1 files changed, 91 insertions, 0 deletions
diff --git a/commit-slab-impl.h b/commit-slab-impl.h
new file mode 100644
index 0000000000..234d9ee5f0
--- /dev/null
+++ b/commit-slab-impl.h
@@ -0,0 +1,91 @@
+#ifndef COMMIT_SLAB_IMPL_H
+#define COMMIT_SLAB_IMPL_H
+
+#define MAYBE_UNUSED __attribute__((__unused__))
+
+#define implement_commit_slab(slabname, elemtype) 			\
+									\
+static int stat_ ##slabname## realloc;					\
+									\
+static MAYBE_UNUSED void init_ ##slabname## _with_stride(struct slabname *s, \
+						   unsigned stride)	\
+{									\
+	unsigned int elem_size;						\
+	if (!stride)							\
+		stride = 1;						\
+	s->stride = stride;						\
+	elem_size = sizeof(elemtype) * stride;				\
+	s->slab_size = COMMIT_SLAB_SIZE / elem_size;			\
+	s->slab_count = 0;						\
+	s->slab = NULL;							\
+}									\
+									\
+static MAYBE_UNUSED void init_ ##slabname(struct slabname *s)		\
+{									\
+	init_ ##slabname## _with_stride(s, 1);				\
+}									\
+									\
+static MAYBE_UNUSED void clear_ ##slabname(struct slabname *s)		\
+{									\
+	unsigned int i;							\
+	for (i = 0; i < s->slab_count; i++)				\
+		free(s->slab[i]);					\
+	s->slab_count = 0;						\
+	FREE_AND_NULL(s->slab);						\
+}									\
+									\
+static MAYBE_UNUSED elemtype *slabname## _at_peek(struct slabname *s,	\
+						  const struct commit *c, \
+						  int add_if_missing)   \
+{									\
+	unsigned int nth_slab, nth_slot;				\
+									\
+	nth_slab = c->index / s->slab_size;				\
+	nth_slot = c->index % s->slab_size;				\
+									\
+	if (s->slab_count <= nth_slab) {				\
+		unsigned int i;						\
+		if (!add_if_missing)					\
+			return NULL;					\
+		REALLOC_ARRAY(s->slab, nth_slab + 1);			\
+		stat_ ##slabname## realloc++;				\
+		for (i = s->slab_count; i <= nth_slab; i++)		\
+			s->slab[i] = NULL;				\
+		s->slab_count = nth_slab + 1;				\
+	}								\
+	if (!s->slab[nth_slab]) {					\
+		if (!add_if_missing)					\
+			return NULL;					\
+		s->slab[nth_slab] = xcalloc(s->slab_size,		\
+					    sizeof(**s->slab) * s->stride);		\
+	}								\
+	return &s->slab[nth_slab][nth_slot * s->stride];		\
+}									\
+									\
+static MAYBE_UNUSED elemtype *slabname## _at(struct slabname *s,	\
+					     const struct commit *c)	\
+{									\
+	return slabname##_at_peek(s, c, 1);				\
+}									\
+									\
+static MAYBE_UNUSED elemtype *slabname## _peek(struct slabname *s,	\
+					     const struct commit *c)	\
+{									\
+	return slabname##_at_peek(s, c, 0);				\
+}									\
+									\
+struct slabname
+
+/*
+ * Note that this redundant forward declaration is required
+ * to allow a terminating semicolon, which makes instantiations look
+ * like function declarations.  I.e., the expansion of
+ *
+ *    implement_commit_slab(indegree, int);
+ *
+ * ends in 'struct indegree;'.  This would otherwise
+ * be a syntax error according (at least) to ISO C.  It's hard to
+ * catch because GCC silently parses it by default.
+ */
+
+#endif	/* COMMIT_SLAB_IMPL_H */