From c7eee6f7c3f5426964c07c6bd9a44247c2017d4e Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Thu, 6 Jan 2022 15:11:22 +0100
Subject: [PATCH 1/3] Refactor to remove internal_cancel helper

To simplify future changes to PQcancel this removes the internal_cancel
helper function. Now PQrequestCancel calls PQcancel internally, instead
of having both PQcancel and PQrequestCancel call the shared
internal_cancel helper function.
---
 src/interfaces/libpq/fe-connect.c | 58 ++++++++++++-------------------
 1 file changed, 22 insertions(+), 36 deletions(-)

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 9b6a6939f0..85fce856a5 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -4406,14 +4406,17 @@ PQfreeCancel(PGcancel *cancel)
 
 
 /*
- * PQcancel and PQrequestCancel: attempt to request cancellation of the
- * current operation.
+ * PQcancel: request query cancel
  *
  * The return value is true if the cancel request was successfully
  * dispatched, false if not (in which case an error message is available).
  * Note: successful dispatch is no guarantee that there will be any effect at
  * the backend.  The application must read the operation result as usual.
  *
+ * On failure, an error message is stored in *errbuf, which must be of size
+ * errbufsize (recommended size is 256 bytes).  *errbuf is not changed on
+ * success return.
+ *
  * CAUTION: we want this routine to be safely callable from a signal handler
  * (for example, an application might want to call it in a SIGINT handler).
  * This means we cannot use any C library routine that might be non-reentrant.
@@ -4421,13 +4424,9 @@ PQfreeCancel(PGcancel *cancel)
  * just as dangerous.  We avoid sprintf here for that reason.  Building up
  * error messages with strcpy/strcat is tedious but should be quite safe.
  * We also save/restore errno in case the signal handler support doesn't.
- *
- * internal_cancel() is an internal helper function to make code-sharing
- * between the two versions of the cancel function possible.
  */
-static int
-internal_cancel(SockAddr *raddr, int be_pid, int be_key,
-				char *errbuf, int errbufsize)
+int
+PQcancel(PGcancel *cancel, char *errbuf, int errbufsize)
 {
 	int			save_errno = SOCK_ERRNO;
 	pgsocket	tmpsock = PGINVALID_SOCKET;
@@ -4439,18 +4438,24 @@ internal_cancel(SockAddr *raddr, int be_pid, int be_key,
 		CancelRequestPacket cp;
 	}			crp;
 
+	if (!cancel)
+	{
+		strlcpy(errbuf, "PQcancel() -- no cancel object supplied", errbufsize);
+		return false;
+	}
+
 	/*
 	 * We need to open a temporary connection to the postmaster. Do this with
 	 * only kernel calls.
 	 */
-	if ((tmpsock = socket(raddr->addr.ss_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
+	if ((tmpsock = socket(cancel->raddr.addr.ss_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
 	{
 		strlcpy(errbuf, "PQcancel() -- socket() failed: ", errbufsize);
 		goto cancel_errReturn;
 	}
 retry3:
-	if (connect(tmpsock, (struct sockaddr *) &raddr->addr,
-				raddr->salen) < 0)
+	if (connect(tmpsock, (struct sockaddr *) &cancel->raddr.addr,
+				cancel->raddr.salen) < 0)
 	{
 		if (SOCK_ERRNO == EINTR)
 			/* Interrupted system call - we'll just try again */
@@ -4467,8 +4472,8 @@ retry3:
 
 	crp.packetlen = pg_hton32((uint32) sizeof(crp));
 	crp.cp.cancelRequestCode = (MsgType) pg_hton32(CANCEL_REQUEST_CODE);
-	crp.cp.backendPID = pg_hton32(be_pid);
-	crp.cp.cancelAuthCode = pg_hton32(be_key);
+	crp.cp.backendPID = pg_hton32(cancel->be_pid);
+	crp.cp.cancelAuthCode = pg_hton32(cancel->be_key);
 
 retry4:
 	if (send(tmpsock, (char *) &crp, sizeof(crp), 0) != (int) sizeof(crp))
@@ -4520,27 +4525,6 @@ cancel_errReturn:
 	return false;
 }
 
-/*
- * PQcancel: request query cancel
- *
- * Returns true if able to send the cancel request, false if not.
- *
- * On failure, an error message is stored in *errbuf, which must be of size
- * errbufsize (recommended size is 256 bytes).  *errbuf is not changed on
- * success return.
- */
-int
-PQcancel(PGcancel *cancel, char *errbuf, int errbufsize)
-{
-	if (!cancel)
-	{
-		strlcpy(errbuf, "PQcancel() -- no cancel object supplied", errbufsize);
-		return false;
-	}
-
-	return internal_cancel(&cancel->raddr, cancel->be_pid, cancel->be_key,
-						   errbuf, errbufsize);
-}
 
 /*
  * PQrequestCancel: old, not thread-safe function for requesting query cancel
@@ -4558,6 +4542,7 @@ int
 PQrequestCancel(PGconn *conn)
 {
 	int			r;
+	PGcancel   *cancel;
 
 	/* Check we have an open connection */
 	if (!conn)
@@ -4573,8 +4558,9 @@ PQrequestCancel(PGconn *conn)
 		return false;
 	}
 
-	r = internal_cancel(&conn->raddr, conn->be_pid, conn->be_key,
-						conn->errorMessage.data, conn->errorMessage.maxlen);
+	cancel = PQgetCancel(conn);
+	r = PQcancel(cancel, conn->errorMessage.data, conn->errorMessage.maxlen);
+	PQfreeCancel(cancel);
 
 	if (!r)
 		conn->errorMessage.len = strlen(conn->errorMessage.data);
-- 
2.17.1