Add macros to ASN.1 module to parse ASN.1 tags
The macros simply extract the component bits of an ASN.1 tag value
#define MBEDTLS_ASN1_PRIMITIVE 0x00
#define MBEDTLS_ASN1_CONSTRUCTED 0x20
#define MBEDTLS_ASN1_CONTEXT_SPECIFIC 0x80
+
+/*
+ * Bit masks for each of the components of an ASN.1 tag as specified in
+ * Information technnology - ASN.1 encoding rules: Specification of Basic
+ * Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished
+ * encoding rules (DER) Section 8.1.2.2:
+ *
+ * Bit 8 7 6 5 1
+ * +-------+-----+------------+
+ * | Class | P/C | Tag number |
+ * +-------+-----+------------+
+ */
+#define MBEDTLS_ASN1_TAG_CLASS_MASK ( 0x03 << 6 )
+#define MBEDTLS_ASN1_TAG_PC_MASK ( 0x01 << 5 )
+#define MBEDTLS_ASN1_TAG_VALUE_MASK ( 0x1F << 0 )
+
/* \} name */
/* \} addtogroup asn1_module */
