Added help message & fixed blocksize bug

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

5 files changed, 48 insertions, 16 deletions

diff --git a/config-parser.c b/config-parser.c
index 5e403f8..075ef47 100644
--- a/config-parser.c
+++ b/config-parser.c
@@ -17,6 +17,7 @@ Result parse_config(int argc, char* argv[]) {
 	Config tmp;
 	tmp.precision = 0;
 	tmp.human_readable = false;
+	tmp.help = false;
 
 	size_t i = 1;
 	char* argument;
@@ -25,6 +26,16 @@ Result parse_config(int argc, char* argv[]) {
 		argument = argv[i];
 		int comp1 = strcmp(argument, "--precision") == 0;
 		if (
+			strcmp(argument, "--help") == 0
+			|| strcmp(argument, "-?") == 0
+		) {
+			tmp.help = true;
+		} else if (
+			strcmp(argument, "--human-readable") == 0
+			|| strcmp(argument, "-h") == 0
+		) {
+			tmp.human_readable = true;
+		} else if (
 			comp1 || strncmp(argument, "-p", 2) == 0
 		) {
 			if (precision != NULL) {
@@ -54,21 +65,6 @@ Result parse_config(int argc, char* argv[]) {
 				return res;
 			}
 			precision = argv[i];
-		} else if (
-			strcmp(argument, "--human-readable") == 0
-			|| strcmp(argument, "-h") == 0
-		) {
-			if (tmp.human_readable != false) {
-				char* error_msg = malloc(52);
-				snprintf(
-					error_msg,
-					52,
-					"human readability can't be specified multiple times"
-				);
-				res.result = error_msg;
-				return res;
-			}
-			tmp.human_readable = true;
 		} else {
 			size_t msg_size = 21 + strlen(argument);
 			char* error_msg = malloc(msg_size);
@@ -126,8 +122,9 @@ Result parse_config(int argc, char* argv[]) {
 	}
 
 	Config* conf = malloc(sizeof(int) + sizeof(bool));
-	conf->precision = tmp.precision;
+	conf->help = tmp.help;
 	conf->human_readable = tmp.human_readable;
+	conf->precision = tmp.precision;
 
 	res.success = true;
 	res.result = conf;
diff --git a/config-parser.h b/config-parser.h
index 1026a98..08aa934 100644
--- a/config-parser.h
+++ b/config-parser.h
@@ -2,6 +2,7 @@
 struct Config {
 	int precision;
 	bool human_readable;
+	bool help;
 };
 typedef struct Config Config;
 struct Result {
diff --git a/intmath.c b/intmath.c
index 9e1f3ed..a4738b9 100644
--- a/intmath.c
+++ b/intmath.c
@@ -14,6 +14,18 @@ int int_pown(unsigned int base, unsigned int exp) {
 	return res;
 }
 
+int int_logn(unsigned int base, unsigned int a) {
+	unsigned int exp = 1;
+	int res = (int) base;
+	int lastres = res - 1;
+	while ((res < a) && (lastres < res)) {
+		lastres = res;
+		res *= base;
+		exp++;
+	}
+	return exp;
+}
+
 unsigned long long ull_pown(unsigned int base, unsigned int exp) {
 	unsigned long long res = 1;
 	while (exp > 0) {
diff --git a/intmath.h b/intmath.h
index 5d0b56b..b86ce72 100644
--- a/intmath.h
+++ b/intmath.h
@@ -1,5 +1,6 @@
 int int_pown(unsigned int base, unsigned int exp);
 unsigned long long ull_pown(unsigned int base, unsigned int exp);
+int int_logn(unsigned int base, unsigned int a);
 int int_pow10(unsigned int exp);
 int int_floor(int x, int precision);
 int int_ceil(int x, int precision);
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,