Addition of the module utilities functions

server/core/modutil.c

@@ -0,0 +1,121 @@
+/*
+ * This file is distributed as part of MaxScale from SkySQL.  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 2014
+ */
+
+/**
+ * @file modutil.c  - Implementation of useful routines for modules
+ *
+ * @verbatim
+ * Revision History
+ *
+ * Date		Who		Description
+ * 04/06/14	Mark Riddoch	Initial implementation
+ *
+ * @endverbatim
+ */
+#include <buffer.h>
+
+/**
+ * Check if a GWBUF structure is a MySQL COM_QUERY packet
+ *
+ * @param	buf	Buffer to check
+ * @return	True if GWBUF is a COM_QUERY packet
+ */
+int
+modutil_is_SQL(GWBUF *buf)
+{
+unsigned char	*ptr;
+
+	if (GWBUF_LENGTH(buf) < 5)
+		return 0;
+	ptr = GWBUF_DATA(buf);
+	return ptr[4] == 0x03;		// COM_QUERY
+}
+
+/**
+ * Extract the SQL portion of a COM_QUERY packet
+ *
+ * NB This sets *sql to point into the packet and does not
+ * allocate any new storage. The string pointed to by *sql is
+ * not NULL terminated.
+ *
+ * This routine is very simplistic and does not deal with SQL text
+ * that spans multiple buffers.
+ *
+ * @param	buf	The packet buffer
+ * @param	sql	Pointer that is set to point at the SQL data
+ * @param	length	Length of the SQL data
+ * @return	True if the packet is a COM_QUERY packet
+ */
+int
+modutil_extract_SQL(GWBUF *buf, char **sql, int *length)
+{
+char	*ptr;
+
+	if (!modutil_is_SQL(buf))
+		return 0;
+	ptr = GWBUF_DATA(buf);
+	*length = *ptr++;
+	*length += (*ptr++ << 8);
+	*length += (*ptr++ << 8);
+        ptr += 2;  // Skip sequence id	and COM_QUERY byte
+	*length = *length - 1;
+	*sql = ptr;
+}
+
+
+GWBUF *
+modutil_replace_SQL(GWBUF *orig, char *sql)
+{
+char	*ptr;
+int	length, newlength;
+GWBUF	*addition;
+
+	if (!modutil_is_SQL(orig))
+		return 0;
+	ptr = GWBUF_DATA(orig);
+	length = *ptr++;
+	length += (*ptr++ << 8);
+	length += (*ptr++ << 8);
+        ptr += 2;  // Skip sequence id	and COM_QUERY byte
+
+	newlength = strlen(sql);
+	if (length - 1 == newlength)
+	{
+		/* New SQL is the same length as old */
+		memcpy(ptr, sql, newlength);
+	}
+	else if (length - 1 > newlength)
+	{
+		/* New SQL is shorter */
+		memcpy(ptr, sql, newlength);
+		GWBUF_RTRIM(orig, (length - 1) - newlength);
+	}
+	else
+	{
+		memcpy(ptr, sql, length - 1);
+		addition = gwbuf_alloc(newlength - (length - 1));
+		memcpy(GWBUF_DATA(addition), &sql[length - 1], newlength - (length - 1));
+		ptr = GWBUF_DATA(orig);
+		*ptr++ = (newlength + 1) & 0xff;
+		*ptr++ = ((newlength + 1) >> 8) & 0xff;
+		*ptr++ = ((newlength + 1) >> 16) & 0xff;
+		orig->next = addition;
+	}
+
+	return orig;
+}