pack: introduce a delta base cache

Many delta bases are re-used. Cache them to avoid inflating the same
data repeatedly.

This version doesn't limit the amount of entries to store, so it can
end up using a considerable amound of memory.

1 files changed, 65 insertions, 0 deletions

diff --git a/src/offmap.h b/src/offmap.h
new file mode 100644
index 000000000..cd46fd687
--- /dev/null
+++ b/src/offmap.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_offmap_h__
+#define INCLUDE_offmap_h__
+
+#include "common.h"
+#include "git2/types.h"
+
+#define kmalloc git__malloc
+#define kcalloc git__calloc
+#define krealloc git__realloc
+#define kfree git__free
+#include "khash.h"
+
+__KHASH_TYPE(off, git_off_t, void *);
+typedef khash_t(off) git_offmap;
+
+#define GIT__USE_OFFMAP \
+	__KHASH_IMPL(off, static kh_inline, git_off_t, void *, 1, kh_int64_hash_func, kh_int64_hash_equal);
+
+#define git_offmap_alloc()  kh_init(off)
+#define git_offmap_free(h)  kh_destroy(off, h), h = NULL
+#define git_offmap_clear(h) kh_clear(off, h)
+
+#define git_offmap_num_entries(h) kh_size(h)
+
+#define git_offmap_lookup_index(h, k)  kh_get(off, h, k)
+#define git_offmap_valid_index(h, idx) (idx != kh_end(h))
+
+#define git_offmap_exists(h, k) (kh_get(off, h, k) != kh_end(h))
+
+#define git_offmap_value_at(h, idx)        kh_val(h, idx)
+#define git_offmap_set_value_at(h, idx, v) kh_val(h, idx) = v
+#define git_offmap_delete_at(h, idx)       kh_del(off, h, idx)
+
+#define git_offmap_insert(h, key, val, rval) do { \
+	khiter_t __pos = kh_put(off, h, key, &rval); \
+	if (rval >= 0) { \
+		if (rval == 0) kh_key(h, __pos) = key; \
+		kh_val(h, __pos) = val; \
+	} } while (0)
+
+#define git_offmap_insert2(h, key, val, oldv, rval) do { \
+	khiter_t __pos = kh_put(off, h, key, &rval); \
+	if (rval >= 0) { \
+		if (rval == 0) { \
+			oldv = kh_val(h, __pos); \
+			kh_key(h, __pos) = key; \
+		} else { oldv = NULL; } \
+		kh_val(h, __pos) = val; \
+	} } while (0)
+
+#define git_offmap_delete(h, key) do { \
+	khiter_t __pos = git_offmap_lookup_index(h, key); \
+	if (git_offmap_valid_index(h, __pos)) \
+		git_offmap_delete_at(h, __pos); } while (0)
+
+#define git_offmap_foreach		kh_foreach
+#define git_offmap_foreach_value	kh_foreach_value
+
+#endif