Command.java

package redis.netty4;

import com.google.common.base.Charsets;
import io.netty.buffer.ByteBuf;

import java.io.IOException;

import static redis.util.Encoding.numToBytes;

/**
 * Command serialization.  We special case when there are few 4 or fewer parameters
 * since most commands fall into that category. Passing bytes, channelbuffers and
 * strings / objects are all allowed. All strings are assumed to be UTF-8.
 */
public class Command {
  public static final byte[] ARGS_PREFIX = "*".getBytes();
  public static final byte[] CRLF = "\r\n".getBytes();
  public static final byte[] BYTES_PREFIX = "$".getBytes();
  public static final byte[] EMPTY_BYTES = new byte[0];

  private final Object name;
  private final Object[] objects;
  private final Object object1;
  private final Object object2;
  private final Object object3;
  private final boolean inline;

  public Command(Object[] objects) {
    this(null, null, null, null, objects, false);
  }

  public Command(Object[] objects, boolean inline) {
    this(null, null, null, null, objects, inline);
  }

  public Command(Object name) {
    this(name, null, null, null, null, false);
  }

  public Command(Object name, Object[] objects) {
    this(name, null, null, null, objects, false);
  }

  public Command(Object name, Object object1) {
    this(name, object1, null, null, null, false);
  }

  public Command(Object name, Object object1, Object object2) {
    this(name, object1, object2, null, null, false);
  }

  public Command(Object name, Object object1, Object object2, Object object3) {
    this(name, object1, object2, object3, null, false);
  }

  private Command(Object name, Object object1, Object object2, Object object3, Object[] objects, boolean inline) {
    this.name = name;
    this.object1 = object1;
    this.object2 = object2;
    this.object3 = object3;
    this.objects = objects;
    this.inline = inline;
  }

  public byte[] getName() {
    // It is either the name or the first objects in the objects array
    if (name != null) return getBytes(name);
    return getBytes(objects[0]);
  }

  public boolean isInline() {
    return inline;
  }

  private byte[] getBytes(Object object) {
    byte[] argument;
    if (object == null) {
      argument = EMPTY_BYTES;
    } else if (object instanceof byte[]) {
      argument = (byte[]) object;
    } else if (object instanceof ByteBuf) {
      argument = ((ByteBuf) object).array();
    } else if (object instanceof String) {
      argument = ((String) object).getBytes(Charsets.UTF_8);
    } else {
      argument = object.toString().getBytes(Charsets.UTF_8);
    }
    return argument;
  }

  public void toArguments(Object[] arguments, Class<?>[] types) {
    int position = 0;
    for (Class<?> type : types) {
      if (type == byte[].class) {
        if (position >= arguments.length) {
          throw new IllegalArgumentException("wrong number of arguments for '" + new String(getName()) + "' command");
        }
        if (objects.length - 1 > position) {
          arguments[position] = objects[1 + position];
        }
      } else {
        int left = objects.length - position - 1;
        byte[][] lastArgument = new byte[left][];
        for (int i = 0; i < left; i++) {
          lastArgument[i] = (byte[]) objects[i + position + 1];
        }
        arguments[position] = lastArgument;
      }
      position++;
    }
  }


  public void write(ByteBuf os) throws IOException {
    writeDirect(os, name, object1, object2, object3, objects);
  }

  public static void writeDirect(ByteBuf os, Object name, Object object1, Object object2, Object object3, Object[] objects) throws IOException {
    int others = (object1 == null ? 0 : 1) + (object2 == null ? 0 : 1) +
            (object3 == null ? 0 : 1) + (name == null ? 0 : 1);
    int length = objects == null ? 0 : objects.length;
    os.writeBytes(ARGS_PREFIX);
    os.writeBytes(numToBytes(length + others, true));
    if (name != null) writeObject(os, name);
    if (object1 != null) writeObject(os, object1);
    if (object2 != null) writeObject(os, object2);
    if (object3 != null) writeObject(os, object3);
    if (objects != null) {
      for (Object object : objects) {
        writeObject(os, object);
      }
    }
  }

  private static void writeObject(ByteBuf os, Object object) throws IOException {
    byte[] argument;
    if (object == null) {
      argument = EMPTY_BYTES;
    } else if (object instanceof byte[]) {
      argument = (byte[]) object;
    } else if (object instanceof ByteBuf) {
      writeArgument(os, (ByteBuf) object);
      return;
    } else if (object instanceof String) {
      argument = ((String) object).getBytes(Charsets.UTF_8);
    } else {
      argument = object.toString().getBytes(Charsets.UTF_8);
    }
    writeArgument(os, argument);
  }

  private static void writeArgument(ByteBuf os, byte[] argument) throws IOException {
    os.writeBytes(BYTES_PREFIX);
    os.writeBytes(numToBytes(argument.length, true));
    os.writeBytes(argument);
    os.writeBytes(CRLF);
  }

  private static void writeArgument(ByteBuf os, ByteBuf argument) throws IOException {
    os.writeBytes(BYTES_PREFIX);
    os.writeBytes(numToBytes(argument.readableBytes(), true));
    os.writeBytes(argument);
    os.writeBytes(CRLF);
  }

}