svn commit: r357975 - head/usr.bin/random
Conrad Meyer
cem at FreeBSD.org
Sat Feb 15 19:13:38 UTC 2020
Author: cem
Date: Sat Feb 15 19:13:37 2020
New Revision: 357975
URL: https://svnweb.freebsd.org/changeset/base/357975
Log:
random(6): Re-add undocumented support for floating point denominators
And document it in the manual page.
PR: 244139
Submitted by: Keith White <kwhite AT site.uottawa.ca> (earlier version)
Modified:
head/usr.bin/random/random.6
head/usr.bin/random/random.c
head/usr.bin/random/randomize_fd.c
head/usr.bin/random/randomize_fd.h
Modified: head/usr.bin/random/random.6
==============================================================================
--- head/usr.bin/random/random.6 Sat Feb 15 18:57:49 2020 (r357974)
+++ head/usr.bin/random/random.6 Sat Feb 15 19:13:37 2020 (r357975)
@@ -28,7 +28,7 @@
.\" @(#)random.6 8.2 (Berkeley) 3/31/94
.\" $FreeBSD$
.\"
-.Dd December 12, 2019
+.Dd February 15, 2020
.Dt RANDOM 6
.Os
.Sh NAME
@@ -42,27 +42,26 @@
.Sh DESCRIPTION
.Nm Random
has two distinct modes of operations.
-The default is to read in lines
-from the standard input and randomly write them out
-to the standard output with a probability of
-1 /
+The default is to read lines from standard input and write them to standard
+output with a probability of 1.0 /
.Ar denominator .
+.Ar ( denominator
+is a real number greater than or equal to 1.0.)
The default
.Ar denominator
-for this mode of operation is 2, giving each line a 50/50 chance of
+for this mode of operation is 2.0, giving each line a 50% chance of
being displayed.
.Pp
-The second mode of operation is to read in a file from
-.Ar filename
-and randomize the contents of the file and send it back out to
+The second mode of operation, selected with the
+.Fl f Ar filename
+option, reads the specified file and outputs the randomized contents to
standard output.
-The contents can be randomized based off of newlines or based off of
-space characters as determined by
-.Xr isspace 3 .
+The contents can be randomized in units of lines (split on newline characters)
+or in units of words (split on space characters as determined by
+.Xr isspace 3 . )
The default
.Ar denominator
-for this mode of operation is 1, which gives each line a chance to be
-displayed, but in a random order.
+for this mode of operation is 1.0, which displays every line.
.Pp
The options are as follows:
.Bl -tag -width Ds
@@ -75,6 +74,9 @@ does not read or write anything, and simply exits with
exit value of 0 to
.Ar denominator
\&- 1, inclusive.
+In this mode,
+.Ar denominator
+must be less than or equal to 256.
.It Fl f Ar filename
The
.Fl f
@@ -83,27 +85,18 @@ option is used to specify the
to read from.
Standard input is used if
.Ar filename
-is set to
-.Sq Fl .
+is
+.Sq - .
.It Fl l
Randomize the input via newlines (the default).
.It Fl r
-The
-.Fl r
-option guarantees that the output is unbuffered.
+Do not buffer output.
.It Fl U
-Tells
-.Xr random 6
-that it is okay for it to reuse any given line or word when creating a
-randomized output.
+Reuse any given line or word when creating a randomized output.
.It Fl u
-Tells
-.Xr random 6
-not to select the same line or word from a file more than once (the
-default).
+Do not select the same line or word from a file more than once (the default).
This does not guarantee uniqueness if there are two of the
-same tokens from the input, but it does prevent selecting the same
-token more than once.
+same tokens in the input.
.It Fl w
Randomize words separated by
.Xr isspace 3
@@ -116,7 +109,12 @@ The
functionality to randomizing lines and words was added in 2003 by
.An Sean Chittenden Aq Mt seanc at FreeBSD.org .
.Sh BUGS
+This tool is a remnant of the "games" collection formerly part of
+.Fx
+base.
+It probably should have been removed to ports with the rest of that collection.
+It does not have a coherent purpose and the motivation for it to be a core base
+utility is nonobvious.
+.Pp
No index is used when printing out tokens from the list which
makes it rather slow for large files (10MB+).
-For smaller
-files, however, it should still be quite fast and efficient.
Modified: head/usr.bin/random/random.c
==============================================================================
--- head/usr.bin/random/random.c Sat Feb 15 18:57:49 2020 (r357974)
+++ head/usr.bin/random/random.c Sat Feb 15 19:13:37 2020 (r357975)
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
#include <fcntl.h>
#include <limits.h>
#include <locale.h>
+#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
@@ -67,11 +68,12 @@ main(int argc, char *argv[])
{
double denom;
int ch, fd, random_exit, randomize_lines, random_type, ret,
- selected, unique_output, unbuffer_output;
+ unique_output, unbuffer_output;
+ bool selected;
char *ep;
const char *filename;
- denom = 0;
+ denom = 0.;
filename = "/dev/fd/0";
random_type = RANDOM_TYPE_UNSET;
random_exit = randomize_lines = unbuffer_output = 0;
@@ -119,16 +121,16 @@ main(int argc, char *argv[])
switch (argc) {
case 0:
- denom = (randomize_lines ? 1 : 2);
+ denom = (randomize_lines ? 1. : 2.);
break;
case 1:
errno = 0;
denom = strtod(*argv, &ep);
if (errno == ERANGE)
err(1, "%s", *argv);
- if (denom <= 0 || *ep != '\0')
+ if (denom < 1. || *ep != '\0')
errx(1, "denominator is not valid.");
- if (random_exit && denom > 256)
+ if (random_exit && denom > 256.)
errx(1, "denominator must be <= 256 for random exit.");
break;
default:
@@ -160,24 +162,25 @@ main(int argc, char *argv[])
return (arc4random_uniform(denom));
/*
- * Select whether to print the first line. (Prime the pump.)
- * We find a random number between 0 and denom - 1 and, if it's
- * 0 (which has a 1 / denom chance of being true), we select the
- * line.
+ * Filter stdin, selecting lines with probability 1/denom, one
+ * character at a time.
*/
- selected = (arc4random_uniform(denom) == 0);
- while ((ch = getchar()) != EOF) {
- if (selected)
- (void)putchar(ch);
- if (ch == '\n') {
- /* End of that line. See if we got an error. */
- if (ferror(stdout))
- err(2, "stdout");
-
- /* Now see if the next line is to be printed. */
- selected = (arc4random_uniform(denom) == 0);
+ do {
+ selected = random_uniform_denom(denom);
+ if (selected) {
+ while ((ch = getchar()) != EOF) {
+ putchar(ch);
+ if (ch == '\n')
+ break;
+ }
+ } else {
+ while ((ch = getchar()) != EOF)
+ if (ch == '\n')
+ break;
}
- }
+ if (ferror(stdout))
+ err(2, "stdout");
+ } while (ch != EOF);
if (ferror(stdin))
err(2, "stdin");
exit (0);
Modified: head/usr.bin/random/randomize_fd.c
==============================================================================
--- head/usr.bin/random/randomize_fd.c Sat Feb 15 18:57:49 2020 (r357974)
+++ head/usr.bin/random/randomize_fd.c Sat Feb 15 19:13:37 2020 (r357975)
@@ -33,6 +33,7 @@ __FBSDID("$FreeBSD$");
#include <ctype.h>
#include <err.h>
#include <errno.h>
+#include <stdbool.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
@@ -218,7 +219,7 @@ make_token:
if (n->cp == NULL)
break;
- if (arc4random_uniform(denom) == 0) {
+ if (random_uniform_denom(denom)) {
ret = printf("%.*s",
(int)n->len - 1, n->cp);
if (ret < 0)
Modified: head/usr.bin/random/randomize_fd.h
==============================================================================
--- head/usr.bin/random/randomize_fd.h Sat Feb 15 18:57:49 2020 (r357974)
+++ head/usr.bin/random/randomize_fd.h Sat Feb 15 19:13:37 2020 (r357975)
@@ -42,4 +42,40 @@ struct rand_node {
int randomize_fd(int fd, int type, int unique, double denom);
+/*
+ * Generates a random number uniformly in the range [0.0, 1.0).
+ */
+static inline double
+random_unit_float(void)
+{
+ static const uint64_t denom = (1ull << 53);
+ static const uint64_t mask = denom - 1;
+
+ uint64_t rand64;
+
+ /*
+ * arc4random_buf(...) in this use generates integer outputs in [0,
+ * UINT64_MAX].
+ *
+ * The double mantissa only has 53 bits, so we uniformly mask off the
+ * high 11 bits and then floating-point divide by 2^53 to achieve a
+ * result in [0, 1).
+ *
+ * We are not allowed to emit 1.0, so denom must be one greater than
+ * the possible range of the preceeding step.
+ */
+ arc4random_buf(&rand64, sizeof(rand64));
+ rand64 &= mask;
+ return ((double)rand64 / denom);
+}
+
+/*
+ * Returns true with probability 1 / denom (a floating point number >= 1).
+ * Otherwise, returns false.
+ */
+static inline bool
+random_uniform_denom(double denom)
+{
+ return ((uint64_t)(denom * random_unit_float()) == 0);
+}
#endif
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