natFileChannelPosix: throw if region is not mapped

[Andrew Haley]

According to the spec, this case is undefined.  However, if we do
attempt to read the data in a nonexistent region we'll get a bus
error.  It makes sense to throw a helpful exception, and it seems that
at least one Java program relies on this behaviour.

This isn't a complete solution.  At some point we'll need to catch the
bus error and do something appropriate.

Andrew.


2006-11-01  Andrew Haley  <aph@redhat.com>

	* gnu/java/nio/channels/natFileChannelPosix.cc (mapImpl): Throw
	IOException if requested region is not completely contained within
	file.
 
Index: gnu/java/nio/channels/natFileChannelPosix.cc
===================================================================
--- gnu/java/nio/channels/natFileChannelPosix.cc	(revision 118387)
+++ gnu/java/nio/channels/natFileChannelPosix.cc	(working copy)
@@ -513,6 +513,17 @@
     throw new IOException (JvNewStringLatin1 (strerror (errno)));
   buf->implPtr = reinterpret_cast<RawData*> (ptr);
   buf->implLen = size+align;
+
+  struct stat st;
+
+  if (fstat (fd, &st))
+    throw new IOException (JvNewStringLatin1 (strerror (errno)));
+
+  if (size+position > st.st_size)
+    throw new IOException (JvNewStringLatin1 
+			   ("mmap: requested region not completely "
+			    "contained within file\n"));
+
   return buf;
 #else
   throw new IOException (JvNewStringUTF ("mmap not implemented"));