Lend a text state's stored extents for its view (079)

A view that shows a text state as it is (pure_module_text_state) now goes
out as the state's stored extents, as a document read does: the answer
holds the store mapping, charged to the budget, until it is sent and its
ticket released; a state with edits not yet stored is copied as before.
Documents and views share one loan path, and the extent array grows as
needed. A 1 MiB note read by 8 connections: 776-817 answers a second
copied, 1,875-1,901 lent, p50 9.2 to 3.5 ms, peak RSS 10.3 to 5.7 MiB.
The load generator learns GET /views/page.

1 files changed, 2 insertions, 2 deletions

diff --git a/prototypes/connections/state.h b/prototypes/connections/state.h
index 0945475..43489c1 100644
--- a/prototypes/connections/state.h
+++ b/prototypes/connections/state.h
@@ -34,8 +34,8 @@ PureResult pure_store_state(PureStore *, const char *name, PureDraft **out);
  * reference to the mapping a draft opened through a handle reads its stored
  * nodes from (NULL for other drafts). Spans that mapping holds stay readable
  * until the reference is released, after the draft closes and after the
- * store moves on. Spans of a draft's unsaved edits are not in it. Use it on
- * the handle's owner thread. */
+ * store moves on. Spans of a draft's unsaved edits are not in it. Take it on
+ * the handle's owner thread; the reference may be released on any thread. */
 typedef struct PureMapping PureMapping;
 PureMapping *pure_draft_mapping(const PureDraft *);
 bool pure_mapping_holds(const PureMapping *, PureSpan);