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//! Get Pseudo Random Bytes
//!
//! <https://developers.yubico.com/YubiHSM2/Commands/Get_Pseudo_Random.html>
//!
use super::{Command, Response};
use session::SessionErrorKind::ProtocolError;
use {Adapter, CommandType, Session, SessionError};

pub(crate) const MAX_RAND_BYTES: u16 = 2048 // packet size
    - 1 // response type byte
    - 2; // length of response data

/// Get some number of bytes of pseudo random data generated on the device
pub fn get_pseudo_random<A: Adapter>(
    session: &mut Session<A>,
    bytes: u16,
) -> Result<Vec<u8>, SessionError> {
    if bytes >= MAX_RAND_BYTES {
        fail!(
            ProtocolError,
            "Requested too many random bytes (>= 2045) to fit in response packet"
        );
    }
    session
        .send_command(GetPseudoRandomCommand { bytes })
        .map(|response| response.bytes)
}

/// Request parameters for `command::get_pseudo_random`
#[derive(Serialize, Deserialize, Debug)]
pub(crate) struct GetPseudoRandomCommand {
    /// Number of random bytes to return
    pub bytes: u16,
}

impl Command for GetPseudoRandomCommand {
    type ResponseType = GetPseudoRandomResponse;
}

/// Response from `command::get_pseudo_random`
#[derive(Serialize, Deserialize, Debug)]
pub(crate) struct GetPseudoRandomResponse {
    /// Bytes of pseudo random data returned from the YubiHSM
    pub bytes: Vec<u8>,
}

impl Response for GetPseudoRandomResponse {
    const COMMAND_TYPE: CommandType = CommandType::GetPseudoRandom;
}