Improved tree iterator internals

This updates the tree iterator internals to be more efficient.

The tree_iterator_entry objects are now kept as pointers that are
allocated from a git_pool, so that we may use git__tsort_r for
sorting (which is better than qsort, given that the tree is
likely mostly ordered already).

Those tree_iterator_entry objects now keep direct pointers to the
data they refer to instead of keeping indirect index values.  This
simplifies a lot of the data structure traversal code.

This also adds bsearch to find the start item position for range-
limited tree iterators, and is more explicit about using
git_path_cmp instead of reimplementing it.  The git_path_cmp
changed a bit to make it easier for tree_iterators to use it (but
it was barely being used previously, so not a big deal).

This adds a git_pool_free_array function that efficiently frees a
list of pool allocated pointers (which the tree_iterator keeps).
Also, added new tests for the git_pool free list functionality
that was not previously being tested (or used).

src/path.c

@@ -679,37 +679,14 @@ int git_path_apply_relative(git_buf *target, const char *relpath)
 
 int git_path_cmp(
 	const char *name1, size_t len1, int isdir1,
-	const char *name2, size_t len2, int isdir2)
+	const char *name2, size_t len2, int isdir2,
+	int (*compare)(const char *, const char *, size_t))
 {
 	unsigned char c1, c2;
 	size_t len = len1 < len2 ? len1 : len2;
 	int cmp;
 
-	cmp = memcmp(name1, name2, len);
-	if (cmp)
-		return cmp;
-
-	c1 = name1[len];
-	c2 = name2[len];
-
-	if (c1 == '\0' && isdir1)
-		c1 = '/';
-
-	if (c2 == '\0' && isdir2)
-		c2 = '/';
-
-	return (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
-}
-
-int git_path_icmp(
-	const char *name1, size_t len1, int isdir1,
-	const char *name2, size_t len2, int isdir2)
-{
-	unsigned char c1, c2;
-	size_t len = len1 < len2 ? len1 : len2;
-	int cmp;
-
-	cmp = strncasecmp(name1, name2, len);
+	cmp = compare(name1, name2, len);
 	if (cmp)
 		return cmp;
 

src/path.h

@@ -265,12 +265,8 @@ extern int git_path_direach(
  */
 extern int git_path_cmp(
 	const char *name1, size_t len1, int isdir1,
-	const char *name2, size_t len2, int isdir2);
-
-/** Path sort function that is case insensitive */
-extern int git_path_icmp(
-	const char *name1, size_t len1, int isdir1,
-	const char *name2, size_t len2, int isdir2);
+	const char *name2, size_t len2, int isdir2,
+	int (*compare)(const char *, const char *, size_t));
 
 /**
  * Invoke callback up path directory by directory until the ceiling is

src/pool.c

@@ -235,10 +235,28 @@ char *git_pool_strcat(git_pool *pool, const char *a, const char *b)
 
 void git_pool_free(git_pool *pool, void *ptr)
 {
-	assert(pool && ptr && pool->item_size >= sizeof(void*));
+	assert(pool && pool->item_size >= sizeof(void*));
 
-	*((void **)ptr) = pool->free_list;
-	pool->free_list = ptr;
+	if (ptr) {
+		*((void **)ptr) = pool->free_list;
+		pool->free_list = ptr;
+	}
+}
+
+void git_pool_free_array(git_pool *pool, size_t count, void **ptrs)
+{
+	size_t i;
+
+	assert(pool && ptrs && pool->item_size >= sizeof(void*));
+
+	if (!count)
+		return;
+
+	for (i = count - 1; i > 0; --i)
+		*((void **)ptrs[i]) = ptrs[i - 1];
+
+	*((void **)ptrs[0]) = pool->free_list;
+	pool->free_list = ptrs[count - 1];
 }
 
 uint32_t git_pool__open_pages(git_pool *pool)

src/pool.h

@@ -126,6 +126,13 @@ extern char *git_pool_strcat(git_pool *pool, const char *a, const char *b);
  */
 extern void git_pool_free(git_pool *pool, void *ptr);
 
+/**
+ * Push an array of pool allocated blocks efficiently onto the free list.
+ *
+ * This has the same constraints as `git_pool_free()` above.
+ */
+extern void git_pool_free_array(git_pool *pool, size_t count, void **ptrs);
+
 /*
  * Misc utilities
  */

src/tree.c

@@ -55,23 +55,28 @@ static int valid_entry_name(const char *filename)
 		  strcmp(filename, DOT_GIT) != 0));
 }
 
-int git_tree_entry_cmp(const git_tree_entry *e1, const git_tree_entry *e2)
+static int entry_sort_cmp(const void *a, const void *b)
 {
+	const git_tree_entry *e1 = (const git_tree_entry *)a;
+	const git_tree_entry *e2 = (const git_tree_entry *)b;
+
 	return git_path_cmp(
 		e1->filename, e1->filename_len, git_tree_entry__is_tree(e1),
-		e2->filename, e2->filename_len, git_tree_entry__is_tree(e2));
+		e2->filename, e2->filename_len, git_tree_entry__is_tree(e2),
+		git__strncmp);
 }
 
-int git_tree_entry_icmp(const git_tree_entry *e1, const git_tree_entry *e2)
+int git_tree_entry_cmp(const git_tree_entry *e1, const git_tree_entry *e2)
 {
-	return git_path_icmp(
-		e1->filename, e1->filename_len, git_tree_entry__is_tree(e1),
-		e2->filename, e2->filename_len, git_tree_entry__is_tree(e2));
+	return entry_sort_cmp(e1, e2);
 }
 
-static int entry_sort_cmp(const void *a, const void *b)
+int git_tree_entry_icmp(const git_tree_entry *e1, const git_tree_entry *e2)
 {
-	return git_tree_entry_cmp((const git_tree_entry *)a, (const git_tree_entry *)b);
+	return git_path_cmp(
+		e1->filename, e1->filename_len, git_tree_entry__is_tree(e1),
+		e2->filename, e2->filename_len, git_tree_entry__is_tree(e2),
+		git__strncasecmp);
 }
 
 static git_tree_entry *alloc_entry(const char *filename)

tests-clar/core/pool.c

@@ -83,3 +83,53 @@ void test_core_pool__2(void)
 
 	git_pool_clear(&p);
 }
+
+void test_core_pool__free_list(void)
+{
+	int i;
+	git_pool p;
+	void *ptr, *ptrs[50];
+
+	cl_git_pass(git_pool_init(&p, 100, 100));
+
+	for (i = 0; i < 10; ++i) {
+		ptr = git_pool_malloc(&p, 1);
+		cl_assert(ptr != NULL);
+	}
+	cl_assert_equal_i(10, (int)p.items);
+
+	for (i = 0; i < 50; ++i) {
+		ptrs[i] = git_pool_malloc(&p, 1);
+		cl_assert(ptrs[i] != NULL);
+	}
+	cl_assert_equal_i(60, (int)p.items);
+
+	git_pool_free(&p, ptr);
+	cl_assert_equal_i(60, (int)p.items);
+
+	git_pool_free_array(&p, 50, ptrs);
+	cl_assert_equal_i(60, (int)p.items);
+
+	for (i = 0; i < 50; ++i) {
+		ptrs[i] = git_pool_malloc(&p, 1);
+		cl_assert(ptrs[i] != NULL);
+	}
+	cl_assert_equal_i(60, (int)p.items);
+
+	for (i = 0; i < 111; ++i) {
+		ptr = git_pool_malloc(&p, 1);
+		cl_assert(ptr != NULL);
+	}
+	cl_assert_equal_i(170, (int)p.items);
+
+	git_pool_free_array(&p, 50, ptrs);
+	cl_assert_equal_i(170, (int)p.items);
+
+	for (i = 0; i < 50; ++i) {
+		ptrs[i] = git_pool_malloc(&p, 1);
+		cl_assert(ptrs[i] != NULL);
+	}
+	cl_assert_equal_i(170, (int)p.items);
+
+	git_pool_clear(&p);
+}