addCertsFromFile

pub fn addCertsFromFile(cb: *Bundle, gpa: Allocator, file_reader: *Io.File.Reader, now_sec: i64) AddCertsFromFileError!void {
    const size = try file_reader.getSize();

    // We borrow `bytes` as a temporary buffer for the base64-encoded data.
    // This is possible by computing the decoded length and reserving the space
    // for the decoded bytes first.
    const decoded_size_upper_bound = size / 4 * 3;
    const needed_capacity = std.math.cast(u32, decoded_size_upper_bound + size) orelse
        return error.CertificateAuthorityBundleTooBig;
    try cb.bytes.ensureUnusedCapacity(gpa, needed_capacity);
    const end_reserved: u32 = @intCast(cb.bytes.items.len + decoded_size_upper_bound);
    const buffer = cb.bytes.allocatedSlice()[end_reserved..];
    const end_index = file_reader.interface.readSliceShort(buffer) catch |err| switch (err) {
        error.ReadFailed => return file_reader.err.?,
    };
    const encoded_bytes = buffer[0..end_index];

    const begin_marker = "-----BEGIN CERTIFICATE-----";
    const end_marker = "-----END CERTIFICATE-----";

    var start_index: usize = 0;
    while (mem.findPos(u8, encoded_bytes, start_index, begin_marker)) |begin_marker_start| {
        const cert_start = begin_marker_start + begin_marker.len;
        const cert_end = mem.findPos(u8, encoded_bytes, cert_start, end_marker) orelse
            return error.MissingEndCertificateMarker;
        start_index = cert_end + end_marker.len;
        const encoded_cert = mem.trim(u8, encoded_bytes[cert_start..cert_end], " \t\r\n");
        const decoded_start: u32 = @intCast(cb.bytes.items.len);
        const dest_buf = cb.bytes.allocatedSlice()[decoded_start..];
        cb.bytes.items.len += try base64.decode(dest_buf, encoded_cert);
        try cb.parseCert(gpa, decoded_start, now_sec);
    }
}