Fix base58 en/decoding of arrays of zero bytes.

Author: ianopolous

src/main/java/io/ipfs/multibase/BaseN.java

@@ -7,13 +7,15 @@ public class BaseN {
      static String encode(final String alphabet, final BigInteger base, final byte[] input) {
         // TODO: This could be a lot more efficient.
         BigInteger bi = new BigInteger(1, input);
+        boolean isZero = bi.equals(BigInteger.ZERO);
         StringBuffer s = new StringBuffer();
         while (bi.compareTo(base) >= 0) {
             BigInteger mod = bi.mod(base);
             s.insert(0, alphabet.charAt(mod.intValue()));
             bi = bi.subtract(mod).divide(base);
         }
-        s.insert(0, alphabet.charAt(bi.intValue()));
+         if (! isZero)
+             s.insert(0, alphabet.charAt(bi.intValue()));
         // Convert leading zeros too.
         for (byte anInput : input) {
             if (anInput == 0)
@@ -33,9 +35,11 @@ static byte[] decode(final String alphabet, final BigInteger base, final String
         boolean stripSignByte = bytes.length > 1 && bytes[0] == 0 && bytes[1] < 0;
         // Count the leading zeros, if any.
         int leadingZeros = 0;
-        for (int i = 0; input.charAt(i) == alphabet.charAt(0); i++) {
+        for (int i = 0; i < input.length() && input.charAt(i) == alphabet.charAt(0); i++) {
             leadingZeros++;
         }
+        if (leadingZeros == input.length())
+            return new byte[leadingZeros];
         // Now cut/pad correctly. Java 6 has a convenience for this, but Android can't use it.
         byte[] tmp = new byte[bytes.length - (stripSignByte ? 1 : 0) + leadingZeros];
         System.arraycopy(bytes, stripSignByte ? 1 : 0, tmp, leadingZeros, tmp.length - leadingZeros);

src/main/main.iml

@@ -1,11 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <module type="JAVA_MODULE" version="4">
-  <component name="NewModuleRootManager" inherit-compiler-output="true">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_8" inherit-compiler-output="true">
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/java" isTestSource="false" />
     </content>
-    <orderEntry type="inheritedJdk" />
+    <orderEntry type="jdk" jdkName="1.8 Oracle" jdkType="JavaSDK" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
 </module>

src/test/java/io/ipfs/multibase/MultibaseTest.java

@@ -12,15 +12,27 @@ public class MultibaseTest {
 
     @Test
     public void base58Test() {
-        List<String> examples = Arrays.asList("zQmPZ9gcCEpqKTo6aq61g2nXGUhM4iCL3ewB6LDXZCtioEB",
-                "zQmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy");
+        List<String> examples = Arrays.asList(
+                "zQmPZ9gcCEpqKTo6aq61g2nXGUhM4iCL3ewB6LDXZCtioEB",
+                "zQmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy",
+                "z11");
         for (String example: examples) {
             byte[] output = Multibase.decode(example);
             String encoded = Multibase.encode(Multibase.Base.Base58BTC, output);
             assertEquals(example, encoded);
         }
     }
 
+    @Test
+    public void zeroBytesBase58() {
+        for (int i=0; i < 32; i++) {
+            String encoded = Multibase.encode(Multibase.Base.Base58BTC, new byte[i]);
+            byte[] output = Multibase.decode(encoded);
+            if (! Arrays.equals(output, new byte[i]))
+                throw new IllegalStateException("Failed to round trip zero array of length " + i);
+        }
+    }
+
     @Test
     public void base16Test() {
         List<String> examples = Arrays.asList("f234abed8debede",

src/test/test.iml

@@ -1,11 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <module type="JAVA_MODULE" version="4">
-  <component name="NewModuleRootManager" inherit-compiler-output="true">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_8" inherit-compiler-output="true">
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/java" isTestSource="true" />
     </content>
-    <orderEntry type="inheritedJdk" />
+    <orderEntry type="jdk" jdkName="1.8 Oracle" jdkType="JavaSDK" />
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="library" name="lib" level="project" />
     <orderEntry type="module" module-name="main" />