/// Lenient base64 decoding for Byte Sequences (RFC 9651 §4.2.7).
///
/// RFC 9651 says parsers SHOULD NOT fail when `=` padding is missing or
/// when the final sextet has non-zero pad bits, because many base64
/// implementations cannot reject them. The decoder here therefore
/// synthesizes missing padding and ignores the low bits of the final
/// sextet, while still rejecting characters outside the base64 alphabet,
/// padding in the middle, and line feeds (which the RFC makes MUST-fail).

///|
/// Decodes base64 content with missing-padding and non-zero-pad-bit
/// tolerance. The content must already have been alphabet-validated by the
/// caller. `base_offset` is the byte offset of `content` inside the
/// original input, used for error reporting.
pub fn decode_base64_lenient(
  content : Bytes,
  base_offset : Int,
) -> Result[Bytes, SfError] {
  let mut acc : Int = 0
  let mut bits : Int = 0
  let mut pad_seen = false
  let mut pad_count = 0
  let mut nonpad = 0
  let out : Array[Byte] = []
  for i in 0..= b'a' && b <= b'z' {
    b.to_int() - 0x61 + 26
  } else if b >= b'0' && b <= b'9' {
    b.to_int() - 0x30 + 52
  } else if b == b'+' {
    62
  } else {
    63
  }
}