factor: support "no-argvs" usage

function                                             old     new   delta
factorize_numstr                                       -      72     +72
packed_usage                                       31562   31566      +4
factor_main                                          109     101      -8
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 76/-8)              Total: 68 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 39 insertions, 17 deletions

diff --git a/coreutils/factor.c b/coreutils/factor.c
index 281753439..818414775 100644
--- a/coreutils/factor.c
+++ b/coreutils/factor.c
@@ -14,7 +14,7 @@
 //kbuild:lib-$(CONFIG_FACTOR) += factor.o
 
 //usage:#define factor_trivial_usage
-//usage:       "NUMBER..."
+//usage:       "[NUMBER]..."
 //usage:#define factor_full_usage "\n\n"
 //usage:       "Print prime factors"
 
@@ -165,6 +165,20 @@ static NOINLINE void factorize(wide_t N)
         bb_putchar('\n');
 }
 
+static void factorize_numstr(const char *numstr)
+{
+        wide_t N;
+
+        /* Leading + is ok (coreutils compat) */
+        if (*numstr == '+')
+                numstr++;
+        N = bb_strtoull(numstr, NULL, 10);
+        if (errno)
+                bb_show_usage();
+        printf("%llu:", N);
+        factorize(N);
+}
+
 int factor_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int factor_main(int argc UNUSED_PARAM, char **argv)
 {
@@ -173,24 +187,32 @@ int factor_main(int argc UNUSED_PARAM, char **argv)
         //argv += optind;
         argv++;
 
-        if (!*argv)
-                //TODO: read from stdin
-                bb_show_usage();
+        if (!*argv) {
+                /* Read from stdin, several numbers per line are accepted */
+                for (;;) {
+                        char *numstr, *line;
+                        line = xmalloc_fgetline(stdin);
+                        if (!line)
+                                return EXIT_SUCCESS;
+                        numstr = line;
+                        for (;;) {
+                                char *end;
+                                numstr = skip_whitespace(numstr);
+                                if (!numstr[0])
+                                        break;
+                                end = skip_non_whitespace(numstr);
+                                if (*end != '\0');
+                                        *end++ = '\0';
+                                factorize_numstr(numstr);
+                                numstr = end;
+                        }
+                        free(line);
+                }
+        }
 
         do {
-                wide_t N;
-                const char *numstr;
-
-                /* Coreutils compat */
-                numstr = skip_whitespace(*argv);
-                if (*numstr == '+')
-                        numstr++;
-
-                N = bb_strtoull(numstr, NULL, 10);
-                if (errno)
-                        bb_show_usage();
-                printf("%llu:", N);
-                factorize(N);
+                /* Leading spaces are ok (coreutils compat) */
+                factorize_numstr(skip_whitespace(*argv));
         } while (*++argv);
 
         return EXIT_SUCCESS;