MINOR: sample: Add converters to parse FIX messages

This patch implements a couple of converters to validate and extract tag value
from a FIX (Financial Information eXchange) message. The validation consists in
a few checks such as mandatory fields and checksum computation. The extraction
can get any tag value based on a tag string or tag id.

This patch requires the istend() function. Thus it depends on "MINOR: ist: Add
istend() function to return a pointer to the end of the string".

Reviewed and Fixed by Christopher Faulet <cfaulet@haproxy.com>

include/haproxy/fix-t.h

@@ -0,0 +1,70 @@
+/*
+ * include/haproxy/fix-t.h
+ * This file contains structure declarations for FIX protocol.
+ *
+ * Copyright 2020 Baptiste Assmann <bedis9@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef _HAPROXY_FIX_T_H
+#define _HAPROXY_FIX_T_H
+
+#include <import/ist.h>
+
+/*
+ * FIX messages are composed by a list of Tag=Value separated by a 'delimiter'
+ */
+#define FIX_DELIMITER 0x01
+
+/*
+ * know FIX version strings
+ */
+#define FIX_4_0     (ist("FIX.4.0"))
+#define FIX_4_1     (ist("FIX.4.1"))
+#define FIX_4_2     (ist("FIX.4.2"))
+#define FIX_4_3     (ist("FIX.4.3"))
+#define FIX_4_4     (ist("FIX.4.4"))
+#define FIX_5_0     (ist("FIXT.1.1"))
+/* FIX_5_0SP1 and FIX_5_0SP2 have the same version string than FIX5_0 */
+
+/*
+ * Supported FIX tag ID
+ */
+#define FIX_TAG_BeginString    8
+#define FIX_TAG_BodyLength     9
+#define FIX_TAG_CheckSum       10
+#define FIX_TAG_MsgType        35
+#define FIX_TAG_SenderComID    49
+#define FIX_TAG_TargetComID    56
+
+
+#define FIX_MSG_MINSIZE        26 /* Minimal length for a FIX Message */
+#define FIX_CHKSUM_SIZE        7  /* Length of the CheckSum tag (10=NNN<delim>) */
+/*
+ * return code when parsing / validating FIX messages
+ */
+#define FIX_INVALID_MESSAGE   -1
+#define FIX_NEED_MORE_DATA     0
+#define FIX_VALID_MESSAGE      1
+
+#endif /* _HAPROXY_FIX_T_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */

include/haproxy/fix.h

@@ -0,0 +1,97 @@
+/*
+ * include/haproxy/fix.h
+ * This file contains functions and macros declarations for FIX protocol decoding.
+ *
+ * Copyright 2020 Baptiste Assmann <bedis9@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef _HAPROXY_FIX_H
+#define _HAPROXY_FIX_H
+
+#include <import/ist.h>
+
+#include <haproxy/fix-t.h>
+#include <haproxy/tools.h>
+
+unsigned int fix_check_id(const struct ist str, const struct ist version);
+int fix_validate_message(const struct ist msg);
+struct ist fix_tag_value(const struct ist msg, unsigned int tagid);
+
+/*
+ * Return the FIX version string (one of FIX_X_Y macros) correspoding to
+ * <str> or IST_NULL if not found.
+ */
+static inline struct ist fix_version(const struct ist str)
+{
+	/* 7 is the minimal size for the FIX version string */
+	if (istlen(str) < 7)
+		return IST_NULL;
+
+	if (isteq(FIX_4_0, str))
+		return FIX_4_0;
+	else if (isteq(FIX_4_1, str))
+		return FIX_4_1;
+	else if (isteq(FIX_4_2, str))
+		return FIX_4_2;
+	else if (isteq(FIX_4_3, str))
+		return FIX_4_3;
+	else if (isteq(FIX_4_4, str))
+		return FIX_4_4;
+	else if (isteq(FIX_5_0, str))
+		return FIX_5_0;
+
+	return IST_NULL;
+}
+
+/*
+ * Return the FIX tag ID corresponding to <tag> if one found or 0 if not.
+ *
+ * full list of tag ID available here, just in case we need to support
+ * more "string" equivalent in the future:
+ *   https://www.onixs.biz/fix-dictionary/4.2/fields_by_tag.html
+ */
+static inline unsigned int fix_tagid(const struct ist tag)
+{
+	unsigned id = fix_check_id(tag, IST_NULL);
+
+	if (id)
+		return id;
+
+	else if (isteqi(tag, ist("MsgType")))
+		return FIX_TAG_MsgType;
+	else if (isteqi(tag, ist("CheckSum")))
+		return FIX_TAG_CheckSum;
+	else if (isteqi(tag, ist("BodyLength")))
+		return FIX_TAG_BodyLength;
+	else if (isteqi(tag, ist("TargetComID")))
+		return FIX_TAG_TargetComID;
+	else if (isteqi(tag, ist("BeginString")))
+		return FIX_TAG_BeginString;
+	else if (isteqi(tag, ist("SenderComID")))
+		return FIX_TAG_SenderComID;
+
+	return 0;
+}
+
+#endif /* _HAPROXY_FIX_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */