Function stbi__get_marker

lite/example/cpp_example/mge/cv/stb_image.h:3128–3141

if there's a pending marker from the entropy stream, return that otherwise, fetch from the stream and get a marker. if there's no marker, return 0xff, which is never a valid marker value

// otherwise, fetch from the stream and get a marker. if there's no
// marker, return 0xff, which is never a valid marker value
static stbi_uc stbi__get_marker(stbi__jpeg* j) {
    stbi_uc x;
    if (j->marker != STBI__MARKER_none) {
        x = j->marker;
        j->marker = STBI__MARKER_none;
        return x;
    }
    x = stbi__get8(j->s);
    if (x != 0xff)
        return STBI__MARKER_none;
    while (x == 0xff)
        x = stbi__get8(j->s);  // consume repeated 0xff fill bytes
    return x;
}

// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]