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/* vi: set sw=4 ts=4: */
/*
* shuf: Write a random permutation of the input lines to standard output.
*
* Copyright (C) 2014 by Bartosz Golaszewski <bartekgola@gmail.com>
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config SHUF
//config: bool "shuf (5.4 kb)"
//config: default y
//config: help
//config: Generate random permutations
//applet:IF_SHUF(APPLET_NOEXEC(shuf, shuf, BB_DIR_USR_BIN, BB_SUID_DROP, shuf))
//kbuild:lib-$(CONFIG_SHUF) += shuf.o
//usage:#define shuf_trivial_usage
//usage: "[-n NUM] [-o FILE] [-z] [FILE | -e [ARG...] | -i L-H]"
//usage:#define shuf_full_usage "\n\n"
//usage: "Randomly permute lines\n"
//usage: "\n -n NUM Output at most NUM lines"
//usage: "\n -o FILE Write to FILE, not standard output"
//usage: "\n -z NUL terminated output"
//usage: "\n -e Treat ARGs as lines"
//usage: "\n -i L-H Treat numbers L-H as lines"
#include "libbb.h"
/* This is a NOEXEC applet. Be very careful! */
#define OPT_e (1 << 0)
#define OPT_i (1 << 1)
#define OPT_n (1 << 2)
#define OPT_o (1 << 3)
#define OPT_z (1 << 4)
#define OPT_STR "ei:n:o:z"
/*
* Use the Fisher-Yates shuffle algorithm on an array of lines.
* If the required number of output lines is less than the total
* we can stop shuffling early.
*/
static void shuffle_lines(char **lines, unsigned numlines, unsigned outlines)
{
srand(monotonic_us());
while (outlines != 0) {
char *tmp;
unsigned r = rand();
/* RAND_MAX can be as small as 32767 */
if (numlines > RAND_MAX)
r ^= rand() << 15;
r %= numlines;
//TODO: the above method is seriously non-uniform when numlines is very large.
//For example, with numlines of 0xf0000000,
//values of (r % numlines) in [0, 0x0fffffff] range
//are more likely: e.g. r=1 and r=0xf0000001 both map to 1,
//whereas only one value, r=0xefffffff, maps to 0xefffffff.
numlines--;
tmp = lines[numlines];
lines[numlines] = lines[r];
lines[r] = tmp;
outlines--;
}
}
int shuf_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int shuf_main(int argc, char **argv)
{
unsigned opts;
char *opt_i_str, *opt_n_str, *opt_o_str;
char **lines;
unsigned long long lo = lo;
unsigned numlines, outlines;
unsigned i;
char eol;
opts = getopt32(argv, "^"
OPT_STR
"\0" "e--i:i--e"/* mutually exclusive */,
&opt_i_str, &opt_n_str, &opt_o_str
);
argc -= optind;
argv += optind;
/* Prepare lines for shuffling - either: */
if (opts & OPT_e) {
/* make lines from command-line arguments */
numlines = argc;
lines = argv;
} else
if (opts & OPT_i) {
/* create a range of numbers */
unsigned long long hi;
char *dash;
if (argv[0])
bb_show_usage();
dash = strchr(opt_i_str, '-');
if (!dash) {
bb_error_msg_and_die("bad range '%s'", opt_i_str);
}
*dash = '\0';
lo = xatoull(opt_i_str);
hi = xatoull(dash + 1);
*dash = '-';
if (hi < lo)
bb_error_msg_and_die("bad range '%s'", opt_i_str);
hi -= lo;
if (sizeof(size_t) > sizeof(numlines)) {
if (hi >= UINT_MAX)
bb_error_msg_and_die("bad range '%s'", opt_i_str);
} else {
if (hi >= UINT_MAX / sizeof(lines[0]))
bb_error_msg_and_die("bad range '%s'", opt_i_str);
}
numlines = hi + 1;
lines = xmalloc((size_t)numlines * sizeof(lines[0]));
for (i = 0; i < numlines; i++) {
lines[i] = (char*)(uintptr_t)i;
}
} else {
/* default - read lines from stdin or the input file */
FILE *fp;
const char *fname = "-";
if (argv[0]) {
if (argv[1])
bb_show_usage();
fname = argv[0];
}
fp = xfopen_stdin(fname);
lines = NULL;
numlines = 0;
for (;;) {
char *line = xmalloc_fgetline(fp);
if (!line)
break;
lines = xrealloc_vector(lines, 6, numlines);
lines[numlines++] = line;
}
fclose_if_not_stdin(fp);
}
outlines = numlines;
if (opts & OPT_n) {
outlines = xatou(opt_n_str);
if (outlines > numlines)
outlines = numlines;
}
shuffle_lines(lines, numlines, outlines);
if (opts & OPT_o)
xmove_fd(xopen(opt_o_str, O_WRONLY|O_CREAT|O_TRUNC), STDOUT_FILENO);
eol = '\n';
if (opts & OPT_z)
eol = '\0';
for (i = numlines - outlines; i < numlines; i++) {
if (opts & OPT_i)
printf("%llu%c", lo + (uintptr_t)lines[i], eol);
else
printf("%s%c", lines[i], eol);
}
fflush_stdout_and_exit(EXIT_SUCCESS);
}
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