libgis: Add reproducible random numbers for parallel tools

include/grass/defs/gis.h

@@ -518,6 +518,21 @@ long G_srand48_auto(void);
 long G_lrand48(void);
 long G_mrand48(void);
 double G_drand48(void);
+void G_random_state_from_seed(struct G_random_state *, int64_t);
+void G_random_init_layout_exact(struct G_random_layout *, int64_t, int64_t,
+                                int64_t);
+void G_random_init_layout_bounded(struct G_random_layout *, int64_t, int64_t,
+                                  int64_t);
+void G_random_init_layout(struct G_random_layout *, int64_t, int64_t);
+int64_t G_random_layout_batches(const struct G_random_layout *);
+int64_t G_random_layout_length(const struct G_random_layout *);
+void G_random_state_for_unit(struct G_random_state *,
+                             const struct G_random_layout *, int64_t);
+void G_random_state_for_batch(struct G_random_state *,
+                              const struct G_random_layout *, int64_t, int64_t);
+void G_random_advance(struct G_random_state *, int64_t);
+double G_random_double(struct G_random_state *);
+int64_t G_random_generate_seed(void);
 
 /* ls.c */
 void G_set_ls_filter(int (*)(const char *, void *), void *);

include/grass/gis.h

@@ -17,6 +17,8 @@
 /*============================= Include Files ==============================*/
 
 /* System include files */
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdarg.h>
 
@@ -628,6 +630,26 @@ struct Popen {
     int pid;
 };
 
+/* A position of a pseudo-random number generator owned by the program;
+ * see G_random_state_from_seed() and G_random_state_for_unit(). The
+ * contents are private to the library and may change with the generator;
+ * read and advance the state only through the G_random_*() functions. It
+ * is a plain value: copying it copies the generator's position. */
+struct G_random_state {
+    uint64_t state;
+};
+
+/* A layout: a seed and the way the generator's span is cut into streams
+ * of stride draws, one per unit of work and batch; see
+ * G_random_init_layout(). Private to the library. */
+struct G_random_layout {
+    uint64_t start; /* generator state at the seed */
+    int64_t units;
+    int64_t stride;
+    int64_t batches; /* batches that fit into the span, 0 when none */
+    bool whole_span; /* a layout of the whole span holds a single batch */
+};
+
 typedef int CELL;
 typedef double DCELL;
 typedef float FCELL;