1 files changed, 319 insertions, 0 deletions

diff --git a/split-index.c b/split-index.c
new file mode 100644
index 0000000000..615f4cac05
--- /dev/null
+++ b/split-index.c
@@ -0,0 +1,319 @@
+#include "cache.h"
+#include "split-index.h"
+#include "ewah/ewok.h"
+
+struct split_index *init_split_index(struct index_state *istate)
+{
+	if (!istate->split_index) {
+		istate->split_index = xcalloc(1, sizeof(*istate->split_index));
+		istate->split_index->refcount = 1;
+	}
+	return istate->split_index;
+}
+
+int read_link_extension(struct index_state *istate,
+			 const void *data_, unsigned long sz)
+{
+	const unsigned char *data = data_;
+	struct split_index *si;
+	int ret;
+
+	if (sz < 20)
+		return error("corrupt link extension (too short)");
+	si = init_split_index(istate);
+	hashcpy(si->base_sha1, data);
+	data += 20;
+	sz -= 20;
+	if (!sz)
+		return 0;
+	si->delete_bitmap = ewah_new();
+	ret = ewah_read_mmap(si->delete_bitmap, data, sz);
+	if (ret < 0)
+		return error("corrupt delete bitmap in link extension");
+	data += ret;
+	sz -= ret;
+	si->replace_bitmap = ewah_new();
+	ret = ewah_read_mmap(si->replace_bitmap, data, sz);
+	if (ret < 0)
+		return error("corrupt replace bitmap in link extension");
+	if (ret != sz)
+		return error("garbage at the end of link extension");
+	return 0;
+}
+
+int write_link_extension(struct strbuf *sb,
+			 struct index_state *istate)
+{
+	struct split_index *si = istate->split_index;
+	strbuf_add(sb, si->base_sha1, 20);
+	if (!si->delete_bitmap && !si->replace_bitmap)
+		return 0;
+	ewah_serialize_strbuf(si->delete_bitmap, sb);
+	ewah_serialize_strbuf(si->replace_bitmap, sb);
+	return 0;
+}
+
+static void mark_base_index_entries(struct index_state *base)
+{
+	int i;
+	/*
+	 * To keep track of the shared entries between
+	 * istate->base->cache[] and istate->cache[], base entry
+	 * position is stored in each base entry. All positions start
+	 * from 1 instead of 0, which is reserved to say "this is a new
+	 * entry".
+	 */
+	for (i = 0; i < base->cache_nr; i++)
+		base->cache[i]->index = i + 1;
+}
+
+void move_cache_to_base_index(struct index_state *istate)
+{
+	struct split_index *si = istate->split_index;
+	int i;
+
+	/*
+	 * do not delete old si->base, its index entries may be shared
+	 * with istate->cache[]. Accept a bit of leaking here because
+	 * this code is only used by short-lived update-index.
+	 */
+	si->base = xcalloc(1, sizeof(*si->base));
+	si->base->version = istate->version;
+	/* zero timestamp disables racy test in ce_write_index() */
+	si->base->timestamp = istate->timestamp;
+	ALLOC_GROW(si->base->cache, istate->cache_nr, si->base->cache_alloc);
+	si->base->cache_nr = istate->cache_nr;
+	COPY_ARRAY(si->base->cache, istate->cache, istate->cache_nr);
+	mark_base_index_entries(si->base);
+	for (i = 0; i < si->base->cache_nr; i++)
+		si->base->cache[i]->ce_flags &= ~CE_UPDATE_IN_BASE;
+}
+
+static void mark_entry_for_delete(size_t pos, void *data)
+{
+	struct index_state *istate = data;
+	if (pos >= istate->cache_nr)
+		die("position for delete %d exceeds base index size %d",
+		    (int)pos, istate->cache_nr);
+	istate->cache[pos]->ce_flags |= CE_REMOVE;
+	istate->split_index->nr_deletions = 1;
+}
+
+static void replace_entry(size_t pos, void *data)
+{
+	struct index_state *istate = data;
+	struct split_index *si = istate->split_index;
+	struct cache_entry *dst, *src;
+
+	if (pos >= istate->cache_nr)
+		die("position for replacement %d exceeds base index size %d",
+		    (int)pos, istate->cache_nr);
+	if (si->nr_replacements >= si->saved_cache_nr)
+		die("too many replacements (%d vs %d)",
+		    si->nr_replacements, si->saved_cache_nr);
+	dst = istate->cache[pos];
+	if (dst->ce_flags & CE_REMOVE)
+		die("entry %d is marked as both replaced and deleted",
+		    (int)pos);
+	src = si->saved_cache[si->nr_replacements];
+	if (ce_namelen(src))
+		die("corrupt link extension, entry %d should have "
+		    "zero length name", (int)pos);
+	src->index = pos + 1;
+	src->ce_flags |= CE_UPDATE_IN_BASE;
+	src->ce_namelen = dst->ce_namelen;
+	copy_cache_entry(dst, src);
+	free(src);
+	si->nr_replacements++;
+}
+
+void merge_base_index(struct index_state *istate)
+{
+	struct split_index *si = istate->split_index;
+	unsigned int i;
+
+	mark_base_index_entries(si->base);
+
+	si->saved_cache	    = istate->cache;
+	si->saved_cache_nr  = istate->cache_nr;
+	istate->cache_nr    = si->base->cache_nr;
+	istate->cache	    = NULL;
+	istate->cache_alloc = 0;
+	ALLOC_GROW(istate->cache, istate->cache_nr, istate->cache_alloc);
+	COPY_ARRAY(istate->cache, si->base->cache, istate->cache_nr);
+
+	si->nr_deletions = 0;
+	si->nr_replacements = 0;
+	ewah_each_bit(si->replace_bitmap, replace_entry, istate);
+	ewah_each_bit(si->delete_bitmap, mark_entry_for_delete, istate);
+	if (si->nr_deletions)
+		remove_marked_cache_entries(istate);
+
+	for (i = si->nr_replacements; i < si->saved_cache_nr; i++) {
+		if (!ce_namelen(si->saved_cache[i]))
+			die("corrupt link extension, entry %d should "
+			    "have non-zero length name", i);
+		add_index_entry(istate, si->saved_cache[i],
+				ADD_CACHE_OK_TO_ADD |
+				ADD_CACHE_KEEP_CACHE_TREE |
+				/*
+				 * we may have to replay what
+				 * merge-recursive.c:update_stages()
+				 * does, which has this flag on
+				 */
+				ADD_CACHE_SKIP_DFCHECK);
+		si->saved_cache[i] = NULL;
+	}
+
+	ewah_free(si->delete_bitmap);
+	ewah_free(si->replace_bitmap);
+	free(si->saved_cache);
+	si->delete_bitmap  = NULL;
+	si->replace_bitmap = NULL;
+	si->saved_cache	   = NULL;
+	si->saved_cache_nr = 0;
+}
+
+void prepare_to_write_split_index(struct index_state *istate)
+{
+	struct split_index *si = init_split_index(istate);
+	struct cache_entry **entries = NULL, *ce;
+	int i, nr_entries = 0, nr_alloc = 0;
+
+	si->delete_bitmap = ewah_new();
+	si->replace_bitmap = ewah_new();
+
+	if (si->base) {
+		/* Go through istate->cache[] and mark CE_MATCHED to
+		 * entry with positive index. We'll go through
+		 * base->cache[] later to delete all entries in base
+		 * that are not marked with either CE_MATCHED or
+		 * CE_UPDATE_IN_BASE. If istate->cache[i] is a
+		 * duplicate, deduplicate it.
+		 */
+		for (i = 0; i < istate->cache_nr; i++) {
+			struct cache_entry *base;
+			/* namelen is checked separately */
+			const unsigned int ondisk_flags =
+				CE_STAGEMASK | CE_VALID | CE_EXTENDED_FLAGS;
+			unsigned int ce_flags, base_flags, ret;
+			ce = istate->cache[i];
+			if (!ce->index)
+				continue;
+			if (ce->index > si->base->cache_nr) {
+				ce->index = 0;
+				continue;
+			}
+			ce->ce_flags |= CE_MATCHED; /* or "shared" */
+			base = si->base->cache[ce->index - 1];
+			if (ce == base)
+				continue;
+			if (ce->ce_namelen != base->ce_namelen ||
+			    strcmp(ce->name, base->name)) {
+				ce->index = 0;
+				continue;
+			}
+			ce_flags = ce->ce_flags;
+			base_flags = base->ce_flags;
+			/* only on-disk flags matter */
+			ce->ce_flags   &= ondisk_flags;
+			base->ce_flags &= ondisk_flags;
+			ret = memcmp(&ce->ce_stat_data, &base->ce_stat_data,
+				     offsetof(struct cache_entry, name) -
+				     offsetof(struct cache_entry, ce_stat_data));
+			ce->ce_flags = ce_flags;
+			base->ce_flags = base_flags;
+			if (ret)
+				ce->ce_flags |= CE_UPDATE_IN_BASE;
+			free(base);
+			si->base->cache[ce->index - 1] = ce;
+		}
+		for (i = 0; i < si->base->cache_nr; i++) {
+			ce = si->base->cache[i];
+			if ((ce->ce_flags & CE_REMOVE) ||
+			    !(ce->ce_flags & CE_MATCHED))
+				ewah_set(si->delete_bitmap, i);
+			else if (ce->ce_flags & CE_UPDATE_IN_BASE) {
+				ewah_set(si->replace_bitmap, i);
+				ce->ce_flags |= CE_STRIP_NAME;
+				ALLOC_GROW(entries, nr_entries+1, nr_alloc);
+				entries[nr_entries++] = ce;
+			}
+		}
+	}
+
+	for (i = 0; i < istate->cache_nr; i++) {
+		ce = istate->cache[i];
+		if ((!si->base || !ce->index) && !(ce->ce_flags & CE_REMOVE)) {
+			assert(!(ce->ce_flags & CE_STRIP_NAME));
+			ALLOC_GROW(entries, nr_entries+1, nr_alloc);
+			entries[nr_entries++] = ce;
+		}
+		ce->ce_flags &= ~CE_MATCHED;
+	}
+
+	/*
+	 * take cache[] out temporarily, put entries[] in its place
+	 * for writing
+	 */
+	si->saved_cache = istate->cache;
+	si->saved_cache_nr = istate->cache_nr;
+	istate->cache = entries;
+	istate->cache_nr = nr_entries;
+}
+
+void finish_writing_split_index(struct index_state *istate)
+{
+	struct split_index *si = init_split_index(istate);
+
+	ewah_free(si->delete_bitmap);
+	ewah_free(si->replace_bitmap);
+	si->delete_bitmap = NULL;
+	si->replace_bitmap = NULL;
+	free(istate->cache);
+	istate->cache = si->saved_cache;
+	istate->cache_nr = si->saved_cache_nr;
+}
+
+void discard_split_index(struct index_state *istate)
+{
+	struct split_index *si = istate->split_index;
+	if (!si)
+		return;
+	istate->split_index = NULL;
+	si->refcount--;
+	if (si->refcount)
+		return;
+	if (si->base) {
+		discard_index(si->base);
+		free(si->base);
+	}
+	free(si);
+}
+
+void save_or_free_index_entry(struct index_state *istate, struct cache_entry *ce)
+{
+	if (ce->index &&
+	    istate->split_index &&
+	    istate->split_index->base &&
+	    ce->index <= istate->split_index->base->cache_nr &&
+	    ce == istate->split_index->base->cache[ce->index - 1])
+		ce->ce_flags |= CE_REMOVE;
+	else
+		free(ce);
+}
+
+void replace_index_entry_in_base(struct index_state *istate,
+				 struct cache_entry *old,
+				 struct cache_entry *new)
+{
+	if (old->index &&
+	    istate->split_index &&
+	    istate->split_index->base &&
+	    old->index <= istate->split_index->base->cache_nr) {
+		new->index = old->index;
+		if (old != istate->split_index->base->cache[new->index - 1])
+			free(istate->split_index->base->cache[new->index - 1]);
+		istate->split_index->base->cache[new->index - 1] = new;
+	}
+}