Subject: bug#9157: [PATCH] dd: sparse conv flag

From: Roman Rybalko <[email-masked]>
Date: Sat, 23 Jul 2011 20:08:01 +0400

---
 doc/coreutils.texi |    4 +++
 src/dd.c           |   22 +++++++++++++++-
 tests/Makefile.am  |    1 +
 tests/dd/sparse    |   70 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 96 insertions(+), 1 deletions(-)
 create mode 100755 tests/dd/sparse

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 424446c..761c698 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -8127,6 +8127,10 @@ Pad every input block to size of @samp{ibs} with trailing zero bytes.
 When used with @samp{block} or @samp{unblock}, pad with spaces instead of
 zero bytes.
 
+@item sparse
+@opindex sparse
+Make sparse output file.
+
 @end table
 
 The following ``conversions'' are really file flags
diff --git a/src/dd.c b/src/dd.c
index 0824f6c..0393740 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -126,7 +126,8 @@ enum
     C_NOCREAT = 010000,
     C_EXCL = 020000,
     C_FDATASYNC = 040000,
-    C_FSYNC = 0100000
+    C_FSYNC = 0100000,
+    C_SPARSE = 0200000
   };
 
 /* Status bit masks.  */
@@ -268,6 +269,7 @@ static struct symbol_value const conversions[] =
   {"sync", C_SYNC},		/* Pad input records to ibs with NULs. */
   {"fdatasync", C_FDATASYNC},	/* Synchronize output data before finishing.  */
   {"fsync", C_FSYNC},		/* Also synchronize output metadata.  */
+  {"sparse", C_SPARSE},		/* Make sparse output file. */
   {"", 0}
 };
 
@@ -533,6 +535,9 @@ Each CONV symbol may be:\n\
   fsync     likewise, but also write metadata\n\
 "), stdout);
       fputs (_("\
+  sparse    make sparse output file\n\
+"), stdout);
+      fputs (_("\
 \n\
 Each FLAG symbol may be:\n\
 \n\
@@ -985,6 +990,21 @@ iwrite (int fd, char const *buf, size_t size)
     {
       ssize_t nwritten;
       process_signals ();
+      if (conversions_mask & C_SPARSE)
+        {
+          off_t seek_size = 0;
+          while (total_written + seek_size < size && buf[total_written + seek_size] == 0)
+            ++seek_size;
+          if (seek_size)
+            {
+              off_t cur_off = 0;
+              cur_off = lseek(fd, seek_size, SEEK_CUR);
+              if (cur_off < 0)
+                break;
+              total_written += seek_size;
+              continue;
+            }
+        }
       nwritten = write (fd, buf + total_written, size - total_written);
       if (nwritten < 0)
         {
diff --git a/tests/Makefile.am b/tests/Makefile.am
index ebd1b11..0f1376a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -364,6 +364,7 @@ TESTS =						\
   dd/skip-seek					\
   dd/skip-seek2					\
   dd/skip-seek-past-file			\
+  dd/sparse                                     \
   dd/stderr					\
   dd/unblock					\
   dd/unblock-sync				\
diff --git a/tests/dd/sparse b/tests/dd/sparse
new file mode 100755
index 0000000..f0e0806
--- /dev/null
+++ b/tests/dd/sparse
@@ -0,0 +1,70 @@
+#!/bin/sh
+# Ensure that dd conv=sparse works.
+
+# Copyright (C) 2003, 2005-2011 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=.}/init.sh"; path_prepend_ ../src
+print_ver_ dd
+
+# sometimes we may read less than 1M
+dd if=/dev/zero of=sample0 count=1 bs=1M 2> /dev/null || fail=1
+[ "`stat -c %s sample0`" = "1048576" ] || fail=1
+dd if=/dev/urandom of=sample1 count=1 bs=1M 2> /dev/null || fail=1
+[ "`stat -c %s sample1`" = "1048576" ] || fail=1
+
+# test 1
+dd if=sample1 of=test1 seek=0 bs=1M 2> /dev/null || fail=1
+dd if=sample0 of=test1 seek=1 bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=test1 seek=2 bs=1M 2> /dev/null || fail=1
+
+# test 1-1
+dd if=test1 of=out1-1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out1-1-check bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out1-1-check seek=2 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out1-1`" = "`stat -c '%s %b %B' out1-1-check`" ] || fail=1
+
+# test 1-2
+dd if=test1 of=out1-2 seek=1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out1-2-check seek=1 bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out1-2-check seek=3 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out1-2`" = "`stat -c '%s %b %B' out1-2-check`" ] || fail=1
+
+# test 1-3
+dd if=test1 of=out1-3 seek=1 skip=1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out1-3-check seek=2 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out1-3`" = "`stat -c '%s %b %B' out1-3-check`" ] || fail=1
+
+# test 2
+dd if=sample0 of=test2 seek=0 bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=test2 seek=1 bs=1M 2> /dev/null || fail=1
+dd if=sample0 of=test2 seek=2 bs=1M 2> /dev/null || fail=1
+
+# test 2-1
+dd if=test2 of=out2-1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out2-1-check seek=1 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out2-1`" = "`stat -c '%s %b %B' out2-1-check`" ] || fail=1
+
+# test 2-2
+dd if=test2 of=out2-2 seek=1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out2-2-check seek=2 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out2-2`" = "`stat -c '%s %b %B' out2-2-check`" ] || fail=1
+
+# test 2-3
+dd if=test2 of=out2-3 seek=1 skip=1 conv=sparse bs=1M 2> /dev/null || fail=1
+dd if=sample1 of=out2-3-check seek=1 bs=1M 2> /dev/null || fail=1
+[ "`stat -c '%s %b %B' out2-3`" = "`stat -c '%s %b %B' out2-3-check`" ] || fail=1
+
+Exit $fail
-- 
1.7.0.4