Merge commit 'b319ef7' into jc/maint-fix-test-perm

* commit 'b319ef7': (8132 commits)
  Add a small patch-mode testing library
  git-apply--interactive: Refactor patch mode code
  t8005: Nobody writes Russian in shift_jis
  Fix severe breakage in "git-apply --whitespace=fix"
  Update release notes for 1.6.4
  After renaming a section, print any trailing variable definitions
  Make section_name_match start on '[', and return the length on success
  send-email: detect cycles in alias expansion
  Show the presence of untracked files in the bash prompt.
  SunOS grep does not understand -C<n> nor -e
  Fix export_marks() error handling.
  git repack: keep commits hidden by a graft
  Add a test showing that 'git repack' throws away grafted-away parents
  git branch: clean up detached branch handling
  git branch: avoid unnecessary object lookups
  git branch: fix performance problem
  git svn: fix shallow clone when upstream revision is too new
  do_one_ref(): null_sha1 check is not about broken ref
  configure.ac: properly unset NEEDS_SSL_WITH_CRYPTO when sha1 func is missing
  janitor: useless checks before free
  ...

1 files changed, 43 insertions, 0 deletions

diff --git a/hash.h b/hash.h
new file mode 100644
index 0000000000..69e33a47b9
--- /dev/null
+++ b/hash.h
@@ -0,0 +1,43 @@
+#ifndef HASH_H
+#define HASH_H
+
+/*
+ * These are some simple generic hash table helper functions.
+ * Not necessarily suitable for all users, but good for things
+ * where you want to just keep track of a list of things, and
+ * have a good hash to use on them.
+ *
+ * It keeps the hash table at roughly 50-75% free, so the memory
+ * cost of the hash table itself is roughly
+ *
+ *	3 * 2*sizeof(void *) * nr_of_objects
+ *
+ * bytes.
+ *
+ * FIXME: on 64-bit architectures, we waste memory. It would be
+ * good to have just 32-bit pointers, requiring a special allocator
+ * for hashed entries or something.
+ */
+struct hash_table_entry {
+	unsigned int hash;
+	void *ptr;
+};
+
+struct hash_table {
+	unsigned int size, nr;
+	struct hash_table_entry *array;
+};
+
+extern void *lookup_hash(unsigned int hash, const struct hash_table *table);
+extern void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table);
+extern int for_each_hash(const struct hash_table *table, int (*fn)(void *));
+extern void free_hash(struct hash_table *table);
+
+static inline void init_hash(struct hash_table *table)
+{
+	table->size = 0;
+	table->nr = 0;
+	table->array = NULL;
+}
+
+#endif