thodg/libgit2/src/util/sortedcache.c

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• Hash : c3b7ace9
  Author :
  Date : 2021-11-14T16:43:53
  

  refactor: make util an object library Instead of simply including the utility files directly, make them a cmake object library for easy reusability between other projects within libgit2. Now the top-level `src` is responsible for platform selection, while the next-level `libgit2` and `util` configurations are responsible for identifying what objects they include.

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• src/util/sortedcache.c

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  
  #include "sortedcache.h"
  
  int git_sortedcache_new(
  	git_sortedcache **out,
  	size_t item_path_offset,
  	git_sortedcache_free_item_fn free_item,
  	void *free_item_payload,
  	git_vector_cmp item_cmp,
  	const char *path)
  {
  	git_sortedcache *sc;
  	size_t pathlen, alloclen;
  
  	pathlen = path ? strlen(path) : 0;
  
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, sizeof(git_sortedcache), pathlen);
  	GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, alloclen, 1);
  	sc = git__calloc(1, alloclen);
  	GIT_ERROR_CHECK_ALLOC(sc);
  
  	if (git_pool_init(&sc->pool, 1) < 0 ||
  	    git_vector_init(&sc->items, 4, item_cmp) < 0 ||
  	    git_strmap_new(&sc->map) < 0)
  		goto fail;
  
  	if (git_rwlock_init(&sc->lock)) {
  		git_error_set(GIT_ERROR_OS, "failed to initialize lock");
  		goto fail;
  	}
  
  	sc->item_path_offset  = item_path_offset;
  	sc->free_item         = free_item;
  	sc->free_item_payload = free_item_payload;
  	GIT_REFCOUNT_INC(sc);
  	if (pathlen)
  		memcpy(sc->path, path, pathlen);
  
  	*out = sc;
  	return 0;
  
  fail:
  	git_strmap_free(sc->map);
  	git_vector_free(&sc->items);
  	git_pool_clear(&sc->pool);
  	git__free(sc);
  	return -1;
  }
  
  void git_sortedcache_incref(git_sortedcache *sc)
  {
  	GIT_REFCOUNT_INC(sc);
  }
  
  const char *git_sortedcache_path(git_sortedcache *sc)
  {
  	return sc->path;
  }
  
  static void sortedcache_clear(git_sortedcache *sc)
  {
  	git_strmap_clear(sc->map);
  
  	if (sc->free_item) {
  		size_t i;
  		void *item;
  
  		git_vector_foreach(&sc->items, i, item) {
  			sc->free_item(sc->free_item_payload, item);
  		}
  	}
  
  	git_vector_clear(&sc->items);
  
  	git_pool_clear(&sc->pool);
  }
  
  static void sortedcache_free(git_sortedcache *sc)
  {
  	/* acquire write lock to make sure everyone else is done */
  	if (git_sortedcache_wlock(sc) < 0)
  		return;
  
  	sortedcache_clear(sc);
  	git_vector_free(&sc->items);
  	git_strmap_free(sc->map);
  
  	git_sortedcache_wunlock(sc);
  
  	git_rwlock_free(&sc->lock);
  	git__free(sc);
  }
  
  void git_sortedcache_free(git_sortedcache *sc)
  {
  	if (!sc)
  		return;
  	GIT_REFCOUNT_DEC(sc, sortedcache_free);
  }
  
  static int sortedcache_copy_item(void *payload, void *tgt_item, void *src_item)
  {
  	git_sortedcache *sc = payload;
  	/* path will already have been copied by upsert */
  	memcpy(tgt_item, src_item, sc->item_path_offset);
  	return 0;
  }
  
  /* copy a sorted cache */
  int git_sortedcache_copy(
  	git_sortedcache **out,
  	git_sortedcache *src,
  	bool lock,
  	int (*copy_item)(void *payload, void *tgt_item, void *src_item),
  	void *payload)
  {
  	int error = 0;
  	git_sortedcache *tgt;
  	size_t i;
  	void *src_item, *tgt_item;
  
  	/* just use memcpy if no special copy fn is passed in */
  	if (!copy_item) {
  		copy_item = sortedcache_copy_item;
  		payload   = src;
  	}
  
  	if ((error = git_sortedcache_new(
  			&tgt, src->item_path_offset,
  			src->free_item, src->free_item_payload,
  			src->items._cmp, src->path)) < 0)
  		return error;
  
  	if (lock && git_sortedcache_rlock(src) < 0) {
  		git_sortedcache_free(tgt);
  		return -1;
  	}
  
  	git_vector_foreach(&src->items, i, src_item) {
  		char *path = ((char *)src_item) + src->item_path_offset;
  
  		if ((error = git_sortedcache_upsert(&tgt_item, tgt, path)) < 0 ||
  			(error = copy_item(payload, tgt_item, src_item)) < 0)
  			break;
  	}
  
  	if (lock)
  		git_sortedcache_runlock(src);
  	if (error)
  		git_sortedcache_free(tgt);
  
  	*out = !error ? tgt : NULL;
  
  	return error;
  }
  
  /* lock sortedcache while making modifications */
  int git_sortedcache_wlock(git_sortedcache *sc)
  {
  	GIT_UNUSED(sc); /* prevent warning when compiled w/o threads */
  
  	if (git_rwlock_wrlock(&sc->lock) < 0) {
  		git_error_set(GIT_ERROR_OS, "unable to acquire write lock on cache");
  		return -1;
  	}
  	return 0;
  }
  
  /* unlock sorted cache when done with modifications */
  void git_sortedcache_wunlock(git_sortedcache *sc)
  {
  	git_vector_sort(&sc->items);
  	git_rwlock_wrunlock(&sc->lock);
  }
  
  /* lock sortedcache for read */
  int git_sortedcache_rlock(git_sortedcache *sc)
  {
  	GIT_UNUSED(sc); /* prevent warning when compiled w/o threads */
  
  	if (git_rwlock_rdlock(&sc->lock) < 0) {
  		git_error_set(GIT_ERROR_OS, "unable to acquire read lock on cache");
  		return -1;
  	}
  	return 0;
  }
  
  /* unlock sorted cache when done reading */
  void git_sortedcache_runlock(git_sortedcache *sc)
  {
  	GIT_UNUSED(sc); /* prevent warning when compiled w/o threads */
  	git_rwlock_rdunlock(&sc->lock);
  }
  
  /* if the file has changed, lock cache and load file contents into buf;
   * returns <0 on error, >0 if file has not changed
   */
  int git_sortedcache_lockandload(git_sortedcache *sc, git_str *buf)
  {
  	int error, fd;
  	struct stat st;
  
  	if ((error = git_sortedcache_wlock(sc)) < 0)
  		return error;
  
  	if ((error = git_futils_filestamp_check(&sc->stamp, sc->path)) <= 0)
  		goto unlock;
  
  	if ((fd = git_futils_open_ro(sc->path)) < 0) {
  		error = fd;
  		goto unlock;
  	}
  
  	if (p_fstat(fd, &st) < 0) {
  		git_error_set(GIT_ERROR_OS, "failed to stat file");
  		error = -1;
  		(void)p_close(fd);
  		goto unlock;
  	}
  
  	if (!git__is_sizet(st.st_size)) {
  		git_error_set(GIT_ERROR_INVALID, "unable to load file larger than size_t");
  		error = -1;
  		(void)p_close(fd);
  		goto unlock;
  	}
  
  	if (buf)
  		error = git_futils_readbuffer_fd(buf, fd, (size_t)st.st_size);
  
  	(void)p_close(fd);
  
  	if (error < 0)
  		goto unlock;
  
  	return 1; /* return 1 -> file needs reload and was successfully loaded */
  
  unlock:
  	git_sortedcache_wunlock(sc);
  	return error;
  }
  
  void git_sortedcache_updated(git_sortedcache *sc)
  {
  	/* update filestamp to latest value */
  	git_futils_filestamp_check(&sc->stamp, sc->path);
  }
  
  /* release all items in sorted cache */
  int git_sortedcache_clear(git_sortedcache *sc, bool wlock)
  {
  	if (wlock && git_sortedcache_wlock(sc) < 0)
  		return -1;
  
  	sortedcache_clear(sc);
  
  	if (wlock)
  		git_sortedcache_wunlock(sc);
  
  	return 0;
  }
  
  /* find and/or insert item, returning pointer to item data */
  int git_sortedcache_upsert(void **out, git_sortedcache *sc, const char *key)
  {
  	size_t keylen, itemlen;
  	int error = 0;
  	char *item_key;
  	void *item;
  
  	if ((item = git_strmap_get(sc->map, key)) != NULL)
  		goto done;
  
  	keylen  = strlen(key);
  	itemlen = sc->item_path_offset + keylen + 1;
  	itemlen = (itemlen + 7) & ~7;
  
  	if ((item = git_pool_mallocz(&sc->pool, itemlen)) == NULL) {
  		/* don't use GIT_ERROR_CHECK_ALLOC b/c of lock */
  		error = -1;
  		goto done;
  	}
  
  	/* one strange thing is that even if the vector or hash table insert
  	 * fail, there is no way to free the pool item so we just abandon it
  	 */
  
  	item_key = ((char *)item) + sc->item_path_offset;
  	memcpy(item_key, key, keylen);
  
  	if ((error = git_strmap_set(sc->map, item_key, item)) < 0)
  		goto done;
  
  	if ((error = git_vector_insert(&sc->items, item)) < 0)
  		git_strmap_delete(sc->map, item_key);
  
  done:
  	if (out)
  		*out = !error ? item : NULL;
  	return error;
  }
  
  /* lookup item by key */
  void *git_sortedcache_lookup(const git_sortedcache *sc, const char *key)
  {
  	return git_strmap_get(sc->map, key);
  }
  
  /* find out how many items are in the cache */
  size_t git_sortedcache_entrycount(const git_sortedcache *sc)
  {
  	return git_vector_length(&sc->items);
  }
  
  /* lookup item by index */
  void *git_sortedcache_entry(git_sortedcache *sc, size_t pos)
  {
  	/* make sure the items are sorted so this gets the correct item */
  	if (!git_vector_is_sorted(&sc->items))
  		git_vector_sort(&sc->items);
  
  	return git_vector_get(&sc->items, pos);
  }
  
  /* helper struct so bsearch callback can know offset + key value for cmp */
  struct sortedcache_magic_key {
  	size_t offset;
  	const char *key;
  };
  
  static int sortedcache_magic_cmp(const void *key, const void *value)
  {
  	const struct sortedcache_magic_key *magic = key;
  	const char *value_key = ((const char *)value) + magic->offset;
  	return strcmp(magic->key, value_key);
  }
  
  /* lookup index of item by key */
  int git_sortedcache_lookup_index(
  	size_t *out, git_sortedcache *sc, const char *key)
  {
  	struct sortedcache_magic_key magic;
  
  	magic.offset = sc->item_path_offset;
  	magic.key    = key;
  
  	return git_vector_bsearch2(out, &sc->items, sortedcache_magic_cmp, &magic);
  }
  
  /* remove entry from cache */
  int git_sortedcache_remove(git_sortedcache *sc, size_t pos)
  {
  	char *item;
  
  	/*
  	 * Because of pool allocation, this can't actually remove the item,
  	 * but we can remove it from the items vector and the hash table.
  	 */
  
  	if ((item = git_vector_get(&sc->items, pos)) == NULL) {
  		git_error_set(GIT_ERROR_INVALID, "removing item out of range");
  		return GIT_ENOTFOUND;
  	}
  
  	(void)git_vector_remove(&sc->items, pos);
  
  	git_strmap_delete(sc->map, item + sc->item_path_offset);
  
  	if (sc->free_item)
  		sc->free_item(sc->free_item_payload, item);
  
  	return 0;
  }
  
  

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