[syslog-ng] [PATCH] basicfuncs: Implement a $(substr START LEN STR) template function.

[Gergely Nagy]

This implements the $(substr) template function - a fairly primitive
one: it does error checking, but there's no error reporting present,
therefore invalid function calls will just get ignored.

Usage should be straightforward.

Reported-By: Jakub Jankowski <shasta at toxcorp.com>
Signed-off-by: Gergely Nagy <algernon at balabit.hu>
---
 modules/basicfuncs/basic-funcs.c |   46 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/modules/basicfuncs/basic-funcs.c b/modules/basicfuncs/basic-funcs.c
index 44b8af3..542c2ec 100644
--- a/modules/basicfuncs/basic-funcs.c
+++ b/modules/basicfuncs/basic-funcs.c
@@ -4,6 +4,9 @@
 #include "filter-expr-parser.h"
 #include "cfg.h"
 
+#include <stdlib.h>
+#include <errno.h>
+
 static void
 tf_echo(LogMessage *msg, gint argc, GString *argv[], GString *result)
 {
@@ -19,6 +22,48 @@ tf_echo(LogMessage *msg, gint argc, GString *argv[], GString *result)
 
 TEMPLATE_FUNCTION_SIMPLE(tf_echo);
 
+static gboolean
+tf_substr_parse_int(const gchar *s, long *d)
+{
+  gchar *endptr;
+  glong val;
+
+  errno = 0;
+  val = strtoll(s, &endptr, 10);
+
+  if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
+      || (errno != 0 && val == 0))
+    return FALSE;
+
+  if (endptr == s || *endptr != '\0')
+    return FALSE;
+
+  *d = val;
+  return TRUE;
+}
+
+static void
+tf_substr(LogMessage *msg, gint argc, GString *argv[], GString *result)
+{
+  glong start, len;
+
+  if (argc != 3)
+    return;
+
+  if (!tf_substr_parse_int (argv[0]->str, &start))
+    return;
+  if (!tf_substr_parse_int (argv[1]->str, &len))
+    return;
+
+  if (start > argv[2]->len ||
+      start + len >= argv[2]->len)
+    return;
+
+  g_string_append_len (result, argv[2]->str + start - 1, len);
+}
+
+TEMPLATE_FUNCTION_SIMPLE(tf_substr);
+
 typedef struct _TFCondState
 {
   FilterExprNode *filter;
@@ -158,6 +203,7 @@ static Plugin basicfuncs_plugins[] =
   TEMPLATE_FUNCTION_PLUGIN(tf_echo, "echo"),
   TEMPLATE_FUNCTION_PLUGIN(tf_grep, "grep"),
   TEMPLATE_FUNCTION_PLUGIN(tf_if, "if"),
+  TEMPLATE_FUNCTION_PLUGIN(tf_substr, "substr"),
 };
 
 gboolean
-- 
1.7.2.5