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List: busybox
Subject: [PATCH] dd: support iflag=skip_bytes
From: Rafał Miłecki <zajec5 () gmail ! com>
Date: 2016-01-28 14:26:25
Message-ID: 1453991185-20288-1-git-send-email-zajec5 () gmail ! com
[Download RAW message or body]
It allows specifying amount of bytes directly (not only amount of
blocks) is also supported by GNU's Coreutils.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
---
coreutils/dd.c | 65 ++++++++++++++++++++++++++++++++++++++--------
docs/posix_conformance.txt | 1 +
2 files changed, 55 insertions(+), 11 deletions(-)
diff --git a/coreutils/dd.c b/coreutils/dd.c
index 6a5288d..de58cb3 100644
--- 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 Treat skip=N value as amount of 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_FIRST = 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)
@@ -209,12 +214,14 @@ 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 +239,7 @@ 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 +259,7 @@ 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;
@@ -335,6 +344,27 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
}
/*continue;*/
}
+ if (what == OP_iflag) {
+ 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(iflag_words, val);
+ if (n < 0)
+ bb_error_msg_and_die(bb_msg_invalid_arg_to, val, "iflag");
+ G.flags |= (1 << (FLAG_IFLAG_FIRST + n));
+ if (!arg) /* no ',' left, so this was the last specifier */
+ break;
+ /* *arg = ','; - to preserve ps listing? */
+ val = arg + 1; /* skip this keyword and ',' */
+ }
+ /*continue;*/
+ }
#endif
if (what == OP_bs) {
ibs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, cwbkMG_suffixes);
@@ -421,14 +451,27 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
outfile = bb_msg_standard_output;
}
if (skip) {
- if (lseek(ifd, skip * ibs, SEEK_CUR) < 0) {
- do {
- ssize_t n = safe_read(ifd, ibuf, ibs);
+ bool skip_bytes = G.flags & FLAG_SKIP_BYTES;
+ size_t bytes = skip * (skip_bytes ? 1 : ibs);
+ ssize_t sought;
+
+ sought = lseek(ifd, bytes, SEEK_CUR);
+ if (sought > 0)
+ bytes -= sought;
+ if (sought < 0 || skip_bytes) {
+ while (bytes) {
+ size_t min = (skip_bytes && bytes < ibs) ? bytes : ibs;
+ ssize_t n = safe_read(ifd, ibuf, min);
if (n < 0)
goto die_infile;
if (n == 0)
break;
- } while (--skip != 0);
+ if (skip_bytes) {
+ bytes -= n;
+ } else {
+ bytes -= ibs;
+ }
+ }
}
}
if (seek) {
diff --git a/docs/posix_conformance.txt b/docs/posix_conformance.txt
index 5b616d7..c0582dc 100644
--- 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
--
1.8.4.5
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