fileupload2.core;
018
019import java.io.ByteArrayOutputStream;
020import java.io.IOException;
021import java.io.InputStream;
022import java.io.OutputStream;
023import java.io.UnsupportedEncodingException;
024import java.nio.charset.Charset;
025
026import org.apache.commons.fileupload2.core.FileItemInput.ItemSkippedException;
027import org.apache.commons.io.Charsets;
028import org.apache.commons.io.IOUtils;
029import org.apache.commons.io.build.AbstractOrigin;
030import org.apache.commons.io.build.AbstractStreamBuilder;
031import org.apache.commons.io.output.NullOutputStream;
032
033/**
034 * Low-level API for processing file uploads.
035 *
036 * <p>
037 * This class can be used to process data streams conforming to MIME 'multipart' format as defined in <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC
038 * 1867</a>. Arbitrarily large amounts of data in the stream can be processed under constant memory usage.
039 * </p>
040 * <p>
041 * The format of the stream is defined in the following way:
042 * </p>
043 * <code>
044 *   multipart-body := preamble 1*encapsulation close-delimiter epilogue<br>
045 *   encapsulation := delimiter body CRLF<br>
046 *   delimiter := "--" boundary CRLF<br>
047 *   close-delimiter := "--" boundary "--"<br>
048 *   preamble := &lt;ignore&gt;<br>
049 *   epilogue := &lt;ignore&gt;<br>
050 *   body := header-part CRLF body-part<br>
051 *   header-part := 1*header CRLF<br>
052 *   header := header-name ":" header-value<br>
053 *   header-name := &lt;printable ascii characters except ":"&gt;<br>
054 *   header-value := &lt;any ascii characters except CR &amp; LF&gt;<br>
055 *   body-data := &lt;arbitrary data&gt;<br>
056 * </code>
057 *
058 * <p>
059 * Note that body-data can contain another mulipart entity. There is limited support for single pass processing of such nested streams. The nested stream is
060 * <strong>required</strong> to have a boundary token of the same length as the parent stream (see {@link #setBoundary(byte[])}).
061 * </p>
062 * <p>
063 * Here is an example of usage of this class:
064 * </p>
065 *
066 * <pre>
067 * try {
068 *     MultipartInput multipartStream = new MultipartInput(input, boundary);
069 *     boolean nextPart = multipartStream.skipPreamble();
070 *     OutputStream output;
071 *     while (nextPart) {
072 *         String header = multipartStream.readHeaders();
073 *         // process headers
074 *         // create some output stream
075 *         multipartStream.readBodyData(output);
076 *         nextPart = multipartStream.readBoundary();
077 *     }
078 * } catch (MultipartInput.MalformedStreamException e) {
079 *     // the stream failed to follow required syntax
080 * } catch (IOException e) {
081 *     // a read or write error occurred
082 * }
083 * </pre>
084 */
085public final class MultipartInput {
086
087    /**
088     * Builds a new {@link MultipartInput} instance.
089     * <p>
090     * For example:
091     * </p>
092     *
093     * <pre>{@code
094     * MultipartInput factory = MultipartInput.builder().setPath(path).setBufferSize(DEFAULT_THRESHOLD).get();
095     * }
096     * </pre>
097     */
098    public static class Builder extends AbstractStreamBuilder<MultipartInput, Builder> {
099
100        /**
101         * Boundary.
102         */
103        private byte[] boundary;
104
105        /**
106         * Progress notifier.
107         */
108        private ProgressNotifier progressNotifier;
109
110        public Builder() {
111            setBufferSizeDefault(DEFAULT_BUFSIZE);
112        }
113
114        /**
115         * Constructs a new instance.
116         * <p>
117         * This builder uses the InputStream, buffer size, boundary and progress notifier aspects.
118         * </p>
119         * <p>
120         * You must provide an origin that can be converted to a Reader by this builder, otherwise, this call will throw an
121         * {@link UnsupportedOperationException}.
122         * </p>
123         *
124         * @return a new instance.
125         * @throws IOException                   if an I/O error occurs.
126         * @throws UnsupportedOperationException if the origin cannot provide a Path.
127         * @see AbstractOrigin#getReader(Charset)
128         */
129        @Override
130        public MultipartInput get() throws IOException {
131            return new MultipartInput(getInputStream(), boundary, getBufferSize(), progressNotifier);
132        }
133
134        /**
135         * Sets the boundary.
136         *
137         * @param boundary the boundary.
138         * @return this
139         */
140        public Builder setBoundary(final byte[] boundary) {
141            this.boundary = boundary;
142            return this;
143        }
144
145        /**
146         * Sets the progress notifier.
147         *
148         * @param progressNotifier progress notifier..
149         * @return this
150         */
151        public Builder setProgressNotifier(final ProgressNotifier progressNotifier) {
152            this.progressNotifier = progressNotifier;
153            return this;
154        }
155
156    }
157
158    /**
159     * Signals an attempt to set an invalid boundary token.
160     */
161    public static class FileUploadBoundaryException extends FileUploadException {
162
163        /**
164         * The UID to use when serializing this instance.
165         */
166        private static final long serialVersionUID = 2;
167
168        /**
169         * Constructs an instance with the specified detail message.
170         *
171         * @param message The detail message (which is saved for later retrieval by the {@link #getMessage()} method)
172         */
173        public FileUploadBoundaryException(final String message) {
174            super(message);
175        }
176
177    }
178
179    /**
180     * An {@link InputStream} for reading an items contents.
181     */
182    public class ItemInputStream extends InputStream {
183
184        /**
185         * Offset when converting negative bytes to integers.
186         */
187        private static final int BYTE_POSITIVE_OFFSET = 256;
188
189        /**
190         * The number of bytes, which have been read so far.
191         */
192        private long total;
193
194        /**
195         * The number of bytes, which must be hold, because they might be a part of the boundary.
196         */
197        private int pad;
198
199        /**
200         * The current offset in the buffer.
201         */
202        private int pos;
203
204        /**
205         * Whether the stream is already closed.
206         */
207        private boolean closed;
208
209        /**
210         * Creates a new instance.
211         */
212        ItemInputStream() {
213            findSeparator();
214        }
215
216        /**
217         * Returns the number of bytes, which are currently available, without blocking.
218         *
219         * @throws IOException An I/O error occurs.
220         * @return Number of bytes in the buffer.
221         */
222        @Override
223        public int available() throws IOException {
224            if (pos == -1) {
225                return tail - head - pad;
226            }
227            return pos - head;
228        }
229
230        private void checkOpen() throws ItemSkippedException {
231            if (closed) {
232                throw new FileItemInput.ItemSkippedException("checkOpen()");
233            }
234        }
235
236        /**
237         * Closes the input stream.
238         *
239         * @throws IOException An I/O error occurred.
240         */
241        @Override
242        public void close() throws IOException {
243            close(false);
244        }
245
246        /**
247         * Closes the input stream.
248         *
249         * @param closeUnderlying Whether to close the underlying stream (hard close)
250         * @throws IOException An I/O error occurred.
251         */
252        public void close(final boolean closeUnderlying) throws IOException {
253            if (closed) {
254                return;
255            }
256            if (closeUnderlying) {
257                closed = true;
258                input.close();
259            } else {
260                for (;;) {
261                    int av = available();
262                    if (av == 0) {
263                        av = makeAvailable();
264                        if (av == 0) {
265                            break;
266                        }
267                    }
268                    skip(av);
269                }
270            }
271            closed = true;
272        }
273
274        /**
275         * Called for finding the separator.
276         */
277        private void findSeparator() {
278            pos = MultipartInput.this.findSeparator();
279            if (pos == -1) {
280                if (tail - head > keepRegion) {
281                    pad = keepRegion;
282                } else {
283                    pad = tail - head;
284                }
285            }
286        }
287
288        /**
289         * Gets the number of bytes, which have been read by the stream.
290         *
291         * @return Number of bytes, which have been read so far.
292         */
293        public long getBytesRead() {
294            return total;
295        }
296
297        public boolean isClosed() {
298            return closed;
299        }
300
301        /**
302         * Attempts to read more data.
303         *
304         * @return Number of available bytes
305         * @throws IOException An I/O error occurred.
306         */
307        private int makeAvailable() throws IOException {
308            if (pos != -1) {
309                return 0;
310            }
311
312            // Move the data to the beginning of the buffer.
313            total += tail - head - pad;
314            System.arraycopy(buffer, tail - pad, buffer, 0, pad);
315
316            // Refill buffer with new data.
317            head = 0;
318            tail = pad;
319
320            for (;;) {
321                final int bytesRead = input.read(buffer, tail, bufSize - tail);
322                if (bytesRead == -1) {
323                    // The last pad amount is left in the buffer.
324                    // Boundary can't be in there so signal an error
325                    // condition.
326                    final String msg = "Stream ended unexpectedly";
327                    throw new MalformedStreamException(msg);
328                }
329                if (notifier != null) {
330                    notifier.noteBytesRead(bytesRead);
331                }
332                tail += bytesRead;
333
334                findSeparator();
335                final int av = available();
336
337                if (av > 0 || pos != -1) {
338                    return av;
339                }
340            }
341        }
342
343        /**
344         * Reads the next byte in the stream.
345         *
346         * @return The next byte in the stream, as a non-negative integer, or -1 for EOF.
347         * @throws IOException An I/O error occurred.
348         */
349        @Override
350        public int read() throws IOException {
351            checkOpen();
352            if (available() == 0 && makeAvailable() == 0) {
353                return -1;
354            }
355            ++total;
356            final int b = buffer[head++];
357            if (b >= 0) {
358                return b;
359            }
360            return b + BYTE_POSITIVE_OFFSET;
361        }
362
363        /**
364         * Reads bytes into the given buffer.
365         *
366         * @param b   The destination buffer, where to write to.
367         * @param off Offset of the first byte in the buffer.
368         * @param len Maximum number of bytes to read.
369         * @return Number of bytes, which have been actually read, or -1 for EOF.
370         * @throws IOException An I/O error occurred.
371         */
372        @Override
373        public int read(final byte[] b, final int off, final int len) throws IOException {
374            checkOpen();
375            if (len == 0) {
376                return 0;
377            }
378            int res = available();
379            if (res == 0) {
380                res = makeAvailable();
381                if (res == 0) {
382                    return -1;
383                }
384            }
385            res = Math.min(res, len);
386            System.arraycopy(buffer, head, b, off, res);
387            head += res;
388            total += res;
389            return res;
390        }
391
392        /**
393         * Skips the given number of bytes.
394         *
395         * @param bytes Number of bytes to skip.
396         * @return The number of bytes, which have actually been skipped.
397         * @throws IOException An I/O error occurred.
398         */
399        @Override
400        public long skip(final long bytes) throws IOException {
401            checkOpen();
402            int av = available();
403            if (av == 0) {
404                av = makeAvailable();
405                if (av == 0) {
406                    return 0;
407                }
408            }
409            final long res = Math.min(av, bytes);
410            head += res;
411            return res;
412        }
413
414    }
415
416    /**
417     * Signals that the input stream fails to follow the required syntax.
418     */
419    public static class MalformedStreamException extends FileUploadException {
420
421        /**
422         * The UID to use when serializing this instance.
423         */
424        private static final long serialVersionUID = 2;
425
426        /**
427         * Constructs an {@code MalformedStreamException} with the specified detail message.
428         *
429         * @param message The detail message.
430         */
431        public MalformedStreamException(final String message) {
432            super(message);
433        }
434
435        /**
436         * Constructs an {@code MalformedStreamException} with the specified detail message.
437         *
438         * @param message The detail message.
439         * @param cause   The cause (which is saved for later retrieval by the {@link #getCause()} method). (A null value is permitted, and indicates that the
440         *                cause is nonexistent or unknown.)
441         */
442        public MalformedStreamException(final String message, final Throwable cause) {
443            super(message, cause);
444        }
445
446    }
447
448    /**
449     * Internal class, which is used to invoke the {@link ProgressListener}.
450     */
451    public static class ProgressNotifier {
452
453        /**
454         * The listener to invoke.
455         */
456        private final ProgressListener progressListener;
457
458        /**
459         * Number of expected bytes, if known, or -1.
460         */
461        private final long contentLength;
462
463        /**
464         * Number of bytes, which have been read so far.
465         */
466        private long bytesRead;
467
468        /**
469         * Number of items, which have been read so far.
470         */
471        private int items;
472
473        /**
474         * Creates a new instance with the given listener and content length.
475         *
476         * @param progressListener The listener to invoke.
477         * @param contentLength    The expected content length.
478         */
479        public ProgressNotifier(final ProgressListener progressListener, final long contentLength) {
480            this.progressListener = progressListener != null ? progressListener : ProgressListener.NOP;
481            this.contentLength = contentLength;
482        }
483
484        /**
485         * Called to indicate that bytes have been read.
486         *
487         * @param byteCount Number of bytes, which have been read.
488         */
489        void noteBytesRead(final int byteCount) {
490            //
491            // Indicates, that the given number of bytes have been read from the input stream.
492            //
493            bytesRead += byteCount;
494            notifyListener();
495        }
496
497        /**
498         * Called to indicate, that a new file item has been detected.
499         */
500        public void noteItem() {
501            ++items;
502            notifyListener();
503        }
504
505        /**
506         * Called for notifying the listener.
507         */
508        private void notifyListener() {
509            progressListener.update(bytesRead, contentLength, items);
510        }
511
512    }
513
514    /**
515     * The Carriage Return ASCII character value.
516     */
517    public static final byte CR = 0x0D;
518
519    /**
520     * The Line Feed ASCII character value.
521     */
522    public static final byte LF = 0x0A;
523
524    /**
525     * The dash (-) ASCII character value.
526     */
527    public static final byte DASH = 0x2D;
528
529    /**
530     * The maximum length of {@code header-part} that will be processed (10 kilobytes = 10240 bytes.).
531     */
532    public static final int HEADER_PART_SIZE_MAX = 10_240;
533
534    /**
535     * The default length of the buffer used for processing a request.
536     */
537    static final int DEFAULT_BUFSIZE = 4096;
538
539    /**
540     * A byte sequence that marks the end of {@code header-part} ({@code CRLFCRLF}).
541     */
542    static final byte[] HEADER_SEPARATOR = { CR, LF, CR, LF };
543
544    /**
545     * A byte sequence that that follows a delimiter that will be followed by an encapsulation ({@code CRLF}).
546     */
547    static final byte[] FIELD_SEPARATOR = { CR, LF };
548
549    /**
550     * A byte sequence that that follows a delimiter of the last encapsulation in the stream ({@code --}).
551     */
552    static final byte[] STREAM_TERMINATOR = { DASH, DASH };
553
554    /**
555     * A byte sequence that precedes a boundary ({@code CRLF--}).
556     */
557    static final byte[] BOUNDARY_PREFIX = { CR, LF, DASH, DASH };
558
559    /**
560     * Compares {@code count} first bytes in the arrays {@code a} and {@code b}.
561     *
562     * @param a     The first array to compare.
563     * @param b     The second array to compare.
564     * @param count How many bytes should be compared.
565     * @return {@code true} if {@code count} first bytes in arrays {@code a} and {@code b} are equal.
566     */
567    static boolean arrayEquals(final byte[] a, final byte[] b, final int count) {
568        for (int i = 0; i < count; i++) {
569            if (a[i] != b[i]) {
570                return false;
571            }
572        }
573        return true;
574    }
575
576    /**
577     * Constructs a new {@link Builder}.
578     *
579     * @return a new {@link Builder}.
580     */
581    public static Builder builder() {
582        return new Builder();
583    }
584
585    /**
586     * The input stream from which data is read.
587     */
588    private final InputStream input;
589
590    /**
591     * The length of the boundary token plus the leading {@code CRLF--}.
592     */
593    private int boundaryLength;
594
595    /**
596     * The amount of data, in bytes, that must be kept in the buffer in order to detect delimiters reliably.
597     */
598    private final int keepRegion;
599
600    /**
601     * The byte sequence that partitions the stream.
602     */
603    private final byte[] boundary;
604
605    /**
606     * The table for Knuth-Morris-Pratt search algorithm.
607     */
608    private final int[] boundaryTable;
609
610    /**
611     * The length of the buffer used for processing the request.
612     */
613    private final int bufSize;
614
615    /**
616     * The buffer used for processing the request.
617     */
618    private final byte[] buffer;
619
620    /**
621     * The index of first valid character in the buffer. <br>
622     * 0 <= head < bufSize
623     */
624    private int head;
625
626    /**
627     * The index of last valid character in the buffer + 1. <br>
628     * 0 <= tail <= bufSize
629     */
630    private int tail;
631
632    /**
633     * The content encoding to use when reading headers.
634     */
635    private Charset headerCharset;
636
637    /**
638     * The progress notifier, if any, or null.
639     */
640    private final ProgressNotifier notifier;
641
642    /**
643     * Constructs a {@code MultipartInput} with a custom size buffer.
644     * <p>
645     * Note that the buffer must be at least big enough to contain the boundary string, plus 4 characters for CR/LF and double dash, plus at least one byte of
646     * data. Too small a buffer size setting will degrade performance.
647     * </p>
648     *
649     * @param input      The {@code InputStream} to serve as a data source.
650     * @param boundary   The token used for dividing the stream into {@code encapsulations}.
651     * @param bufferSize The size of the buffer to be used, in bytes.
652     * @param notifier   The notifier, which is used for calling the progress listener, if any.
653     * @throws IllegalArgumentException If the buffer size is too small.
654     */
655    private MultipartInput(final InputStream input, final byte[] boundary, final int bufferSize, final ProgressNotifier notifier) {
656        if (boundary == null) {
657            throw new IllegalArgumentException("boundary may not be null");
658        }
659        // We prepend CR/LF to the boundary to chop trailing CR/LF from
660        // body-data tokens.
661        this.boundaryLength = boundary.length + BOUNDARY_PREFIX.length;
662        if (bufferSize < this.boundaryLength + 1) {
663            throw new IllegalArgumentException("The buffer size specified for the MultipartInput is too small");
664        }
665
666        this.input = input;
667        this.bufSize = Math.max(bufferSize, boundaryLength * 2);
668        this.buffer = new byte[this.bufSize];
669        this.notifier = notifier;
670
671        this.boundary = new byte[this.boundaryLength];
672        this.boundaryTable = new int[this.boundaryLength + 1];
673        this.keepRegion = this.boundary.length;
674
675        System.arraycopy(BOUNDARY_PREFIX, 0, this.boundary, 0, BOUNDARY_PREFIX.length);
676        System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length, boundary.length);
677        computeBoundaryTable();
678
679        head = 0;
680        tail = 0;
681    }
682
683    /**
684     * Computes the table used for Knuth-Morris-Pratt search algorithm.
685     */
686    private void computeBoundaryTable() {
687        int position = 2;
688        int candidate = 0;
689
690        boundaryTable[0] = -1;
691        boundaryTable[1] = 0;
692
693        while (position <= boundaryLength) {
694            if (boundary[position - 1] == boundary[candidate]) {
695                boundaryTable[position] = candidate + 1;
696                candidate++;
697                position++;
698            } else if (candidate > 0) {
699                candidate = boundaryTable[candidate];
700            } else {
701                boundaryTable[position] = 0;
702                position++;
703            }
704        }
705    }
706
707    /**
708     * Reads {@code body-data} from the current {@code encapsulation} and discards it.
709     * <p>
710     * Use this method to skip encapsulations you don't need or don't understand.
711     * </p>
712     *
713     * @return The amount of data discarded.
714     * @throws MalformedStreamException if the stream ends unexpectedly.
715     * @throws IOException              if an i/o error occurs.
716     */
717    public long discardBodyData() throws MalformedStreamException, IOException {
718        return readBodyData(NullOutputStream.INSTANCE);
719    }
720
721    /**
722     * Searches for a byte of specified value in the {@code buffer}, starting at the specified {@code position}.
723     *
724     * @param value The value to find.
725     * @param pos   The starting position for searching.
726     *
727     * @return The position of byte found, counting from beginning of the {@code buffer}, or {@code -1} if not found.
728     */
729    protected int findByte(final byte value, final int pos) {
730        for (int i = pos; i < tail; i++) {
731            if (buffer[i] == value) {
732                return i;
733            }
734        }
735
736        return -1;
737    }
738
739    /**
740     * Searches for the {@code boundary} in the {@code buffer} region delimited by {@code head} and {@code tail}.
741     *
742     * @return The position of the boundary found, counting from the beginning of the {@code buffer}, or {@code -1} if not found.
743     */
744    protected int findSeparator() {
745        int bufferPos = this.head;
746        int tablePos = 0;
747        while (bufferPos < this.tail) {
748            while (tablePos >= 0 && buffer[bufferPos] != boundary[tablePos]) {
749                tablePos = boundaryTable[tablePos];
750            }
751            bufferPos++;
752            tablePos++;
753            if (tablePos == boundaryLength) {
754                return bufferPos - boundaryLength;
755            }
756        }
757        return -1;
758    }
759
760    /**
761     * Gets the character encoding used when reading the headers of an individual part. When not specified, or {@code null}, the platform default encoding is
762     * used.
763     *
764     * @return The encoding used to read part headers.
765     */
766    public Charset getHeaderCharset() {
767        return headerCharset;
768    }
769
770    /**
771     * Creates a new {@link ItemInputStream}.
772     *
773     * @return A new instance of {@link ItemInputStream}.
774     */
775    public ItemInputStream newInputStream() {
776        return new ItemInputStream();
777    }
778
779    /**
780     * Reads {@code body-data} from the current {@code encapsulation} and writes its contents into the output {@code Stream}.
781     * <p>
782     * Arbitrary large amounts of data can be processed by this method using a constant size buffer. (see {@link MultipartInput#builder()}).
783     * </p>
784     *
785     * @param output The {@code Stream} to write data into. May be null, in which case this method is equivalent to {@link #discardBodyData()}.
786     * @return the amount of data written.
787     * @throws MalformedStreamException if the stream ends unexpectedly.
788     * @throws IOException              if an i/o error occurs.
789     */
790    public long readBodyData(final OutputStream output) throws MalformedStreamException, IOException {
791        try (ItemInputStream inputStream = newInputStream()) {
792            return IOUtils.copyLarge(inputStream, output);
793        }
794    }
795
796    /**
797     * Skips a {@code boundary} token, and checks whether more {@code encapsulations} are contained in the stream.
798     *
799     * @return {@code true} if there are more encapsulations in this stream; {@code false} otherwise.
800     * @throws FileUploadSizeException  if the bytes read from the stream exceeded the size limits
801     * @throws MalformedStreamException if the stream ends unexpectedly or fails to follow required syntax.
802     */
803    public boolean readBoundary() throws FileUploadSizeException, MalformedStreamException {
804        final byte[] marker = new byte[2];
805        final boolean nextChunk;
806        head += boundaryLength;
807        try {
808            marker[0] = readByte();
809            if (marker[0] == LF) {
810                // Work around IE5 Mac bug with input type=image.
811                // Because the boundary delimiter, not including the trailing
812                // CRLF, must not appear within any file (RFC 2046, section
813                // 5.1.1), we know the missing CR is due to a buggy browser
814                // rather than a file containing something similar to a
815                // boundary.
816                return true;
817            }
818
819            marker[1] = readByte();
820            if (arrayEquals(marker, STREAM_TERMINATOR, 2)) {
821                nextChunk = false;
822            } else if (arrayEquals(marker, FIELD_SEPARATOR, 2)) {
823                nextChunk = true;
824            } else {
825                throw new MalformedStreamException("Unexpected characters follow a boundary");
826            }
827        } catch (final FileUploadSizeException e) {
828            throw e;
829        } catch (final IOException e) {
830            throw new MalformedStreamException("Stream ended unexpectedly", e);
831        }
832        return nextChunk;
833    }
834
835    /**
836     * Reads a byte from the {@code buffer}, and refills it as necessary.
837     *
838     * @return The next byte from the input stream.
839     * @throws IOException if there is no more data available.
840     */
841    public byte readByte() throws IOException {
842        // Buffer depleted ?
843        if (head == tail) {
844            head = 0;
845            // Refill.
846            tail = input.read(buffer, head, bufSize);
847            if (tail == -1) {
848                // No more data available.
849                throw new IOException("No more data is available");
850            }
851            if (notifier != null) {
852                notifier.noteBytesRead(tail);
853            }
854        }
855        return buffer[head++];
856    }
857
858    /**
859     * Reads the {@code header-part} of the current {@code encapsulation}.
860     * <p>
861     * Headers are returned verbatim to the input stream, including the trailing {@code CRLF} marker. Parsing is left to the application.
862     * </p>
863     *
864     * @return The {@code header-part} of the current encapsulation.
865     * @throws FileUploadSizeException  if the bytes read from the stream exceeded the size limits.
866     * @throws MalformedStreamException if the stream ends unexpectedly.
867     */
868    public String readHeaders() throws FileUploadSizeException, MalformedStreamException {
869        int i = 0;
870        byte b;
871        // to support multi-byte characters
872        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
873        int size = 0;
874        while (i < HEADER_SEPARATOR.length) {
875            try {
876                b = readByte();
877            } catch (final FileUploadSizeException e) {
878                // wraps a FileUploadSizeException, re-throw as it will be unwrapped later
879                throw e;
880            } catch (final IOException e) {
881                throw new MalformedStreamException("Stream ended unexpectedly", e);
882            }
883            if (++size > HEADER_PART_SIZE_MAX) {
884                throw new MalformedStreamException(
885                        String.format("Header section has more than %s bytes (maybe it is not properly terminated)", HEADER_PART_SIZE_MAX));
886            }
887            if (b == HEADER_SEPARATOR[i]) {
888                i++;
889            } else {
890                i = 0;
891            }
892            baos.write(b);
893        }
894
895        try {
896            return baos.toString(Charsets.toCharset(headerCharset, Charset.defaultCharset()).name());
897        } catch (final UnsupportedEncodingException e) {
898            // not possible
899            throw new IllegalStateException(e);
900        }
901    }
902
903    /**
904     * Changes the boundary token used for partitioning the stream.
905     * <p>
906     * This method allows single pass processing of nested multipart streams.
907     * </p>
908     * <p>
909     * The boundary token of the nested stream is {@code required} to be of the same length as the boundary token in parent stream.
910     * </p>
911     * <p>
912     * Restoring the parent stream boundary token after processing of a nested stream is left to the application.
913     * </p>
914     *
915     * @param boundary The boundary to be used for parsing of the nested stream.
916     * @throws FileUploadBoundaryException if the {@code boundary} has a different length than the one being currently parsed.
917     */
918    public void setBoundary(final byte[] boundary) throws FileUploadBoundaryException {
919        if (boundary.length != boundaryLength - BOUNDARY_PREFIX.length) {
920            throw new FileUploadBoundaryException("The length of a boundary token cannot be changed");
921        }
922        System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length, boundary.length);
923        computeBoundaryTable();
924    }
925
926    /**
927     * Sets the character encoding to be used when reading the headers of individual parts. When not specified, or {@code null}, the platform default encoding
928     * is used.
929     *
930     * @param headerCharset The encoding used to read part headers.
931     */
932    public void setHeaderCharset(final Charset headerCharset) {
933        this.headerCharset = headerCharset;
934    }
935
936    /**
937     * Finds the beginning of the first {@code encapsulation}.
938     *
939     * @return {@code true} if an {@code encapsulation} was found in the stream.
940     * @throws IOException if an i/o error occurs.
941     */
942    public boolean skipPreamble() throws IOException {
943        // First delimiter may be not preceded with a CRLF.
944        System.arraycopy(boundary, 2, boundary, 0, boundary.length - 2);
945        boundaryLength = boundary.length - 2;
946        computeBoundaryTable();
947        try {
948            // Discard all data up to the delimiter.
949            discardBodyData();
950
951            // Read boundary - if succeeded, the stream contains an
952            // encapsulation.
953            return readBoundary();
954        } catch (final MalformedStreamException e) {
955            return false;
956        } finally {
957            // Restore delimiter.
958            System.arraycopy(boundary, 0, boundary, 2, boundary.length - 2);
959            boundaryLength = boundary.length;
960            boundary[0] = CR;
961            boundary[1] = LF;
962            computeBoundaryTable();
963        }
964    }
965
966}