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List: busybox
Subject: Re: [PATCH] dd: support iflag=skip_bytes
From: Denys Vlasenko <vda.linux () googlemail ! com>
Date: 2016-02-01 1:18:08
Message-ID: CAK1hOcPUkOj1FVXenuzAw53G=UvBk0URLN9nu7K+PhWq1EvTpg () mail ! gmail ! com
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Applied, thanks!
On Thu, Jan 28, 2016 at 3:26 PM, Rafał Miłecki <zajec5@gmail.com> wrote:
> 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
>
> _______________________________________________
> busybox mailing list
> busybox@busybox.net
> http://lists.busybox.net/mailman/listinfo/busybox
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