CensusInputStream.java

/*
   Copyright (C) 2005-2012, by the President and Fellows of Harvard College.

   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.

   Dataverse Network - A web application to share, preserve and analyze research data.
   Developed at the Institute for Quantitative Social Science, Harvard University.
   Version 3.0.
*/
package edu.harvard.iq.dvn.core.web.dataaccess;

// java core imports:
import java.io.IOException;
import java.io.InputStream;
import java.io.FilterInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.logging.*;

public class CensusInputStream extends FilterInputStream {

    public CensusInputStream(InputStream in) {
        super(in);

        this.rd = new BufferedReader(new InputStreamReader(in));
    }
    private static Logger dbgLog = Logger.getLogger(CensusInputStream.class.getPackage().getName());
    private BufferedReader rd = null;
    private Boolean initialized = false;
    private byte[] cachedData;
    private String[] requestedVariables = null;
    private int[] positions = null;

    @Override
    public int read(byte[] buffer) throws IOException {
        // it ain't pretty, yet;
        // still testing the concept, experimenting with performance, etc.

        String line = null;
        String[] valueTokens;
        int byteLen = 0;

        if (!initialized) {

            dbgLog.fine("initializing CensusInputStream with " + requestedVariables.length + " requested variables");

            positions = new int[requestedVariables.length];

            line = rd.readLine();
            if (line == null) {
                throw new IOException("Could not read input from Census download servlet.");
            }

            // chop the newlines:
            line = line.replaceFirst("[\r\n]*$", "");

            // split on TABs:
            valueTokens = line.split("\t", -2);

            // determine the location of the variables that we want:
            for (int i = 0; i < requestedVariables.length; i++) {
                int j = 0;
                int position = -1;

                while (j < valueTokens.length && position < 0) {
                    if (requestedVariables[i].equals(valueTokens[j])) {
                        position = j;
                    }
                    j++;
                }

                if (position > -1) {
                    this.positions[i] = position;
                } else {
                    throw new IOException("Requested variable " + requestedVariables[i] +
                            " not found in the Census data stream.");
                }
            }

            initialized = true;
            dbgLog.fine("successfully initialized CensusInputStream");
        }

        if (cachedData != null && cachedData.length > 0) {

            if (cachedData.length < buffer.length) {
                for (int i = 0; i < cachedData.length; i++) {
                    buffer[i] = cachedData[i];
                }
                byteLen = cachedData.length;
                cachedData = null;

            } else {
                for (int i = 0; i < buffer.length; i++) {
                    buffer[i] = cachedData[i];
                }
                byte[] leftoverCache = new byte[cachedData.length - buffer.length];
                for (int i = 0; i < cachedData.length - buffer.length; i++) {
                    leftoverCache[i] = cachedData[buffer.length + i];
                }
                cachedData = leftoverCache;
                return buffer.length;
            }
        }

        while (byteLen < buffer.length) {
            try {
                line = rd.readLine();
            } catch (IOException ex) {
                if (byteLen > 0) {
                    dbgLog.info("exception caught while reading data; returning "+byteLen+" bytes read.");
                    return byteLen;
                }
                dbgLog.info("exception caught while reading data; returning -1.");
                return -1;
            }

            if (line == null) {
                if (byteLen > 0) {
                    dbgLog.info("end of data reached; returning "+byteLen+" bytes read.");

                    return byteLen;
                }
                dbgLog.info("end of data reached; returning -1.");
                return -1;
            }

            line = line.replaceFirst("[\r\n]*$", "");
            valueTokens = line.split("\t", -2);

            int byteLenLocal = 0;

            for (int i = 0; i < positions.length; i++) {
                byteLenLocal += (valueTokens[positions[i]].length()+1);
            }

            byte[] dataSelected = new byte[byteLenLocal];

            int k = 0;

            for (int i = 0; i < positions.length; i++) {
                byte[] valueTokenBytes = valueTokens[positions[i]].getBytes();
                for (int j = 0; j < valueTokenBytes.length; j++) {
                    dataSelected[k++] = valueTokenBytes[j];
                }
                if (i == positions.length-1) {
                    dataSelected[k++] = '\n';
                } else {
                    dataSelected[k++] = '\t';
                }
            }

            if (k != byteLenLocal) {
                throw new IOException("error parsing Census byte stream");
            }

            if (byteLen + byteLenLocal < buffer.length) {
                for (int i = 0; i < byteLenLocal; i++) {
                    buffer[byteLen + i] = dataSelected[i];
                }
                byteLen += byteLenLocal;
            } else {
                for (int i = 0; i < buffer.length - byteLen; i++) {
                    buffer[byteLen + i] = dataSelected[i];
                }

                if (byteLenLocal - buffer.length + byteLen > 0) {
                    cachedData = new byte[byteLenLocal - buffer.length + byteLen];
                    for (int i = 0; i < cachedData.length; i++) {
                        cachedData[i] = dataSelected[i + buffer.length - byteLen];
                    }

                    dbgLog.fine("stored "+cachedData.length+" bytes of cached data.");
                }

                return buffer.length;
            }
        }

        return byteLen;
    }

    @Override
    public int read() throws IOException {
        if (true) {
            throw new IOException("Census input stream: read() not supported.");
        }
        return 0;
    }

    @Override
    public int read(byte[] buffer, int a, int b) throws IOException {
        if (true) {
            throw new IOException("Census input stream: read(byte[], int, int) not supported.");
        }

        return 0;
    }

    public void setRequestedVariables(String[] requestedVariables) {
        this.requestedVariables = requestedVariables;
        this.positions = new int[requestedVariables.length];
    }
}