From ebaff1c4dce5fb2e34d1122dc75064492413db52 Mon Sep 17 00:00:00 2001
From: Michael McCandless <mikemccand@apache.org>
Date: Mon, 24 Aug 2015 12:27:47 +0000
Subject: [PATCH] add more detail to exception message

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1697364 13f79535-47bb-0310-9956-ffa450edef68
---
 .../src/java/org/apache/lucene/store/ChecksumIndexInput.java | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lucene/core/src/java/org/apache/lucene/store/ChecksumIndexInput.java b/lucene/core/src/java/org/apache/lucene/store/ChecksumIndexInput.java
index be090e42a9d..e19c3a41058 100644
--- a/lucene/core/src/java/org/apache/lucene/store/ChecksumIndexInput.java
+++ b/lucene/core/src/java/org/apache/lucene/store/ChecksumIndexInput.java
@@ -44,9 +44,10 @@ public abstract class ChecksumIndexInput extends IndexInput {
    */
   @Override
   public void seek(long pos) throws IOException {
-    final long skip = pos - getFilePointer();
+    final long curFP = getFilePointer();
+    final long skip = pos - curFP;
     if (skip < 0) {
-      throw new IllegalStateException(getClass() + " cannot seek backwards");
+      throw new IllegalStateException(getClass() + " cannot seek backwards (pos=" + pos + " getFilePointer()=" + curFP + ")");
     }
     skipBytes(skip);
   }