Add integer generator

m-genint.h

@@ -0,0 +1,128 @@
+/*
+ * M*LIB - GENINT module
+ *
+ * Copyright (c) 2017, Patrick Pelissier
+ * All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * + Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * + Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+#ifndef __M_GENINT_H
+#define __M_GENINT_H
+
+#include "m-core.h"
+#include "m-atomic.h"
+
+/* GENINT is a container of integers with the following properties:
+
+   - it stores integer from [0..N) (N is fixed).
+   - an integer can have only one occurence in the container
+   (makeing the container a kind of permutation of [0..N) )
+   - you can atomically push in / pop out integer from this container.
+
+   This can be used to map integers to index of ressources in a table.
+*/
+
+typedef unsigned long genint_limb_t;
+
+typedef struct genint_s {
+  size_t n;
+  atomic_ulong *data;
+} genint_t[1];
+
+#define GENINT_LIMBSIZE (sizeof(genint_limb_t) * CHAR_BIT)
+
+#define GENINT_CONTRACT(s)                              do {    \
+    assert (s != NULL);                                         \
+    assert (s->n > 0);                                          \
+    assert (s->data != NULL);                                   \
+  } while (0)
+
+#define GENINT_ONE ((genint_limb_t)1)
+
+static inline void genint_init(genint_t s, size_t n)
+{
+  assert (s != NULL && n > 0);
+  const size_t alloc = (n + GENINT_LIMBSIZE - 1) / GENINT_LIMBSIZE;
+  atomic_ulong *ptr = M_MEMORY_REALLOC (atomic_ulong, NULL, alloc);
+  s->n = n;
+  s->data = ptr;
+  if (M_UNLIKELY (ptr == NULL)) {
+    M_MEMORY_FULL(alloc);
+    return;
+  }
+  GENINT_CONTRACT(s);
+}
+
+static inline void genint_clear(genint_t s)
+{
+  GENINT_CONTRACT(s);
+  M_MEMORY_FREE(s->data);
+  s->data = NULL;
+}
+
+static inline unsigned int m_core_clz(unsigned long limb)
+{
+  return limb == 0 ? GENINT_LIMBSIZE : __builtin_clzl(limb);
+}
+
+static inline size_t genint_pop(genint_t s)
+{
+  GENINT_CONTRACT(s);
+  const size_t max = (s->n + GENINT_LIMBSIZE - 1) / GENINT_LIMBSIZE;
+  const size_t index  = s->n % GENINT_LIMBSIZE;
+  const genint_limb_t mask0 = (index == 0) ? -GENINT_ONE : (GENINT_ONE<<index)-1;
+  // O(n) approach, but with a really low constant factor
+  for(size_t i = 0; i < max; i++)
+    {
+      const size_t mask = (i+1 == max) ? mask0 : -GENINT_ONE;
+      unsigned int bit;
+      genint_limb_t next, org = atomic_load(&s->data[i]);
+      do {
+        if (org == mask)
+          goto next_element;
+        // At least one bit is free in the limb
+        bit = GENINT_LIMBSIZE - m_core_clz(org);
+        assert ((org & (GENINT_ONE<<bit)) == 0);
+        // Set & reserve the integer as being used.
+        next = org | (GENINT_ONE << bit);
+      } while (!atomic_compare_exchange_weak (&s->data[i], &org, next));
+      // Return the new number
+      GENINT_CONTRACT(s);
+      return i * GENINT_LIMBSIZE + bit;
+    next_element: (void)1;
+    }
+  GENINT_CONTRACT(s);
+  return -(size_t)1; // No more ressource available
+}
+
+static inline void genint_push(genint_t s, size_t n)
+{
+  GENINT_CONTRACT(s);
+  assert (n < s->n);
+  size_t i    = n / GENINT_LIMBSIZE;
+  size_t bit  = n % GENINT_LIMBSIZE;
+  genint_limb_t next, org = atomic_load(&s->data[i]);
+  do {
+    assert ((org & (GENINT_ONE<<bit)) != 0);
+    next = org & (~(GENINT_ONE << bit));
+  } while (!atomic_compare_exchange_weak (&s->data[i], &org, next));
+  GENINT_CONTRACT(s);
+}
+
+#endif

tests/test-mgenint.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2017, Patrick Pelissier
+ * All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * + Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * + Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+#include <stdio.h>
+#include "m-genint.h"
+
+static void test(size_t n)
+{
+  genint_t s;
+  size_t i;
+  
+  genint_init(s, n);
+  for(int k = 0; k < 3; k++) {
+    for(size_t j = 0; j< n ; j++) {
+      i = genint_pop(s);
+      assert (i == j);
+    }
+    i = genint_pop(s);
+    assert (genint_pop(s) == -1UL);
+    
+    for(size_t j = 0; j< n ; j++) {
+      genint_push(s, (j+k) % n );
+    }
+  }
+  
+  genint_clear(s);
+}
+
+int main(void)
+{
+  for(size_t n = 1; n < 256; n++) {
+    test(n);
+  }
+}