package com.fasterxml.jackson.core.format;
import java.io.*;
import java.util.*;
import com.fasterxml.jackson.core.*;
/**
* Simple helper class that allows data format (content type) auto-detection,
* given an ordered set of {@link JsonFactory} instances to use for actual low-level
* detection.
*/
public class DataFormatDetector
{
/**
* By default we will look ahead at most 64 bytes; in most cases,
* much less (4 bytes or so) is needed, but we will allow bit more
* leniency to support data formats that need more complex heuristics.
*/
public final static int DEFAULT_MAX_INPUT_LOOKAHEAD = 64;
/**
* Ordered list of factories which both represent data formats to
* detect (in precedence order, starting with highest) and are used
* for actual detection.
*/
protected final JsonFactory[] _detectors;
/**
* Strength of match we consider to be good enough to be used
* without checking any other formats.
* Default value is {@link MatchStrength#SOLID_MATCH},
*/
protected final MatchStrength _optimalMatch;
/**
* Strength of minimal match we accept as the answer, unless
* better matches are found.
* Default value is {@link MatchStrength#WEAK_MATCH},
*/
protected final MatchStrength _minimalMatch;
/**
* Maximum number of leading bytes of the input that we can read
* to determine data format.
*<p>
* Default value is {@link #DEFAULT_MAX_INPUT_LOOKAHEAD}.
*/
protected final int _maxInputLookahead;
/*
/**********************************************************
/* Construction
/**********************************************************
*/
public DataFormatDetector(JsonFactory... detectors) {
this(detectors, MatchStrength.SOLID_MATCH, MatchStrength.WEAK_MATCH,
DEFAULT_MAX_INPUT_LOOKAHEAD);
}
public DataFormatDetector(Collection<JsonFactory> detectors) {
this(detectors.toArray(new JsonFactory[detectors.size()]));
}
/**
* Method that will return a detector instance that uses given
* optimal match level (match that is considered sufficient to return, without
* trying to find stronger matches with other formats).
*/
public DataFormatDetector withOptimalMatch(MatchStrength optMatch) {
if (optMatch == _optimalMatch) {
return this;
}
return new DataFormatDetector(_detectors, optMatch, _minimalMatch, _maxInputLookahead);
}
/**
* Method that will return a detector instance that uses given
* minimal match level; match that may be returned unless a stronger match
* is found with other format detectors.
*/
public DataFormatDetector withMinimalMatch(MatchStrength minMatch) {
if (minMatch == _minimalMatch) {
return this;
}
return new DataFormatDetector(_detectors, _optimalMatch, minMatch, _maxInputLookahead);
}
/**
* Method that will return a detector instance that allows detectors to
* read up to specified number of bytes when determining format match strength.
*/
public DataFormatDetector withMaxInputLookahead(int lookaheadBytes)
{
if (lookaheadBytes == _maxInputLookahead) {
return this;
}
return new DataFormatDetector(_detectors, _optimalMatch, _minimalMatch, lookaheadBytes);
}
private DataFormatDetector(JsonFactory[] detectors,
MatchStrength optMatch, MatchStrength minMatch,
int maxInputLookahead)
{
_detectors = detectors;
_optimalMatch = optMatch;
_minimalMatch = minMatch;
_maxInputLookahead = maxInputLookahead;
}
/*
/**********************************************************
/* Public API
/**********************************************************
*/
/**
* Method to call to find format that content (accessible via given
* {@link InputStream}) given has, as per configuration of this detector
* instance.
*
* @return Matcher object which contains result; never null, even in cases
* where no match (with specified minimal match strength) is found.
*/
public DataFormatMatcher findFormat(InputStream in) throws IOException
{
return _findFormat(new InputAccessor.Std(in, new byte[_maxInputLookahead]));
}
/**
* Method to call to find format that given content (full document)
* has, as per configuration of this detector instance.
*
* @return Matcher object which contains result; never null, even in cases
* where no match (with specified minimal match strength) is found.
*/
public DataFormatMatcher findFormat(byte[] fullInputData) throws IOException
{
return _findFormat(new InputAccessor.Std(fullInputData));
}
/*
/**********************************************************
/* Internal methods
/**********************************************************
*/
private DataFormatMatcher _findFormat(InputAccessor.Std acc) throws IOException
{
JsonFactory bestMatch = null;
MatchStrength bestMatchStrength = null;
for (JsonFactory f : _detectors) {
acc.reset();
MatchStrength strength = f.hasFormat(acc);
// if not better than what we have so far (including minimal level limit), skip
if (strength == null || strength.ordinal() < _minimalMatch.ordinal()) {
continue;
}
// also, needs to better match than before
if (bestMatch != null) {
if (bestMatchStrength.ordinal() >= strength.ordinal()) {
continue;
}
}
// finally: if it's good enough match, we are done
bestMatch = f;
bestMatchStrength = strength;
if (strength.ordinal() >= _optimalMatch.ordinal()) {
break;
}
}
return acc.createMatcher(bestMatch, bestMatchStrength);
}
}