diff --git a/libasn1fix/asn1fix_crange.h b/libasn1fix/asn1fix_crange.h
new file mode 100644
index 0000000..9873e3b
--- /dev/null
+++ b/libasn1fix/asn1fix_crange.h
@@ -0,0 +1,59 @@
+#ifndef	ASN1FIX_CRANGE_H
+#define	ASN1FIX_CRANGE_H
+
+typedef struct asn1cnst_edge_s {
+	enum asn1cnst_range_edge {
+		ARE_MIN,
+		ARE_MAX,
+		ARE_VALUE,
+	} type;
+	int lineno;	/* Line where the corresponding token was found */
+	asn1_integer_t value;	/* Value when type is ARE_VALUE */
+} asn1cnst_edge_t;
+
+typedef struct asn1cnst_range_s {
+	asn1cnst_edge_t left;	/* MIN from (MIN..10) */
+	asn1cnst_edge_t right;	/* 10 from (MIN..10) */
+
+	/* If range is split in parts, these are the parts */
+	struct asn1cnst_range_s **elements;
+	int el_count;
+	int el_size;
+
+	int empty_constraint;	/* If yes, too bad. */
+	int extensible;		/* Extension marker (...) present. */
+
+	int not_PER_visible;	/* Contains non PER-visible components */
+} asn1cnst_range_t;
+
+/*
+ * Compute the PER-visible constraint range.
+ * 
+ * (expr_type) must have the type of the top-level parent ASN.1 type.
+ * (required_type) must be one of ACT_EL_RANGE, ACT_CT_SIZE or ACT_CT_FROM.
+ * (minmax) and (expectation_met) should be 0.
+ * ERRORS:
+ * 	EINVAL:	Mandatory arguments missing.
+ * 	ENOMEM:	Memory allocation failure.
+ * 	EPERM:	Invalid constraint reference.
+ */
+asn1cnst_range_t *asn1constraint_compute_PER_range(asn1p_expr_type_e expr_type,
+	const asn1p_constraint_t *ct,
+	enum asn1p_constraint_type_e required_type,
+	const asn1cnst_range_t *minmax,
+	int *expectation_met);
+void asn1constraint_range_free(asn1cnst_range_t *);
+
+/*
+ * Check that a specific constraint is compatible
+ * with the given expression type.
+ */
+int asn1constraint_compatible(asn1p_expr_type_e expr_type,
+	enum asn1p_constraint_type_e constr_type);
+
+/*
+ * Fetch a default alphabet for this type.
+ */
+asn1cnst_range_t *asn1constraint_default_alphabet(asn1p_expr_type_e expr_type);
+
+#endif	/* ASN1FIX_CRANGE_H */