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//! DER Parser (and Writer)
//!
//! ```
//! extern crate derp;
//! extern crate untrusted;
//!
//! use derp::{Tag, Der};
//! use untrusted::Input;
//!
//! const MY_DATA: &'static [u8] = &[
//!     0x30, 0x18,                                             // sequence
//!         0x05, 0x00,                                         // null
//!         0x30, 0x0e,                                         // sequence
//!             0x02, 0x06, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, // x
//!             0x02, 0x04, 0x0a, 0x0b, 0x0c, 0x0d,             // y
//!         0x03, 0x04, 0x00, 0xff, 0xff, 0xff,                 // bits
//! ];
//!
//! fn main() {
//!     let input = Input::from(MY_DATA);
//!     let (x, y, bits) = input.read_all(derp::Error::Read, |input| {
//!         derp::nested(input, Tag::Sequence, |input| {
//!             derp::read_null(input)?;
//!             let (x, y) = derp::nested(input, Tag::Sequence, |input| {
//!                 let x = derp::positive_integer(input)?;
//!                 let y = derp::positive_integer(input)?;
//!                 Ok((x, y))
//!             })?;
//!             let bits = derp::bit_string_with_no_unused_bits(input)?;
//!             Ok((x, y, bits))
//!         })
//!     }).unwrap();
//!
//!     assert_eq!(x, Input::from(&[0x01, 0x02, 0x03, 0x04, 0x05, 0x06]));
//!     assert_eq!(y, Input::from(&[0x0a, 0x0b, 0x0c, 0x0d]));
//!     assert_eq!(bits, Input::from(&[0xff, 0xff, 0xff]));
//!
//!     let mut buf = Vec::new();
//!     {
//!         let mut der = Der::new(&mut buf);
//!         der.write_sequence(|der| {
//!             der.write_null()?;
//!             der.write_sequence(|der| {
//!                 der.write_integer(x)?;
//!                 der.write_integer(y)
//!             })?;
//!             der.write_bit_string(0, |der| {
//!                 der.write_raw(bits)
//!             })
//!         }).unwrap();
//!     }
//!
//!     assert_eq!(buf.as_slice(), MY_DATA);
//! }
//! ```
extern crate untrusted;

mod der;
mod writer;

pub use der::*;
pub use writer::*;

#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Error {
    BadBooleanValue,
    LeadingZero,
    LessThanMinimum,
    LongLengthNotSupported,
    HighTagNumberForm,
    Io,
    NegativeValue,
    NonCanonical,
    NonZeroUnusedBits,
    Read,
    UnexpectedEnd,
    UnknownTag,
    WrongTag,
    WrongValue,
}

impl From<untrusted::EndOfInput> for Error {
    fn from(_: untrusted::EndOfInput) -> Error {
        Error::UnexpectedEnd
    }
}

impl From<::std::io::Error> for Error {
    fn from(_: ::std::io::Error) -> Error {
        Error::Io
    }
}

/// Alias for `Result<T, Error>`
pub type Result<T> = ::std::result::Result<T, Error>;