1 files changed, 80 insertions, 0 deletions
diff --git a/unmarshal.c b/unmarshal.c
new file mode 100644
index 0000000..2a47b92
--- /dev/null
+++ b/unmarshal.c
@@ -0,0 +1,80 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Unmarshal a state from a buffer
+ * 
+ * @param   state    Output parameter for the unmarshalled state
+ * @param   buf      The buffer from which the state shall be unmarshalled
+ * @param   bufsize  The maximum number of bytes that can be unmarshalled
+ * @return           The number of read bytes, 0 on failure
+ */
+size_t
+libsha2_unmarshal(struct libsha2_state *restrict state, const char *restrict buf, size_t bufsize)
+{
+	size_t off = 0;
+
+	if (bufsize < sizeof(int) + sizeof(enum libsha2_algorithm) + sizeof(size_t)) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	if (*(int *)buf) { /* version */
+		errno = EINVAL;
+		return 0;
+	}
+	off += sizeof(int);
+
+	state->algorithm = *(enum libsha2_algorithm *)&buf[off];
+	off += sizeof(enum libsha2_algorithm);
+	state->message_size = *(size_t *)&buf[off];
+	off += sizeof(size_t);
+
+	switch (state->algorithm) {
+	case LIBSHA2_224:
+	case LIBSHA2_256:
+		if (bufsize - off < sizeof(state->k.b32) + sizeof(state->w.b32) + sizeof(state->h.b32)) {
+			errno = EINVAL;
+			return 0;
+		}
+		memcpy(state->k.b32, &buf[off], sizeof(state->k.b32));
+		off += sizeof(state->k.b32);
+		memcpy(state->w.b32, &buf[off], sizeof(state->w.b32));
+		off += sizeof(state->w.b32);
+		memcpy(state->h.b32, &buf[off], sizeof(state->h.b32));
+		off += sizeof(state->h.b32);
+		break;
+
+	case LIBSHA2_384:
+	case LIBSHA2_512:
+	case LIBSHA2_512_224:
+	case LIBSHA2_512_256:
+		if (bufsize - off < sizeof(state->k.b64) + sizeof(state->w.b64) + sizeof(state->h.b64)) {
+			errno = EINVAL;
+			return 0;
+		}
+		memcpy(state->k.b64, &buf[off], sizeof(state->k.b64));
+		off += sizeof(state->k.b64);
+		memcpy(state->w.b64, &buf[off], sizeof(state->w.b64));
+		off += sizeof(state->w.b64);
+		memcpy(state->h.b64, &buf[off], sizeof(state->h.b64));
+		off += sizeof(state->h.b64);
+		break;
+
+	default:
+		errno = EINVAL;
+		return 0;
+	}
+
+	if (bufsize - off < sizeof(state->chunk) + sizeof(size_t)) {
+		errno = EINVAL;
+		return 0;
+	}
+	memcpy(state->chunk, &buf[off], sizeof(state->chunk));
+	off += sizeof(state->chunk);
+	state->chunk_size = *(size_t *)&buf[off];
+	off += sizeof(size_t);
+
+	return off;
+}