Index: src/java/org/apache/lucene/store/RAMInputStream.java
===================================================================
--- src/java/org/apache/lucene/store/RAMInputStream.java	(revision 555478)
+++ src/java/org/apache/lucene/store/RAMInputStream.java	(working copy)
@@ -41,6 +41,7 @@
   public RAMInputStream(RAMFile f) {
     file = f;
     length = file.length;
+    assert length/BUFFER_SIZE < Integer.MAX_VALUE : "Too large RAMFile! "+length; 
 
     // make sure that we switch to the
     // first needed buffer lazily
@@ -87,11 +88,9 @@
     } else {
       currentBuffer = (byte[]) file.buffers.get(currentBufferIndex);
       bufferPosition = 0;
-      bufferStart = BUFFER_SIZE * currentBufferIndex;
-      bufferLength = (int) (length - bufferStart);
-      if (bufferLength > BUFFER_SIZE) {
-        bufferLength = BUFFER_SIZE;
-      }
+      bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
+      long buflen = length - bufferStart;
+      bufferLength = buflen > BUFFER_SIZE ? BUFFER_SIZE : (int) buflen;
     }
   }
 
@@ -100,8 +99,7 @@
   }
 
   public void seek(long pos) throws IOException {
-    long bufferStart = currentBufferIndex * BUFFER_SIZE;
-    if (pos < bufferStart || pos >= bufferStart + BUFFER_SIZE) {
+    if (currentBuffer==null || pos < bufferStart || pos >= bufferStart + BUFFER_SIZE) {
       currentBufferIndex = (int) (pos / BUFFER_SIZE);
       switchCurrentBuffer();
     }