[−][src]Struct iso7816_tlv::ber::Tag

pub struct Tag { /* fields omitted */ }

Tag for BER-TLV data as defined in [ISO7816-4]. Valid tags are defined as follow:

ISO/IEC 7816 supports tag fields of one, two and three bytes; longer tag fields are reserved for future use

In tag fields of two or more bytes, the values '00' to '1E' and '80' are invalid for the second byte.

In two-byte tag fields, the second byte consists of bit 8 set to 0 and bits 7 to 1.

In three-byte tag fields, the second byte consists of bit 8 set to 1 and bits 7 to 1 not all set to 0; the third byte consists of bit 8 set to 0 and bits 7 to 1 with any value.

Tags can be generated using the TryFrom trait from integer types (see Trait Implementations for valid input types) or hex str.

Example

use std::convert::TryFrom;
use iso7816_tlv::ber::Tag;

assert!(Tag::try_from("80").is_ok());
assert!(Tag::try_from(8u8).is_ok());
assert!(Tag::try_from(8u16).is_ok());
assert!(Tag::try_from(8u32).is_ok());
assert!(Tag::try_from(8i32).is_ok());
assert!(Tag::try_from("7f22").is_ok());

assert!(Tag::try_from("error ").is_err());
assert!(Tag::try_from("7fffff01").is_err());
assert!(Tag::try_from("7f00").is_err());
assert!(Tag::try_from("7f80ff").is_err());
assert!(Tag::try_from("7f1e").is_err());

Methods

`impl Tag`[src]

`#[must_use]pub fn to_bytes(&self) -> &[u8]`[src]

serializes the tag as byte array

`#[must_use]pub fn len_as_bytes(&self) -> usize`[src]

length of the tag as byte array

Example

use std::convert::TryFrom;
use iso7816_tlv::ber::Tag;

let tag = Tag::try_from("80")?;
assert_eq!(1, tag.len_as_bytes());

let tag = Tag::try_from("7f22")?;
assert_eq!(2, tag.len_as_bytes());  

let tag = Tag::try_from("7f8022")?;
assert_eq!(3, tag.len_as_bytes());

let tag = Tag::try_from("5fff22")?;
assert_eq!(3, tag.len_as_bytes());

let tag = Tag::try_from("5f2d")?;
assert_eq!(2, tag.len_as_bytes());

`#[must_use]pub fn is_constructed(&self) -> bool`[src]

Wether the tag is constructed or not

Bit 6 of the first byte of the tag field indicates an encoding.

The value 0 indicates a primitive encoding of the data object, i.e., the value field is not encoded in BER - TLV .

The value 1 indicates a constructed encoding of the data object, i.e., the value field is encoded in BER - TLV

Example

use std::convert::TryFrom;
use iso7816_tlv::ber::Tag;

let valid = Tag::try_from(0b0010_0000)?;
assert!(valid.is_constructed());

let invalid = Tag::try_from(0b0000_0001)?;
assert!(!invalid.is_constructed());

`#[must_use]pub fn class(&self) -> Class`[src]

Get the tag class.

Example

use std::convert::TryFrom;
use iso7816_tlv::ber::{Tag, Class};

let tag = Tag::try_from(0b0010_0000)?;
assert_eq!(Class::Universal, tag.class());
let tag = Tag::try_from(0b1100_0000)?;
assert_eq!(Class::Private, tag.class());