1 files changed, 295 insertions, 0 deletions
diff --git a/name-hash.c b/name-hash.c
new file mode 100644
index 0000000000..e5b6e1ad23
--- /dev/null
+++ b/name-hash.c
@@ -0,0 +1,295 @@
+/*
+ * name-hash.c
+ *
+ * Hashing names in the index state
+ *
+ * Copyright (C) 2008 Linus Torvalds
+ */
+#define NO_THE_INDEX_COMPATIBILITY_MACROS
+#include "cache.h"
+
+/*
+ * This removes bit 5 if bit 6 is set.
+ *
+ * That will make US-ASCII characters hash to their upper-case
+ * equivalent. We could easily do this one whole word at a time,
+ * but that's for future worries.
+ */
+static inline unsigned char icase_hash(unsigned char c)
+{
+	return c & ~((c & 0x40) >> 1);
+}
+
+static unsigned int hash_name(const char *name, int namelen)
+{
+	unsigned int hash = 0x123;
+
+	while (namelen--) {
+		unsigned char c = *name++;
+		c = icase_hash(c);
+		hash = hash*101 + c;
+	}
+	return hash;
+}
+
+struct dir_entry {
+	struct dir_entry *next;
+	struct dir_entry *parent;
+	struct cache_entry *ce;
+	int nr;
+	unsigned int namelen;
+};
+
+static struct dir_entry *find_dir_entry(struct index_state *istate,
+		const char *name, unsigned int namelen)
+{
+	unsigned int hash = hash_name(name, namelen);
+	struct dir_entry *dir;
+
+	for (dir = lookup_hash(hash, &istate->dir_hash); dir; dir = dir->next)
+		if (dir->namelen == namelen &&
+		    !strncasecmp(dir->ce->name, name, namelen))
+			return dir;
+	return NULL;
+}
+
+static struct dir_entry *hash_dir_entry(struct index_state *istate,
+		struct cache_entry *ce, int namelen)
+{
+	/*
+	 * Throw each directory component in the hash for quick lookup
+	 * during a git status. Directory components are stored without their
+	 * closing slash.  Despite submodules being a directory, they never
+	 * reach this point, because they are stored
+	 * in index_state.name_hash (as ordinary cache_entries).
+	 *
+	 * Note that the cache_entry stored with the dir_entry merely
+	 * supplies the name of the directory (up to dir_entry.namelen). We
+	 * track the number of 'active' files in a directory in dir_entry.nr,
+	 * so we can tell if the directory is still relevant, e.g. for git
+	 * status. However, if cache_entries are removed, we cannot pinpoint
+	 * an exact cache_entry that's still active. It is very possible that
+	 * multiple dir_entries point to the same cache_entry.
+	 */
+	struct dir_entry *dir;
+
+	/* get length of parent directory */
+	while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
+		namelen--;
+	if (namelen <= 0)
+		return NULL;
+	namelen--;
+
+	/* lookup existing entry for that directory */
+	dir = find_dir_entry(istate, ce->name, namelen);
+	if (!dir) {
+		/* not found, create it and add to hash table */
+		void **pdir;
+		unsigned int hash = hash_name(ce->name, namelen);
+
+		dir = xcalloc(1, sizeof(struct dir_entry));
+		dir->namelen = namelen;
+		dir->ce = ce;
+
+		pdir = insert_hash(hash, dir, &istate->dir_hash);
+		if (pdir) {
+			dir->next = *pdir;
+			*pdir = dir;
+		}
+
+		/* recursively add missing parent directories */
+		dir->parent = hash_dir_entry(istate, ce, namelen);
+	}
+	return dir;
+}
+
+static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
+{
+	/* Add reference to the directory entry (and parents if 0). */
+	struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
+	while (dir && !(dir->nr++))
+		dir = dir->parent;
+}
+
+static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
+{
+	/*
+	 * Release reference to the directory entry (and parents if 0).
+	 *
+	 * Note: we do not remove / free the entry because there's no
+	 * hash.[ch]::remove_hash and dir->next may point to other entries
+	 * that are still valid, so we must not free the memory.
+	 */
+	struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
+	while (dir && dir->nr && !(--dir->nr))
+		dir = dir->parent;
+}
+
+static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
+{
+	void **pos;
+	unsigned int hash;
+
+	if (ce->ce_flags & CE_HASHED)
+		return;
+	ce->ce_flags |= CE_HASHED;
+	ce->next = NULL;
+	hash = hash_name(ce->name, ce_namelen(ce));
+	pos = insert_hash(hash, ce, &istate->name_hash);
+	if (pos) {
+		ce->next = *pos;
+		*pos = ce;
+	}
+
+	if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
+		add_dir_entry(istate, ce);
+}
+
+static void lazy_init_name_hash(struct index_state *istate)
+{
+	int nr;
+
+	if (istate->name_hash_initialized)
+		return;
+	if (istate->cache_nr)
+		preallocate_hash(&istate->name_hash, istate->cache_nr);
+	for (nr = 0; nr < istate->cache_nr; nr++)
+		hash_index_entry(istate, istate->cache[nr]);
+	istate->name_hash_initialized = 1;
+}
+
+void add_name_hash(struct index_state *istate, struct cache_entry *ce)
+{
+	/* if already hashed, add reference to directory entries */
+	if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
+		add_dir_entry(istate, ce);
+
+	ce->ce_flags &= ~CE_UNHASHED;
+	if (istate->name_hash_initialized)
+		hash_index_entry(istate, ce);
+}
+
+/*
+ * We don't actually *remove* it, we can just mark it invalid so that
+ * we won't find it in lookups.
+ *
+ * Not only would we have to search the lists (simple enough), but
+ * we'd also have to rehash other hash buckets in case this makes the
+ * hash bucket empty (common). So it's much better to just mark
+ * it.
+ */
+void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
+{
+	/* if already hashed, release reference to directory entries */
+	if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
+		remove_dir_entry(istate, ce);
+
+	ce->ce_flags |= CE_UNHASHED;
+}
+
+static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
+{
+	if (len1 != len2)
+		return 0;
+
+	while (len1) {
+		unsigned char c1 = *name1++;
+		unsigned char c2 = *name2++;
+		len1--;
+		if (c1 != c2) {
+			c1 = toupper(c1);
+			c2 = toupper(c2);
+			if (c1 != c2)
+				return 0;
+		}
+	}
+	return 1;
+}
+
+static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
+{
+	int len = ce_namelen(ce);
+
+	/*
+	 * Always do exact compare, even if we want a case-ignoring comparison;
+	 * we do the quick exact one first, because it will be the common case.
+	 */
+	if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
+		return 1;
+
+	if (!icase)
+		return 0;
+
+	return slow_same_name(name, namelen, ce->name, len);
+}
+
+struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
+{
+	struct cache_entry *ce;
+	struct dir_entry *dir;
+
+	lazy_init_name_hash(istate);
+	dir = find_dir_entry(istate, name, namelen);
+	if (dir && dir->nr)
+		return dir->ce;
+
+	/*
+	 * It might be a submodule. Unlike plain directories, which are stored
+	 * in the dir-hash, submodules are stored in the name-hash, so check
+	 * there, as well.
+	 */
+	ce = index_file_exists(istate, name, namelen, 1);
+	if (ce && S_ISGITLINK(ce->ce_mode))
+		return ce;
+
+	return NULL;
+}
+
+struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
+{
+	unsigned int hash = hash_name(name, namelen);
+	struct cache_entry *ce;
+
+	lazy_init_name_hash(istate);
+	ce = lookup_hash(hash, &istate->name_hash);
+
+	while (ce) {
+		if (!(ce->ce_flags & CE_UNHASHED)) {
+			if (same_name(ce, name, namelen, icase))
+				return ce;
+		}
+		ce = ce->next;
+	}
+	return NULL;
+}
+
+struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
+{
+	if (namelen > 0 && name[namelen - 1] == '/')
+		return index_dir_exists(istate, name, namelen - 1);
+	return index_file_exists(istate, name, namelen, icase);
+}
+
+static int free_dir_entry(void *entry, void *unused)
+{
+	struct dir_entry *dir = entry;
+	while (dir) {
+		struct dir_entry *next = dir->next;
+		free(dir);
+		dir = next;
+	}
+	return 0;
+}
+
+void free_name_hash(struct index_state *istate)
+{
+	if (!istate->name_hash_initialized)
+		return;
+	istate->name_hash_initialized = 0;
+	if (ignore_case)
+		/* free directory entries */
+		for_each_hash(&istate->dir_hash, free_dir_entry, NULL);
+
+	free_hash(&istate->name_hash);
+	free_hash(&istate->dir_hash);
+}