Function stbi__refill_buffer

lite/example/cpp_example/mge/cv/stb_image.h:1632–1646

enum { STBI__SCAN_load = 0, STBI__SCAN_type, STBI__SCAN_header };

static void stbi__refill_buffer(stbi__context* s) {
    int n = (s->io.read)(s->io_user_data, (char*)s->buffer_start, s->buflen);
    s->callback_already_read += (int)(s->img_buffer - s->img_buffer_original);
    if (n == 0) {
        // at end of file, treat same as if from memory, but need to handle case
        // where s->img_buffer isn't pointing to safe memory, e.g. 0-byte file
        s->read_from_callbacks = 0;
        s->img_buffer = s->buffer_start;
        s->img_buffer_end = s->buffer_start + 1;
        *s->img_buffer = 0;
    } else {
        s->img_buffer = s->buffer_start;
        s->img_buffer_end = s->buffer_start + n;
    }
}

stbi_inline static stbi_uc stbi__get8(stbi__context* s) {
    if (s->img_buffer < s->img_buffer_end)