io.sirix.index.art.BinaryComparables Maven / Gradle / Ivy

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package io.sirix.index.art;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;

// noninstantiable companion class

/**
 * Provides implementation of {@link BinaryComparable} for primitives and {@link String}
 */
public class BinaryComparables {

  private BinaryComparables() {
    throw new AssertionError();
  }

  public static BinaryComparable forInteger() {
    return INTEGER;
  }

  public static BinaryComparable forLong() {
    return LONG;
  }

  public static BinaryComparable forShort() {
    return SHORT;
  }

  public static BinaryComparable forByte() {
    return BYTE;
  }

  public static BinaryComparable forString() {
    return String::getBytes;
  }

  /**
   * Uses {@link String#getBytes(Charset)} to get bytes in the lexicographic order of Unicode code points,
   * as defined in {@link String#compareTo(String)} 

   * Note: Use Collators if you want locale dependent comparisons
   *
   * @see Collator
   */
  public static BinaryComparable forString(Charset charset) {
    return (key) -> key.getBytes(charset);
  }

  private static final BinaryComparable INTEGER =
      (key) -> BinaryComparableUtils.unsigned(ByteBuffer.allocate(Integer.BYTES).putInt(key).array());
  private static final BinaryComparable LONG =
      (key) -> BinaryComparableUtils.unsigned(ByteBuffer.allocate(Long.BYTES).putLong(key).array());
  private static final BinaryComparable SHORT =
      (key) -> BinaryComparableUtils.unsigned(ByteBuffer.allocate(Short.BYTES).putShort(key).array());
  private static final BinaryComparable BYTE =
      (key) -> BinaryComparableUtils.unsigned(ByteBuffer.allocate(Byte.BYTES).put(key).array());
	/*
	 extract from https://docs.oracle.com/javase/tutorial/i18n/text/collationintro.html:
	 If your application audience is limited to people who speak English,
	 you can probably perform string comparisons with the String.compareTo method.
	 The String.compareTo method performs a binary comparison of the Unicode characters within the two strings.
	 For most languages, however, this binary comparison cannot be relied on to sort strings,
	 because the Unicode values do not correspond to the relative order of the characters.
	 */
}