/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.transport;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;

import org.eclipse.jgit.errors.TransportException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.internal.storage.file.RefDirectory;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdRef;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.util.IO;

Transfers object data through a dumb transport.

Implementations are responsible for resolving path names relative to the
objects/ subdirectory of a single remote Git repository or naked object database and make the content available as a Java input stream for reading during fetch. The actual object traversal logic to determine the names of files to retrieve is handled through the generic, protocol independent WalkFetchConnection. /**
 * Transfers object data through a dumb transport.
 * <p>
 * Implementations are responsible for resolving path names relative to the
 * <code>objects/</code> subdirectory of a single remote Git repository or
 * naked object database and make the content available as a Java input stream
 * for reading during fetch. The actual object traversal logic to determine the
 * names of files to retrieve is handled through the generic, protocol
 * independent {@link WalkFetchConnection}.
 */
abstract class WalkRemoteObjectDatabase {
	static final String ROOT_DIR = "../"; //$NON-NLS-1$

	static final String INFO_PACKS = "info/packs"; //$NON-NLS-1$

	static final String INFO_REFS = ROOT_DIR + Constants.INFO_REFS;

	abstract URIish getURI();

	
Obtain the list of available packs (if any).

Pack names should be the file name in the packs directory, that is
pack-035760ab452d6eebd123add421f253ce7682355a.pack. Index
names should not be included in the returned collection.
Throws:
IOException – 
            The connection is unable to read the remote repository's list
            of available pack files.
Returns:
list of pack names; null or empty list if none are available./**
	 * Obtain the list of available packs (if any).
	 * <p>
	 * Pack names should be the file name in the packs directory, that is
	 * <code>pack-035760ab452d6eebd123add421f253ce7682355a.pack</code>. Index
	 * names should not be included in the returned collection.
	 *
	 * @return list of pack names; null or empty list if none are available.
	 * @throws IOException
	 *             The connection is unable to read the remote repository's list
	 *             of available pack files.
	 */
	abstract Collection<String> getPackNames() throws IOException;

	
Obtain alternate connections to alternate object databases (if any).
 Alternates are typically read from the file Constants.INFO_ALTERNATES or Constants.INFO_HTTP_ALTERNATES. The content of each line must be resolved by the implementation and a new database reference should be returned to represent the additional location. 
 Alternates may reuse the same network connection handle, however the fetch connection will close() each created alternate. 
Throws:
IOException – 
            The connection is unable to read the remote repository's list
            of configured alternates.
Returns:
list of additional object databases the caller could fetch from;
        null or empty list if none are configured./**
	 * Obtain alternate connections to alternate object databases (if any).
	 * <p>
         * Alternates are typically read from the file
         * {@link org.eclipse.jgit.lib.Constants#INFO_ALTERNATES} or
         * {@link org.eclipse.jgit.lib.Constants#INFO_HTTP_ALTERNATES}.
         * The content of each line must be resolved
	 * by the implementation and a new database reference should be returned to
	 * represent the additional location.
	 * <p>
	 * Alternates may reuse the same network connection handle, however the
	 * fetch connection will {@link #close()} each created alternate.
	 *
	 * @return list of additional object databases the caller could fetch from;
	 *         null or empty list if none are configured.
	 * @throws IOException
	 *             The connection is unable to read the remote repository's list
	 *             of configured alternates.
	 */
	abstract Collection<WalkRemoteObjectDatabase> getAlternates()
			throws IOException;

	
Open a single file for reading.
 Implementors should make every attempt possible to ensure FileNotFoundException is used when the remote object does not exist. However when fetching over HTTP some misconfigured servers may generate a 200 OK status message (rather than a 404 Not Found) with an HTML formatted message explaining the requested resource does not exist. Callers such as WalkFetchConnection are prepared to handle this by validating the content received, and assuming content that fails to match its hash is an incorrectly phrased FileNotFoundException. 
 This method is recommended for already compressed files like loose objects and pack files. For text files, see openReader(String). 
Params:
path – 
           location of the file to read, relative to this objects
           directory (e.g.
           cb/95df6ab7ae9e57571511ef451cf33767c26dd2 or
           pack/pack-035760ab452d6eebd123add421f253ce7682355a.pack).
Throws:
FileNotFoundException – 
            the requested file does not exist at the given location.
IOException – 
            The connection is unable to read the remote's file, and the
            failure occurred prior to being able to determine if the file
            exists, or after it was determined to exist but before the
            stream could be created.
Returns:
a stream to read from the file. Never null./**
	 * Open a single file for reading.
	 * <p>
	 * Implementors should make every attempt possible to ensure
	 * {@link FileNotFoundException} is used when the remote object does not
	 * exist. However when fetching over HTTP some misconfigured servers may
	 * generate a 200 OK status message (rather than a 404 Not Found) with an
	 * HTML formatted message explaining the requested resource does not exist.
	 * Callers such as {@link WalkFetchConnection} are prepared to handle this
	 * by validating the content received, and assuming content that fails to
	 * match its hash is an incorrectly phrased FileNotFoundException.
	 * <p>
	 * This method is recommended for already compressed files like loose objects
	 * and pack files. For text files, see {@link #openReader(String)}.
	 *
	 * @param path
	 *            location of the file to read, relative to this objects
	 *            directory (e.g.
	 *            <code>cb/95df6ab7ae9e57571511ef451cf33767c26dd2</code> or
	 *            <code>pack/pack-035760ab452d6eebd123add421f253ce7682355a.pack</code>).
	 * @return a stream to read from the file. Never null.
	 * @throws FileNotFoundException
	 *             the requested file does not exist at the given location.
	 * @throws IOException
	 *             The connection is unable to read the remote's file, and the
	 *             failure occurred prior to being able to determine if the file
	 *             exists, or after it was determined to exist but before the
	 *             stream could be created.
	 */
	abstract FileStream open(String path) throws FileNotFoundException,
			IOException;

	
Create a new connection for a discovered alternate object database
 This method is typically called by readAlternates(String) when subclasses us the generic alternate parsing logic for their implementation of getAlternates(). 
Params:
location – 
           the location of the new alternate, relative to the current
           object database.
Throws:
IOException – 
            The database connection cannot be established with the
            alternate, such as if the alternate location does not
            actually exist and the connection's constructor attempts to
            verify that.
Returns:
a new database connection that can read from the specified
        alternate./**
	 * Create a new connection for a discovered alternate object database
	 * <p>
	 * This method is typically called by {@link #readAlternates(String)} when
	 * subclasses us the generic alternate parsing logic for their
	 * implementation of {@link #getAlternates()}.
	 *
	 * @param location
	 *            the location of the new alternate, relative to the current
	 *            object database.
	 * @return a new database connection that can read from the specified
	 *         alternate.
	 * @throws IOException
	 *             The database connection cannot be established with the
	 *             alternate, such as if the alternate location does not
	 *             actually exist and the connection's constructor attempts to
	 *             verify that.
	 */
	abstract WalkRemoteObjectDatabase openAlternate(String location)
			throws IOException;

	
Close any resources used by this connection.

If the remote repository is contacted by a network socket this method
must close that network socket, disconnecting the two peers. If the
remote repository is actually local (same system) this method must close
any open file handles used to read the "remote" repository.
/**
	 * Close any resources used by this connection.
	 * <p>
	 * If the remote repository is contacted by a network socket this method
	 * must close that network socket, disconnecting the two peers. If the
	 * remote repository is actually local (same system) this method must close
	 * any open file handles used to read the "remote" repository.
	 */
	abstract void close();

	
Delete a file from the object database.

Path may start with ../ to request deletion of a file that
resides in the repository itself.

When possible empty directories must be removed, up to but not including
the current object database directory itself.

This method does not support deletion of directories.
Params:
path – 
           name of the item to be removed, relative to the current object
           database.
Throws:
IOException – 
            deletion is not supported, or deletion failed./**
	 * Delete a file from the object database.
	 * <p>
	 * Path may start with <code>../</code> to request deletion of a file that
	 * resides in the repository itself.
	 * <p>
	 * When possible empty directories must be removed, up to but not including
	 * the current object database directory itself.
	 * <p>
	 * This method does not support deletion of directories.
	 *
	 * @param path
	 *            name of the item to be removed, relative to the current object
	 *            database.
	 * @throws IOException
	 *             deletion is not supported, or deletion failed.
	 */
	void deleteFile(String path) throws IOException {
		throw new IOException(MessageFormat.format(JGitText.get().deletingNotSupported, path));
	}

	
Open a remote file for writing.

Path may start with ../ to request writing of a file that
resides in the repository itself.

The requested path may or may not exist. If the path already exists as a
file the file should be truncated and completely replaced.

This method creates any missing parent directories, if necessary.
Params:
path – 
           name of the file to write, relative to the current object
           database.
monitor – 
           (optional) progress monitor to post write completion to during
           the stream's close method.
monitorTask – 
           (optional) task name to display during the close method.
Throws:
IOException – 
            writing is not supported, or attempting to write the file
            failed, possibly due to permissions or remote disk full, etc.
Returns:
stream to write into this file. Caller must close the stream to
        complete the write request. The stream is not buffered and each
        write may cause a network request/response so callers should
        buffer to smooth out small writes./**
	 * Open a remote file for writing.
	 * <p>
	 * Path may start with <code>../</code> to request writing of a file that
	 * resides in the repository itself.
	 * <p>
	 * The requested path may or may not exist. If the path already exists as a
	 * file the file should be truncated and completely replaced.
	 * <p>
	 * This method creates any missing parent directories, if necessary.
	 *
	 * @param path
	 *            name of the file to write, relative to the current object
	 *            database.
	 * @return stream to write into this file. Caller must close the stream to
	 *         complete the write request. The stream is not buffered and each
	 *         write may cause a network request/response so callers should
	 *         buffer to smooth out small writes.
	 * @param monitor
	 *            (optional) progress monitor to post write completion to during
	 *            the stream's close method.
	 * @param monitorTask
	 *            (optional) task name to display during the close method.
	 * @throws IOException
	 *             writing is not supported, or attempting to write the file
	 *             failed, possibly due to permissions or remote disk full, etc.
	 */
	OutputStream writeFile(final String path, final ProgressMonitor monitor,
			final String monitorTask) throws IOException {
		throw new IOException(MessageFormat.format(JGitText.get().writingNotSupported, path));
	}

	
Atomically write a remote file.

This method attempts to perform as atomic of an update as it can,
reducing (or eliminating) the time that clients might be able to see
partial file content. This method is not suitable for very large
transfers as the complete content must be passed as an argument.

Path may start with ../ to request writing of a file that
resides in the repository itself.

The requested path may or may not exist. If the path already exists as a
file the file should be truncated and completely replaced.

This method creates any missing parent directories, if necessary.
Params:
path – 
           name of the file to write, relative to the current object
           database.
data – 
           complete new content of the file.
Throws:
IOException – 
            writing is not supported, or attempting to write the file
            failed, possibly due to permissions or remote disk full, etc./**
	 * Atomically write a remote file.
	 * <p>
	 * This method attempts to perform as atomic of an update as it can,
	 * reducing (or eliminating) the time that clients might be able to see
	 * partial file content. This method is not suitable for very large
	 * transfers as the complete content must be passed as an argument.
	 * <p>
	 * Path may start with <code>../</code> to request writing of a file that
	 * resides in the repository itself.
	 * <p>
	 * The requested path may or may not exist. If the path already exists as a
	 * file the file should be truncated and completely replaced.
	 * <p>
	 * This method creates any missing parent directories, if necessary.
	 *
	 * @param path
	 *            name of the file to write, relative to the current object
	 *            database.
	 * @param data
	 *            complete new content of the file.
	 * @throws IOException
	 *             writing is not supported, or attempting to write the file
	 *             failed, possibly due to permissions or remote disk full, etc.
	 */
	void writeFile(String path, byte[] data) throws IOException {
		try (OutputStream os = writeFile(path, null, null)) {
			os.write(data);
		}
	}

	
Delete a loose ref from the remote repository.
Params:
name – 
           name of the ref within the ref space, for example
           refs/heads/pu.
Throws:
IOException – 
            deletion is not supported, or deletion failed./**
	 * Delete a loose ref from the remote repository.
	 *
	 * @param name
	 *            name of the ref within the ref space, for example
	 *            <code>refs/heads/pu</code>.
	 * @throws IOException
	 *             deletion is not supported, or deletion failed.
	 */
	void deleteRef(String name) throws IOException {
		deleteFile(ROOT_DIR + name);
	}

	
Delete a reflog from the remote repository.
Params:
name – 
           name of the ref within the ref space, for example
           refs/heads/pu.
Throws:
IOException – 
            deletion is not supported, or deletion failed./**
	 * Delete a reflog from the remote repository.
	 *
	 * @param name
	 *            name of the ref within the ref space, for example
	 *            <code>refs/heads/pu</code>.
	 * @throws IOException
	 *             deletion is not supported, or deletion failed.
	 */
	void deleteRefLog(String name) throws IOException {
		deleteFile(ROOT_DIR + Constants.LOGS + "/" + name); //$NON-NLS-1$
	}

	
Overwrite (or create) a loose ref in the remote repository.

This method creates any missing parent directories, if necessary.
Params:
name – 
           name of the ref within the ref space, for example
           refs/heads/pu.
value – 
           new value to store in this ref. Must not be null.
Throws:
IOException – 
            writing is not supported, or attempting to write the file
            failed, possibly due to permissions or remote disk full, etc./**
	 * Overwrite (or create) a loose ref in the remote repository.
	 * <p>
	 * This method creates any missing parent directories, if necessary.
	 *
	 * @param name
	 *            name of the ref within the ref space, for example
	 *            <code>refs/heads/pu</code>.
	 * @param value
	 *            new value to store in this ref. Must not be null.
	 * @throws IOException
	 *             writing is not supported, or attempting to write the file
	 *             failed, possibly due to permissions or remote disk full, etc.
	 */
	void writeRef(String name, ObjectId value) throws IOException {
		final ByteArrayOutputStream b;

		b = new ByteArrayOutputStream(Constants.OBJECT_ID_STRING_LENGTH + 1);
		value.copyTo(b);
		b.write('\n');

		writeFile(ROOT_DIR + name, b.toByteArray());
	}

	
Rebuild the INFO_PACKS for dumb transport clients. 
 This method rebuilds the contents of the INFO_PACKS file to match the passed list of pack names. 
Params:
packNames – 
           names of available pack files, in the order they should appear
           in the file. Valid pack name strings are of the form
           pack-035760ab452d6eebd123add421f253ce7682355a.pack.
Throws:
IOException – 
            writing is not supported, or attempting to write the file
            failed, possibly due to permissions or remote disk full, etc./**
	 * Rebuild the {@link #INFO_PACKS} for dumb transport clients.
	 * <p>
	 * This method rebuilds the contents of the {@link #INFO_PACKS} file to
	 * match the passed list of pack names.
	 *
	 * @param packNames
	 *            names of available pack files, in the order they should appear
	 *            in the file. Valid pack name strings are of the form
	 *            <code>pack-035760ab452d6eebd123add421f253ce7682355a.pack</code>.
	 * @throws IOException
	 *             writing is not supported, or attempting to write the file
	 *             failed, possibly due to permissions or remote disk full, etc.
	 */
	void writeInfoPacks(Collection<String> packNames) throws IOException {
		final StringBuilder w = new StringBuilder();
		for (String n : packNames) {
			w.append("P "); //$NON-NLS-1$
			w.append(n);
			w.append('\n');
		}
		writeFile(INFO_PACKS, Constants.encodeASCII(w.toString()));
	}

	
Open a buffered reader around a file.

This method is suitable for reading line-oriented resources like
info/packs, info/refs, and the alternates list.
Params:
path – 
           location of the file to read, relative to this objects
           directory (e.g. info/packs).
Throws:
FileNotFoundException – 
            the requested file does not exist at the given location.
IOException – 
            The connection is unable to read the remote's file, and the
            failure occurred prior to being able to determine if the file
            exists, or after it was determined to exist but before the
            stream could be created.
Returns:
a stream to read from the file. Never null./**
	 * Open a buffered reader around a file.
	 * <p>
	 * This method is suitable for reading line-oriented resources like
	 * <code>info/packs</code>, <code>info/refs</code>, and the alternates list.
	 *
	 * @return a stream to read from the file. Never null.
	 * @param path
	 *            location of the file to read, relative to this objects
	 *            directory (e.g. <code>info/packs</code>).
	 * @throws FileNotFoundException
	 *             the requested file does not exist at the given location.
	 * @throws IOException
	 *             The connection is unable to read the remote's file, and the
	 *             failure occurred prior to being able to determine if the file
	 *             exists, or after it was determined to exist but before the
	 *             stream could be created.
	 */
	BufferedReader openReader(String path) throws IOException {
		final InputStream is = open(path).in;
		return new BufferedReader(new InputStreamReader(is, UTF_8));
	}

	
Read a standard Git alternates file to discover other object databases.

This method is suitable for reading the standard formats of the
alternates file, such as found in objects/info/alternates
or objects/info/http-alternates within a Git repository.

Alternates appear one per line, with paths expressed relative to this
object database.
Params:
listPath – 
           location of the alternate file to read, relative to this
           object database (e.g. info/alternates).
Throws:
FileNotFoundException – 
            the requested file does not exist at the given location.
IOException – 
            The connection is unable to read the remote's file, and the
            failure occurred prior to being able to determine if the file
            exists, or after it was determined to exist but before the
            stream could be created.
Returns:
the list of discovered alternates. Empty list if the file exists,
        but no entries were discovered./**
	 * Read a standard Git alternates file to discover other object databases.
	 * <p>
	 * This method is suitable for reading the standard formats of the
	 * alternates file, such as found in <code>objects/info/alternates</code>
	 * or <code>objects/info/http-alternates</code> within a Git repository.
	 * <p>
	 * Alternates appear one per line, with paths expressed relative to this
	 * object database.
	 *
	 * @param listPath
	 *            location of the alternate file to read, relative to this
	 *            object database (e.g. <code>info/alternates</code>).
	 * @return the list of discovered alternates. Empty list if the file exists,
	 *         but no entries were discovered.
	 * @throws FileNotFoundException
	 *             the requested file does not exist at the given location.
	 * @throws IOException
	 *             The connection is unable to read the remote's file, and the
	 *             failure occurred prior to being able to determine if the file
	 *             exists, or after it was determined to exist but before the
	 *             stream could be created.
	 */
	Collection<WalkRemoteObjectDatabase> readAlternates(final String listPath)
			throws IOException {
		try (BufferedReader br = openReader(listPath)) {
			final Collection<WalkRemoteObjectDatabase> alts = new ArrayList<>();
			for (;;) {
				String line = br.readLine();
				if (line == null)
					break;
				if (!line.endsWith("/")) //$NON-NLS-1$
					line += "/"; //$NON-NLS-1$
				alts.add(openAlternate(line));
			}
			return alts;
		}
	}

	
Read a standard Git packed-refs file to discover known references.
Params:
avail – 
           return collection of references. Any existing entries will be
           replaced if they are found in the packed-refs file.
Throws:
TransportException – 
            an error occurred reading from the packed refs file./**
	 * Read a standard Git packed-refs file to discover known references.
	 *
	 * @param avail
	 *            return collection of references. Any existing entries will be
	 *            replaced if they are found in the packed-refs file.
	 * @throws org.eclipse.jgit.errors.TransportException
	 *             an error occurred reading from the packed refs file.
	 */
	protected void readPackedRefs(Map<String, Ref> avail)
			throws TransportException {
		try (BufferedReader br = openReader(ROOT_DIR + Constants.PACKED_REFS)) {
			readPackedRefsImpl(avail, br);
		} catch (FileNotFoundException notPacked) {
			// Perhaps it wasn't worthwhile, or is just an older repository.
		} catch (IOException e) {
			throw new TransportException(getURI(), JGitText.get().errorInPackedRefs, e);
		}
	}

	private void readPackedRefsImpl(final Map<String, Ref> avail,
			final BufferedReader br) throws IOException {
		Ref last = null;
		boolean peeled = false;
		for (;;) {
			String line = br.readLine();
			if (line == null)
				break;
			if (line.charAt(0) == '#') {
				if (line.startsWith(RefDirectory.PACKED_REFS_HEADER)) {
					line = line.substring(RefDirectory.PACKED_REFS_HEADER.length());
					peeled = line.contains(RefDirectory.PACKED_REFS_PEELED);
				}
				continue;
			}
			if (line.charAt(0) == '^') {
				if (last == null)
					throw new TransportException(JGitText.get().peeledLineBeforeRef);
				final ObjectId id = ObjectId.fromString(line.substring(1));
				last = new ObjectIdRef.PeeledTag(Ref.Storage.PACKED, last
						.getName(), last.getObjectId(), id);
				avail.put(last.getName(), last);
				continue;
			}

			final int sp = line.indexOf(' ');
			if (sp < 0)
				throw new TransportException(MessageFormat.format(JGitText.get().unrecognizedRef, line));
			final ObjectId id = ObjectId.fromString(line.substring(0, sp));
			final String name = line.substring(sp + 1);
			if (peeled)
				last = new ObjectIdRef.PeeledNonTag(Ref.Storage.PACKED, name, id);
			else
				last = new ObjectIdRef.Unpeeled(Ref.Storage.PACKED, name, id);
			avail.put(last.getName(), last);
		}
	}

	static final class FileStream {
		final InputStream in;

		final long length;

		
Create a new stream of unknown length.
Params:
i – 
           stream containing the file data. This stream will be
           closed by the caller when reading is complete./**
		 * Create a new stream of unknown length.
		 *
		 * @param i
		 *            stream containing the file data. This stream will be
		 *            closed by the caller when reading is complete.
		 */
		FileStream(InputStream i) {
			in = i;
			length = -1;
		}

		
Create a new stream of known length.
Params:
i – 
           stream containing the file data. This stream will be
           closed by the caller when reading is complete.
n – 
           total number of bytes available for reading through
           i./**
		 * Create a new stream of known length.
		 *
		 * @param i
		 *            stream containing the file data. This stream will be
		 *            closed by the caller when reading is complete.
		 * @param n
		 *            total number of bytes available for reading through
		 *            <code>i</code>.
		 */
		FileStream(InputStream i, long n) {
			in = i;
			length = n;
		}

		byte[] toArray() throws IOException {
			try {
				if (length >= 0) {
					final byte[] r = new byte[(int) length];
					IO.readFully(in, r, 0, r.length);
					return r;
				}

				final ByteArrayOutputStream r = new ByteArrayOutputStream();
				final byte[] buf = new byte[2048];
				int n;
				while ((n = in.read(buf)) >= 0)
					r.write(buf, 0, n);
				return r.toByteArray();
			} finally {
				in.close();
			}
		}
	}
}