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//! Base64 reader support (constant-time).

use crate::{Decode, Error, Reader, Result};

/// Inner constant-time Base64 reader type from the `base64ct` crate.
type Inner<'i> = base64ct::Decoder<'i, base64ct::Base64>;

/// Constant-time Base64 reader implementation.
pub struct Base64Reader<'i> {
    /// Inner Base64 reader.
    inner: Inner<'i>,

    /// Custom length of remaining data, used for nested length-prefixed reading.
    remaining_len: usize,
}

impl<'i> Base64Reader<'i> {
    /// Create a new Base64 reader for a byte slice containing contiguous (non-newline-delimited)
    /// Base64-encoded data.
    ///
    /// # Returns
    /// - `Ok(reader)` on success.
    /// - `Err(Error::Base64)` if the input buffer is empty.
    pub fn new(input: &'i [u8]) -> Result<Self> {
        let inner = Inner::new(input)?;
        let remaining_len = inner.remaining_len();

        Ok(Self {
            inner,
            remaining_len,
        })
    }
}

impl_reader_for_newtype!(Base64Reader<'_>);