[PATCH 1/6] Don't hang if something goes wrong reading from a tar archive

[Jon TURNEY <jon dot turney at dronecode dot org dot uk>]

Returning EIO (a small positive integer) as the result of archive_tar_file::read()
on an error isn't a good idea, it's indistinguishable from successfully reading
a small number of bytes.

This causes io_stream::copy() to spin forever if it's reading from an archive stream
which terminates unexpectedly early, which can happen on an decompression error.

So, return -1 and set lasterr instead.  This matches the behaviour of POSIX
read(), so shouldn't surprise anyone :-)

Make the same change for archive_tar_file::write(), archive_tar_file::tell()
and archive_tar_file::peek() for consistency

2011-04-08  Jon TURNEY  <jon.turney@dronecode.org.uk>

	* archive_tar_file.cc (read, write, peek, seek): Consistently return -1
	and set lasterr on an error.

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
---
 archive_tar_file.cc |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/archive_tar_file.cc b/archive_tar_file.cc
index 29a2df7..5ffb3a1 100644
--- a/archive_tar_file.cc
+++ b/archive_tar_file.cc
@@ -65,7 +65,7 @@ ssize_t archive_tar_file::read (void *buffer, size_t len)
 	  /* unexpected EOF or read error in the tar parent stream */
 	  /* the user can query the parent for the error */
 	  state.lasterr = EIO;
-	  return EIO;
+	  return -1;
 	}
     }
   return 0;
@@ -75,7 +75,8 @@ ssize_t archive_tar_file::read (void *buffer, size_t len)
 ssize_t archive_tar_file::write (const void *buffer, size_t len)
 {
   /* write not supported */
-  return EBADF;
+  state.lasterr = EBADF;
+  return -1;
 }
 
 /* read data without removing it from the class's internal buffer */
@@ -96,7 +97,7 @@ ssize_t archive_tar_file::peek (void *buffer, size_t len)
 	  /* unexpected EOF or read error in the tar parent stream */
 	  /* the user can query the parent for the error */
 	  state.lasterr = EIO;
-	  return EIO;
+	  return -1;
 	}
     }
   return 0;
@@ -113,6 +114,7 @@ archive_tar_file::seek (long where, io_stream_seek_t whence)
 {
   /* nothing needs seeking here yet. Implement when needed 
    */
+  state.lasterr = EINVAL;
   return -1;
 }
 
-- 
1.7.4