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, 110 insertions, 0 deletions

diff --git a/hash.c b/hash.c
new file mode 100644
index 000000000..1cd4c9d5c
--- /dev/null
+++ b/hash.c
@@ -0,0 +1,110 @@
+/*
+ * Some generic hashing helpers.
+ */
+#include "cache.h"
+#include "hash.h"
+
+/*
+ * Look up a hash entry in the hash table. Return the pointer to
+ * the existing entry, or the empty slot if none existed. The caller
+ * can then look at the (*ptr) to see whether it existed or not.
+ */
+static struct hash_table_entry *lookup_hash_entry(unsigned int hash, const struct hash_table *table)
+{
+	unsigned int size = table->size, nr = hash % size;
+	struct hash_table_entry *array = table->array;
+
+	while (array[nr].ptr) {
+		if (array[nr].hash == hash)
+			break;
+		nr++;
+		if (nr >= size)
+			nr = 0;
+	}
+	return array + nr;
+}
+
+
+/*
+ * Insert a new hash entry pointer into the table.
+ *
+ * If that hash entry already existed, return the pointer to
+ * the existing entry (and the caller can create a list of the
+ * pointers or do anything else). If it didn't exist, return
+ * NULL (and the caller knows the pointer has been inserted).
+ */
+static void **insert_hash_entry(unsigned int hash, void *ptr, struct hash_table *table)
+{
+	struct hash_table_entry *entry = lookup_hash_entry(hash, table);
+
+	if (!entry->ptr) {
+		entry->ptr = ptr;
+		entry->hash = hash;
+		table->nr++;
+		return NULL;
+	}
+	return &entry->ptr;
+}
+
+static void grow_hash_table(struct hash_table *table)
+{
+	unsigned int i;
+	unsigned int old_size = table->size, new_size;
+	struct hash_table_entry *old_array = table->array, *new_array;
+
+	new_size = alloc_nr(old_size);
+	new_array = xcalloc(sizeof(struct hash_table_entry), new_size);
+	table->size = new_size;
+	table->array = new_array;
+	table->nr = 0;
+	for (i = 0; i < old_size; i++) {
+		unsigned int hash = old_array[i].hash;
+		void *ptr = old_array[i].ptr;
+		if (ptr)
+			insert_hash_entry(hash, ptr, table);
+	}
+	free(old_array);
+}
+
+void *lookup_hash(unsigned int hash, const struct hash_table *table)
+{
+	if (!table->array)
+		return NULL;
+	return lookup_hash_entry(hash, table)->ptr;
+}
+
+void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table)
+{
+	unsigned int nr = table->nr;
+	if (nr >= table->size/2)
+		grow_hash_table(table);
+	return insert_hash_entry(hash, ptr, table);
+}
+
+int for_each_hash(const struct hash_table *table, int (*fn)(void *))
+{
+	int sum = 0;
+	unsigned int i;
+	unsigned int size = table->size;
+	struct hash_table_entry *array = table->array;
+
+	for (i = 0; i < size; i++) {
+		void *ptr = array->ptr;
+		array++;
+		if (ptr) {
+			int val = fn(ptr);
+			if (val < 0)
+				return val;
+			sum += val;
+		}
+	}
+	return sum;
+}
+
+void free_hash(struct hash_table *table)
+{
+	free(table->array);
+	table->array = NULL;
+	table->size = 0;
+	table->nr = 0;
+}