Add module zero.c/zero.h
diff --git a/zero.c b/zero.c
new file mode 100644
index 0000000..9ed2f30
--- /dev/null
+++ b/zero.c
@@ -0,0 +1,105 @@
+/*
+ * This file is part of ltrace.
+ * Copyright (C) 2011,2012 Petr Machata, Red Hat Inc.
+ *
+ * This program 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; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * 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 St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <error.h>
+#include <errno.h>
+
+#include "zero.h"
+#include "common.h"
+#include "type.h"
+#include "value.h"
+#include "expr.h"
+
+static int
+zero_callback_max(struct value *ret_value, struct value *lhs,
+ struct value_dict *arguments,
+ size_t max, void *data)
+{
+ size_t i;
+ for (i = 0; i < max; ++i) {
+ struct value element;
+ if (value_init_element(&element, lhs, i) < 0)
+ return -1;
+
+ int zero = value_is_zero(&element, arguments);
+
+ value_destroy(&element);
+
+ if (zero)
+ break;
+ }
+
+ struct arg_type_info *long_type = type_get_simple(ARGTYPE_LONG);
+ value_init_detached(ret_value, NULL, long_type, 0);
+ value_set_long(ret_value, i);
+ return 0;
+}
+
+/* LHS->zero(RHS). Looks for a length of zero-terminated array, but
+ * looks no further than first RHS bytes. */
+static int
+zero_callback(struct value *ret_value, struct value *lhs,
+ struct value *rhs, struct value_dict *arguments, void *data)
+{
+ long l;
+ if (value_extract_word(rhs, &l, arguments) < 0)
+ return -1;
+ if (l < 0)
+ /* It might just be a positive value >2GB, but that's
+ * not likely. */
+ report_global_error("maximum array length seems negative");
+ size_t max = (size_t)l;
+ return zero_callback_max(ret_value, lhs, arguments, max, data);
+}
+
+/* LHS->zero. Looks for a length of zero-terminated array, without
+ * limit. */
+static int
+zero1_callback(struct value *ret_value, struct value *lhs,
+ struct value_dict *arguments, void *data)
+{
+ return zero_callback_max(ret_value, lhs, arguments, (size_t)-1, data);
+}
+
+struct expr_node *
+build_zero_w_arg(struct expr_node *expr, int own)
+{
+ struct expr_node *e_z = malloc(sizeof(*e_z));
+ if (e_z == NULL)
+ return NULL;
+
+ expr_init_cb2(e_z, &zero_callback,
+ expr_self(), 0, expr, own, NULL);
+ return e_z;
+}
+
+struct expr_node *
+expr_node_zero(void)
+{
+ static struct expr_node *node = NULL;
+ if (node == NULL) {
+ node = malloc(sizeof(*node));
+ if (node == NULL)
+ error(1, errno, "malloc expr_node_zero");
+ expr_init_cb1(node, &zero1_callback,
+ expr_self(), 0, (void *)-1);
+ }
+ return node;
+}