com.github.kristofa.brave.IdConversion Maven / Gradle / Ivy

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package com.github.kristofa.brave;

/**
 * Contains conversion utilities for converting trace and span ids from long to string and vice
 * versa.
 * 
 * The string representation is used when transferring trace context from client to server
 * as http headers.
 * 

 * This implementation is expected to be compatible with Zipkin. This is important in case you
 * mix brave services with zipkin / finagle services.
 * 
 * The only difference between the zipkin implementation and this implementation 
 * is that zipkin prepends '0' characters in case String does not contain 16 characters. 
 * For example instead of generating String 
 * "0" for long id 0 it generates "0000000000000000". But zipkin will properly convert String
 * representations in case they are not prepended with 0's. 
 * 
 * @author kristof
 */
public class IdConversion {
	
	/**
	 * Converts long trace or span id to String.
	 * 
	 * @param id trace, span or parent span id.
	 * @return String representation.
	 */
	public static String convertToString(final long id) {
            return Long.toHexString(id);
	}
	
	/**
	 * Converts String trace or span id to long.
	 * 
	 * @param id trace, span or parent span id.
	 * @return Long representation.
	 */
	public static long convertToLong(final String id) {
	  if (id.length() == 0 || id.length() > 16) {
	    throw new NumberFormatException(
		id + " should be a <=16 character lower-hex string with no prefix");
	  }

	  long result = 0;

	  for (char c : id.toCharArray()) {
	    result <<= 4;

	    if (c >= '0' && c <= '9') {
	      result |= c - '0';
	    } else if (c >= 'a' && c <= 'f') {
	      result |= c - 'a' + 10;
	    } else {
	      throw new NumberFormatException("character " + c + " not lower hex in " + id);
	    }
	  }

	  return result;
	}

}