1 files changed, 82 insertions, 0 deletions
diff --git a/src/humane.c b/src/humane.c
new file mode 100644
index 0000000..3fdce03
--- /dev/null
+++ b/src/humane.c
@@ -0,0 +1,82 @@
+/*
+ *  Copyright (C) 2020 - Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "humane.h"
+
+/* Print bytes as a "human-readable" string in Si storage units into humane->buf and return it. */
+char * humane_bytes(humane_t *humane, uint64_t bytes)
+{
+	double	z = bytes;
+
+	static const char * units[] = {
+		"B",
+		"KiB",
+		"MiB",
+		"GiB",
+		"TiB",
+		"PiB",
+		"EiB",
+	};
+	int		order = 0;
+
+	while (z >= 1024) {
+		order++;
+		z /= 1024;
+	}
+
+	/* FIXME: isn't there a format specifier for adaptive precision? where %.2 means
+	 * use a maximum of two digits but only extend a non-zero fraction up to that limit,
+	 * i.e. don't produce outputs like 1.00. but produce 1.1 or 1.01, but 1.00 should be 1.
+	 * I can't remember if there's a double format to do that, and can't waste more time
+	 * reading the printf(3) man page.
+	 */
+	snprintf(humane->buf, sizeof(humane->buf), "%.2f %s", z, units[order]);
+
+	return humane->buf;
+}
+
+
+#if 0
+/* TODO: when/if unit tests become a thing in this tree, turn this into one of them and assert the
+ * stringified "humane" outputs match expectations.
+ */
+
+#define U64(x)	UINT64_C(x)
+int main(int argc, char *argv[])
+{
+	uint64_t	nums[] = {
+		0,
+		U64(1),
+		U64(512),
+		U64(1024),
+		U64(1024) + U64(512),
+		U64(1024) * U64(1024),
+		U64(1024) * U64(1024) * U64(1024),
+		U64(1024) * U64(1024) * U64(1024) * U64(1024),
+		U64(1024) * U64(1024) * U64(1024) * U64(1024) * U64(1024),
+		U64(1024) * U64(1024) * U64(1024) * U64(1024) * U64(1024) * U64(1024),
+		UINT64_MAX,
+	};
+	humane_t		humane = {};
+
+	for (int i = 0; i < sizeof(nums) / sizeof(*nums); i++)
+		printf("%"PRIu64" humane: %s\n", nums[i], humane_bytes(&humane, nums[i]));
+}
+#endif