stef...@apache.org wrote on Sat, Apr 16, 2011 at 13:06:07 -0000:
> Author: stefan2
> Date: Sat Apr 16 13:06:07 2011
> New Revision: 1093983
>
> URL: http://svn.apache.org/viewvc?rev=1093983&view=rev
> Log:
> In symmetry to svn_cache__get_partial, introduce a partial
> setter / modifier API function that enabled the caller to
> modify changed items without the full deserialization -
> modification - serialization chain. Therefore, adding entries
> to e.g. directories becomes O(1) instead of O(n).
>
...
> +++ subversion/trunk/subversion/libsvn_subr/cache-membuffer.c Sat Apr 16
> 13:06:07 2011
> @@ -1174,6 +1174,12 @@ membuffer_cache_get(svn_membuffer_t *cac
> return deserializer(item, buffer, entry->size, pool);
> }
>
> +/* Look for the cache entry identified by KEY and KEY_LEN. FOUND indicates
> + * whether that entry exists. If not found, *ITEM will be NULL. Otherwise,
> + * the DESERIALIZER is called with that entry and the BATON provided
> + * and will extract the desired information. The result is set in *ITEM.
> + * Allocations will be done in POOL.
> + */
> static svn_error_t *
> membuffer_cache_get_partial(svn_membuffer_t *cache,
> const void *key,
> @@ -1239,6 +1245,105 @@ membuffer_cache_get_partial(svn_membuffe
> return unlock_cache(cache, err);
> }
>
> +/* Look for the cache entry identified by KEY and KEY_LEN. If no entry
> + * has been found, the function returns without modifying the cache.
> + * Otherwise, FUNC is called with that entry and the BATON provided
> + * and may modify the cache entry. Allocations will be done in POOL.
> + */
> +static svn_error_t *
> +membuffer_cache_set_partial(svn_membuffer_t *cache,
> + const void *key,
> + apr_size_t key_len,
> + svn_cache__partial_setter_func_t func,
> + void *baton,
> + DEBUG_CACHE_MEMBUFFER_TAG_ARG
> + apr_pool_t *pool)
> +{
> + apr_uint32_t group_index;
> + unsigned char to_find[KEY_SIZE];
> + entry_t *entry;
> + svn_error_t *err = SVN_NO_ERROR;
> +
> + /* cache item lookup
> + */
> + group_index = get_group_index(&cache, key, key_len, to_find, pool);
> +
> + SVN_ERR(lock_cache(cache));
> +
> + entry = find_entry(cache, group_index, to_find, FALSE);
> + cache->total_reads++;
> +
> + /* this function is a no-op if the item is not in cache
> + */
> + if (entry != NULL)
> + {
> + /* access the serialized cache item */
> + char *data = (char*)cache->data + entry->offset;
> + char *orig_data = data;
> + apr_size_t size = entry->size;
> +
> + entry->hit_count++;
> + cache->hit_count++;
> + cache->total_writes++;
> +
> +#ifdef DEBUG_CACHE_MEMBUFFER
> +
> + /* Check for overlapping entries.
> + */
> + SVN_ERR_ASSERT(entry->next == NO_INDEX ||
> + entry->offset + size
> + <= get_entry(cache, entry->next)->offset);
> +
> + /* Compare original content, type and key (hashes)
> + */
> + SVN_ERR(store_content_part(tag, data, size, pool));
> + SVN_ERR(assert_equal_tags(&entry->tag, tag));
> +
> +#endif
> +
> + /* modify it, preferrably in-situ.
> + */
> + err = func(&data, &size, baton, pool);
> +
> + /* if modification caused a re-allocation, we need to remove the old
> + * entry and to copy the new data back into cache.
> + */
> + if (data != orig_data)
Shouldn't you be checking ERR before storing the change made by FUNC?
> + {
> + /* Remove the old entry and try to make space for the new one.
> + */
> + drop_entry(cache, entry);
> + if ( (cache->data_size / 4 > size)
> + && ensure_data_insertable(cache, size))
> + {
> + /* Write the new entry.
> + */
> + entry->size = size;
> + entry->offset = cache->current_data;
> + if (size)
> + memcpy(cache->data + entry->offset, data, size);
> +
> + /* Link the entry properly.
> + */
> + insert_entry(cache, entry);
> +
> +#ifdef DEBUG_CACHE_MEMBUFFER
> +
> + /* Remember original content, type and key (hashes)
> + */
> + SVN_ERR(store_content_part(tag, data, size, pool));
> + memcpy(&entry->tag, tag, sizeof(*tag));
> +
> +#endif
> + }
> + }
> + }
> +
> + /* done here -> unlock the cache
> + */
> + return unlock_cache(cache, err);
> +}
> +
