move Rust sources to top level, C sources into c_src

[bcachefs-tools-debian] / c_src / raid / combo.h

diff --git a/c_src/raid/combo.h b/c_src/raid/combo.h
new file mode 100644 (file)
index 0000000..8efc31a
--- /dev/null
+++ b/c_src/raid/combo.h
@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2013 Andrea Mazzoleni
+ *
+ * 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.
+ */
+
+#ifndef __RAID_COMBO_H
+#define __RAID_COMBO_H
+
+#include <assert.h>
+
+/**
+ * Get the first permutation with repetition of r of n elements.
+ *
+ * Typical use is with permutation_next() in the form :
+ *
+ * int i[R];
+ * permutation_first(R, N, i);
+ * do {
+ *    code using i[0], i[1], ..., i[R-1]
+ * } while (permutation_next(R, N, i));
+ *
+ * It's equivalent at the code :
+ *
+ * for(i[0]=0;i[0]<N;++i[0])
+ *     for(i[1]=0;i[1]<N;++i[1])
+ *        ...
+ *            for(i[R-2]=0;i[R-2]<N;++i[R-2])
+ *                for(i[R-1]=0;i[R-1]<N;++i[R-1])
+ *                    code using i[0], i[1], ..., i[R-1]
+ */
+static __always_inline void permutation_first(int r, int n, int *c)
+{
+       int i;
+
+       (void)n; /* unused, but kept for clarity */
+       assert(0 < r && r <= n);
+
+       for (i = 0; i < r; ++i)
+               c[i] = 0;
+}
+
+/**
+ * Get the next permutation with repetition of r of n elements.
+ * Return ==0 when finished.
+ */
+static __always_inline int permutation_next(int r, int n, int *c)
+{
+       int i = r - 1; /* present position */
+
+recurse:
+       /* next element at position i */
+       ++c[i];
+
+       /* if the position has reached the max */
+       if (c[i] >= n) {
+
+               /* if we are at the first level, we have finished */
+               if (i == 0)
+                       return 0;
+
+               /* increase the previous position */
+               --i;
+               goto recurse;
+       }
+
+       ++i;
+
+       /* initialize all the next positions, if any */
+       while (i < r) {
+               c[i] = 0;
+               ++i;
+       }
+
+       return 1;
+}
+
+/**
+ * Get the first combination without repetition of r of n elements.
+ *
+ * Typical use is with combination_next() in the form :
+ *
+ * int i[R];
+ * combination_first(R, N, i);
+ * do {
+ *    code using i[0], i[1], ..., i[R-1]
+ * } while (combination_next(R, N, i));
+ *
+ * It's equivalent at the code :
+ *
+ * for(i[0]=0;i[0]<N-(R-1);++i[0])
+ *     for(i[1]=i[0]+1;i[1]<N-(R-2);++i[1])
+ *        ...
+ *            for(i[R-2]=i[R-3]+1;i[R-2]<N-1;++i[R-2])
+ *                for(i[R-1]=i[R-2]+1;i[R-1]<N;++i[R-1])
+ *                    code using i[0], i[1], ..., i[R-1]
+ */
+static __always_inline void combination_first(int r, int n, int *c)
+{
+       int i;
+
+       (void)n; /* unused, but kept for clarity */
+       assert(0 < r && r <= n);
+
+       for (i = 0; i < r; ++i)
+               c[i] = i;
+}
+
+/**
+ * Get the next combination without repetition of r of n elements.
+ * Return ==0 when finished.
+ */
+static __always_inline int combination_next(int r, int n, int *c)
+{
+       int i = r - 1; /* present position */
+       int h = n; /* high limit for this position */
+
+recurse:
+       /* next element at position i */
+       ++c[i];
+
+       /* if the position has reached the max */
+       if (c[i] >= h) {
+
+               /* if we are at the first level, we have finished */
+               if (i == 0)
+                       return 0;
+
+               /* increase the previous position */
+               --i;
+               --h;
+               goto recurse;
+       }
+
+       ++i;
+
+       /* initialize all the next positions, if any */
+       while (i < r) {
+               /* each position start at the next value of the previous one */
+               c[i] = c[i - 1] + 1;
+               ++i;
+       }
+
+       return 1;
+}
+#endif
+