/**
 * Little-endian primitives for reading the walk/snapshot wire buffers. Shared by
 * the hand-written decoders and the generated layout decoder so both interpret
 * the bytes identically.
 */
const textDecoder = new TextDecoder("utf-8");
/** Read a u16 (LE) at `off`. */
export function ru16(view, off) {
    return view.getUint16(off, true);
}
/** Read a u32 (LE) at `off`. */
export function ru32(view, off) {
    return view.getUint32(off, true);
}
/** Read a UTF-8 string of `len` bytes at `off`. Very short ASCII runs decode
 *  with a charCode loop — TextDecoder's per-call overhead dominates there. The
 *  threshold is lower than the encode-side `INLINE_STR_MAX`: decoding builds a
 *  JS string by concatenation, which costs more per char than storing bytes.
 *  Measured crossover ~8-12 bytes (Node 24: 8B 30 vs 57 ns, 16B 64 vs 57). */
export function rstr(buf, off, len) {
    if (len === 0)
        return "";
    if (len <= 8) {
        let ascii = true;
        for (let i = 0; i < len; i++) {
            if (buf[off + i] > 127) {
                ascii = false;
                break;
            }
        }
        if (ascii) {
            let s = "";
            for (let i = 0; i < len; i++)
                s += String.fromCharCode(buf[off + i]);
            return s;
        }
    }
    return textDecoder.decode(buf.subarray(off, off + len));
}
/**
 * Decode the 24-byte position block ([startOffset, endOffset, startLine,
 * startColumn, endLine, endColumn], u32 LE each) shared by the walk prefixes
 * and the snapshot node structs. A zero start line is the sentinel for
 * synthesized nodes with no source range (e.g. GFM autolink-literal nodes, or a
 * plugin-built replacement spliced by the rebuild): unist lines are 1-based, so
 * line 0 always means "no source position" — even when the rebuild has rebased
 * the (otherwise zero) offset by the spliced subtree's source base. Surfaced as
 * `undefined` so a node reads the same however it's reached.
 */
export function readPosition(view, off) {
    const startLine = ru32(view, off + 8);
    if (startLine === 0)
        return undefined;
    const startOffset = ru32(view, off);
    return {
        start: { offset: startOffset, line: startLine, column: ru32(view, off + 12) },
        end: { offset: ru32(view, off + 4), line: ru32(view, off + 16), column: ru32(view, off + 20) },
    };
}