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Diffstat (limited to 'src/pool.h')
-rw-r--r-- | src/pool.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/src/pool.h b/src/pool.h new file mode 100644 index 000000000..54a2861ed --- /dev/null +++ b/src/pool.h @@ -0,0 +1,125 @@ +/* + * Copyright (C) 2012 the libgit2 contributors + * + * This file is part of libgit2, distributed under the GNU GPL v2 with + * a Linking Exception. For full terms see the included COPYING file. + */ +#ifndef INCLUDE_pool_h__ +#define INCLUDE_pool_h__ + +#include "common.h" + +typedef struct git_pool_page git_pool_page; + +/** + * Chunked allocator. + * + * A `git_pool` can be used when you want to cheaply allocate + * multiple items of the same type and are willing to free them + * all together with a single call. The two most common cases + * are a set of fixed size items (such as lots of OIDs) or a + * bunch of strings. + * + * Internally, a `git_pool` allocates pages of memory and then + * deals out blocks from the trailing unused portion of each page. + * The pages guarantee that the number of actual allocations done + * will be much smaller than the number of items needed. + * + * For examples of how to set up a `git_pool` see `git_pool_init`. + */ +typedef struct { + git_pool_page *open; /* pages with space left */ + git_pool_page *full; /* pages with no space left */ + void *free_list; /* optional: list of freed blocks */ + uint32_t item_size; /* size of single alloc unit in bytes */ + uint32_t page_size; /* size of page in bytes */ + uint32_t items; + unsigned has_string_alloc : 1; /* was the strdup function used */ + unsigned has_multi_item_alloc : 1; /* was items ever > 1 in malloc */ + unsigned has_large_page_alloc : 1; /* are any pages > page_size */ +} git_pool; + +#define GIT_POOL_INIT_STRINGPOOL { 0, 0, 0, 1, 4000, 0, 0, 0, 0 } + +/** + * Initialize a pool. + * + * To allocation strings, use like this: + * + * git_pool_init(&string_pool, 1, 0); + * my_string = git_pool_strdup(&string_pool, your_string); + * + * To allocate items of fixed size, use like this: + * + * git_pool_init(&pool, sizeof(item), 0); + * my_item = git_pool_malloc(&pool, 1); + * + * Of course, you can use this in other ways, but those are the + * two most common patterns. + */ +extern int git_pool_init( + git_pool *pool, uint32_t item_size, uint32_t items_per_page); + +/** + * Free all items in pool + */ +extern void git_pool_clear(git_pool *pool); + +/** + * Swap two pools with one another + */ +extern void git_pool_swap(git_pool *a, git_pool *b); + +/** + * Allocate space for one or more items from a pool. + */ +extern void *git_pool_malloc(git_pool *pool, uint32_t items); + +/** + * Allocate space and duplicate string data into it. + * + * This is allowed only for pools with item_size == sizeof(char) + */ +extern char *git_pool_strndup(git_pool *pool, const char *str, size_t n); + +/** + * Allocate space and duplicate a string into it. + * + * This is allowed only for pools with item_size == sizeof(char) + */ +extern char *git_pool_strdup(git_pool *pool, const char *str); + +/** + * Allocate space for the concatenation of two strings. + * + * This is allowed only for pools with item_size == sizeof(char) + */ +extern char *git_pool_strcat(git_pool *pool, const char *a, const char *b); + +/** + * Push a block back onto the free list for the pool. + * + * This is allowed only if the item_size is >= sizeof(void*). + * + * In some cases, it is helpful to "release" an allocated block + * for reuse. Pools don't support a general purpose free, but + * they will keep a simple free blocks linked list provided the + * native block size is large enough to hold a void pointer + */ +extern void git_pool_free(git_pool *pool, void *ptr); + +/* + * Misc utilities + */ + +extern uint32_t git_pool__open_pages(git_pool *pool); + +extern uint32_t git_pool__full_pages(git_pool *pool); + +extern bool git_pool__ptr_in_pool(git_pool *pool, void *ptr); + +extern uint32_t git_pool__system_page_size(void); + +extern uint32_t git_pool__suggest_items_per_page(uint32_t item_size); + +#endif |