Rework hash implementations to provide additional algorithms.

[cumulus.git] / hash.h

diff --git a/hash.h b/hash.h
new file mode 100644 (file)
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--- /dev/null
+++ b/hash.h
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+/* Cumulus: Smart Filesystem Backup to Dumb Servers
+ *
+ * Copyright (C) 2012  Michael Vrable <vrable@cs.hmc.edu>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/* A generic interface for computing digests of data, used for both
+ * content-based deduplication and for data integrity verification. */
+
+#ifndef CUMULUS_HASH_H
+#define CUMULUS_HASH_H 1
+
+#include <stdint.h>
+#include <string>
+
+/* An object-oriented wrapper around checksumming functionality. */
+class Hash {
+public:
+    Hash() : digest_bytes(NULL) { }
+    virtual ~Hash() { }
+
+    // 
+    virtual void update(const void *data, size_t len) = 0;
+    // Returns the size of the buffer returned by digest, in bytes.
+    virtual size_t digest_size() const = 0;
+    // Returns the name of the hash algorithm.
+    virtual std::string name() const = 0;
+
+    // Calls update with the contents of the data found in the specified file.
+    bool update_from_file(const char *filename);
+    // Finalizes the digest and returns a pointer to a raw byte array
+    // containing the hash.
+    const uint8_t *digest();
+
+    // Returns the digest in text form: "<digest name>=<hex digits>".
+    std::string digest_str();
+
+    //typedef Hash *(*HashConstructor)();
+    static void Register(const std::string& name, Hash *(*constructor)());
+    static Hash *New();
+    static Hash *New(const std::string& name);
+
+protected:
+    virtual const uint8_t *finalize() = 0;
+
+private:
+    const uint8_t *digest_bytes;
+};
+
+void hash_init();
+
+#endif