1 files changed, 71 insertions, 0 deletions
diff --git a/utils/midpoint.c b/utils/midpoint.c
new file mode 100644
index 0000000..1a2e6f3
--- /dev/null
+++ b/utils/midpoint.c
@@ -0,0 +1,71 @@
+#include <dht.c>
+#include <error.h>
+#define S0(x) (x ? x : "")
+
+/**
+ * converts a hexadecimal string to bytes
+ *
+ * b and h may not overlap, unless they are the same address
+ *
+ * @param b	[out]	array of bytes to write to with capacity l
+ * @param h	[in]	array of hex to read from with 2l hex digits
+ * @param l	[in]	length of output array
+ */
+
+void hex2bin (unsigned char * b, const char * h, int l) {
+	for (int i = 0; i < l; i++) {
+		char ms = *h++;
+		char ls = *h++;
+		b[i] = (ms >= 'a' ? ms - 'a' + 10 : (ms >= 'A' ? ms - 'A' + 10 : ms - '0')) << 4;
+		b[i] |= (ls >= 'a' ? ls - 'a' + 10 : (ls >= 'A' ? ls - 'A' + 10 : ls - '0'));
+	}
+}
+
+int main (int argc, char ** argv) {
+	if (argc < 3)
+		error_at_line(1, 0, __FILE__, __LINE__, "%s <bin|add|subtract|divide|midpoint> <a> [b]", S0(argv[0]));
+	if (argv[1][0] == 'b' || argv[1][0] == 'B') {
+		unsigned char a[strlen(argv[2])/2+1];
+		a[strlen(argv[2])/2] = '\0';
+		hex2bin(a, argv[2], strlen(argv[2])/2);
+		if (strlen(argv[2]) != 40 || (argv[2] && strlen(argv[2]) != 40)) {
+			printf("%s\n", a);
+			return 0;
+		}
+		return 0;
+	}
+	if (strlen(argv[2]) != 40)
+		error_at_line(3, 0, __FILE__, __LINE__, "strlen(a) != 40 && !bin");
+	if (argv[1][0] == 'd' || argv[1][0] == 'D') {
+		unsigned char a[20];
+		hex2bin(a, argv[2], 20);
+		divide(a);
+		char out[41];
+		out[40] = '\0';
+		bin2hex(out, a, 20);
+		printf("%s\n", out);
+		return 0;
+	}
+	if (!argv[3])
+		error_at_line(2, 0, __FILE__, __LINE__, "!b && !bin && !divide");
+	if (strlen(argv[3]) != 40)
+		error_at_line(3, 0, __FILE__, __LINE__, "strlen(b) != 40 && !bin && !divide");
+	unsigned char a[20];
+	unsigned char b[20];
+	hex2bin(a, argv[2], 20);
+	hex2bin(b, argv[3], 20);
+	char out[41];
+	out[40] = '\0';
+	unsigned char r[20];
+	if (argv[1][0] == 'a' || argv[1][0] == 'A') {
+		memcpy(r, a, 20);
+		add(r, b);
+	} else if (argv[1][0] == 's' || argv[1][0] == 'S') {
+		memcpy(r, a, 20);
+		subtract(r, b);
+	} else {
+		midpoint(r, a, b);
+	}
+	bin2hex(out, r, 20);
+	printf("%s\n", out);
+}