diff --git a/src/asn1c/constraints.h b/src/asn1c/constraints.h
new file mode 100644
index 0000000..5032345
--- /dev/null
+++ b/src/asn1c/constraints.h
@@ -0,0 +1,63 @@
+/*-
+ * Copyright (c) 2004, 2006 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#ifndef	_ASN1_CONSTRAINTS_VALIDATOR_H_
+#define	_ASN1_CONSTRAINTS_VALIDATOR_H_
+
+#include <asn_system.h>		/* Platform-dependent types */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct asn_TYPE_descriptor_s;		/* Forward declaration */
+
+/*
+ * Validate the structure according to the ASN.1 constraints.
+ * If errbuf and errlen are given, they shall be pointing to the appropriate
+ * buffer space and its length before calling this function. Alternatively,
+ * they could be passed as NULL's. If constraints validation fails,
+ * errlen will contain the actual number of bytes taken from the errbuf
+ * to encode an error message (properly 0-terminated).
+ * 
+ * RETURN VALUES:
+ * This function returns 0 in case all ASN.1 constraints are met
+ * and -1 if one or more constraints were failed.
+ */
+int
+asn_check_constraints(struct asn_TYPE_descriptor_s *type_descriptor,
+	const void *struct_ptr,	/* Target language's structure */
+	char *errbuf,		/* Returned error description */
+	size_t *errlen		/* Length of the error description */
+	);
+
+
+/*
+ * Generic type for constraint checking callback,
+ * associated with every type descriptor.
+ */
+typedef int (asn_constr_check_f)(
+	struct asn_TYPE_descriptor_s *type_descriptor,
+	const void *struct_ptr,
+	asn_app_constraint_failed_f *optional_callback,	/* Log the error */
+	void *optional_app_key		/* Opaque key passed to a callback */
+	);
+
+/*******************************
+ * INTERNALLY USEFUL FUNCTIONS *
+ *******************************/
+
+asn_constr_check_f asn_generic_no_constraint;	/* No constraint whatsoever */
+asn_constr_check_f asn_generic_unknown_constraint; /* Not fully supported */
+
+/*
+ * Invoke the callback with a complete error message.
+ */
+#define	_ASN_CTFAIL	if(ctfailcb) ctfailcb
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif	/* _ASN1_CONSTRAINTS_VALIDATOR_H_ */