Fix URL encoding and decoding

The methods `uriEncode` and `uriDecode` did not properly handle
percent-encoding. In particular, `uriEncode` didn't properly output two
uppercase hex digits and `urlDecode` did not properly handle non-ASCII
characters.

Aditionally, if no percent-encoding was performed, these methods will
now return the original string.

Fixes package-url#150
Closes package-url#153
Fixes package-url#154

Author: dwalluck

src/main/java/com/github/packageurl/PackageURL.java

@@ -21,6 +21,7 @@
  */
 package com.github.packageurl;
 
+import java.io.ByteArrayOutputStream;
 import java.io.Serializable;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -441,22 +442,26 @@ private String percentEncode(final String input) {
     }
 
     private static String uriEncode(String source, Charset charset) {
-        if (source == null || source.length() == 0) {
+        if (source == null || source.isEmpty()) {
             return source;
         }
 
+        boolean changed = false;
         StringBuilder builder = new StringBuilder();
-        for (byte b : source.getBytes(charset)) {
+        byte[] bytes = source.getBytes(charset);
+
+        for (byte b : bytes) {
             if (isUnreserved(b)) {
                 builder.append((char) b);
             }
             else {
-                // Substitution: A '%' followed by the hexadecimal representation of the ASCII value of the replaced character
                 builder.append('%');
-                builder.append(Integer.toHexString(b).toUpperCase());
+                builder.append(Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, 16)));
+                builder.append(Character.toUpperCase(Character.forDigit(b & 0xF, 16)));
+                changed = true;
             }
         }
-        return builder.toString();
+        return changed ? builder.toString() : source;
     }
 
     private static boolean isUnreserved(int c) {
@@ -479,34 +484,37 @@ private static boolean isDigit(int c) {
      * @return a decoded String
      */
     private String percentDecode(final String input) {
-        if (input == null) {
-            return null;
-        }
-        final String decoded = uriDecode(input);
-        if (!decoded.equals(input)) {
-            return decoded;
-        }
-        return input;
+        return uriDecode(input);
     }
 
     public static String uriDecode(String source) {
         if (source == null) {
-            return source;
+            return null;
         }
-        int length = source.length();
-        StringBuilder builder = new StringBuilder();
-        for (int i = 0; i < length; i++) {
-            if (source.charAt(i) == '%') {
-                String str = source.substring(i + 1, i + 3);
-                char c = (char) Integer.parseInt(str, 16);
-                builder.append(c);
-                i += 2;
-            }
-            else {
-                builder.append(source.charAt(i));
+
+        boolean changed = false;
+        byte[] bytes = source.getBytes(StandardCharsets.UTF_8);
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream(bytes.length);
+
+        for (int i = 0; i < bytes.length; i++) {
+            int b = bytes[i];
+
+            if (b == '%') {
+                    if (i + 2 >= bytes.length) {
+                        return source;
+                    }
+
+                    int b1 = Character.digit(bytes[++i], 16);
+                    int b2 = Character.digit(bytes[++i], 16);
+                    buffer.write((char) ((b1 << 4) + b2));
+                    changed = true;
+            } else {
+                buffer.write(b);
             }
         }
-        return builder.toString();
+
+        byte[] b = buffer.toByteArray();
+        return changed ? new String(b, StandardCharsets.UTF_8) : source;
     }
 
     /**

src/test/java/com/github/packageurl/PackageURLTest.java

@@ -55,6 +55,19 @@ public static void setup() throws IOException {
         json = new JSONArray(jsonTxt);
     }
 
+    @Test
+    public void testEncoding1() throws MalformedPackageURLException {
+        PackageURL purl = new PackageURL("maven", "com.google.summit", "summit-ast", "2.2.0\n", null, null);
+        Assert.assertEquals("pkg:maven/com.google.summit/summit-ast@2.2.0%0A", purl.toString());
+    }
+
+    @Test
+    public void testEncoding2() throws MalformedPackageURLException {
+        PackageURL purl = new PackageURL("pkg:nuget/%D0%9Cicros%D0%BEft.%D0%95ntit%D1%83Fram%D0%B5work%D0%A1%D0%BEr%D0%B5");
+        Assert.assertEquals("Мicrosоft.ЕntitуFramеworkСоrе", purl.getName());
+        Assert.assertEquals("pkg:nuget/%D0%9Cicros%D0%BEft.%D0%95ntit%D1%83Fram%D0%B5work%D0%A1%D0%BEr%D0%B5", purl.toString());
+    }
+
     @Test
     public void testConstructorParsing() throws Exception {
         exception = ExpectedException.none();