crypto: hash - Added scatter list walking helper

This patch adds the walking helpers for hash algorithms akin to
those of block ciphers.  This is a necessary step before we can
reimplement existing hash algorithms using the new ahash interface.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/internal/hash.h

@@ -0,0 +1,41 @@
+/*
+ * Hash algorithms.
+ * 
+ * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option) 
+ * any later version.
+ *
+ */
+
+#ifndef _CRYPTO_INTERNAL_HASH_H
+#define _CRYPTO_INTERNAL_HASH_H
+
+#include <crypto/algapi.h>
+
+struct ahash_request;
+struct scatterlist;
+
+struct crypto_hash_walk {
+	char *data;
+
+	unsigned int offset;
+	unsigned int alignmask;
+
+	struct page *pg;
+	unsigned int entrylen;
+
+	unsigned int total;
+	struct scatterlist *sg;
+
+	unsigned int flags;
+};
+
+int crypto_hash_walk_done(struct crypto_hash_walk *walk, int err);
+int crypto_hash_walk_first(struct ahash_request *req,
+			   struct crypto_hash_walk *walk);
+
+#endif	/* _CRYPTO_INTERNAL_HASH_H */
+