From 9f8be4b0b83d1e0cbf1326f8cb7e077d026d9b0b Mon Sep 17 00:00:00 2001

From: Kamil Dudka <kdudka@redhat.com>

Date: Wed, 23 Jul 2008 11:29:21 +0200

Subject: [PATCH] dd: iflag=fullblock now read full blocks if possible

* src/dd.c (iread_fullblock): New function for reading full blocks.

(scanargs): Check for new parameter iflag=fullblock.

(skip): Use iread_fnc pointer instead of iread function.

(dd_copy): Use iread_fnc pointer instead of iread function.

* tests/dd/misc: Add test for dd - read full blocks.

* doc/coretuils.texi: Mention new parameter iflag=fullblock.

* NEWS: Mentioned the change.

---

 NEWS               |    4 ++++

 doc/coreutils.texi |    6 ++++++

 src/dd.c           |   39 +++++++++++++++++++++++++++++++++++++--

 tests/dd/misc      |    9 +++++++++

 4 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/doc/coreutils.texi b/doc/coreutils.texi

index 81e3b91..b95f8dc 100644

--- a/doc/coreutils.texi

+++ b/doc/coreutils.texi

@@ -7719,6 +7719,12 @@ platforms that distinguish binary from text I/O.

 Use text I/O.  Like @samp{binary}, this option has no effect on

 standard platforms.

+@item fullblock

+@opindex fullblock

+Read full blocks from input if possible. read() may return early

+if a full block is not available, so retry until data is available

+or end of file is reached. This flag can be used only for the iflag option.

+

 @end table

 These flags are not supported on all systems, and @samp{dd} rejects

diff --git a/src/dd.c b/src/dd.c

index ead9574..1b620df 100644

--- a/src/dd.c

+++ b/src/dd.c

@@ -225,6 +225,9 @@ static sig_atomic_t volatile interrupt_signal;

 /* A count of the number of pending info signals that have been received.  */

 static sig_atomic_t volatile info_signal_count;

+/* Function used for read (to handle iflag=fullblock parameter) */

+static ssize_t (*iread_fnc) (int fd, char *buf, size_t size);

+

 /* A longest symbol in the struct symbol_values tables below.  */

 #define LONGEST_SYMBOL "fdatasync"

@@ -257,6 +260,7 @@ static struct symbol_value const conversions[] =

 };

 /* Flags, for iflag="..." and oflag="...".  */

+#define O_FULLBLOCK 010000000 /* Read only full blocks from input */

 static struct symbol_value const flags[] =

 {

   {"append",	O_APPEND},

@@ -271,6 +275,7 @@ static struct symbol_value const flags[] =

   {"nonblock",	O_NONBLOCK},

   {"sync",	O_SYNC},

   {"text",	O_TEXT},

+  {"fullblock", O_FULLBLOCK}, /* Read only full blocks from input */

   {"",		0}

 };

@@ -762,6 +767,27 @@ iread (int fd, char *buf, size_t size)

     }

 }

+/* Wrapper around iread function which reads full blocks if possible */

+static ssize_t

+iread_fullblock (int fd, char *buf, size_t size)

+{

+  ssize_t nread = 0;

+

+  while (0 < size)

+    {

+      ssize_t ncurr = iread(fd, buf, size);

+      if (ncurr < 0)

+	return ncurr;

+      if (ncurr == 0)

+	break;

+      nread += ncurr;

+      buf   += ncurr;

+      size  -= ncurr;

+    }

+

+  return nread;

+}

+

 /* Write to FD the buffer BUF of size SIZE, processing any signals

    that arrive.  Return the number of bytes written, setting errno if

    this is less than SIZE.  Keep trying if there are partial

@@ -1000,6 +1026,15 @@ scanargs (int argc, char *const *argv)

   if (input_flags & (O_DSYNC | O_SYNC))

     input_flags |= O_RSYNC;

+  if (output_flags & O_FULLBLOCK)

+    {

+      error (0, 0, "%s: %s", _("invalid output flag"), "'fullblock'");

+      usage (EXIT_FAILURE);

+    }

+  iread_fnc = (input_flags & O_FULLBLOCK)?

+    iread_fullblock:

+    iread;

+

   if (multiple_bits_set (conversions_mask & (C_ASCII | C_EBCDIC | C_IBM)))

     error (EXIT_FAILURE, 0, _("cannot combine any two of {ascii,ebcdic,ibm}"));

   if (multiple_bits_set (conversions_mask & (C_BLOCK | C_UNBLOCK)))

@@ -1197,7 +1232,7 @@ skip (int fdesc, char const *file, uintmax_t records, size_t blocksize,

       do

 	{

-	  ssize_t nread = iread (fdesc, buf, blocksize);

+	  ssize_t nread = iread_fnc (fdesc, buf, blocksize);

 	  if (nread < 0)

 	    {

 	      if (fdesc == STDIN_FILENO)

@@ -1508,7 +1543,7 @@ dd_copy (void)

 		(conversions_mask & (C_BLOCK | C_UNBLOCK)) ? ' ' : '\0',

 		input_blocksize);

-      nread = iread (STDIN_FILENO, ibuf, input_blocksize);

+      nread = iread_fnc (STDIN_FILENO, ibuf, input_blocksize);

       if (nread == 0)

 	break;			/* EOF.  */

diff --git a/tests/dd/misc b/tests/dd/misc

index d54fbfa..24e5eba 100755

--- a/tests/dd/misc

+++ b/tests/dd/misc

@@ -88,6 +88,15 @@ fi

 outbytes=`echo x | dd bs=3 ibs=10 obs=10 conv=sync 2>/dev/null | wc -c`

 test "$outbytes" -eq 3 || fail=1

+(echo a; sleep .1; echo b) \

+  | LC_ALL=C dd bs=4 status=noxfer iflag=fullblock >out 2>err || fail=1

+echo "a

+b" > out_ok

+echo "1+0 records in

+1+0 records out" > err_ok

+compare out out_ok || fail=1

+compare err err_ok || fail=1

+

 test $fail -eq 0 && fail=$warn

 (exit $fail); exit $fail

diff -ruN coreutils-6.12.old/doc/coreutils.info coreutils-6.12/doc/coreutils.info

--- coreutils-6.12.old/doc/coreutils.info	2008-07-24 12:49:57.000000000 +0200

+++ coreutils-6.12/doc/coreutils.info	2008-07-24 12:52:17.000000000 +0200

@@ -6112,6 +6112,12 @@

           Use text I/O.  Like `binary', this option has no effect on

           standard platforms.

+    'fullblock'

+          Read full blocks from input if possible. read() may return

+	  early if a full block is not available, so retry until data

+	  is available or end of file is reached. This flag can be used

+	  only for the iflag option.

+

      These flags are not supported on all systems, and `dd' rejects

      attempts to use them when they are not supported.  When reading

diff -ruN coreutils-6.12.old/man/dd.1 coreutils-6.12/man/dd.1

--- coreutils-6.12.old/man/dd.1	2008-07-24 12:51:06.000000000 +0200

+++ coreutils-6.12/man/dd.1	2008-07-24 12:59:06.000000000 +0200

@@ -111,6 +111,13 @@

 .TP

 direct

 use direct I/O for data

+.PP

+FLAG symbols only for iflag option:

+.TP

+fullblock

+Read full blocks from input if possible. read() may return early

+if a full block is not available, so retry until data is available

+or end of file is reached.

 .IP

 directory fail unless a directory

 dsync     use synchronized I/O for data