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, 34 insertions, 0 deletions

diff --git a/core/module-text.h b/core/module-text.h
new file mode 100644
index 0000000..4843928
--- /dev/null
+++ b/core/module-text.h
@@ -0,0 +1,34 @@
+#ifndef PURE_MODULE_TEXT_H
+#define PURE_MODULE_TEXT_H
+#include "flow.h"
+#include "state.h"
+#include <stdbool.h>
+#include <stddef.h>
+
+/* Text helpers of the module executor. Text is valid UTF-8; a character is a
+ * Unicode scalar value, so every position these return is a scalar boundary. */
+
+/* Strict UTF-8: no overlongs, surrogates or values past U+10FFFF. state
+ * carries a sequence split across spans; start it at 0 and finish with
+ * pure_utf8_complete. */
+bool pure_utf8_step(unsigned *state, PureSpan span);
+bool pure_utf8_complete(unsigned state);
+bool pure_utf8_valid(PureSpan span);
+
+/* Scalars (bytes that are not 10xxxxxx) and newlines in a span. */
+size_t pure_utf8_scalars(PureSpan span);
+size_t pure_utf8_newlines(PureSpan span);
+
+/* Shortest decimal that reads back to the same finite double: integers
+ * below 1e15 without a point or exponent, otherwise %g form with a trimmed
+ * exponent. -0 prints as 0. Returns the length written (at most 32). */
+size_t pure_format_number(double value, char out[32]);
+
+/* Positions in one version of a text draft (size is version.bytes). */
+size_t pure_text_step(const PureDraft *, PureVersion, size_t position, double count);
+size_t pure_text_line_step(const PureDraft *, PureVersion, size_t position, double count);
+size_t pure_text_line_start(const PureDraft *, PureVersion, size_t position);
+size_t pure_text_line_end(const PureDraft *, PureVersion, size_t position);
+/* Scalars (unit 0) or line number counting from 1 (unit 1) before position. */
+size_t pure_text_count(const PureDraft *, PureVersion, size_t position, unsigned unit);
+#endif