1 files changed, 97 insertions, 0 deletions
diff --git a/commit-slab.h b/commit-slab.h
new file mode 100644
index 0000000000..d4c8286470
--- /dev/null
+++ b/commit-slab.h
@@ -0,0 +1,97 @@
+#ifndef COMMIT_SLAB_H
+#define COMMIT_SLAB_H
+
+/*
+ * define_commit_slab(slabname, elemtype) creates boilerplate code to define
+ * a new struct (struct slabname) that is used to associate a piece of data
+ * of elemtype to commits, and a few functions to use that struct.
+ *
+ * After including this header file, using:
+ *
+ * define_commit_slab(indegee, int);
+ *
+ * will let you call the following functions:
+ *
+ * - int *indegree_at(struct indegree *, struct commit *);
+ *
+ *   This function locates the data associated with the given commit in
+ *   the indegree slab, and returns the pointer to it.
+ *
+ * - void init_indegree(struct indegree *);
+ *   void init_indegree_with_stride(struct indegree *, int);
+ *
+ *   Initializes the indegree slab that associates an array of integers
+ *   to each commit. 'stride' specifies how big each array is.  The slab
+ *   that id initialied by the variant without "_with_stride" associates
+ *   each commit with an array of one integer.
+ */
+
+/* allocate ~512kB at once, allowing for malloc overhead */
+#ifndef COMMIT_SLAB_SIZE
+#define COMMIT_SLAB_SIZE (512*1024-32)
+#endif
+
+#define define_commit_slab(slabname, elemtype) 				\
+									\
+struct slabname {							\
+	unsigned slab_size;						\
+	unsigned stride;						\
+	unsigned slab_count;						\
+	elemtype **slab;						\
+};									\
+static int stat_ ##slabname## realloc;					\
+									\
+static 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 void init_ ##slabname(struct slabname *s)			\
+{									\
+	init_ ##slabname## _with_stride(s, 1);				\
+}									\
+									\
+static void clear_ ##slabname(struct slabname *s)			\
+{									\
+	int i;								\
+	for (i = 0; i < s->slab_count; i++)				\
+		free(s->slab[i]);					\
+	s->slab_count = 0;						\
+	free(s->slab);							\
+	s->slab = NULL;							\
+}									\
+									\
+static elemtype *slabname## _at(struct slabname *s,			\
+				const struct commit *c)			\
+{									\
+	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) {				\
+		int i;							\
+		s->slab = xrealloc(s->slab,				\
+				   (nth_slab + 1) * sizeof(s->slab));	\
+		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])						\
+		s->slab[nth_slab] = xcalloc(s->slab_size,		\
+					    sizeof(**s->slab) * s->stride);		\
+	return &s->slab[nth_slab][nth_slot * s->stride];				\
+}									\
+									\
+static int stat_ ##slabname## realloc
+
+#endif /* COMMIT_SLAB_H */