IOUtils.java

package com.android.volley.misc;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class IOUtils {

    private IOUtils() {}

    /*
     * Homebrewed simple serialization system used for reading and writing cache
     * headers on disk. Once upon a time, this used the standard Java
     * Object{Input,Output}Stream, but the default implementation relies heavily
     * on reflection (even for standard types) and generates a ton of garbage.
     */

    /**
     * Simple wrapper around {@link InputStream#read()} that throws EOFException
     * instead of returning -1.
     */
	public static int read(InputStream is) throws IOException {
        int b = is.read();
        if (b == -1) {
            throw new EOFException();
        }
        return b;
    }

    public static void writeInt(OutputStream os, int n) throws IOException {
        os.write((n >> 0) & 0xff);
        os.write((n >> 8) & 0xff);
        os.write((n >> 16) & 0xff);
        os.write((n >> 24) & 0xff);
    }

    public static int readInt(InputStream is) throws IOException {
        int n = 0;
        n |= (read(is) << 0);
        n |= (read(is) << 8);
        n |= (read(is) << 16);
        n |= (read(is) << 24);
        return n;
    }

    public static void writeLong(OutputStream os, long n) throws IOException {
        os.write((byte)(n >>> 0));
        os.write((byte)(n >>> 8));
        os.write((byte)(n >>> 16));
        os.write((byte)(n >>> 24));
        os.write((byte)(n >>> 32));
        os.write((byte)(n >>> 40));
        os.write((byte)(n >>> 48));
        os.write((byte)(n >>> 56));
    }

    public static long readLong(InputStream is) throws IOException {
        long n = 0;
        n |= ((read(is) & 0xFFL) << 0);
        n |= ((read(is) & 0xFFL) << 8);
        n |= ((read(is) & 0xFFL) << 16);
        n |= ((read(is) & 0xFFL) << 24);
        n |= ((read(is) & 0xFFL) << 32);
        n |= ((read(is) & 0xFFL) << 40);
        n |= ((read(is) & 0xFFL) << 48);
        n |= ((read(is) & 0xFFL) << 56);
        return n;
    }

    public static void writeString(OutputStream os, String s) throws IOException {
        byte[] b = s.getBytes("UTF-8");
        writeLong(os, b.length);
        os.write(b, 0, b.length);
    }

    public static String readString(InputStream is) throws IOException {
        int n = (int) readLong(is);
        byte[] b = streamToBytes(is, n);
        return new String(b, "UTF-8");
    }

    public static void writeStringStringMap(Map<String, String> map, OutputStream os) throws IOException {
        if (map != null) {
            writeInt(os, map.size());
            for (Map.Entry<String, String> entry : map.entrySet()) {
                writeString(os, entry.getKey());
                writeString(os, entry.getValue());
            }
        } else {
            writeInt(os, 0);
        }
    }

    public static Map<String, String> readStringStringMap(InputStream is) throws IOException {
        int size = readInt(is);
        Map<String, String> result = (size == 0)
                ? Collections.<String, String>emptyMap()
                : new HashMap<String, String>(size);
        for (int i = 0; i < size; i++) {
            String key = readString(is).intern();
            String value = readString(is).intern();
            result.put(key, value);
        }
        return result;
    }
    

    /**
     * Reads the contents of an InputStream into a byte[].
     * */
    public static byte[] streamToBytes(InputStream in, int length) throws IOException {
        byte[] bytes = new byte[length];
        int count;
        int pos = 0;
        while (pos < length && ((count = in.read(bytes, pos, length - pos)) != -1)) {
            pos += count;
        }
        if (pos != length) {
            throw new IOException("Expected " + length + " bytes, read " + pos + " bytes");
        }
        return bytes;
    }
}