Lay Pure out as a core with the parts selected around it

The app model, the tree store and the HTTP host lived in
prototypes/connections among the earlier document runtime, the store was
known only by its format's name, and Vega compiled six Pure sources by path.
Now, as the README's principle has it:

  core/   runtime, flow and the app model (module*.c), with what the core
          asks of storage (state.h, store.h)
  store/  the tree store (PURETRE3, PUREREC1)
  serve/  pure-serve: HTTP host, outbound delivery, JSON in place
  cli/    pure-run, pure-edit-module

A top-level make builds libpure.a (app model and store, for hosts to link)
and the hosts; make check runs the store's and the app model's tests. The
earlier runtime still builds from prototypes/connections against core/ and
store/ (check, check-tree and check-core pass). Design 009 records the rule:
parts by role behind libraries; git repositories split by coupling, so the
store stays here while its contract moves with the core, and Vega stays apart.

1 files changed, 25 insertions, 0 deletions

diff --git a/core/flow.h b/core/flow.h
new file mode 100644
index 0000000..6e27c58
--- /dev/null
+++ b/core/flow.h
@@ -0,0 +1,25 @@
+#ifndef PURE_FLOW_H
+#define PURE_FLOW_H
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef struct { const unsigned char *data; size_t size; } PureSpan;
+typedef void (*PureRelease)(void *owner);
+
+/* A borrowed body stays alive until every byte is consumed or the transfer is
+ * aborted. A successful send() consumes bytes; peer receipt is a separate fact.
+ * Single owner thread; callbacks must not reenter or reuse this transfer. */
+typedef struct {
+    PureSpan spans[2];
+    size_t part, offset;
+    void *owner;
+    PureRelease release;
+    bool active;
+} PureTransfer;
+
+void pure_transfer_init(PureTransfer *, PureSpan header, PureSpan body,
+                        void *owner, PureRelease);
+PureSpan pure_transfer_next(const PureTransfer *, size_t limit);
+bool pure_transfer_consume(PureTransfer *, size_t bytes);
+void pure_transfer_abort(PureTransfer *);
+#endif