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Used for reading, writing and validating WARC files.
Implemented to follow the WARC/1.0 ISO specification as closely as possible.
/**
* Java Web Archive Toolkit - Software to read and validate ARC, WARC
* and GZip files. (http://jwat.org/)
* Copyright 2011-2012 Netarkivet.dk (http://netarkivet.dk/)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jwat.warc;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.jwat.common.Diagnosis;
import org.jwat.common.Diagnostics;
import org.jwat.common.HeaderLineReader;
import org.jwat.common.UriProfile;
/**
* Base class for WARC reader implementations.
*
* @author nicl
*/
public abstract class WarcReader implements Closeable, Iterable {
/*
* Settings.
*/
/** WARC-Target-URI profile. */
protected UriProfile warcTargetUriProfile;
/** URI profile. */
protected UriProfile uriProfile;
/** Default block digest algorithm to use if none is present in the
* record. */
protected String blockDigestAlgorithm;
/** Default encoding scheme used to encode block digest into a string,
* if none is detected from the record. */
protected String blockDigestEncoding = "base32";
/** Payload Digest enabled/disabled. */
protected boolean bPayloadDigest = false;
/** Default payload digest algorithm to use if none is present in the
* record. */
protected String payloadDigestAlgorithm;
/** Default encoding scheme used to encode payload digest into a string,
* if none is detected from the record. */
protected String payloadDigestEncoding = "base32";
/** Block Digest enabled/disabled. */
protected boolean bBlockDigest = false;
/** Max size allowed for a record header. */
protected int recordHeaderMaxSize;
/** Max size allowed for a payload header. */
protected int payloadHeaderMaxSize;
/** Line reader used to read version lines. */
protected HeaderLineReader lineReader;
/** Header line reader used to read the WARC headers. */
protected HeaderLineReader headerLineReader;
/** WARC field parser used. */
protected WarcFieldParsers fieldParsers;
/*
* State.
*/
/** Reader level errors and warnings or when no record is available. */
public final Diagnostics diagnostics = new Diagnostics();
/** Compliance status for records parsed up to now. */
protected boolean bIsCompliant = true;
/** Number of bytes consumed by this reader. */
protected long consumed = 0;
/** Records parsed. */
protected int records = 0;
/** Aggregated number of errors encountered while parsing. */
protected int errors = 0;
/** Aggregate number of warnings encountered while parsing. */
protected int warnings = 0;
/** Current WARC record object. */
protected WarcRecord currentRecord;
/** Exception thrown while using the iterator. */
protected Exception iteratorExceptionThrown;
/**
* Method used to initialize a readers internal state.
* Must be called by all constructors.
*/
protected void init() {
warcTargetUriProfile = UriProfile.RFC3986;
uriProfile = UriProfile.RFC3986;
recordHeaderMaxSize = 8192;
payloadHeaderMaxSize = 32768;
lineReader = HeaderLineReader.getReader();
lineReader.bNameValue = false;
lineReader.encoding = HeaderLineReader.ENC_US_ASCII;
headerLineReader = HeaderLineReader.getReader();
headerLineReader.bNameValue = true;
headerLineReader.encoding = HeaderLineReader.ENC_UTF8;
headerLineReader.bLWS = true;
headerLineReader.bQuotedText = true;
headerLineReader.bEncodedWords = true;
fieldParsers = new WarcFieldParsers();
}
/**
* Reset reader for reuse.
*/
public void reset() {
diagnostics.reset();
bIsCompliant = true;
consumed = 0;
records = 0;
errors = 0;
warnings = 0;
currentRecord = null;
}
/**
* Returns a boolean indicating if all records parsed so far are compliant.
* @return a boolean indicating if all records parsed so far are compliant
*/
public boolean isCompliant() {
return bIsCompliant;
}
/**
* Is this reader assuming GZip compressed input.
* @return boolean indicating the assumption of GZip compressed input
*/
public abstract boolean isCompressed();
/**
* Set the URI profile used to validate WARC-Target URIs.
* If null, the uriProfile is set to RCF3986.
* @param uriProfile URI profile to use
*/
public void setWarcTargetUriProfile(UriProfile uriProfile) {
if (uriProfile == null) {
uriProfile = UriProfile.RFC3986;
}
this.warcTargetUriProfile = uriProfile;
}
/**
* Get the URI profile used to validate WARC-Target URIs.
* @return the URI profile used to validate WARC-Target URIs
*/
public UriProfile getWarcTargetUriProfile() {
return warcTargetUriProfile;
}
/**
* Set the URI profile used to validate URIs.
* If null, the uriProfile is set to RCF3986.
* @param uriProfile URI profile to use
*/
public void setUriProfile(UriProfile uriProfile) {
if (uriProfile == null) {
uriProfile = UriProfile.RFC3986;
}
this.uriProfile = uriProfile;
}
/**
* Get the URI profile used to validate URIs.
* @return the URI profile used to validate URIs
*/
public UriProfile getUriProfile() {
return uriProfile;
}
/**
* Get the readers block digest on/off status.
* @return boolean indicating block digest on/off
*/
public boolean getBlockDigestEnabled() {
return bBlockDigest;
}
/**
* Set the readers block digest on/off status. Digest, however,
* will only be computed if either a Warc-Block-Digest header is
* present or an optional algorithm has been chosen.
* The Warc-Block-Digest always takes precedence.
* @param enabled boolean indicating block digest on/off
*/
public void setBlockDigestEnabled(boolean enabled) {
bBlockDigest = enabled;
}
/**
* Get the readers payload digest on/off status.
* @return boolean indicating payload digest on/off
*/
public boolean getPayloadDigestEnabled() {
return bPayloadDigest;
}
/**
* Set the readers payload digest on/off status. Digest, however,
* will only be computed if either a Warc-Payload-Digest header is
* present or an optional algorithm has been chosen.
* The Warc-Payload-Digest always takes precedence.
* @param enabled boolean indicating payload digest on/off
*/
public void setPayloadDigestEnabled(boolean enabled) {
bPayloadDigest = enabled;
}
/**
* Get the default block digest algorithm.
* @return default block digest algorithm
*/
public String getBlockDigestAlgorithm() {
return blockDigestAlgorithm;
}
/**
* Tries to set the default block digest algorithm and returns a boolean
* indicating whether the algorithm was accepted or not. This algorithm is
* only used in case no WARC payload digest header is present in the record.
* @param digestAlgorithm block digest algorithm
* (null means no default block digest algorithm is selected)
* @return boolean indicating the validity of the algorithm supplied
*/
public boolean setBlockDigestAlgorithm(String digestAlgorithm) {
if (digestAlgorithm == null || digestAlgorithm.length() == 0) {
blockDigestAlgorithm = null;
return true;
}
if (WarcDigest.digestAlgorithmLength(digestAlgorithm) > 0) {
blockDigestAlgorithm = digestAlgorithm;
return true;
}
return false;
}
/**
* Get the default payload digest algorithm.
* @return default payload digest algorithm
*/
public String getPayloadDigestAlgorithm() {
return payloadDigestAlgorithm;
}
/**
* Tries to set the default payload digest algorithm and returns a boolean
* indicating whether the algorithm was accepted or not. This algorithm is
* only used in case no WARC payload digest header is present in the record.
* @param digestAlgorithm payload digest algorithm
* (null means no default payload digest algorithm is selected)
* @return boolean indicating the validity of the algorithm supplied
*/
public boolean setPayloadDigestAlgorithm(String digestAlgorithm) {
if (digestAlgorithm == null || digestAlgorithm.length() == 0) {
payloadDigestAlgorithm = null;
return true;
}
if (WarcDigest.digestAlgorithmLength(digestAlgorithm) > 0) {
payloadDigestAlgorithm = digestAlgorithm;
return true;
}
return false;
}
/**
* Get the default block digest encoding scheme.
* @return default block digest encoding scheme
*/
public String getBlockDigestEncoding() {
return blockDigestEncoding;
}
/**
* Set the default block digest encoding scheme. This scheme is only
* used if none can be inferred from an existing block digest header.
* @param encodingScheme encoding scheme
* (null means default block digest is not encoded)
*/
public void setBlockDigestEncoding(String encodingScheme) {
if (encodingScheme != null && encodingScheme.length() > 0) {
blockDigestEncoding = encodingScheme.toLowerCase();
} else {
blockDigestEncoding = null;
}
}
/**
* Get the default payload digest encoding scheme.
* @return default payload digest encoding scheme
*/
public String getPayloadDigestEncoding() {
return payloadDigestEncoding;
}
/**
* Set the default payload digest encoding scheme. This scheme is only
* used if none can be inferred from an existing payload digest header.
* @param encodingScheme encoding scheme
* (null means default payload digest is not encoded)
*/
public void setPayloadDigestEncoding(String encodingScheme) {
if (encodingScheme != null && encodingScheme.length() > 0) {
payloadDigestEncoding = encodingScheme.toLowerCase();
} else {
payloadDigestEncoding = null;
}
}
/**
* Get the max size allowed for a record header.
* @return max size allowed for a record header
*/
public int getRecordHeaderMaxSize() {
return recordHeaderMaxSize;
}
/**
* Set the max size allowed for a record header.
* @param size max size allowed
*/
public void setRecordHeaderMaxSize(int size) {
recordHeaderMaxSize = size;
}
/**
* Get the max size allowed for a payload header.
* @return max size allowed for a payload header
*/
public int getPayloadHeaderMaxSize() {
return payloadHeaderMaxSize;
}
/**
* Set the max size allowed for a payload header.
* @param size max size allowed
*/
public void setPayloadHeaderMaxSize(int size) {
payloadHeaderMaxSize = size;
}
/**
* Close current record resource(s) and input stream(s).
*/
public abstract void close();
/**
* Callback method called when the payload has been processed.
*/
protected abstract void recordClosed();
/**
* Get the offset of the current WARC record or -1 if none have been read.
* @return offset of the current WARC record or -1
*/
public abstract long getStartOffset();
/**
* Get the current offset in the WARC InputStream.
* @return offset in WARC InputStream
*/
public abstract long getOffset();
/**
* Get number of bytes consumed by this reader.
* @return number of bytes consumed by this reader
*/
public abstract long getConsumed();
/**
* Parses and gets the next record.
* This method is for linear access to records.
* @return the next record
* @throws IOException i/o exception in parsing process
*/
public abstract WarcRecord getNextRecord() throws IOException;
/**
* Parses and gets the next record from an Inputstream.
* This method is mainly for random access use since there are serious
* side-effects involved in using multiple PushBackInputStream
* instances.
* @param in InputStream used to read next record
* @param offset offset provided by caller
* @return the next record
* @throws IOException i/o exception in parsing process
*/
public abstract WarcRecord getNextRecordFrom(InputStream in, long offset)
throws IOException;
/**
* Parses and gets the next record from an Inputstream wrapped
* by a BufferedInputStream.
* This method is mainly for random access use since there are serious
* side-effects involved in using multiple PushBackInputStream
* instances.
* @param in InputStream used to read next record
* @param offset offset provided by caller
* @param buffer_size buffer size to use
* @return the next record
* @throws IOException i/o exception in parsing process
*/
public abstract WarcRecord getNextRecordFrom(InputStream in, long offset,
int buffer_size) throws IOException;
/**
* Gets an exception thrown in the iterator if any or null.
* @return exception thrown in the iterator if any or null
*/
public Exception getIteratorExceptionThrown() {
return iteratorExceptionThrown;
}
/**
* Returns an Iterator over the records as they are being
* parsed. Any exception thrown during parsing is accessible through the
* getIteratorExceptionThrown method.
* @return Iterator over the records
*/
public Iterator iterator() {
return new Iterator() {
/** Internal next record updated by either hasNext() or next(). */
private WarcRecord next;
/** Entry returned by next(). */
private WarcRecord current;
@Override
public boolean hasNext() {
if (next == null) {
iteratorExceptionThrown = null;
try {
next = getNextRecord();
} catch (IOException e) {
iteratorExceptionThrown = e;
}
}
return (next != null);
}
@Override
public WarcRecord next() {
if (next == null) {
iteratorExceptionThrown = null;
try {
next = getNextRecord();
} catch (IOException e) {
iteratorExceptionThrown = e;
}
}
if (next == null) {
throw new NoSuchElementException();
}
current = next;
next = null;
return current;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
}