api: Remove the NNG_FLAG_ALLOC

This flag failed to provide real zero copy that it was intended for,
and it also involved extra allocations.  Further, the API for it was
brittle and error prone.

Modern code should just work directly with nng_msg structures.

3 files changed, 21 insertions, 52 deletions

diff --git a/src/core/sock_test.c b/src/core/sock_test.c
index e311634d..f6f1bd7d 100644
--- a/src/core/sock_test.c
+++ b/src/core/sock_test.c
@@ -102,8 +102,8 @@ test_send_recv(void)
 	int          len;
 	size_t       sz;
 	nng_duration to = 3000; // 3 seconds
-	char        *buf;
-	char        *a = "inproc://t1";
+	char        *a  = "inproc://t1";
+	char         rxbuf[32];
 
 	NUTS_OPEN(s1);
 	NUTS_OPEN(s2);
@@ -124,11 +124,10 @@ test_send_recv(void)
 	NUTS_PASS(nng_dial(s2, a, NULL, 0));
 
 	NUTS_PASS(nng_send(s1, "abc", 4, 0));
-	NUTS_PASS(nng_recv(s2, &buf, &sz, NNG_FLAG_ALLOC));
-	NUTS_TRUE(buf != NULL);
+	sz = sizeof(rxbuf);
+	NUTS_PASS(nng_recv(s2, rxbuf, &sz, 0));
 	NUTS_TRUE(sz == 4);
-	NUTS_TRUE(memcmp(buf, "abc", 4) == 0);
-	nng_free(buf, sz);
+	NUTS_TRUE(memcmp(rxbuf, "abc", 4) == 0);
 
 	NUTS_CLOSE(s1);
 	NUTS_CLOSE(s2);
@@ -142,7 +141,7 @@ test_send_recv_zero_length(void)
 	int          len;
 	size_t       sz;
 	nng_duration to = 3000; // 3 seconds
-	char        *buf;
+	char         buf[32];
 	char        *a = "inproc://send-recv-zero-length";
 
 	NUTS_OPEN(s1);
@@ -164,10 +163,9 @@ test_send_recv_zero_length(void)
 	NUTS_PASS(nng_dial(s2, a, NULL, 0));
 
 	NUTS_PASS(nng_send(s1, "", 0, 0));
-	NUTS_PASS(nng_recv(s2, &buf, &sz, NNG_FLAG_ALLOC));
-	NUTS_TRUE(buf == NULL);
+	sz = sizeof(buf);
+	NUTS_PASS(nng_recv(s2, buf, &sz, 0));
 	NUTS_TRUE(sz == 0);
-	nng_free(buf, sz);
 
 	NUTS_CLOSE(s1);
 	NUTS_CLOSE(s2);
@@ -186,7 +184,7 @@ test_connection_refused(void)
 void
 test_late_connection(void)
 {
-	char      *buf;
+	char       buf[32];
 	size_t     sz;
 	nng_socket s1;
 	nng_socket s2;
@@ -202,10 +200,10 @@ test_late_connection(void)
 	NUTS_PASS(nng_listen(s2, a, NULL, 0));
 	nng_msleep(100);
 	NUTS_PASS(nng_send(s1, "abc", 4, 0));
-	NUTS_PASS(nng_recv(s2, &buf, &sz, NNG_FLAG_ALLOC));
+	sz = sizeof(buf);
+	NUTS_PASS(nng_recv(s2, &buf, &sz, 0));
 	NUTS_TRUE(sz == 4);
 	NUTS_TRUE(memcmp(buf, "abc", 4) == 0);
-	nng_free(buf, sz);
 
 	NUTS_CLOSE(s1);
 	NUTS_CLOSE(s2);
diff --git a/src/nng.c b/src/nng.c
index 55e23214..c4bad311 100644
--- a/src/nng.c
+++ b/src/nng.c
@@ -79,35 +79,12 @@ nng_recv(nng_socket s, void *buf, size_t *szp, int flags)
 
 	// Note that while it would be nice to make this a zero copy operation,
 	// its not normally possible if a size was specified.
-	if ((rv = nng_recvmsg(s, &msg, flags & ~(NNG_FLAG_ALLOC))) != 0) {
+	if ((rv = nng_recvmsg(s, &msg, flags)) != 0) {
 		return (rv);
 	}
-	if (!(flags & NNG_FLAG_ALLOC)) {
-		memcpy(buf, nng_msg_body(msg),
-		    *szp > nng_msg_len(msg) ? nng_msg_len(msg) : *szp);
-		*szp = nng_msg_len(msg);
-	} else {
-		// We'd really like to avoid a separate data copy, but since
-		// we have allocated messages with headroom, we can't really
-		// make free() work on the base pointer.  We'd have to have
-		// some other API for this.  Folks that want zero copy had
-		// better use nng_recvmsg() instead.
-		void *nbuf;
-
-		if (nng_msg_len(msg) != 0) {
-			if ((nbuf = nni_alloc(nng_msg_len(msg))) == NULL) {
-				nng_msg_free(msg);
-				return (NNG_ENOMEM);
-			}
-
-			*(void **) buf = nbuf;
-			memcpy(nbuf, nni_msg_body(msg), nni_msg_len(msg));
-			*szp = nng_msg_len(msg);
-		} else {
-			*(void **) buf = NULL;
-			*szp           = 0;
-		}
-	}
+	memcpy(buf, nng_msg_body(msg),
+	    *szp > nng_msg_len(msg) ? nng_msg_len(msg) : *szp);
+	*szp = nng_msg_len(msg);
 	nni_msg_free(msg);
 	return (0);
 }
@@ -159,10 +136,6 @@ nng_send(nng_socket s, void *buf, size_t len, int flags)
 	if ((rv = nng_sendmsg(s, msg, flags)) != 0) {
 		// If nng_sendmsg() succeeded, then it took ownership.
 		nng_msg_free(msg);
-	} else {
-		if (flags & NNG_FLAG_ALLOC) {
-			nni_free(buf, len);
-		}
 	}
 	return (rv);
 }
diff --git a/src/sp/nonblock_test.c b/src/sp/nonblock_test.c
index 7b2251c4..c06fa64d 100644
--- a/src/sp/nonblock_test.c
+++ b/src/sp/nonblock_test.c
@@ -1,5 +1,5 @@
 //
-// Copyright 2024 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2025 Staysail Systems, Inc. <info@staysail.tech>
 // Copyright 2018 Capitar IT Group BV <info@capitar.com>
 //
 // This software is supplied under the terms of the MIT License, a
@@ -46,8 +46,7 @@ repthr(void *arg)
 	for (;;) {
 		fd_set         fset;
 		struct timeval tmo;
-		char          *msgbuf;
-		size_t         msglen;
+		nng_msg       *msg;
 
 		FD_ZERO(&fset);
 		FD_SET(fd, &fset);
@@ -59,14 +58,13 @@ repthr(void *arg)
 
 		for (;;) {
 			int rv;
-			rv = nng_recv(rep, &msgbuf, &msglen,
-			    NNG_FLAG_NONBLOCK | NNG_FLAG_ALLOC);
+			rv = nng_recvmsg(rep, &msg, NNG_FLAG_NONBLOCK);
 			if (rv != 0) {
 				return;
 			}
-			nng_free(msgbuf, msglen);
-			int ok = 0;
-			rv     = nng_send(rep, &ok, 4, NNG_FLAG_NONBLOCK);
+			nng_msg_clear(msg);
+			nng_msg_append_u32(msg, 0);
+			rv = nng_sendmsg(rep, msg, NNG_FLAG_NONBLOCK);
 			if (rv == NNG_ECLOSED) {
 				return;
 			}