Added help message & fixed blocksize bug

The bug was caused by integer overflow with too large precisions.

1 files changed, 21 insertions, 0 deletions

diff --git a/stdu.c b/stdu.c
index 64f19a5..466d2f5 100644
--- a/stdu.c
+++ b/stdu.c
@@ -4,6 +4,7 @@
 #include <string.h>
 #include <errno.h>
 #include <stdbool.h>
+#include <limits.h>
 
 #include "intmath.h"
 #include "formatting.h"
@@ -26,6 +27,17 @@ int main (int argc, char* argv[]) {
 
 	Config* conf = (Config*) res.result;
 
+	if (conf->help) {
+		printf(
+"Usage: stdu [-h] [-p n]\n\
+Print amount of data piped to stdin.\n\
+--help | -?: print this help message\n\
+--human-readable | -h: output in a human readable format\n\
+--precision n | -p n | -pn: output with n significant digits\n "
+		);
+		return 0;
+	}
+
 	unsigned int base = 10;
 	if (conf->human_readable && conf->precision == 0) {
 		conf->precision = 1;
@@ -38,6 +50,15 @@ int main (int argc, char* argv[]) {
 	unsigned long long bytes_read = 0;
 	size_t new_read_bytes = 0;
 	if (conf->precision != 0) {
+		int max_precision = int_logn(base, (unsigned int) INT_MAX);
+		if (conf->precision > max_precision) {
+			fprintf(
+				stderr,
+				"Overflow error: precision may not be greater than %d\n",
+				max_precision
+			);
+			return 1;
+		}
 		blocksize = exp_notated_to_ull(ull_ceiled_exponent_notation_base(
 			bytes_read + 1,
 			conf->precision,