busybox: backport dd support for iflag=count_bytes

It's very useful flag for handling various formats in sysupgrade. This
commit comes from the 1.34.0 release.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

diff --git a/package/utils/busybox/patches/001-dd-support-iflag-count_bytes.patch b/package/utils/busybox/patches/001-dd-support-iflag-count_bytes.patch
new file mode 100644 (file)
index 0000000..c195c10
--- /dev/null
+++ b/package/utils/busybox/patches/001-dd-support-iflag-count_bytes.patch
@@ -0,0 +1,140 @@
+From 4eb46e1be6d88eaf077252ce93127ebf00aa8ef2 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Wed, 24 Mar 2021 16:01:42 +0100
+Subject: [PATCH] dd: support iflag=count_bytes
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+It allows passing amount of bytes in the count=
+
+function                                             old     new   delta
+packed_usage                                       33599   33617     +18
+static.iflag_words                                    29      41     +12
+dd_main                                             1601    1607      +6
+------------------------------------------------------------------------------
+(add/remove: 0/0 grow/shrink: 3/0 up/down: 36/0)               Total: 36 bytes
+
+Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
+Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
+---
+ coreutils/dd.c              | 50 ++++++++++++++++++++++++-------------
+ testsuite/dd/dd-count-bytes |  1 +
+ 2 files changed, 33 insertions(+), 18 deletions(-)
+ create mode 100644 testsuite/dd/dd-count-bytes
+
+--- a/coreutils/dd.c
++++ b/coreutils/dd.c
+@@ -59,7 +59,7 @@
+ //usage:       "[if=FILE] [of=FILE] [" IF_FEATURE_DD_IBS_OBS("ibs=N obs=N/") "bs=N] [count=N] [skip=N] [seek=N]\n"
+ //usage:      IF_FEATURE_DD_IBS_OBS(
+ //usage:       "      [conv=notrunc|noerror|sync|fsync]\n"
+-//usage:       "      [iflag=skip_bytes|fullblock|direct] [oflag=seek_bytes|append|direct]"
++//usage:       "      [iflag=skip_bytes|count_bytes|fullblock|direct] [oflag=seek_bytes|append|direct]"
+ //usage:      )
+ //usage:#define dd_full_usage "\n\n"
+ //usage:       "Copy a file with converting and formatting\n"
+@@ -82,6 +82,7 @@
+ //usage:     "\n      conv=fsync      Physically write data out before finishing"
+ //usage:     "\n      conv=swab       Swap every pair of bytes"
+ //usage:     "\n      iflag=skip_bytes        skip=N is in bytes"
++//usage:     "\n      iflag=count_bytes       count=N is in bytes"
+ //usage:     "\n      oflag=seek_bytes        seek=N is in bytes"
+ //usage:     "\n      iflag=direct    O_DIRECT input"
+ //usage:     "\n      oflag=direct    O_DIRECT output"
+@@ -136,21 +137,22 @@ enum {
+       FLAG_SWAB    = (1 << 4) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of conv flags */
+       /* start of input flags */
+-      FLAG_IFLAG_SHIFT = 5,
+-      FLAG_SKIP_BYTES = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
+-      FLAG_FULLBLOCK = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
+-      FLAG_IDIRECT = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_IFLAG_SHIFT   = 5,
++      FLAG_SKIP_BYTES    = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_COUNT_BYTES   = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_FULLBLOCK     = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_IDIRECT       = (1 << 8) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of input flags */
+       /* start of output flags */
+-      FLAG_OFLAG_SHIFT = 8,
+-      FLAG_SEEK_BYTES = (1 << 8) * ENABLE_FEATURE_DD_IBS_OBS,
+-      FLAG_APPEND = (1 << 9) * ENABLE_FEATURE_DD_IBS_OBS,
+-      FLAG_ODIRECT = (1 << 10) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_OFLAG_SHIFT   = 9,
++      FLAG_SEEK_BYTES    = (1 << 9) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_APPEND        = (1 << 10) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_ODIRECT       = (1 << 11) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of output flags */
+-      FLAG_TWOBUFS = (1 << 11) * ENABLE_FEATURE_DD_IBS_OBS,
+-      FLAG_COUNT   = 1 << 12,
+-      FLAG_STATUS_NONE = 1 << 13,
+-      FLAG_STATUS_NOXFER = 1 << 14,
++      FLAG_TWOBUFS       = (1 << 12) * ENABLE_FEATURE_DD_IBS_OBS,
++      FLAG_COUNT         = 1 << 13,
++      FLAG_STATUS_NONE   = 1 << 14,
++      FLAG_STATUS_NOXFER = 1 << 15,
+ };
+ 
+ static void dd_output_status(int UNUSED_PARAM cur_signal)
+@@ -175,8 +177,9 @@ static void dd_output_status(int UNUSED_
+       //So far we react to it (we print the stats),
+       //status=none only suppresses final, non-USR1 generated status message.
+ # endif
+-      fprintf(stderr, "%llu bytes (%sB) copied, ",
+-                      G.total_bytes,
++      fprintf(stderr, /*G.total_bytes < 1024
++                              ? "%llu bytes copied, " : */ "%llu bytes (%sB) copied, "
++                      , G.total_bytes,
+                       /* show fractional digit, use suffixes */
+                       make_human_readable_str(G.total_bytes, 1, 0)
+       );
+@@ -317,7 +320,7 @@ int dd_main(int argc UNUSED_PARAM, char
+       static const char conv_words[] ALIGN1 =
+               "notrunc\0""sync\0""noerror\0""fsync\0""swab\0";
+       static const char iflag_words[] ALIGN1 =
+-              "skip_bytes\0""fullblock\0""direct\0";
++              "skip_bytes\0""count_bytes\0""fullblock\0""direct\0";
+       static const char oflag_words[] ALIGN1 =
+               "seek_bytes\0append\0""direct\0";
+ #endif
+@@ -359,6 +362,7 @@ int dd_main(int argc UNUSED_PARAM, char
+       /* Partially implemented: */
+       //swab          swap every pair of input bytes: will abort on non-even reads
+               OP_iflag_skip_bytes,
++              OP_iflag_count_bytes,
+               OP_iflag_fullblock,
+               OP_iflag_direct,
+               OP_oflag_seek_bytes,
+@@ -551,8 +555,17 @@ int dd_main(int argc UNUSED_PARAM, char
+                       goto die_outfile;
+       }
+ 
+-      while (!(G.flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
+-              ssize_t n = dd_read(ibuf, ibs);
++      while (1) {
++              ssize_t n = ibs;
++
++              if (G.flags & FLAG_COUNT) {
++                      if (count == 0)
++                              break;
++                      if ((G.flags & FLAG_COUNT_BYTES) && count < ibs)
++                              n = count;
++              }
++
++              n = dd_read(ibuf, n);
+               if (n == 0)
+                       break;
+               if (n < 0) {
+@@ -587,6 +600,7 @@ int dd_main(int argc UNUSED_PARAM, char
+                               p16++;
+                       }
+               }
++              count -= (G.flags & FLAG_COUNT_BYTES) ? n : 1;
+               if ((size_t)n == ibs)
+                       G.in_full++;
+               else {
+--- /dev/null
++++ b/testsuite/dd/dd-count-bytes
+@@ -0,0 +1 @@
++test "$(echo I WANT | busybox dd count=3 iflag=count_bytes 2>/dev/null)" = "I W"