Make ipc work 100% async.

The connect & accept logic for IPC is now fully asynchronous.
This will serve as a straight-forward template for TCP. Note that
the upper logic still uses a thread to run this "synchronously", but
that will be able to be removed once the last transport (TCP) is made
fully async.

The unified ipcsock is also now separated, and we anticipate being
able to remove the posix_sock.c logic shortly.  Separating out the
endpoint logic from the pipe logic helps makes things clearer, and
may faciliate a day where endpoints have multiple addresses (for
example with a connect() endpoint that uses a round-robin DNS list
and tries to run the entire list in parallel, stopping with the first
connection made.)

The platform header got a little cleanup while we were here.

1 files changed, 75 insertions, 39 deletions

diff --git a/src/core/platform.h b/src/core/platform.h
index 7e6dfbbe..971c6a5d 100644
--- a/src/core/platform.h
+++ b/src/core/platform.h
@@ -37,6 +37,10 @@
 // they do not need in the child.  (Note that posix_spawn() does *NOT*
 // arrange for pthread_atfork() handlers to be called on some platforms.)
 
+//
+// Debugging Support
+//
+
 // nni_plat_abort crashes the system; it should do whatever is appropriate
 // for abnormal programs on the platform, such as calling abort().
 extern void nni_plat_abort(void);
@@ -46,6 +50,18 @@ extern void nni_plat_abort(void);
 // not contain newlines, but the output will add them.
 extern void nni_plat_println(const char *);
 
+// nni_plat_strerror allows the platform to use additional error messages
+// for additional error codes.  The err code passed in should be the
+// equivalent of errno or GetLastError, without the NNG_ESYSERR component.
+// The platform should make sure that the returned value will be valid
+// after the call returns.  (If necessary, thread-local storage can be
+// used.)
+extern const char *nni_plat_strerror(int);
+
+//
+// Memory Management
+//
+
 // nni_alloc allocates memory.  In most cases this can just be malloc().
 // However, you may provide a different allocator, for example it is
 // possible to use a slab allocator or somesuch.  It is permissible for this
@@ -64,9 +80,10 @@ typedef struct nni_plat_mtx		nni_plat_mtx;
 typedef struct nni_plat_cv		nni_plat_cv;
 typedef struct nni_plat_thr		nni_plat_thr;
 typedef struct nni_plat_tcpsock		nni_plat_tcpsock;
-typedef struct nni_plat_ipcsock		nni_plat_ipcsock;
 
-// Mutex handling.
+//
+// Threading & Synchronization Support
+//
 
 // nni_plat_mtx_init initializes a mutex structure.  This may require dynamic
 // allocation, depending on the platform.  It can return NNG_ENOMEM if that
@@ -127,6 +144,10 @@ extern int nni_plat_thr_init(nni_plat_thr *, void (*)(void *), void *);
 // is an error to reference the thread in any further way.
 extern void nni_plat_thr_fini(nni_plat_thr *);
 
+//
+// Clock Support
+//
+
 // nn_plat_clock returns a number of microseconds since some arbitrary time
 // in the past.  The values returned by nni_clock must use the same base
 // as the times used in nni_plat_cond_waituntil.  The nni_plat_clock() must
@@ -138,6 +159,16 @@ extern nni_time nni_plat_clock(void);
 // nni_plat_usleep sleeps for the specified number of microseconds (at least).
 extern void nni_plat_usleep(nni_duration);
 
+//
+// Entropy Support
+//
+
+// nni_plat_seed_prng seeds the PRNG subsystem.  The specified number
+// of bytes of entropy should be stashed.  When possible, cryptographic
+// quality entropy sources should be used.  Note that today we prefer
+// to seed up to 256 bytes of data.
+extern void nni_plat_seed_prng(void *, size_t);
+
 // nni_plat_init is called to allow the platform the chance to
 // do any necessary initialization.  This routine MUST be idempotent,
 // and threadsafe, and will be called before any other API calls, and
@@ -157,13 +188,6 @@ extern int nni_plat_init(int (*)(void));
 // will be called until nni_platform_init is called.
 extern void nni_plat_fini(void);
 
-// nni_plat_strerror allows the platform to use additional error messages
-// for additional error codes.  The err code passed in should be the
-// equivalent of errno or GetLastError, without the NNG_ESYSERR component.
-// The platform should make sure that the returned value will be valid
-// after the call returns.  (If necessary, thread-local storage can be
-// used.)
-extern const char *nni_plat_strerror(int);
 
 // nni_plat_lookup_host looks up a hostname in DNS, or the local hosts
 // file, or whatever.  If your platform lacks support for naming, it must
@@ -172,6 +196,10 @@ extern const char *nni_plat_strerror(int);
 // returned on dual stack machines.
 extern int nni_plat_lookup_host(const char *, nni_sockaddr *, int);
 
+//
+// TCP Support.
+//
+
 // nni_plat_tcp_init initializes the socket, for example it can
 // set underlying file descriptors to -1, etc.
 extern int nni_plat_tcp_init(nni_plat_tcpsock **);
@@ -214,48 +242,56 @@ extern void nni_plat_tcp_aio_send(nni_plat_tcpsock *, nni_aio *);
 // full, or an error condition occurs.
 extern void nni_plat_tcp_aio_recv(nni_plat_tcpsock *, nni_aio *);
 
-// nni_plat_ipc_init initializes the socket, for example it can
-// set underlying file descriptors to -1, etc.
-extern int nni_plat_ipc_init(nni_plat_ipcsock **);
+//
+// IPC (UNIX Domain Sockets & Named Pipes) Support.
+//
 
-// nni_plat_ipc_fini just closes an IPC socket, and releases any related
-// resources.
-extern void nni_plat_ipc_fini(nni_plat_ipcsock *);
+typedef struct nni_plat_ipc_ep		nni_plat_ipc_ep;
+typedef struct nni_plat_ipc_pipe	nni_plat_ipc_pipe;
 
-// nni_plat_ipc_shutdown performs a shutdown of the socket.  For
-// BSD sockets, this closes both sides of the IPC connection gracefully,
-// but the underlying file descriptor is left open.  (This part is critical
-// to prevention of close() related races.)
-extern void nni_plat_ipc_shutdown(nni_plat_ipcsock *);
+// nni_plat_ipc_ep_init creates a new endpoint associated with the path.
+extern int nni_plat_ipc_ep_init(nni_plat_ipc_ep **, const char *);
+
+// nni_plat_ipc_ep_fini closes the endpoint and releases resources.
+extern void nni_plat_ipc_ep_fini(nni_plat_ipc_ep *);
+
+// nni_plat_ipc_ep_close closes the endpoint; this might not close the
+// actual underlying socket, but it should call shutdown on it.
+// Further operations on the pipe should return NNG_ECLOSED.
+extern void nni_plat_ipc_ep_close(nni_plat_ipc_ep *);
 
 // nni_plat_tcp_listen creates an IPC socket in listening mode, bound
 // to the specified path.  Note that nni_plat_ipcsock should be defined
 // to whatever your platform uses.  For most systems its just "int".
-extern int nni_plat_ipc_listen(nni_plat_ipcsock *, const char *);
+extern int nni_plat_ipc_ep_listen(nni_plat_ipc_ep *);
 
-// nni_plat_ipc_accept does the accept to accept an inbound connection.
-// The ipcsock used for the server will have been set up with the
-// nni_plat_ipc_listen.
-extern int nni_plat_ipc_accept(nni_plat_ipcsock *, nni_plat_ipcsock *);
+// nni_plat_ipc_ep_accept starts an accept to receive an incoming connection.
+// An accepted connection will be passed back in the a_pipe member.
+extern void nni_plat_ipc_ep_accept(nni_plat_ipc_ep *, nni_aio *);
 
 // nni_plat_ipc_connect is the client side.
-extern int nni_plat_ipc_connect(nni_plat_ipcsock *, const char *);
+// An accepted connection will be passed back in the a_pipe member.
+extern void nni_plat_ipc_ep_connect(nni_plat_ipc_ep *, nni_aio *);
 
-// nni_plat_ipc_aio_send sends data to the peer.  The platform is responsible
-// for attempting to send all of the data.  The iov count will never be
-// larger than 4.  The platform may modify the iovs.
-extern void nni_plat_ipc_send(nni_plat_ipcsock *, nni_aio *);
+// nni_plat_ipc_pipe_fini closes the pipe, and releases all resources
+// associated with it.
+extern void nni_plat_ipc_pipe_fini(nni_plat_ipc_pipe *);
 
-// nni_plat_ipc_aio_recv recvs data into the buffers provided by the
-// iovs.  The implementation does not return until the iovs are completely
-// full, or an error condition occurs.
-extern void nni_plat_ipc_recv(nni_plat_ipcsock *, nni_aio *);
+// nni_plat_ipc_pipe_close closes the socket, or at least shuts it down.
+// Further operations on the pipe should return NNG_ECLOSED.
+extern void nni_plat_ipc_pipe_close(nni_plat_ipc_pipe *);
 
-// nni_plat_seed_prng seeds the PRNG subsystem.  The specified number
-// of bytes of entropy should be stashed.  When possible, cryptographic
-// quality entropy sources should be used.  Note that today we prefer
-// to seed up to 256 bytes of data.
-extern void nni_plat_seed_prng(void *, size_t);
+// nni_plat_ipc_pipe_send sends data in the iov buffers to the peer.
+// The platform may modify the iovs.
+extern void nni_plat_ipc_pipe_send(nni_plat_ipc_pipe *, nni_aio *);
+
+// nni_plat_ipc_pipe_recv recvs data into the buffers provided by the iovs.
+// The platform may modify the iovs.
+extern void nni_plat_ipc_pipe_recv(nni_plat_ipc_pipe *, nni_aio *);
+
+//
+// Notification Pipe Pairs
+//
 
 // nni_plat_pipe creates a pair of linked file descriptors that are
 // suitable for notification via SENDFD/RECVFD.  These are platform