Deliver wires on the sending loop, a step at a time (017, 2b-2)

A wire is now a sender of link/sending.h: its request goes on a
non-blocking socket as far as the socket takes it (connect, TLS
handshake, write, answer read), and its round waits for the socket or
its deadline (10 s with nothing moved). The answer is read as it comes:
the head whole, then a sized body counted down, a chunked one (few and
small) parsed again as it grows, or a body to the close. The crypto
table (version 6) takes the TLS handshake a step at a time, and reads
and writes say what they wait for. The owner pushes a wire once a turn,
as it does a link. A host whose app sends to ten links and ten wires
has 5 threads where it had 24 (none: 3).

1 files changed, 12 insertions, 3 deletions

diff --git a/link/tls.h b/link/tls.h
index 3939f21..232e192 100644
--- a/link/tls.h
+++ b/link/tls.h
@@ -8,10 +8,19 @@
 typedef struct PureTls PureTls;
 /* The context, made once; false with why in error when it cannot be. */
 bool pure_tls_start(const char *ca_file, char *error, size_t size);
-/* A session over a connected socket to host (a DNS name, or an IP address
- * written as one), its certificate verified; NULL when it fails. */
+/* A session over a connected, non-blocking socket to host (a DNS name, or
+ * an IP address written as one); NULL when it cannot be. Its handshake is
+ * made a step at a time, as the socket is ready, by pure_tls_step. */
 PureTls *pure_tls_open(const char *host, int fd);
-/* As SSL_read and SSL_write: the bytes moved, or <= 0. */
+/* What a step, a read or a write says when it moved no bytes: the session
+ * ended (the peer closed it), failed, or waits for the socket to be
+ * readable or writable (then the same again). */
+enum { PURE_TLS_CLOSED = 0, PURE_TLS_FAILED = -1, PURE_TLS_WANTS_READ = -2, PURE_TLS_WANTS_WRITE = -3 };
+/* The handshake: 1 once it is made and the receiver's certificate
+ * verified, else what it waits for, or PURE_TLS_FAILED. */
+int pure_tls_step(PureTls *);
+/* As SSL_read and SSL_write: the bytes moved (a write may move part), or
+ * one of the above. */
 int pure_tls_read(PureTls *, void *bytes, int size);
 int pure_tls_write(PureTls *, const void *bytes, int size);
 void pure_tls_close(PureTls *);