1 files changed, 67 insertions, 0 deletions
diff --git a/lib/e2p/percent.c b/lib/e2p/percent.c
new file mode 100644
index 0000000..e340cd7
--- /dev/null
+++ b/lib/e2p/percent.c
@@ -0,0 +1,67 @@
+/*
+ * percent.c		- Take percentage of a number
+ *
+ * Copyright (C) 2006  Theodore Ts'o <tytso@mit.edu>
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#include "config.h"
+#include "e2p.h"
+
+#include <stdlib.h>
+
+/*
+ * We work really hard to calculate this accurately, while avoiding
+ * an overflow.  "Is there a hyphen in anal-retentive?"  :-)
+ */
+unsigned int e2p_percent(int percent, unsigned int base)
+{
+	unsigned int mask = ~((1 << (sizeof(unsigned int) - 1) * 8) - 1);
+
+	if (!percent)
+		return 0;
+	if (100 % percent == 0)
+		return base / (100 / percent);
+	if (mask & base)
+		return (base / 100) * percent;
+	return base * percent / 100;
+}
+
+#ifdef DEBUG
+#include <unistd.h>
+#include <stdio.h>
+
+main(int argc, char **argv)
+{
+	unsigned int base;
+	int percent;
+	char *p;
+	int log_block_size = 0;
+
+	if (argc != 3) {
+		fprintf(stderr, "Usage: %s percent base\n", argv[0]);
+		exit(1);
+	}
+
+	percent = strtoul(argv[1], &p, 0);
+	if (p[0] && p[1]) {
+		fprintf(stderr, "Bad percent: %s\n", argv[1]);
+		exit(1);
+	}
+
+	base = strtoul(argv[2], &p, 0);
+	if (p[0] && p[1]) {
+		fprintf(stderr, "Bad base: %s\n", argv[2]);
+		exit(1);
+	}
+
+	printf("%d percent of %u is %u.\n", percent, base,
+	       e2p_percent(percent, base));
+
+	exit(0);
+}
+#endif