Fixing Uuid Parse Error (#66)

In Uuid, ids are 32 bit unsigned integers. As Java does not supported unsigned integers, when converting to a string, the 32 bit integer is converted to a long so that it can be written to a string as a positive integer (using all 32 bits).

When converting from a string to a Uuid, the integer value is not handled correctly as values that would be acceptable as a 32 bit unsigned integer fail to be parsed as a 32 bit signed integer.

If the id value of a Uuid is 0xFFFFFFFF and is converted to the string 4294967295. When 4294967295 is parsed, it will fail as it is not expressible as a 32 bit signed integer.

Parsing needs to parse the unsigned integer and convert and store the bit pattern correctly in a signed integer.

Closes #62

Author: vaage

src/codeu/chat/RelayMain.java

@@ -137,7 +137,7 @@ private static void loadTeamInfo(Server relay, String file) {
             // this line that it is not worth trying to handle ahead of time.
             // So instead just try to parse it and catch any exception.
 
-            final Uuid id = Uuid.fromString(tokens[0].trim());
+            final Uuid id = Uuid.parse(tokens[0].trim());
             final byte[] secret = Secret.parse(tokens[1].trim());
 
             relay.addTeam(id, secret);

src/codeu/chat/ServerMain.java

@@ -46,10 +46,16 @@ public static void main(String[] args) {
 
     LOG.info("============================= START OF LOG =============================");
 
-    final Uuid id = Uuid.fromString(args[0]);
+    final int myPort = Integer.parseInt(args[2]);
     final byte[] secret = Secret.parse(args[1]);
 
-    final int myPort = Integer.parseInt(args[2]);
+    Uuid id = null;
+    try {
+      id = Uuid.parse(args[0]);
+    } catch (IOException ex) {
+      System.out.println("Invalid id - shutting down server");
+      System.exit(1);
+    }
 
     // This is the directory where it is safe to store data accross runs
     // of the server.

src/codeu/chat/util/Uuid.java

@@ -179,23 +179,29 @@ private static void buildString(Uuid current, StringBuilder build) {
     }
   }
 
-  // FROM STRING
+  // Parse
   //
   // Create a uuid from a sting.
-  public static Uuid fromString(String string) {
-    return fromString(null, string.split("\\."), 0);
+  public static Uuid parse(String string) throws IOException {
+    return parse(null, string.split("\\."), 0);
   }
 
-  private static Uuid fromString(final Uuid root, String[] tokens, int index) {
+  private static Uuid parse(final Uuid root, String[] tokens, int index) throws IOException {
 
-    final int id = Integer.parseInt(tokens[index]);
+    final long id = Long.parseLong(tokens[index]);
 
-    final Uuid link = new Uuid(root, id);
+    if ((id >> 32) != 0) {
+      throw new IOException(String.format(
+          "ID value '%s' is too large to be an unsigned 32 bit integer",
+          tokens[index]));
+    }
+
+    final Uuid link = new Uuid(root, (int)(id & 0xFFFFFFFF));
 
     final int nextIndex = index + 1;
 
     return nextIndex < tokens.length ?
-        fromString(link, tokens, nextIndex) :
+        parse(link, tokens, nextIndex) :
         link;
   }
 }

test/codeu/chat/util/UuidTest.java

@@ -14,6 +14,7 @@
 
 package codeu.chat.util;
 
+import java.io.IOException;
 import static org.junit.Assert.*;
 import org.junit.Test;
 
@@ -103,21 +104,21 @@ public void testRootEqualNot() {
   }
 
   @Test
-  public void testValidSingleLink() {
+  public void testValidSingleLink() throws IOException {
 
     final String string = "100";
-    final Uuid id = Uuid.fromString(string);
+    final Uuid id = Uuid.parse(string);
 
     assertNotNull(id);
     assertNull(id.root());
     assertEquals(id.id(), 100);
   }
 
   @Test
-  public void testValidMultiLink() {
+  public void testValidMultiLink() throws IOException {
 
     final String string = "100.200";
-    final Uuid id = Uuid.fromString(string);
+    final Uuid id = Uuid.parse(string);
 
     assertNotNull(id);
     assertNotNull(id.root());
@@ -126,4 +127,16 @@ public void testValidMultiLink() {
     assertEquals(id.id(), 200);
     assertEquals(id.root().id(), 100);
   }
+
+  @Test
+  public void testLargeId() throws IOException {
+
+    // Use a id value that would be too large for Integer.parseInt to handle
+    // but would still parse if we could use unsigned integers.
+    final String string = Long.toString(0xFFFFFFFFL);
+    final Uuid id = Uuid.parse(string);
+
+    assertNotNull(id);
+    assertEquals(id.id(), 0xFFFFFFFF);
+  }
 }