1 files changed, 294 insertions, 0 deletions

diff --git a/src/pool.c b/src/pool.c
new file mode 100644
index 000000000..641292d06
--- /dev/null
+++ b/src/pool.c
@@ -0,0 +1,294 @@
+#include "pool.h"
+#ifndef GIT_WIN32
+#include <unistd.h>
+#endif
+
+struct git_pool_page {
+	git_pool_page *next;
+	uint32_t size;
+	uint32_t avail;
+	char data[GIT_FLEX_ARRAY];
+};
+
+#define GIT_POOL_MIN_USABLE	4
+#define GIT_POOL_MIN_PAGESZ	2 * sizeof(void*)
+
+static void *pool_alloc_page(git_pool *pool, uint32_t size);
+static void pool_insert_page(git_pool *pool, git_pool_page *page);
+
+int git_pool_init(
+	git_pool *pool, uint32_t item_size, uint32_t items_per_page)
+{
+	assert(pool);
+
+	if (!item_size)
+		item_size = 1;
+	/* round up item_size for decent object alignment */
+	if (item_size > 4)
+		item_size = (item_size + 7) & ~7;
+	else if (item_size == 3)
+		item_size = 4;
+
+	if (!items_per_page)
+		items_per_page = git_pool__suggest_items_per_page(item_size);
+	if (item_size * items_per_page < GIT_POOL_MIN_PAGESZ)
+		items_per_page = (GIT_POOL_MIN_PAGESZ + item_size - 1) / item_size;
+
+	memset(pool, 0, sizeof(git_pool));
+	pool->item_size = item_size;
+	pool->page_size = item_size * items_per_page;
+
+	return 0;
+}
+
+void git_pool_clear(git_pool *pool)
+{
+	git_pool_page *scan, *next;
+
+	for (scan = pool->open; scan != NULL; scan = next) {
+		next = scan->next;
+		git__free(scan);
+	}
+	pool->open = NULL;
+
+	for (scan = pool->full; scan != NULL; scan = next) {
+		next = scan->next;
+		git__free(scan);
+	}
+	pool->full = NULL;
+
+	pool->free_list = NULL;
+
+	pool->items = 0;
+
+	pool->has_string_alloc     = 0;
+	pool->has_multi_item_alloc = 0;
+	pool->has_large_page_alloc = 0;
+}
+
+void git_pool_swap(git_pool *a, git_pool *b)
+{
+	git_pool temp;
+
+	if (a == b)
+		return;
+
+	memcpy(&temp, a, sizeof(temp));
+	memcpy(a, b, sizeof(temp));
+	memcpy(b, &temp, sizeof(temp));
+}
+
+static void pool_insert_page(git_pool *pool, git_pool_page *page)
+{
+	git_pool_page *scan;
+
+	/* If there are no open pages or this page has the most open space,
+	 * insert it at the beginning of the list.  This is the common case.
+	 */
+	if (pool->open == NULL || pool->open->avail < page->avail) {
+		page->next = pool->open;
+		pool->open = page;
+		return;
+	}
+
+	/* Otherwise insert into sorted position. */
+	for (scan = pool->open;
+		 scan->next && scan->next->avail > page->avail;
+		 scan = scan->next);
+	page->next = scan->next;
+	scan->next = page;
+}
+
+static void *pool_alloc_page(git_pool *pool, uint32_t size)
+{
+	git_pool_page *page;
+	uint32_t alloc_size;
+
+	if (size <= pool->page_size)
+		alloc_size = pool->page_size;
+	else {
+		alloc_size = size;
+		pool->has_large_page_alloc = 1;
+	}
+
+	page = git__calloc(1, alloc_size + sizeof(git_pool_page));
+	if (!page)
+		return NULL;
+
+	page->size  = alloc_size;
+	page->avail = alloc_size - size;
+
+	if (page->avail > 0)
+		pool_insert_page(pool, page);
+	else {
+		page->next = pool->full;
+		pool->full = page;
+	}
+
+	pool->items++;
+
+	return page->data;
+}
+
+GIT_INLINE(void) pool_remove_page(
+	git_pool *pool, git_pool_page *page, git_pool_page *prev)
+{
+	if (prev == NULL)
+		pool->open = page->next;
+	else
+		prev->next = page->next;
+}
+
+void *git_pool_malloc(git_pool *pool, uint32_t items)
+{
+	git_pool_page *scan = pool->open, *prev;
+	uint32_t size = items * pool->item_size;
+	void *ptr = NULL;
+
+	pool->has_string_alloc = 0;
+	if (items > 1)
+		pool->has_multi_item_alloc = 1;
+	else if (pool->free_list != NULL) {
+		ptr = pool->free_list;
+		pool->free_list = *((void **)pool->free_list);
+		return ptr;
+	}
+
+	/* just add a block if there is no open one to accomodate this */
+	if (size >= pool->page_size || !scan || scan->avail < size)
+		return pool_alloc_page(pool, size);
+
+	pool->items++;
+
+	/* find smallest block in free list with space */
+	for (scan = pool->open, prev = NULL;
+		 scan->next && scan->next->avail >= size;
+		 prev = scan, scan = scan->next);
+
+	/* allocate space from the block */
+	ptr = &scan->data[scan->size - scan->avail];
+	scan->avail -= size;
+
+	/* move to full list if there is almost no space left */
+	if (scan->avail < pool->item_size || scan->avail < GIT_POOL_MIN_USABLE) {
+		pool_remove_page(pool, scan, prev);
+		scan->next = pool->full;
+		pool->full = scan;
+	}
+	/* reorder list if block is now smaller than the one after it */
+	else if (scan->next != NULL && scan->next->avail > scan->avail) {
+		pool_remove_page(pool, scan, prev);
+		pool_insert_page(pool, scan);
+	}
+
+	return ptr;
+}
+
+char *git_pool_strndup(git_pool *pool, const char *str, size_t n)
+{
+	void *ptr = NULL;
+
+	assert(pool && str && pool->item_size == sizeof(char));
+
+	if ((ptr = git_pool_malloc(pool, (uint32_t)(n + 1))) != NULL) {
+		memcpy(ptr, str, n);
+		*(((char *)ptr) + n) = '\0';
+	}
+	pool->has_string_alloc = 1;
+
+	return ptr;
+}
+
+char *git_pool_strdup(git_pool *pool, const char *str)
+{
+	assert(pool && str && pool->item_size == sizeof(char));
+
+	return git_pool_strndup(pool, str, strlen(str));
+}
+
+char *git_pool_strcat(git_pool *pool, const char *a, const char *b)
+{
+	void *ptr;
+	size_t len_a, len_b;
+
+	assert(pool && a && b && pool->item_size == sizeof(char));
+
+	len_a = a ? strlen(a) : 0;
+	len_b = b ? strlen(b) : 0;
+
+	if ((ptr = git_pool_malloc(pool, (uint32_t)(len_a + len_b + 1))) != NULL) {
+		if (len_a)
+			memcpy(ptr, a, len_a);
+		if (len_b)
+			memcpy(((char *)ptr) + len_a, b, len_b);
+		*(((char *)ptr) + len_a + len_b) = '\0';
+	}
+	pool->has_string_alloc = 1;
+
+	return ptr;
+}
+
+void git_pool_free(git_pool *pool, void *ptr)
+{
+	assert(pool && ptr && pool->item_size >= sizeof(void*));
+
+	*((void **)ptr) = pool->free_list;
+	pool->free_list = ptr;
+}
+
+uint32_t git_pool__open_pages(git_pool *pool)
+{
+	uint32_t ct = 0;
+	git_pool_page *scan;
+	for (scan = pool->open; scan != NULL; scan = scan->next) ct++;
+	return ct;
+}
+
+uint32_t git_pool__full_pages(git_pool *pool)
+{
+	uint32_t ct = 0;
+	git_pool_page *scan;
+	for (scan = pool->full; scan != NULL; scan = scan->next) ct++;
+	return ct;
+}
+
+bool git_pool__ptr_in_pool(git_pool *pool, void *ptr)
+{
+	git_pool_page *scan;
+	for (scan = pool->open; scan != NULL; scan = scan->next)
+		if ((void *)scan->data <= ptr &&
+			(void *)(((char *)scan->data) + scan->size) > ptr)
+			return true;
+	for (scan = pool->full; scan != NULL; scan = scan->next)
+		if ((void *)scan->data <= ptr &&
+			(void *)(((char *)scan->data) + scan->size) > ptr)
+			return true;
+	return false;
+}
+
+uint32_t git_pool__system_page_size(void)
+{
+	static uint32_t size = 0;
+
+	if (!size) {
+#ifdef GIT_WIN32
+		SYSTEM_INFO info;
+		GetSystemInfo(&info);
+		size = (uint32_t)info.dwPageSize;
+#else
+		size = (uint32_t)sysconf(_SC_PAGE_SIZE);
+#endif
+
+		size -= 2 * sizeof(void *); /* allow space for malloc overhead */
+	}
+
+	return size;
+}
+
+uint32_t git_pool__suggest_items_per_page(uint32_t item_size)
+{
+	uint32_t page_bytes =
+		git_pool__system_page_size() - sizeof(git_pool_page);
+	return page_bytes / item_size;
+}
+