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diff --git a/src/prng.h b/src/prng.h
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+/*
+ *  prng.h: Pseudo Random Number Generator abstractions for nwipe.
+ *
+ *  Copyright Darik Horn <dajhorn-dban@vanadac.com>.
+ *
+ *  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, version 2.
+ *
+ *  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.
+ *
+ */
+
+#ifndef PRNG_H_
+#define PRNG_H_
+
+#include <sys/types.h>
+
+/* A chunk of random data. */
+typedef struct
+{
+    size_t length;  // Length of the entropy string in bytes.
+    u8* s;  // The actual bytes of the entropy string.
+} nwipe_entropy_t;
+
+#define NWIPE_PRNG_INIT_SIGNATURE void **state, nwipe_entropy_t *seed
+#define NWIPE_PRNG_READ_SIGNATURE void **state, void *buffer, size_t count
+
+/* Function pointers for PRNG actions. */
+typedef int ( *nwipe_prng_init_t )( NWIPE_PRNG_INIT_SIGNATURE );
+typedef int ( *nwipe_prng_read_t )( NWIPE_PRNG_READ_SIGNATURE );
+
+/* The generic PRNG definition. */
+typedef struct
+{
+    const char* label;  // The name of the pseudo random number generator.
+    nwipe_prng_init_t init;  // Inialize the prng state with the seed.
+    nwipe_prng_read_t read;  // Read data from the prng.
+} nwipe_prng_t;
+
+/* Mersenne Twister prototypes. */
+int nwipe_twister_init( NWIPE_PRNG_INIT_SIGNATURE );
+int nwipe_twister_read( NWIPE_PRNG_READ_SIGNATURE );
+
+/* ISAAC prototypes. */
+int nwipe_isaac_init( NWIPE_PRNG_INIT_SIGNATURE );
+int nwipe_isaac_read( NWIPE_PRNG_READ_SIGNATURE );
+int nwipe_isaac64_init( NWIPE_PRNG_INIT_SIGNATURE );
+int nwipe_isaac64_read( NWIPE_PRNG_READ_SIGNATURE );
+
+/* Size of the twister is not derived from the architecture, but it is strictly 4 bytes */
+#define SIZE_OF_TWISTER 4
+
+/* Size of the isaac/isaac64 is not derived from the architecture, but it is strictly 4 or 8 bytes */
+#define SIZE_OF_ISAAC 4
+#define SIZE_OF_ISAAC64 8
+
+#endif /* PRNG_H_ */