1 files changed, 29 insertions, 0 deletions
diff --git a/libkeccak_unhex.c b/libkeccak_unhex.c
new file mode 100644
index 0000000..a12beb1
--- /dev/null
+++ b/libkeccak_unhex.c
@@ -0,0 +1,29 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Convert a hexadecimal hashsum (both lower case, upper
+ * case and mixed is supported) to binary representation
+ * 
+ * @param  output   Output array, should have an allocation size of at least `strlen(hashsum) / 2`
+ * @param  hashsum  The hashsum to convert
+ */
+void
+libkeccak_unhex(void *restrict output_, const char *restrict hashsum)
+{
+	unsigned char *restrict output = output_;
+	size_t n = strlen(hashsum) / 2;
+	unsigned char a, b;
+	while (n--) {
+		a = (unsigned char)hashsum[2 * n + 0];
+		b = (unsigned char)hashsum[2 * n + 1];
+
+		a = (unsigned char)((a & 15) + (a > '9' ? 9 : 0));
+		b = (unsigned char)((b & 15) + (b > '9' ? 9 : 0));
+
+		a <<= 4;
+		a |= b;
+		output[n] = a;
+	}
+}