Util.java

package org.stellar.sdk;

import com.google.common.io.BaseEncoding;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import org.stellar.sdk.xdr.ClaimableBalanceID;
import org.stellar.sdk.xdr.SorobanTransactionData;
import org.stellar.sdk.xdr.XdrDataInputStream;
import org.stellar.sdk.xdr.XdrDataOutputStream;

public class Util {

  public static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();

  public static String bytesToHex(byte[] bytes) {
    char[] hexChars = new char[bytes.length * 2];
    for (int j = 0; j < bytes.length; j++) {
      int v = bytes[j] & 0xFF;
      hexChars[j * 2] = HEX_ARRAY[v >>> 4];
      hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
    }
    return new String(hexChars);
  }

  public static byte[] hexToBytes(String s) {
    int len = s.length();
    byte[] data = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
      data[i / 2] =
          (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
    }
    return data;
  }

  /**
   * Returns SHA-256 hash of <code>data</code>.
   *
   * @param data
   */
  public static byte[] hash(byte[] data) {
    try {
      MessageDigest md = MessageDigest.getInstance("SHA-256");
      md.update(data);
      return md.digest();
    } catch (NoSuchAlgorithmException e) {
      throw new RuntimeException("SHA-256 not implemented");
    }
  }

  /**
   * Pads <code>bytes</code> array to <code>length</code> with zeros.
   *
   * @param bytes
   * @param length
   */
  static byte[] paddedByteArray(byte[] bytes, int length) {
    byte[] finalBytes = new byte[length];
    Arrays.fill(finalBytes, (byte) 0);
    System.arraycopy(bytes, 0, finalBytes, 0, bytes.length);
    return finalBytes;
  }

  /**
   * Pads <code>string</code> to <code>length</code> with zeros.
   *
   * @param string
   * @param length
   */
  static byte[] paddedByteArray(String string, int length) {
    return Util.paddedByteArray(string.getBytes(), length);
  }

  /**
   * Remove zeros from the end of <code>bytes</code> array.
   *
   * @param bytes
   */
  static String paddedByteArrayToString(byte[] bytes) {
    String[] strArray = new String(bytes).split("\0");
    if (strArray.length > 0) {
      return strArray[0];
    }
    return "";
  }

  /**
   * Get the version of the SDK
   *
   * @return version
   */
  public static String getSdkVersion() {
    String clientVersion = "dev";
    String implementationVersion = Util.class.getPackage().getImplementationVersion();
    if (implementationVersion != null) {
      clientVersion = implementationVersion;
    }
    return clientVersion;
  }

  public static ClaimableBalanceID claimableBalanceIdToXDR(String balanceId) {
    byte[] balanceIdBytes = BaseEncoding.base16().lowerCase().decode(balanceId.toLowerCase());
    XdrDataInputStream balanceIdXdrDataInputStream =
        new XdrDataInputStream(new ByteArrayInputStream(balanceIdBytes));

    try {
      return ClaimableBalanceID.decode(balanceIdXdrDataInputStream);
    } catch (IOException e) {
      throw new IllegalArgumentException("invalid balanceId: " + balanceId, e);
    }
  }

  public static String xdrToClaimableBalanceId(ClaimableBalanceID balanceId) {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    XdrDataOutputStream xdrDataOutputStream = new XdrDataOutputStream(byteArrayOutputStream);
    try {
      balanceId.encode(xdrDataOutputStream);
    } catch (IOException e) {
      throw new IllegalArgumentException("invalid claimClaimableBalanceOp.", e);
    }
    return BaseEncoding.base16().lowerCase().encode(byteArrayOutputStream.toByteArray());
  }

  /**
   * Convert {@link SorobanTransactionData} XDR String representation to {@link
   * SorobanTransactionData} object.
   *
   * @param sorobanData XDR String representation of a {@link SorobanTransactionData}
   * @return {@link SorobanTransactionData}
   */
  public static SorobanTransactionData sorobanTransactionDataToXDR(String sorobanData) {
    BaseEncoding base64Encoding = BaseEncoding.base64();
    byte[] bytes = base64Encoding.decode(sorobanData);
    ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes);
    XdrDataInputStream xdrInputStream = new XdrDataInputStream(inputStream);
    try {
      return SorobanTransactionData.decode(xdrInputStream);
    } catch (IOException e) {
      throw new IllegalArgumentException("invalid sorobanData: " + sorobanData, e);
    }
  }

  /**
   * Convert {@link SorobanTransactionData} object to XDR String representation.
   *
   * @param sorobanData {@link SorobanTransactionData} object
   * @return XDR String representation of a {@link SorobanTransactionData}
   */
  public static String xdrToSorobanTransactionData(SorobanTransactionData sorobanData) {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    XdrDataOutputStream xdrDataOutputStream = new XdrDataOutputStream(byteArrayOutputStream);
    try {
      sorobanData.encode(xdrDataOutputStream);
    } catch (IOException e) {
      throw new IllegalArgumentException("invalid sorobanData.", e);
    }
    BaseEncoding base64Encoding = BaseEncoding.base64();
    return base64Encoding.encode(byteArrayOutputStream.toByteArray());
  }

  public static AssetTypeCreditAlphaNum assertNonNativeAsset(Asset asset) {
    if (asset instanceof AssetTypeCreditAlphaNum) {
      return (AssetTypeCreditAlphaNum) asset;
    }
    throw new IllegalArgumentException("native assets are not supported");
  }
}