FileUtils.java

package cc.blynk.utils;

import cc.blynk.server.core.model.AppName;
import cc.blynk.server.core.model.auth.User;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.SeekableByteChannel;
import java.nio.file.*;

/**
 * The Blynk Project.
 * Created by Dmitriy Dumanskiy.
 * Created on 04.01.16.
 */
public class FileUtils {

    private final static Logger log = LogManager.getLogger(FileUtils.class);

    public static void deleteQuietly(Path path) {
        try {
            Files.deleteIfExists(path);
        } catch (Exception ignored) {
            //ignore
        }
    }

    public static boolean move(Path source, Path target) {
        try {
            Path targetFile = Paths.get(target.toString(), source.getFileName().toString());
            Files.move(source, targetFile, StandardCopyOption.REPLACE_EXISTING);
        } catch (IOException e) {
            log.debug("Failed to move file. {}" , e.getMessage());
            return false;
        }
        return true;
    }

    /**
     * Simply writes single reporting entry to disk (16 bytes).
     * Reporting entry is value (double) and timestamp (long)
     *
     * @param reportingPath - path to user specific reporting file
     * @param value - sensor data
     * @param ts - time when entry was created
     * @throws IOException
     */
    public static void write(Path reportingPath, double value, long ts) throws IOException {
        try (DataOutputStream dos = new DataOutputStream(
                Files.newOutputStream(reportingPath, StandardOpenOption.CREATE, StandardOpenOption.APPEND))) {
            dos.writeDouble(value);
            dos.writeLong(ts);
            dos.flush();
        }
    }

    private static final int SIZE_OF_REPORT_ENTRY = 16;

    /**
     * Read bunch of last records from file.
     *
     * @param userDataFile - file to read
     * @param count = number of records to read
     * @return - byte buffer with data
     * @throws IOException
     */
    public static ByteBuffer read(Path userDataFile, int count) throws IOException {
        try (SeekableByteChannel channel = Files.newByteChannel(userDataFile, StandardOpenOption.READ)) {
            final int size = (int) Files.size(userDataFile);
            final int dataSize = count * SIZE_OF_REPORT_ENTRY;
            final int readDataSize = Math.min(dataSize, size);

            ByteBuffer buf = ByteBuffer.allocate(readDataSize);
            channel.position(Math.max(0, size - dataSize));
            channel.read(buf);
            return buf;
        }
    }

    public static String getUserReportingDir(User user) {
        return getUserReportingDir(user.email, user.appName);
    }

    public static String getUserReportingDir(String email, String appName) {
        if (appName.equals(AppName.BLYNK)) {
            return email;
        }
        return email + "_" + appName;
    }

    public static String csvDownloadUrl(String host, String httpPort) {
        return "http://" + host + ":" + httpPort + "/";
    }
}