Add iflag=fullblock to dd

Normally, count=n means read(2) will be called n times on the input to dd. If
the read() returns short, as may happen when reading from a pipe, fewer bytes
will be copied from the input. With conv=sync the buffer is padded with zeros
to fill the rest of the block.

iflag=fullblock causes dd to continue reading until the block is full, so that
count=n means n full blocks are copied. This flag is compatible with illumos
and GNU dd and is used in the ZFS test suite.

Submitted by:	Ryan Moeller
Reviewed by:	manpages, mmacy@
MFC after:	1 week
Sponsored by:	 iXsystems, Inc.
Differential Revision:	https://reviews.freebsd.org/D21441
This commit is contained in:
Matt Macy 2019-09-30 22:00:48 +00:00
parent 919156e34c
commit b52c534bff
4 changed files with 80 additions and 25 deletions

View File

@ -57,6 +57,7 @@ __FBSDID("$FreeBSD$");
static int c_arg(const void *, const void *);
static int c_conv(const void *, const void *);
static int c_iflag(const void *, const void *);
static int c_oflag(const void *, const void *);
static void f_bs(char *);
static void f_cbs(char *);
@ -66,6 +67,7 @@ static void f_files(char *);
static void f_fillchar(char *);
static void f_ibs(char *);
static void f_if(char *);
static void f_iflag(char *);
static void f_obs(char *);
static void f_of(char *);
static void f_oflag(char *);
@ -89,6 +91,7 @@ static const struct arg {
{ "fillchar", f_fillchar, C_FILL, C_FILL },
{ "ibs", f_ibs, C_IBS, C_BS|C_IBS },
{ "if", f_if, C_IF, C_IF },
{ "iflag", f_iflag, 0, 0 },
{ "iseek", f_skip, C_SKIP, C_SKIP },
{ "obs", f_obs, C_OBS, C_BS|C_OBS },
{ "of", f_of, C_OF, C_OF },
@ -259,6 +262,38 @@ f_if(char *arg)
in.name = arg;
}
static const struct iflag {
const char *name;
uint64_t set, noset;
} ilist[] = {
{ "fullblock", C_IFULLBLOCK, C_SYNC },
};
static void
f_iflag(char *arg)
{
struct iflag *ip, tmp;
while (arg != NULL) {
tmp.name = strsep(&arg, ",");
ip = bsearch(&tmp, ilist, nitems(ilist), sizeof(struct iflag),
c_iflag);
if (ip == NULL)
errx(1, "unknown iflag %s", tmp.name);
if (ddflags & ip->noset)
errx(1, "%s: illegal conversion combination", tmp.name);
ddflags |= ip->set;
}
}
static int
c_iflag(const void *a, const void *b)
{
return (strcmp(((const struct iflag *)a)->name,
((const struct iflag *)b)->name));
}
static void
f_obs(char *arg)
{
@ -339,7 +374,7 @@ static const struct conv {
{ "parset", C_PARSET, C_PARODD|C_PAREVEN|C_PARNONE, NULL},
{ "sparse", C_SPARSE, 0, NULL },
{ "swab", C_SWAB, 0, NULL },
{ "sync", C_SYNC, 0, NULL },
{ "sync", C_SYNC, C_IFULLBLOCK, NULL },
{ "ucase", C_UCASE, C_LCASE, NULL },
{ "unblock", C_UNBLOCK, C_BLOCK, NULL },
};

View File

@ -102,6 +102,22 @@ bytes instead of the default 512.
Read input from
.Ar file
instead of the standard input.
.It Cm iflag Ns = Ns Ar value Ns Op , Ns Ar value ...
Where
.Cm value
is one of the symbols from the following list.
.Bl -tag -width "fullblock"
.It Cm fullblock
Reading from the input file may not obtain a full block.
When a read returns short, continue reading to fill the block.
Without this flag,
.Cm count
limits the number of times
.Xr read 2
is called on the input rather than the number of blocks copied in full.
May not be combined with
.Cm conv=sync .
.El
.It Cm iseek Ns = Ns Ar n
Seek on the input file
.Ar n

View File

@ -408,13 +408,15 @@ dd_in(void)
memset(in.dbp, 0, in.dbsz);
}
n = read(in.fd, in.dbp, in.dbsz);
if (n == 0) {
in.dbrcnt = 0;
return;
}
in.dbrcnt = 0;
fill:
n = read(in.fd, in.dbp + in.dbrcnt, in.dbsz - in.dbrcnt);
/* Read error. */
/* EOF */
if (n == 0 && in.dbrcnt == 0)
return;
/* Read error */
if (n == -1) {
/*
* If noerror not specified, die. POSIX requires that
@ -438,26 +440,26 @@ dd_in(void)
/* If sync not specified, omit block and continue. */
if (!(ddflags & C_SYNC))
continue;
/* Read errors count as full blocks. */
in.dbcnt += in.dbrcnt = in.dbsz;
++st.in_full;
/* Handle full input blocks. */
} else if ((size_t)n == (size_t)in.dbsz) {
in.dbcnt += in.dbrcnt = n;
++st.in_full;
/* Handle partial input blocks. */
} else {
/* If sync, use the entire block. */
if (ddflags & C_SYNC)
in.dbcnt += in.dbrcnt = in.dbsz;
else
in.dbcnt += in.dbrcnt = n;
++st.in_part;
}
/* If conv=sync, use the entire block. */
if (ddflags & C_SYNC)
n = in.dbsz;
/* Count the bytes read for this block. */
in.dbrcnt += n;
/* Count the number of full and partial blocks. */
if (in.dbrcnt == in.dbsz)
++st.in_full;
else if (ddflags & C_IFULLBLOCK && n != 0)
goto fill; /* these don't count */
else
++st.in_part;
/* Count the total bytes read for this file. */
in.dbcnt += in.dbrcnt;
/*
* POSIX states that if bs is set and no other conversions
* than noerror, notrunc or sync are specified, the block
@ -478,6 +480,7 @@ dd_in(void)
swapbytes(in.dbp, (size_t)n);
}
/* Advance to the next block. */
in.dbp += in.dbrcnt;
(*cfunc)();
if (need_summary)

View File

@ -104,6 +104,7 @@ typedef struct {
#define C_FSYNC 0x0000000080000000ULL
#define C_FDATASYNC 0x0000000100000000ULL
#define C_OFSYNC 0x0000000200000000ULL
#define C_IFULLBLOCK 0x0000000400000000ULL
#define C_PARITY (C_PAREVEN | C_PARODD | C_PARNONE | C_PARSET)