int len = FFMIN(f->end - f->rptr, buf_size);
if(func) func(dest, f->rptr, len);
else{
memcpy(dest, f->rptr, len);
dest = (uint8_t*)dest + len;
}
int len = FFMIN(f->end - f->rptr, buf_size);
if(func) func(dest, f->rptr, len);
else{
memcpy(dest, f->rptr, len);
dest = (uint8_t*)dest + len;
}