dd: support iflag=skip_bytes

It allows specifying amount of bytes directly (not only amount of
blocks) is also supported by GNU's Coreutils.

function                                             old     new   delta
parse_comma_flags                                      -      93     +93
static.iflag_words                                     -      12     +12
dd_main                                             1569    1580     +11
packed_usage                                       30591   30600      +9
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 2/0 up/down: 125/0)             Total: 125 bytes

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/coreutils/dd.c b/coreutils/dd.c
index 6a5288da17754b97718d4873006a07ac5556f786..0c0ea07b95bc5bcc0c943c1a1962cc80a5fbc1d0 100644 (file)
--- a/coreutils/dd.c
+++ b/coreutils/dd.c
@@ -55,7 +55,7 @@
 
 //usage:#define dd_trivial_usage
 //usage:       "[if=FILE] [of=FILE] " IF_FEATURE_DD_IBS_OBS("[ibs=N] [obs=N] ") "[bs=N] [count=N] [skip=N]\n"
-//usage:       "       [seek=N]" IF_FEATURE_DD_IBS_OBS(" [conv=notrunc|noerror|sync|fsync]")
+//usage:       "       [seek=N]" IF_FEATURE_DD_IBS_OBS(" [conv=notrunc|noerror|sync|fsync] [iflag=skip_bytes]")
 //usage:#define dd_full_usage "\n\n"
 //usage:       "Copy a file with converting and formatting\n"
 //usage:     "\n       if=FILE         Read from FILE instead of stdin"
@@ -76,6 +76,7 @@
 //usage:     "\n       conv=sync       Pad blocks with zeros"
 //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:       )
 //usage:       IF_FEATURE_DD_STATUS(
 //usage:     "\n       status=noxfer   Suppress rate output"
@@ -122,11 +123,15 @@ enum {
        FLAG_FSYNC   = (1 << 3) * ENABLE_FEATURE_DD_IBS_OBS,
        FLAG_SWAB    = (1 << 4) * ENABLE_FEATURE_DD_IBS_OBS,
        /* end of conv flags */
-       FLAG_TWOBUFS = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
-       FLAG_COUNT   = 1 << 6,
-       FLAG_STATUS  = 1 << 7,
-       FLAG_STATUS_NONE = 1 << 7,
-       FLAG_STATUS_NOXFER = 1 << 8,
+       /* start of input flags */
+       FLAG_IFLAG_SHIFT = 5,
+       FLAG_SKIP_BYTES = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
+       /* end of input flags */
+       FLAG_TWOBUFS = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
+       FLAG_COUNT   = 1 << 7,
+       FLAG_STATUS  = 1 << 8,
+       FLAG_STATUS_NONE = 1 << 9,
+       FLAG_STATUS_NOXFER = 1 << 10,
 };
 
 static void dd_output_status(int UNUSED_PARAM cur_signal)
@@ -203,18 +208,47 @@ static bool write_and_stats(const void *buf, size_t len, size_t obs,
 # define XATOU_SFX xatoul_sfx
 #endif
 
+#if ENABLE_FEATURE_DD_IBS_OBS
+static int parse_comma_flags(char *val, const char *words, const char *error_in)
+{
+       int flags = 0;
+       while (1) {
+               int n;
+               char *arg;
+               /* find ',', replace them with NUL so we can use val for
+                * index_in_strings() without copying.
+                * We rely on val being non-null, else strchr would fault.
+                */
+               arg = strchr(val, ',');
+               if (arg)
+                       *arg = '\0';
+               n = index_in_strings(words, val);
+               if (n < 0)
+                       bb_error_msg_and_die(bb_msg_invalid_arg_to, val, error_in);
+               flags |= (1 << n);
+               if (!arg) /* no ',' left, so this was the last specifier */
+                       break;
+               *arg = ','; /* to preserve ps listing */
+               val = arg + 1; /* skip this keyword and ',' */
+       }
+       return flags;
+}
+#endif
+
 int dd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int dd_main(int argc UNUSED_PARAM, char **argv)
 {
        static const char keywords[] ALIGN1 =
                "bs\0""count\0""seek\0""skip\0""if\0""of\0"IF_FEATURE_DD_STATUS("status\0")
 #if ENABLE_FEATURE_DD_IBS_OBS
-               "ibs\0""obs\0""conv\0"
+               "ibs\0""obs\0""conv\0""iflag\0"
 #endif
                ;
 #if ENABLE_FEATURE_DD_IBS_OBS
        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";
 #endif
 #if ENABLE_FEATURE_DD_STATUS
        static const char status_words[] ALIGN1 =
@@ -232,6 +266,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
                OP_ibs,
                OP_obs,
                OP_conv,
+               OP_iflag,
                /* Must be in the same order as FLAG_XXX! */
                OP_conv_notrunc = 0,
                OP_conv_sync,
@@ -251,6 +286,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
        //ibm           from ASCII to alternate EBCDIC
        /* Partially implemented: */
        //swab          swap every pair of input bytes: will abort on non-even reads
+               OP_iflag_skip_bytes,
 #endif
        };
        smallint exitcode = EXIT_FAILURE;
@@ -315,24 +351,11 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
                        /*continue;*/
                }
                if (what == OP_conv) {
-                       while (1) {
-                               int n;
-                               /* find ',', replace them with NUL so we can use val for
-                                * index_in_strings() without copying.
-                                * We rely on val being non-null, else strchr would fault.
-                                */
-                               arg = strchr(val, ',');
-                               if (arg)
-                                       *arg = '\0';
-                               n = index_in_strings(conv_words, val);
-                               if (n < 0)
-                                       bb_error_msg_and_die(bb_msg_invalid_arg_to, val, "conv");
-                               G.flags |= (1 << n);
-                               if (!arg) /* no ',' left, so this was the last specifier */
-                                       break;
-                               /* *arg = ','; - to preserve ps listing? */
-                               val = arg + 1; /* skip this keyword and ',' */
-                       }
+                       G.flags |= parse_comma_flags(val, conv_words, "conv");
+                       /*continue;*/
+               }
+               if (what == OP_iflag) {
+                       G.flags |= parse_comma_flags(val, iflag_words, "iflag") << FLAG_IFLAG_SHIFT;
                        /*continue;*/
                }
 #endif
@@ -421,9 +444,10 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
                outfile = bb_msg_standard_output;
        }
        if (skip) {
-               if (lseek(ifd, skip * ibs, SEEK_CUR) < 0) {
+               size_t blocksz = (G.flags & FLAG_SKIP_BYTES) ? 1 : ibs;
+               if (lseek(ifd, skip * blocksz, SEEK_CUR) < 0) {
                        do {
-                               ssize_t n = safe_read(ifd, ibuf, ibs);
+                               ssize_t n = safe_read(ifd, ibuf, blocksz);
                                if (n < 0)
                                        goto die_infile;
                                if (n == 0)

diff --git a/docs/posix_conformance.txt b/docs/posix_conformance.txt
index 5b616d70127d3d09fec933d350fab0eca60dcdd6..c0582dc231db964e993efde5a4e768273f8df1cf 100644 (file)
--- a/docs/posix_conformance.txt
+++ b/docs/posix_conformance.txt
@@ -178,6 +178,7 @@ dd POSIX options:
   conv=noerror    |  yes   |           |
   conv=notrunc    |  yes   |           |
   conv=sync       |  yes   |           |
+  iflag=skip_bytes|  yes   |           |
 dd Busybox specific options:
  conv=fsync