com.mappn.gfan.common.download.DownloadThread.java Source code

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/*
 * Copyright (C) 2010 mAPPn.Inc
 *
 * 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 com.mappn.gfan.common.download;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.SyncFailedException;
import java.net.URI;
import java.net.URISyntaxException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Locale;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;

import android.content.ContentValues;
import android.content.Context;
import android.os.PowerManager;
import android.os.Process;
import android.text.TextUtils;

import com.mappn.gfan.common.AndroidHttpClient;
import com.mappn.gfan.common.HttpClientFactory;
import com.mappn.gfan.common.download.DownloadManager.Impl;
import com.mappn.gfan.common.util.Utils;

/**
 * Runs an actual download
 */
public class DownloadThread extends Thread {

    private Context mContext;
    private DownloadInfo mInfo;

    public DownloadThread(Context context, DownloadInfo info) {
        mContext = context;
        mInfo = info;
    }

    /**
     * State for the entire run() method.
     */
    private static class State {
        public String mFilename;
        public FileOutputStream mStream;
        public String mMimeType;
        public boolean mCountRetry = false;
        public int mRetryAfter = 0;
        public int mRedirectCount = 0;
        public String mNewUri;
        public boolean mGotData = false;
        public String mRequestUri;
        public MessageDigest mDigester;
        public int mSourceType = -1;

        public State(DownloadInfo info) {
            mMimeType = sanitizeMimeType(info.mMimeType);
            mRedirectCount = info.mRedirectCount;
            mRequestUri = info.mUri;
            mFilename = info.mFileName;
            mSourceType = info.mSource;
            try {
                mDigester = MessageDigest.getInstance("MD5");
            } catch (NoSuchAlgorithmException e) {
                Utils.D("no algorithm for md5");
            }
        }
    }

    /**
     * State within executeDownload()
     */
    private static class InnerState {
        public int mBytesSoFar = 0;
        public String mHeaderETag;
        public boolean mContinuingDownload = false;
        public String mHeaderContentLength;
        public String mHeaderContentLocation;
        public int mBytesNotified = 0;
        public long mTimeLastNotification = 0;
    }

    /**
     * Raised from methods called by run() to indicate that the current request should be stopped
     * immediately.
     *
     * Note the message passed to this exception will be logged and therefore must be guaranteed
     * not to contain any PII, meaning it generally can't include any information about the request
     * URI, headers, or destination filename.
     */
    private class StopRequest extends Throwable {

        /**serialVersionUID */
        private static final long serialVersionUID = -8371899395848839220L;

        public int mFinalStatus;

        public StopRequest(int finalStatus, String message) {
            super(message);
            mFinalStatus = finalStatus;
        }

        public StopRequest(int finalStatus, String message, Throwable throwable) {
            super(message, throwable);
            mFinalStatus = finalStatus;
        }
    }

    /**
     * Raised from methods called by executeDownload() to indicate that the download should be
     * retried immediately.
     */
    private class RetryDownload extends Throwable {

        /** serialVersionUID */
        private static final long serialVersionUID = 1L;
    }

    /**
     * Executes the download in a separate thread
     */
    public void run() {

        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);

        State state = new State(mInfo);
        AndroidHttpClient client = null;
        PowerManager.WakeLock wakeLock = null;
        int finalStatus = DownloadManager.Impl.STATUS_UNKNOWN_ERROR;

        try {
            PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
            wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, com.mappn.gfan.common.util.Utils.sLogTag);
            wakeLock.acquire();

            Utils.D("initiating download for " + mInfo.mUri);

            client = HttpClientFactory.get().getHttpClient();

            boolean finished = false;
            while (!finished) {

                Utils.D("Initiating request for download " + mInfo.mId + " url " + mInfo.mUri);

                HttpGet request = new HttpGet(state.mRequestUri);
                try {
                    executeDownload(state, client, request);
                    finished = true;
                } catch (RetryDownload exc) {
                    // fall through
                } finally {
                    request.abort();
                    request = null;
                }
            }

            Utils.D("download completed for " + mInfo.mUri);

            if (!checkFile(state)) {
                throw new Throwable("File MD5 code is not the same as server");
            }

            finalizeDestinationFile(state);
            finalStatus = DownloadManager.Impl.STATUS_SUCCESS;
        } catch (StopRequest error) {
            // remove the cause before printing, in case it contains PII
            Utils.W("Aborting request for download " + mInfo.mId + " url: " + mInfo.mUri + " : "
                    + error.getMessage());
            finalStatus = error.mFinalStatus;
            // fall through to finally block
        } catch (Throwable ex) { //sometimes the socket code throws unchecked exceptions
            Utils.W("Exception for id " + mInfo.mId + " url: " + mInfo.mUri + ": " + ex);
            // falls through to the code that reports an error
        } finally {
            if (wakeLock != null) {
                wakeLock.release();
                wakeLock = null;
            }
            if (client != null) {
                client = null;
            }
            cleanupDestination(state, finalStatus);
            notifyDownloadCompleted(finalStatus, state.mCountRetry, state.mRetryAfter, state.mRedirectCount,
                    state.mGotData, state.mFilename, state.mNewUri, state.mMimeType);
            mInfo.mHasActiveThread = false;
        }
    }

    /**
     * ???MD5??
     */
    private boolean checkFile(State state) {
        final String targetMD5 = mInfo.mMD5;

        if (TextUtils.isEmpty(targetMD5))
            // if server don't have md5 code then no need to check
            return true;

        // otherwise, check the file Integrity
        byte[] digest = state.mDigester.digest();
        String fileMD5 = convertToHex(digest);
        if (targetMD5.equalsIgnoreCase(fileMD5)) {
            return true;
        }
        return false;
    }

    private static String convertToHex(byte[] data) {
        StringBuilder buf = new StringBuilder();
        for (int i = 0; i < data.length; i++) {
            int halfbyte = (data[i] >>> 4) & 0x0F;
            int two_halfs = 0;
            do {
                if ((0 <= halfbyte) && (halfbyte <= 9))
                    buf.append((char) ('0' + halfbyte));
                else
                    buf.append((char) ('a' + (halfbyte - 10)));
                halfbyte = data[i] & 0x0F;
            } while (two_halfs++ < 1);
        }
        return buf.toString();
    }

    /**
     * Fully execute a single download request - setup and send the request, handle the response,
     * and transfer the data to the destination file.
     */
    private void executeDownload(State state, AndroidHttpClient client, HttpGet request)
            throws StopRequest, RetryDownload {
        InnerState innerState = new InnerState();
        byte data[] = new byte[Constants.BUFFER_SIZE];

        // set up the download file information
        setupDestinationFile(state, innerState);

        // add request headers for continue downloading
        addRequestHeaders(innerState, request);

        // check just before sending the request to avoid using an invalid connection at all
        checkConnectivity(state);

        HttpResponse response = sendRequest(state, client, request);
        handleExceptionalStatus(state, innerState, response);

        Utils.D("received response for " + mInfo.mUri);

        processResponseHeaders(state, innerState, response);
        InputStream entityStream = openResponseEntity(state, response);
        DigestInputStream responseStream = new DigestInputStream(entityStream, state.mDigester);
        transferData(state, innerState, data, responseStream);
    }

    /**
     * Check if current connectivity is valid for this request.
     */
    private void checkConnectivity(State state) throws StopRequest {
        int networkUsable = mInfo.checkCanUseNetwork();
        if (networkUsable != DownloadInfo.NETWORK_OK) {
            int status = DownloadManager.Impl.STATUS_WAITING_FOR_NETWORK;
            throw new StopRequest(status, mInfo.getLogMessageForNetworkError(networkUsable));
        }
    }

    /**
     * Transfer as much data as possible from the HTTP response to the destination file.
     * @param data buffer to use to read data
     * @param entityStream stream for reading the HTTP response entity
     */
    private void transferData(State state, InnerState innerState, byte[] data, InputStream entityStream)
            throws StopRequest {
        for (;;) {
            int bytesRead = readFromResponse(state, innerState, data, entityStream);
            if (bytesRead == -1) {
                // XXX success, end of stream already reached
                handleEndOfStream(state, innerState);
                return;
            }

            state.mGotData = true;
            writeDataToDestination(state, data, bytesRead);
            innerState.mBytesSoFar += bytesRead;
            reportProgress(state, innerState);

            checkPausedOrCanceled(state);
        }
    }

    /**
     * Called after a successful completion to take any necessary action on the downloaded file.
     */
    private void finalizeDestinationFile(State state) throws StopRequest {
        syncDestination(state);
    }

    /**
     * Called just before the thread finishes, regardless of status, to take any necessary action on
     * the downloaded file.
     */
    private void cleanupDestination(State state, int finalStatus) {
        closeDestination(state);
        if (state.mFilename != null && DownloadManager.Impl.isStatusError(finalStatus)) {
            new File(state.mFilename).delete();
            state.mFilename = null;
        }
    }

    /**
     * Sync the destination file to storage.
     */
    private void syncDestination(State state) {
        FileOutputStream downloadedFileStream = null;
        try {
            downloadedFileStream = new FileOutputStream(state.mFilename, true);
            downloadedFileStream.getFD().sync();
        } catch (FileNotFoundException ex) {
            Utils.W("file " + state.mFilename + " not found: " + ex);
        } catch (SyncFailedException ex) {
            Utils.W("file " + state.mFilename + " sync failed: " + ex);
        } catch (IOException ex) {
            Utils.W("IOException trying to sync " + state.mFilename + ": " + ex);
        } catch (RuntimeException ex) {
            Utils.W("exception while syncing file: ", ex);
        } finally {
            if (downloadedFileStream != null) {
                try {
                    downloadedFileStream.close();
                } catch (IOException ex) {
                    Utils.W("IOException while closing synced file: ", ex);
                } catch (RuntimeException ex) {
                    Utils.W("exception while closing file: ", ex);
                }
            }
        }
    }

    /**
     * Close the destination output stream.
     */
    private void closeDestination(State state) {
        try {
            // close the file
            if (state.mStream != null) {
                state.mStream.close();
                state.mStream = null;
            }
        } catch (IOException ex) {
            Utils.D("exception when closing the file after download : " + ex);
            // nothing can really be done if the file can't be closed
        }
    }

    /**
     * Check if the download has been paused or canceled, stopping the request appropriately if it
     * has been.
     */
    private void checkPausedOrCanceled(State state) throws StopRequest {
        synchronized (mInfo) {
            if (mInfo.mControl == DownloadManager.Impl.CONTROL_PAUSED) {
                throw new StopRequest(DownloadManager.Impl.STATUS_PAUSED_BY_APP, "download paused by owner");
            } else if (mInfo.mControl == DownloadManager.Impl.CONTROL_PENDING) {
                throw new StopRequest(DownloadManager.Impl.STATUS_QUEUED_FOR_WIFI, "download is in pending status");
            }
        }
        if (mInfo.mStatus == DownloadManager.Impl.STATUS_CANCELED) {
            throw new StopRequest(DownloadManager.Impl.STATUS_CANCELED, "download canceled");
        }
    }

    /**
     * Report download progress through the database if necessary.
     */
    private void reportProgress(State state, InnerState innerState) {
        long now = System.currentTimeMillis();
        if (innerState.mBytesSoFar - innerState.mBytesNotified > Constants.MIN_PROGRESS_STEP
                && now - innerState.mTimeLastNotification > Constants.MIN_PROGRESS_TIME) {
            ContentValues values = new ContentValues();
            values.put(DownloadManager.Impl.COLUMN_CURRENT_BYTES, innerState.mBytesSoFar);
            mContext.getContentResolver().update(mInfo.getMyDownloadsUri(), values, null, null);
            innerState.mBytesNotified = innerState.mBytesSoFar;
            innerState.mTimeLastNotification = now;
        }
    }

    /**
     * Write a data buffer to the destination file.
     * @param data buffer containing the data to write
     * @param bytesRead how many bytes to write from the buffer
     */
    private void writeDataToDestination(State state, byte[] data, int bytesRead) throws StopRequest {
        try {
            if (state.mStream == null) {
                state.mStream = new FileOutputStream(state.mFilename, true);
            }
            state.mStream.write(data, 0, bytesRead);
            if (mInfo.mDestination == DownloadManager.Impl.DESTINATION_EXTERNAL) {
                closeDestination(state);
            }
            return;
        } catch (IOException ex) {
            throw new StopRequest(DownloadManager.Impl.STATUS_FILE_ERROR,
                    "while writing destination file: " + ex.toString(), ex);
        }
    }

    /**
     * Called when we've reached the end of the HTTP response stream, to update the database and
     * check for consistency.
     */
    private void handleEndOfStream(State state, InnerState innerState) throws StopRequest {
        ContentValues values = new ContentValues();
        values.put(DownloadManager.Impl.COLUMN_CURRENT_BYTES, innerState.mBytesSoFar);
        if (innerState.mHeaderContentLength == null) {
            values.put(DownloadManager.Impl.COLUMN_TOTAL_BYTES, innerState.mBytesSoFar);
        }
        mContext.getContentResolver().update(mInfo.getMyDownloadsUri(), values, null, null);

        boolean lengthMismatched = (innerState.mHeaderContentLength != null)
                && (innerState.mBytesSoFar != Integer.parseInt(innerState.mHeaderContentLength));
        if (lengthMismatched) {
            if (cannotResume(innerState)) {
                throw new StopRequest(DownloadManager.Impl.STATUS_CANNOT_RESUME, "mismatched content length");
            } else {
                throw new StopRequest(getFinalStatusForHttpError(state), "closed socket before end of file");
            }
        }
    }

    private boolean cannotResume(InnerState innerState) {
        return innerState.mBytesSoFar > 0 && innerState.mHeaderETag == null;
    }

    /**
     * Read some data from the HTTP response stream, handling I/O errors.
     * @param data buffer to use to read data
     * @param entityStream stream for reading the HTTP response entity
     * @return the number of bytes actually read or -1 if the end of the stream has been reached
     */
    private int readFromResponse(State state, InnerState innerState, byte[] data, InputStream entityStream)
            throws StopRequest {
        try {
            return entityStream.read(data);
        } catch (IOException ex) {
            logNetworkState();
            ContentValues values = new ContentValues();
            values.put(DownloadManager.Impl.COLUMN_CURRENT_BYTES, innerState.mBytesSoFar);
            mContext.getContentResolver().update(mInfo.getMyDownloadsUri(), values, null, null);
            if (cannotResume(innerState)) {
                String message = "while reading response: " + ex.toString()
                        + ", can't resume interrupted download with no ETag";
                throw new StopRequest(DownloadManager.Impl.STATUS_CANNOT_RESUME, message, ex);
            } else {
                throw new StopRequest(getFinalStatusForHttpError(state), "while reading response: " + ex.toString(),
                        ex);
            }
        }
    }

    /**
     * Open a stream for the HTTP response entity, handling I/O errors.
     * @return an InputStream to read the response entity
     */
    private InputStream openResponseEntity(State state, HttpResponse response) throws StopRequest {
        try {
            return response.getEntity().getContent();
        } catch (IOException ex) {
            logNetworkState();
            throw new StopRequest(getFinalStatusForHttpError(state), "while getting entity: " + ex.toString(), ex);
        }
    }

    private void logNetworkState() {
        Utils.I("Net " + (Helper.isNetworkAvailable(mContext) ? "Up" : "Down"));
    }

    /**
     * Read HTTP response headers and take appropriate action, including setting up the destination
     * file and updating the database.
     */
    private void processResponseHeaders(State state, InnerState innerState, HttpResponse response)
            throws StopRequest {
        if (innerState.mContinuingDownload) {
            // ignore response headers on resume requests
            return;
        }

        readResponseHeaders(state, innerState, response);

        try {
            state.mFilename = Helper.generateSaveFile(mContext, mInfo.mUri, mInfo.mHint,
                    innerState.mHeaderContentLocation, state.mMimeType, mInfo.mDestination, mInfo.mTotalBytes,
                    mInfo.mSource);
        } catch (Helper.GenerateSaveFileError exc) {
            throw new StopRequest(exc.mStatus, exc.mMessage);
        }
        try {
            state.mStream = new FileOutputStream(state.mFilename);
        } catch (FileNotFoundException exc) {
            throw new StopRequest(DownloadManager.Impl.STATUS_FILE_ERROR,
                    "while opening destination file: " + exc.toString(), exc);
        }
        Utils.D("writing " + mInfo.mUri + " to " + state.mFilename);
        Utils.D("totalbytes " + mInfo.mTotalBytes);
        updateDatabaseFromHeaders(state, innerState);
        // check connectivity again now that we know the total size
        checkConnectivity(state);
    }

    /**
     * Update necessary database fields based on values of HTTP response headers that have been
     * read.
     */
    private void updateDatabaseFromHeaders(State state, InnerState innerState) {
        ContentValues values = new ContentValues();
        values.put(DownloadManager.Impl.COLUMN_DATA, state.mFilename);
        if (innerState.mHeaderETag != null) {
            values.put(Impl.COLUMN_ETAG, innerState.mHeaderETag);
        }
        if (state.mMimeType != null) {
            values.put(DownloadManager.Impl.COLUMN_MIME_TYPE, state.mMimeType);
        }
        long totalBytes = Long.parseLong(innerState.mHeaderContentLength);
        values.put(DownloadManager.Impl.COLUMN_TOTAL_BYTES, totalBytes);

        Utils.D("update the header : " + mInfo.mPackageName + " values " + values);
        mContext.getContentResolver().update(mInfo.getMyDownloadsUri(), values, null, null);
    }

    /**
     * Read headers from the HTTP response and store them into local state.
     */
    private void readResponseHeaders(State state, InnerState innerState, HttpResponse response) throws StopRequest {
        Header header = response.getFirstHeader("Content-Location");
        if (header != null) {
            innerState.mHeaderContentLocation = header.getValue();
        }
        if (state.mMimeType == null) {
            header = response.getFirstHeader("Content-Type");
            if (header != null) {
                state.mMimeType = sanitizeMimeType(header.getValue());
            }
        }
        header = response.getFirstHeader("ETag");
        if (header != null) {
            innerState.mHeaderETag = header.getValue();
        }
        String headerTransferEncoding = null;
        header = response.getFirstHeader("Transfer-Encoding");
        if (header != null) {
            headerTransferEncoding = header.getValue();
        }
        if (headerTransferEncoding == null) {
            header = response.getFirstHeader("Content-Length");
            if (header != null) {
                innerState.mHeaderContentLength = header.getValue();
                mInfo.mTotalBytes = Long.parseLong(innerState.mHeaderContentLength);
            }
        } else {
            // Ignore content-length with transfer-encoding - 2616 4.4 3
            Utils.D("ignoring content-length because of xfer-encoding");
        }

        Utils.D("Content-Length: " + innerState.mHeaderContentLength);
        Utils.D("Content-Location: " + innerState.mHeaderContentLocation);
        Utils.D("Content-Type: " + state.mMimeType);
        Utils.D("ETag: " + innerState.mHeaderETag);
        Utils.D("Transfer-Encoding: " + headerTransferEncoding);
        Utils.D("total-bytes: " + mInfo.mTotalBytes);

        boolean noSizeInfo = innerState.mHeaderContentLength == null
                && (headerTransferEncoding == null || !headerTransferEncoding.equalsIgnoreCase("chunked"));
        if (noSizeInfo) {
            throw new StopRequest(DownloadManager.Impl.STATUS_HTTP_DATA_ERROR,
                    "can't know size of download, giving up");
        }
    }

    /**
     * Check the HTTP response status and handle anything unusual (e.g. not 200/206).
     */
    private void handleExceptionalStatus(State state, InnerState innerState, HttpResponse response)
            throws StopRequest, RetryDownload {
        int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode == 503 && mInfo.mNumFailed < Constants.MAX_RETRIES) {
            handleServiceUnavailable(state, response);
        }
        if (statusCode == 301 || statusCode == 302 || statusCode == 303 || statusCode == 307) {
            handleRedirect(state, response, statusCode);
        }
        int expectedStatus = innerState.mContinuingDownload ? 206 : DownloadManager.Impl.STATUS_SUCCESS;
        if (statusCode != expectedStatus) {
            handleOtherStatus(state, innerState, statusCode);
        }
    }

    /**
     * Handle a status that we don't know how to deal with properly.
     */
    private void handleOtherStatus(State state, InnerState innerState, int statusCode) throws StopRequest {
        int finalStatus;
        if (DownloadManager.Impl.isStatusError(statusCode)) {
            finalStatus = statusCode;
        } else if (statusCode >= 300 && statusCode < 400) {
            finalStatus = DownloadManager.Impl.STATUS_UNHANDLED_REDIRECT;
        } else if (innerState.mContinuingDownload && statusCode == DownloadManager.Impl.STATUS_SUCCESS) {
            finalStatus = DownloadManager.Impl.STATUS_CANNOT_RESUME;
        } else {
            finalStatus = DownloadManager.Impl.STATUS_UNHANDLED_HTTP_CODE;
        }
        Utils.D("throw new stop request ----> " + finalStatus + " statusCode " + statusCode + " isContinuing "
                + innerState.mContinuingDownload + " fileName " + state.mFilename);
        throw new StopRequest(finalStatus, "http error " + statusCode);
    }

    /**
     * Handle a 3xx redirect status.
     */
    private void handleRedirect(State state, HttpResponse response, int statusCode)
            throws StopRequest, RetryDownload {

        Utils.D("got HTTP redirect " + statusCode);

        if (state.mRedirectCount >= Constants.MAX_REDIRECTS) {
            throw new StopRequest(DownloadManager.Impl.STATUS_TOO_MANY_REDIRECTS, "too many redirects");
        }
        Header header = response.getFirstHeader("Location");
        if (header == null) {
            return;
        }
        Utils.D("Location :" + header.getValue());

        String newUri;
        try {
            newUri = new URI(mInfo.mUri).resolve(new URI(header.getValue())).toString();
        } catch (URISyntaxException ex) {
            Utils.D("Couldn't resolve redirect URI " + header.getValue() + " for " + mInfo.mUri);
            throw new StopRequest(DownloadManager.Impl.STATUS_HTTP_DATA_ERROR, "Couldn't resolve redirect URI");
        }
        ++state.mRedirectCount;
        state.mRequestUri = newUri;
        if (statusCode == 301 || statusCode == 303) {
            // use the new URI for all future requests (should a retry/resume be necessary)
            state.mNewUri = newUri;
        }
        throw new RetryDownload();
    }

    /**
     * Handle a 503 Service Unavailable status by processing the Retry-After header.
     */
    private void handleServiceUnavailable(State state, HttpResponse response) throws StopRequest {

        Utils.D("got HTTP response code 503");

        state.mCountRetry = true;
        Header header = response.getFirstHeader("Retry-After");
        if (header != null) {
            try {

                Utils.D("Retry-After :" + header.getValue());

                state.mRetryAfter = Integer.parseInt(header.getValue());
                if (state.mRetryAfter < 0) {
                    state.mRetryAfter = 0;
                } else {
                    if (state.mRetryAfter < Constants.MIN_RETRY_AFTER) {
                        state.mRetryAfter = Constants.MIN_RETRY_AFTER;
                    } else if (state.mRetryAfter > Constants.MAX_RETRY_AFTER) {
                        state.mRetryAfter = Constants.MAX_RETRY_AFTER;
                    }
                    state.mRetryAfter += Helper.rnd.nextInt(Constants.MIN_RETRY_AFTER + 1);
                    state.mRetryAfter *= 1000;
                }
            } catch (NumberFormatException ex) {
                // ignored - retryAfter stays 0 in this case.
            }
        }
        throw new StopRequest(DownloadManager.Impl.STATUS_WAITING_TO_RETRY,
                "got 503 Service Unavailable, will retry later");
    }

    /**
     * Send the request to the server, handling any I/O exceptions.
     */
    private HttpResponse sendRequest(State state, AndroidHttpClient client, HttpGet request) throws StopRequest {
        try {
            return client.execute(request);
        } catch (IllegalArgumentException ex) {
            throw new StopRequest(DownloadManager.Impl.STATUS_HTTP_DATA_ERROR,
                    "while trying to execute request: " + ex.toString(), ex);
        } catch (IOException ex) {
            logNetworkState();
            throw new StopRequest(getFinalStatusForHttpError(state),
                    "while trying to execute request: " + ex.toString(), ex);
        }
    }

    private int getFinalStatusForHttpError(State state) {
        if (!Helper.isNetworkAvailable(mContext)) {
            return DownloadManager.Impl.STATUS_WAITING_FOR_NETWORK;
        } else if (mInfo.mNumFailed < Constants.MAX_RETRIES) {
            state.mCountRetry = true;
            return DownloadManager.Impl.STATUS_WAITING_TO_RETRY;
        } else {
            Utils.D("reached max retries for " + mInfo.mId);
            return DownloadManager.Impl.STATUS_HTTP_DATA_ERROR;
        }
    }

    /**
     * Prepare the destination file to receive data.  If the file already exists, we'll set up
     * appropriately for resumption.
     */
    private void setupDestinationFile(State state, InnerState innerState) throws StopRequest {

        if (!TextUtils.isEmpty(state.mFilename)) {
            // only true if we've already run a thread for this download
            if (!Helper.isFilenameValid(state.mFilename, state.mSourceType)) {
                // this should never happen
                throw new StopRequest(DownloadManager.Impl.STATUS_FILE_ERROR,
                        "found invalid internal destination filename");
            }

            // We're resuming a download that got interrupted
            File f = new File(state.mFilename);
            if (f.exists()) {
                long fileLength = f.length();
                if (fileLength == 0) {
                    // The download hadn't actually started, we can restart from scratch
                    f.delete();
                    state.mFilename = null;
                } else if (mInfo.mETag == null) {
                    // This should've been caught upon failure
                    f.delete();
                    throw new StopRequest(DownloadManager.Impl.STATUS_CANNOT_RESUME,
                            "Trying to resume a download that can't be resumed");
                } else {
                    // All right, we'll be able to resume this download
                    try {
                        state.mStream = new FileOutputStream(state.mFilename, true);
                        FileInputStream fis = new FileInputStream(state.mFilename);
                        DigestInputStream dis = new DigestInputStream(fis, state.mDigester);
                        byte[] buffer = new byte[8192];
                        while (dis.read(buffer) != -1) {
                            // read the digest
                        }
                        dis.close();
                        fis.close();
                    } catch (FileNotFoundException exc) {
                        throw new StopRequest(DownloadManager.Impl.STATUS_FILE_ERROR,
                                "while opening destination for resuming: " + exc.toString(), exc);
                    } catch (IOException e) {
                        throw new StopRequest(DownloadManager.Impl.STATUS_FILE_ERROR,
                                "while opening destination for resuming: " + e.toString(), e);
                    }
                    innerState.mBytesSoFar = (int) fileLength;
                    if (mInfo.mTotalBytes != -1) {
                        innerState.mHeaderContentLength = Long.toString(mInfo.mTotalBytes);
                    }
                    innerState.mHeaderETag = mInfo.mETag;
                    innerState.mContinuingDownload = true;
                }
            }
        }

        if (state.mStream != null && mInfo.mDestination == DownloadManager.Impl.DESTINATION_EXTERNAL) {
            closeDestination(state);
        }
    }

    /**
     * Add custom headers for this download to the HTTP request.
     */
    private void addRequestHeaders(InnerState innerState, HttpGet request) {

        if (innerState.mContinuingDownload) {
            if (innerState.mHeaderETag != null) {
                request.addHeader("If-Match", innerState.mHeaderETag);
            }
            request.addHeader("Range", "bytes=" + innerState.mBytesSoFar + "-");
        }
    }

    /**
     * Stores information about the completed download, and notifies the initiating application.
     */
    private void notifyDownloadCompleted(int status, boolean countRetry, int retryAfter, int redirectCount,
            boolean gotData, String filename, String uri, String mimeType) {
        notifyThroughDatabase(status, countRetry, retryAfter, redirectCount, gotData, filename, uri, mimeType);
        if (DownloadManager.Impl.isStatusCompleted(status)) {
            mInfo.sendIntentIfRequested();
        }
    }

    /**
     * ?? 
     */
    private void notifyThroughDatabase(int status, boolean countRetry, int retryAfter, int redirectCount,
            boolean gotData, String filename, String uri, String mimeType) {
        ContentValues values = new ContentValues();
        values.put(Impl.COLUMN_STATUS, status);
        values.put(Impl.COLUMN_DATA, filename);
        if (uri != null) {
            values.put(Impl.COLUMN_URI, uri);
        }
        values.put(Impl.COLUMN_MIME_TYPE, mimeType);
        values.put(Impl.COLUMN_LAST_MODIFICATION, System.currentTimeMillis());
        values.put(Impl.COLUMN_RETRY_AFTER_REDIRECT_COUNT, retryAfter + (redirectCount << 28));
        if (!countRetry) {
            values.put(Impl.COLUMN_FAILED_CONNECTIONS, 0);
        } else if (gotData) {
            values.put(Impl.COLUMN_FAILED_CONNECTIONS, 1);
        } else {
            values.put(Impl.COLUMN_FAILED_CONNECTIONS, mInfo.mNumFailed + 1);
        }

        mContext.getContentResolver().update(mInfo.getMyDownloadsUri(), values, null, null);
    }

    /**
     * Clean up a mimeType string so it can be used to dispatch an intent to
     * view a downloaded asset.
     * @param mimeType either null or one or more mime types (semi colon separated).
     * @return null if mimeType was null. Otherwise a string which represents a
     * single mimetype in lowercase and with surrounding whitespaces trimmed.
     */
    private static String sanitizeMimeType(String mimeType) {
        try {
            mimeType = mimeType.trim().toLowerCase(Locale.ENGLISH);

            final int semicolonIndex = mimeType.indexOf(';');
            if (semicolonIndex != -1) {
                mimeType = mimeType.substring(0, semicolonIndex);
            }
            return mimeType;
        } catch (NullPointerException npe) {
            return null;
        }
    }
}