src.it.unimi.dsi.io.SegmentedInputStream Maven / Gradle / Ivy
Show all versions of dsiutils Show documentation
package it.unimi.dsi.io;
/*
* DSI utilities
*
* Copyright (C) 2006-2019 Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see An instance of this class wraps a given input stream (usually a replicable one, such as
* a {@link java.io.FileInputStream}) and exposes its contents as a number of separated input
* streams. Each such stream, called a block, is defined by a start and a stop position (gaps
* between blocks are possible). Inside each block we can have one or more segments: each
* segment is again a separate input stream, but calling {@link SegmentedInputStream#reset()} moves
* from one segment to the following one, whereas calling {@link SegmentedInputStream#close()}
* moves from a block to the following one.
*
*
An instance of this class is enriched with blocks by calling {@link #addBlock(long[])}. This
* can also be done on-the-fly, while the underlying input stream is being scanned.
*
* @author Alessio Orlandi
* @author Luca Natali
* @author Sebastiano Vigna
*/
public class SegmentedInputStream extends MeasurableInputStream {
private static final boolean DEBUG = false;
private static final Logger LOGGER = LoggerFactory.getLogger(SegmentedInputStream.class);
/** Underlying input stream. */
private InputStream in;
/** Relative position within the current segment. */
private int relativePos;
/** Byte length of the current segment. */
private int segmentLen;
/** List of known blocks. */
private ObjectArrayList blocks;
/** The start marker of the current segment. */
private long currentStartMarker;
/** The stop marker of the current segment. */
private long currentStopMarker;
/** Index in {@link #blocks}, -1 when no blocks are in. */
private int currentBlock;
/** Whether we actually closed the whole thing. */
private boolean closed;
/** A block. */
private static class SegmentBlock {
/** Segments delimiters, strictly increasing. */
final long[] delimiter;
/** The segment we're currently reading. */
int currSegment;
/** Creates a new block with given delimiters.
*
* @param delimiter a list of segment delimiters.
* @throws IllegalArgumentException if the elements of delimiter are negative or not increasing.
*/
public SegmentBlock(long... delimiter) throws IllegalArgumentException {
if (delimiter.length == 0) throw new IllegalArgumentException();
for (int i = 0; i < delimiter.length - 1; i++)
if (delimiter[i] > delimiter[i + 1]) throw new IllegalArgumentException("Segment " + (i + 1) + " is inconsistent as it starts after the next one: " + Arrays.toString(delimiter));
this.delimiter = delimiter;
this.currSegment = -1;
}
@Override
public String toString() {
return "[segments=" + Arrays.toString(delimiter) + ", curr= " + currSegment + "]";
}
/**
* Skips to the next segment. Now {@link #currentStartMarker()} and {@link #currentStopMarker()} can be used.
*/
public void nextSegment() {
if (! hasMoreSegments()) throw new NoSuchElementException();
currSegment++;
}
public boolean hasMoreSegments() {
return currSegment < delimiter.length - 2;
}
/** Start marker of the current segment (block start if the first segment is selected). */
public long currentStartMarker() {
return delimiter[currSegment];
}
/** Stop marker of the current segment (block stop if the last segment is selected) */
public long currentStopMarker() {
return delimiter[currSegment + 1];
}
}
private void ensureBlocksNotEmpty() {
if (blocks.isEmpty()) throw new IllegalStateException("You must add at least one block before reading or closing a segmented stream");
}
private void ensureNotClosed() {
if (closed) throw new IllegalStateException("This segmented input stream has been closed");
}
/** Creates a segmented input stream with no markers.
*
* @param in the underlying input stream.
*/
public SegmentedInputStream(final InputStream in) {
if (in == null) throw new NullPointerException();
this.in = in;
this.blocks = new ObjectArrayList<>();
this.currentBlock = -1;
}
/** Creats a stream with one marker in.
*
* @param in the underlying input stream.
* @param delimiter an array of segment delimiters.
*/
public SegmentedInputStream(final InputStream in, final long... delimiter) throws NullPointerException, IOException, IllegalStateException {
this(in);
addBlock(delimiter);
}
/** Checks if the current position is a stop marker.
*
* @return false if a skip has to be done or eof has been reached, true otherwise.
*/
private boolean eofInBlock() {
ensureBlocksNotEmpty();
ensureNotClosed();
return relativePos >= segmentLen;
}
/** Skips the underlying input stream to the next segment. */
private void nextSegment() throws IOException {
ensureNotClosed();
final SegmentBlock block = blocks.get(currentBlock);
if (! block.hasMoreSegments()) return;
block.nextSegment();
long absPos = currentStartMarker + relativePos;
currentStartMarker = block.currentStartMarker();
currentStopMarker = block.currentStopMarker();
if (currentStartMarker - absPos > 0) {
long diff = in.skip(currentStartMarker - absPos);
if (diff != currentStartMarker - absPos) throw new IllegalStateException("Should have skipped " + (currentStartMarker - absPos) + " bytes, got " + diff);
}
relativePos = 0;
segmentLen = (int)(currentStopMarker - currentStartMarker);
if (DEBUG) LOGGER.debug("New segment for block # " + currentBlock);
}
/** Skips to the first segment of the next block, if any. In such case, it returns true, or false
* otherwise.
*/
public void nextBlock() throws IOException {
if (! hasMoreBlocks()) throw new NoSuchElementException();
currentBlock++;
if (DEBUG) LOGGER.debug("Moving to block # " + currentBlock);
nextSegment();
}
/** Checks whether there are more blocks.
*
* @return true if we there are more blocks.
*/
public boolean hasMoreBlocks() {
return currentBlock < blocks.size() - 1;
}
/** Adds a new block defined by its array of segment delimiters.
*
* The block has length defined by the difference between the last and first
* delimiter.
*
*
This method performs the initial call to {@link #nextBlock()} when the first marker
* is put in.
*
* @param delimiter a list of segment delimiters.
* @throws IllegalArgumentException if the elements of delimiter are negative or not increasing.
*/
public void addBlock(final long... delimiter) throws IllegalArgumentException, IOException {
ensureNotClosed();
blocks.add(new SegmentBlock(delimiter));
if (DEBUG) LOGGER.debug("Adding a new block with delimiters " + Arrays.toString(delimiter));
if (currentBlock == -1) nextBlock();
}
@Override
public int read() throws IOException {
ensureNotClosed();
if (eofInBlock()) return -1;
final int r = in.read();
relativePos++;
return r;
}
@Override
public int read(final byte b[], final int off, final int len) throws IOException {
ensureNotClosed();
ByteArrays.ensureOffsetLength(b, off, len);
if (len == 0) return 0; // Requested by InputStream.
if (eofInBlock()) return -1;
int effectivelen = Math.min(segmentLen - relativePos, len);
effectivelen = in.read(b, off, effectivelen);
relativePos += effectivelen;
return effectivelen;
}
@Override
public long skip(final long n) throws IOException {
ensureNotClosed();
if (eofInBlock()) return 0;
long effectiveskip = Math.max(Math.min(segmentLen - relativePos, n), 0);
effectiveskip = in.skip(effectiveskip);
relativePos += effectiveskip;
return effectiveskip;
}
@Override
public int available() throws IOException {
ensureNotClosed();
if (eofInBlock()) return 0;
return Math.min(in.available(), segmentLen - relativePos);
}
@Override
public long length() throws IOException {
ensureNotClosed();
return segmentLen;
}
@Override
public long position() throws IOException {
ensureNotClosed();
return relativePos;
}
/** Skips to the next block, closing this segmented input stream if there are no more blocks. */
@Override
public void close() throws IOException {
ensureBlocksNotEmpty();
if (closed) return;
if (hasMoreBlocks()) {
nextBlock();
return;
}
if (DEBUG) LOGGER.debug("Closing the underlying input stream of this segmented input stream");
closed = true;
in.close();
}
/** Moves into the next segment of the current block. */
@Override
public void reset() throws IOException {
ensureNotClosed();
nextSegment();
}
}