Function render_ansi_to 

pub fn render_ansi_to(
    source: &str,
    document: &HighlightedDocument,
    options: &AnsiOptions,
    output: &mut dyn Write,
) -> Result<HighlightStatus>

Available on crate feature ansi only.

Writes ANSI output to a caller-provided writer and returns tokenization status.

Uses the same options, sanitization, and source validation as render_ansi. Validation finishes before writing anything. Writer failures return Error::Render and may leave partial output (including an active SGR style); the renderer does not flush or roll it back.