dd: avoid buffer allocations unless needed

* src/dd.c: Add new static global variable ibuf.
(alloc_ibuf, alloc_obuf): New functions factored from dd_copy().
(dd_copy): Call the new functions to allocate memory for
ibuf and obuf when necessary.
(skip): Likewise.
* tests/dd/no-allocate.sh: New test.
* tests/local.mk: Reference the test.

1 files changed, 53 insertions, 0 deletions

diff --git a/tests/dd/no-allocate.sh b/tests/dd/no-allocate.sh
new file mode 100755
index 000000000..e45dd5cf9
--- /dev/null
+++ b/tests/dd/no-allocate.sh
@@ -0,0 +1,53 @@
+#!/bin/sh
+# make sure that dd doesn't allocate memory unnecessarily
+
+# Copyright (C) 2013 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ dd
+require_ulimit_
+
+# count and skip is zero, we don't need to allocate memory
+(ulimit -v 20000; dd  bs=30M count=0) || fail=1
+(ulimit -v 20000; dd ibs=30M count=0) || fail=1
+(ulimit -v 20000; dd obs=30M count=0) || fail=1
+
+
+# Use a fifo for which seek fails, but read does not
+if mkfifo tape; then
+  # for non seekable output we need to allocate buffer when needed
+  echo 1 > tape&
+  (ulimit -v 20000; dd  bs=30M skip=1 count=0 if=tape) && fail=1
+
+  echo 1 > tape&
+  (ulimit -v 20000; dd ibs=30M skip=1 count=0 if=tape) && fail=1
+
+  echo 1 > tape&
+  (ulimit -v 20000; dd obs=30M skip=1 count=0 if=tape) || fail=1
+
+
+  # for non seekable output we need to allocate buffer when needed
+  echo 1 > tape&
+  (ulimit -v 20000; dd  bs=30M seek=1 count=0 of=tape) && fail=1
+
+  echo 1 > tape&
+  (ulimit -v 20000; dd obs=30M seek=1 count=0 of=tape) && fail=1
+
+  echo 1 > tape&
+  (ulimit -v 20000; dd ibs=30M seek=1 count=0 of=tape) || fail=1
+fi
+
+Exit $fail