fix toHex()

Author: celeduc

pom.xml

@@ -78,6 +78,10 @@
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-surefire-plugin</artifactId>
 				<version>2.19.1</version>
+				<configuration>
+					<!-- Sets the VM argument line used when unit tests are run. -->
+					<argLine>${surefireArgLine}</argLine>
+				</configuration>
 			</plugin>
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
@@ -91,6 +95,49 @@
 					</archive>
 				</configuration>
 			</plugin>
+			<plugin>
+				<groupId>org.jacoco</groupId>
+				<artifactId>jacoco-maven-plugin</artifactId>
+				<version>0.7.8</version>
+				<executions>
+					<!--
+					Prepares the property pointing to the JaCoCo runtime agent which
+					is passed as VM argument when Maven the Surefire plugin is executed.
+					-->
+					<execution>
+						<id>pre-unit-test</id>
+						<goals>
+						<goal>prepare-agent</goal>
+			            		</goals>
+						<configuration>
+							<!-- Sets the path to the file which contains the execution data. -->
+							<destFile>${project.build.directory}/coverage-reports/jacoco-ut.exec</destFile>
+							<!--
+							Sets the name of the property containing the settings
+							for JaCoCo runtime agent.
+							-->
+							<propertyName>surefireArgLine</propertyName>
+						</configuration>
+					</execution>
+					<!--
+					Ensures that the code coverage report for unit tests is created after
+					unit tests have been run.
+					-->
+					<execution>
+						<id>post-unit-test</id>
+						<phase>test</phase>
+						<goals>
+							<goal>report</goal>
+						</goals>
+						<configuration>
+							<!-- Sets the path to the file which contains the execution data. -->
+							<dataFile>${project.build.directory}/coverage-reports/jacoco-ut.exec</dataFile>
+							<!-- Sets the output directory for the code coverage report. -->
+							<outputDirectory>${project.reporting.outputDirectory}/jacoco-ut</outputDirectory>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
 		</plugins>
 	</build>
 </project>

src/main/java/io/ipfs/multihash/Multihash.java

@@ -92,11 +92,17 @@ public int hashCode() {
         return Arrays.hashCode(hash) ^ type.hashCode();
     }
 
+    final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
+
     public String toHex() {
-        StringBuilder res = new StringBuilder();
-        for (byte b: toBytes())
-            res.append(String.format("%x", b&0xff));
-        return res.toString();
+        byte[] bytes = toBytes();
+        char[] hexChars = new char[bytes.length * 2];
+        for ( int j = 0; j < bytes.length; j++ ) {
+            int v = bytes[j] & 0xFF;
+            hexChars[j * 2] = hexArray[v >>> 4];
+            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
+        }
+        return new String(hexChars);
     }
 
     public String toBase58() {

src/test/java/io/ipfs/multihash/MultihashTest.java

@@ -4,6 +4,8 @@
 import io.ipfs.multibase.*;
 import java.util.*;
 import java.security.MessageDigest;
+import java.io.PipedInputStream;
+import java.io.PipedOutputStream;
 
 public class MultihashTest {
 
@@ -43,9 +45,11 @@ public void multihashTest() {
                 // Test conversions
                 assert(m.toBase58().equals(m2.toBase58()));
                 assert(m.toBase58().equals((String)ex[2]));
+                // Test fromHex and toHex
+                Multihash m3 = Multihash.fromHex(m.toHex());
+                assert(m3.equals(m));
             }
             catch (Exception e){
-                // Usually because a hash function not supported
                 System.out.println(e.getMessage());
                 assert(false);
             }