Re: luaL_loadbuffer API cannot deal with shebang

[Francisco Olarte <folarte@...>]

Baozeng:

On Thu, May 23, 2019 at 6:46 AM Baozeng <sploving1@gmail.com> wrote:
> Could we add some check in luaL_loadbuffer like the following?
>   size_t ignore_sz = 3;
>   if (size >= 2 && buff[0] == '#' && buff[1] == '!') {
>      while(ignore_sz <= size && buff[ignore_sz-1] != '\n') {
>       ignore_sz ++;
>      }
>      if(ignore_sz >= size) return -1;
>      else {
>        size = size - ignore_sz;
>        buff = buff + ignore_sz;
>      }
>   }

I would not do that, it could break some things, and doing the same
thing as load_file, which skips a potential BOM and a 1st line
STARTING WITH A SINGLE '#' ( not with a shebang, it skips every "shell
like comment" ) is pretty easy with a wrapper:
/** Could be better named loadbufferx_like_loadfile_does ;-> */
int luaL_loadbufferx_skip (lua_State *L,
               const char *buff,
               size_t sz,
               const char *name,
               const char *mode)
{
  const char BOM[]={0xEF,0xBB,0xBF};
  if (sz>=sizeof(BOM) && memcmp(buff, p, sizeof(BOM))==0) {
    buf+=sizeof(BOM);
    sz+=sizeof(BOM);
  }
  if (sz>0 && *buff=='#') {
    do {
      --sz;
      ++buf;
    } while(sz>0 && *buff!='\n');
    if (sz>0) { /* exit due to newline. */
      --sz;
      ++buf;
    }
  }
  /* let base function decide what to do with empty buffer if sz==0. */
  return luaL_loadbufferx(L, buff,sz, name,mode);
}
( UNTESTED, JUST A DRAFT ).

Francisco Olarte.