1 files changed, 39 insertions, 0 deletions
diff --git a/src/lib.c b/src/lib.c
new file mode 100644
index 0000000..891fd27
--- /dev/null
+++ b/src/lib.c
@@ -0,0 +1,39 @@
+/**
+ * writes a hexadecimal representation of a binary string. does not NULL terminate destination.
+ *
+ * h and b may not overlap. period.
+ * 
+ * @param h	[out]	destination (requires 2l space)
+ * @param b	[in]	source
+ * @param l	[in]	length of source
+ */
+
+void bin2hex (char * h, const unsigned char * b, size_t l) {
+	for (size_t i = 0; i < l; i++) {
+		int ms = b[i] >> 4;
+		int ls = b[i] & 0xF;
+		assert(ms < 16);
+		assert(ls < 16);
+		*h++ = ms < 10 ? '0'+ms : 'a'+ms-10;
+		*h++ = ls < 10 ? '0'+ls : 'a'+ls-10;
+	}
+}
+
+/**
+ * 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'));
+	}
+}