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diff --git a/lib/util/rand.h b/lib/util/rand.h
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+/* Interface header file for random number generator functions in libnetpbm */
+
+#ifndef RAND_H_INCLUDED
+#define RAND_H_INCLUDED
+
+#include <inttypes.h>
+
+#include "netpbm/pm_c_util.h"
+#include "netpbm/mallocvar.h"
+
+/*
+  Definitions for selecting the random number generator
+
+  The default random number generator is Mersenne Twister.  Here we
+  provide a means to revert to the system rand() generator if need be.
+
+  Glibc provides generators: rand(), random() and drand48().  Each has
+  its own associated functions.  In the Glibc documentation rand() is
+  called "ISO", random() is called "BSD" and drand48() is called "SVID".
+  If your system has the glibc documentation installed "info rand" should
+  get you to the relevant page.  The documentation is available online
+  from:
+
+  https://www.gnu.org/software/libc/manual/html_node/Pseudo_002dRandom-Numbers.html
+  Pseudo-Random Numbers (The GNU C Library)
+
+  Glibc's choice of name is confusing for what it calls "ISO" rand()
+  was available in early BSD systems.
+
+  Functions by these names appear on most Unix systems, but generation
+  formulas and default initial states are known to differ.  On systems
+  which do not use glibc, what is called rand() may have no relation
+  with the formula of the ISO C standard.  Likewise random() may have
+  no relation with the BSD formula.
+*/
+
+enum PmRandEngine {PM_RAND_SYS_RAND,         /* rand()   */
+                   PM_RAND_SYS_RANDOM,       /* random() */
+                   PM_RAND_SYS_DRAND48,      /* drand48()  reserved */
+                   PM_RAND_MERSENNETWISTER   /* default */};
+
+#ifndef PM_RANDOM_NUMBER_GENERATOR
+  #define PM_RANDOM_NUMBER_GENERATOR PM_RAND_MERSENNETWISTER
+#endif
+
+
+/* Structure to hold random number generator profile and internal state */
+
+struct pm_randSt;
+
+struct pm_rand_vtable {
+    void
+    (*init)(struct pm_randSt * const randStP);
+
+    void
+    (*srand)(struct pm_randSt * const randStP,
+              unsigned int       const seed);
+
+    unsigned long int
+    (*rand)(struct pm_randSt * const randStP);
+};
+
+extern struct pm_rand_vtable const pm_randsysrand_vtable;
+extern struct pm_rand_vtable const pm_randsysrandom_vtable;
+extern struct pm_rand_vtable const pm_randmersenne_vtable;
+
+struct pm_randSt {
+    struct pm_rand_vtable vtable;
+    void *                stateP;  /* Internal state */
+    unsigned int          max;
+    unsigned int          seed;
+    bool                  gaussCacheValid;
+    double                gaussCache;
+};
+
+/* Function declarations */
+
+extern void
+pm_randinit(struct pm_randSt * const randStP);
+
+extern void
+pm_randterm(struct pm_randSt * const randStP);
+
+extern void
+pm_srand(struct pm_randSt * const randStP,
+         unsigned int       const seed);
+
+
+extern void
+pm_srand2(struct pm_randSt * const randStP,
+          bool               const withSeed,
+          unsigned int       const seedVal);
+
+extern unsigned long int
+pm_rand(struct pm_randSt * const randStP);
+
+extern double
+pm_drand(struct pm_randSt * const randStP);
+
+extern double
+pm_drand1(struct pm_randSt * const randStP);
+
+extern double
+pm_drand2(struct pm_randSt * const randStP);
+
+extern void
+pm_gaussrand2(struct pm_randSt * const randStP,
+              double *           const r1P,
+              double *           const r2P);
+
+extern double
+pm_gaussrand(struct pm_randSt * const randStP);
+
+extern uint32_t
+pm_rand32(struct pm_randSt * const randStP);
+
+
+#endif