private BandAnalysisResults analyseBand()

in src/main/java/org/apache/commons/compress/harmony/pack200/BandSet.java [214:312]
82 lines of code
18 McCabe index (conditional complexity)

    private BandAnalysisResults analyseBand(final String name, final int[] band, final BHSDCodec defaultCodec) throws Pack200Exception {

        final BandAnalysisResults results = new BandAnalysisResults();

        if (canonicalLargest == null) {
            canonicalLargest = new long[116];
            canonicalSmallest = new long[116];
            for (int i = 1; i < canonicalLargest.length; i++) {
                canonicalLargest[i] = CodecEncoding.getCanonicalCodec(i).largest();
                canonicalSmallest[i] = CodecEncoding.getCanonicalCodec(i).smallest();
            }
        }
        final BandData bandData = new BandData(band);

        // Check that there is a reasonable saving to be made
        final byte[] encoded = defaultCodec.encode(band);
        results.encodedBand = encoded;

        // Note: these values have been tuned - please test carefully if changing them
        if (encoded.length <= band.length + 23 - 2 * effort) { // TODO: tweak
            return results;
        }

        // Check if we can use BYTE1 as that's a 1:1 mapping if we can
        if (!bandData.anyNegatives() && bandData.largest <= Codec.BYTE1.largest()) {
            results.encodedBand = Codec.BYTE1.encode(band);
            results.betterCodec = Codec.BYTE1;
            return results;
        }

        // Consider a population codec (but can't be nested)
        if (effort > 3 && !name.equals("POPULATION")) {
            final int numDistinctValues = bandData.numDistinctValues();
            final float distinctValuesAsProportion = (float) numDistinctValues / (float) band.length;

            // Note: these values have been tuned - please test carefully if changing them
            if (numDistinctValues < 100 || distinctValuesAsProportion < 0.02 || effort > 6 && distinctValuesAsProportion < 0.04) { // TODO: tweak
                encodeWithPopulationCodec(band, defaultCodec, bandData, results);
                if (timeToStop(results)) {
                    return results;
                }
            }
        }

        final List<BHSDCodec[]> codecFamiliesToTry = new ArrayList<>();

        // See if the deltas are mainly small increments
        if (bandData.mainlyPositiveDeltas() && bandData.mainlySmallDeltas()) {
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs2);
        }

        if (bandData.wellCorrelated()) { // Try delta encodings
            if (bandData.mainlyPositiveDeltas()) {
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs1);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs3);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs4);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs5);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs1);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs3);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs4);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs5);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs2);
            } else {
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs1);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs3);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs2);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs4);
                codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs5);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaSignedCodecs1);
                codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaSignedCodecs2);
            }
        } else if (bandData.anyNegatives()) {
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaSignedCodecs1);
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaSignedCodecs2);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs1);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs2);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs3);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs4);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaSignedCodecs5);
        } else {
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs1);
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs3);
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs4);
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs5);
            codecFamiliesToTry.add(CanonicalCodecFamilies.nonDeltaUnsignedCodecs2);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs1);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs3);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs4);
            codecFamiliesToTry.add(CanonicalCodecFamilies.deltaUnsignedCodecs5);
        }
        for (final BHSDCodec[] family : codecFamiliesToTry) {
            tryCodecs(band, defaultCodec, bandData, results, encoded, family);
            if (timeToStop(results)) {
                break;
            }
        }

        return results;
    }