Split the backend read function as an example, this still needs to be reorganised into protocols

Addition of DCB diagnostics, and free routine

core/dcb.c

@@ -0,0 +1,168 @@
+/*
+ * This file is distributed as part of the SkySQL Gateway.  It is free
+ * software: you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation,
+ * version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Copyright SkySQL Ab 2013
+ */
+
+/*
+ * dcb.c  -  Descriptor Control Block generic functions
+ *
+ * Revision History
+ *
+ * Date		Who		Description
+ * 12/06/13	Mark Riddoch	Initial implementation
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <dcb.h>
+#include <spinlock.h>
+
+static	DCB		*allDCBs = NULL;	/* Diagnotics need a list of DCBs */
+static	SPINLOCK	*dcbspin = NULL;
+
+/*
+ * Allocate a new DCB. 
+ *
+ * This routine performs the generic initialisation on the DCB before returning
+ * the newly allocated DCB.
+ *
+ * @return A newly allocated DCB or NULL if non could be allocated.
+ */
+DCB *
+alloc_dcb()
+{
+DCB	*rval;
+
+	if (dcbspin == NULL)
+	{
+		if ((dcbspin = malloc(sizeof(SPINLOCK))) == NULL)
+			return NULL;
+		spinlock_init(dcbspin);
+	}
+
+	if ((rval = malloc(sizeof(DCB))) == NULL)
+	{
+		return NULL;
+	}
+	spinlock_init(&rval->writeqlock);
+	rval->writeq = NULL;
+	rval->state = DCB_STATE_ALLOC;
+
+	spinlock_acquire(dcbspin);
+	if (allDCBs == NULL)
+		allDCBs = rval;
+	else
+	{
+		DCB *ptr = allDCBs;
+		while (ptr->next)
+			ptr = ptr->next;
+		ptr->next = rval;
+	}
+	spinlock_release(dcbspin);
+	return rval;
+}
+
+/*
+ * Free a DCB and remove it from the chain of all DCBs
+ *
+ * @param dcb THe DCB to free
+ */
+void
+free_dcb(DCB *dcb)
+{
+	dcb->state = DCB_STATE_FREED;
+
+	/* First remove this DCB from the chain */
+	spinlock_acquire(dcbspin);
+	if (allDCBs == dcb)
+		allDCBs = dcb->next;
+	else
+	{
+		DCB *ptr = allDCBs;
+		while (ptr && ptr->next != dcb)
+			ptr = ptr->next;
+		if (ptr)
+			ptr->next = dcb->next;
+	}
+	spinlock_release(dcbspin);
+
+	free(dcb);
+}
+
+/*
+ * Diagnostic to print a DCB
+ *
+ * @param dcb	The DCB to print
+ *
+ */
+void
+printDCB(DCB *dcb)
+{
+	(void)printf("DCB: 0x%x\n", (void *)dcb);
+	(void)printf("\tDCB state: %s\n", gw_dcb_state2string(dcb->state));
+	(void)printf("\tQueued write data: %d\n", gwbuf_length(dcb->writeq));
+}
+
+/*
+ * Diagnostic to print all DCB allocated in the system
+ *
+ */
+void printAllDCBs()
+{
+DCB	*dcb;
+
+	if (dcbspin == NULL)
+	{
+		if ((dcbspin = malloc(sizeof(SPINLOCK))) == NULL)
+			return;
+		spinlock_init(dcbspin);
+	}
+	spinlock_acquire(dcbspin);
+	dcb = allDCBs;
+	while (dcb)
+	{
+		printDCB(dcb);
+		dcb = dcb->next;
+	}
+	spinlock_release(dcbspin);
+}
+
+/*
+ * Return a string representation of a DCB state.
+ *
+ * @param state	The DCB state
+ * @return String representation of the state
+ *
+ */
+const char *
+gw_dcb_state2string (int state) {
+	switch(state) {
+		case DCB_STATE_ALLOC:
+			return "DCB Allocated";
+		case DCB_STATE_IDLE:
+			return "DCB not yet in polling";
+		case DCB_STATE_POLLING:
+			return "DCB in the EPOLL";
+		case DCB_STATE_PROCESSING:
+			return "DCB processing event";
+		case DCB_STATE_LISTENING:
+			return "DCB for listening socket";
+		case DCB_STATE_DISCONNECTED:
+			return "DCB socket closed";
+		default:
+			return "DCB (unknown)";
+	}
+}