1 files changed, 51 insertions, 0 deletions
diff --git a/libkeccak_hmac_fast_update.c b/libkeccak_hmac_fast_update.c
new file mode 100644
index 0000000..d4a3fbe
--- /dev/null
+++ b/libkeccak_hmac_fast_update.c
@@ -0,0 +1,51 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Absorb more, or the first part, of the message
+ * without wiping sensitive data when possible
+ * 
+ * @param   state   The hashing state
+ * @param   msg     The partial message
+ * @param   msglen  The length of the partial message, in bytes
+ * @return          Zero on success, -1 on error
+ */
+int
+libkeccak_hmac_fast_update(libkeccak_hmac_state_t *restrict state, const void *restrict msg_, size_t msglen)
+{
+	const char *restrict msg = msg_;
+	char *old;
+	size_t i;
+	int n, cn;
+
+	if (state->key_ipad) {
+		if (libkeccak_fast_update(&state->sponge, state->key_ipad, state->key_length >> 3) < 0)
+			return -1;
+		if (state->key_length & 7)
+			state->leftover = state->key_ipad[state->key_length >> 3];
+		state->key_ipad = NULL;
+	}
+
+	if (!msg || !msglen)
+		return 0;
+
+	if (!(state->key_length & 7))
+		return libkeccak_fast_update(&state->sponge, msg, msglen);
+
+	if (msglen != state->buffer_size) {
+		state->buffer = realloc(old = state->buffer, msglen);
+		if (!state->buffer)
+			return state->buffer = old, -1;
+		state->buffer_size = msglen;
+	}
+
+	n = (int)(state->key_length & 7);
+	cn = 8 - n;
+	for (i = 1; i < msglen; i++)
+		state->buffer[i] = (char)((msg[i - 1] >> cn) | (msg[i] << n));
+	state->buffer[0] = (char)((state->leftover & ((1 << n) - 1)) | (msg[0] << n));
+	state->leftover = (char)((unsigned char)msg[msglen - 1] >> cn);
+
+	return libkeccak_fast_update(&state->sponge, state->buffer, msglen);
+}