Function str_gsub

third-party/lua-5.2.4/src/lstrlib.c:735–777

static int str_gsub (lua_State *L) {
  size_t srcl, lp;
  const char *src = luaL_checklstring(L, 1, &srcl);
  const char *p = luaL_checklstring(L, 2, &lp);
  int tr = lua_type(L, 3);
  size_t max_s = luaL_optinteger(L, 4, srcl+1);
  int anchor = (*p == '^');
  size_t n = 0;
  MatchState ms;
  luaL_Buffer b;
  luaL_argcheck(L, tr == LUA_TNUMBER || tr == LUA_TSTRING ||
                   tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3,
                      "string/function/table expected");
  luaL_buffinit(L, &b);
  if (anchor) {
    p++; lp--;  /* skip anchor character */
  }
  ms.L = L;
  ms.matchdepth = MAXCCALLS;
  ms.src_init = src;
  ms.src_end = src+srcl;
  ms.p_end = p + lp;
  while (n < max_s) {
    const char *e;
    ms.level = 0;
    lua_assert(ms.matchdepth == MAXCCALLS);
    e = match(&ms, src, p);
    if (e) {
      n++;
      add_value(&ms, &b, src, e, tr);
    }
    if (e && e>src) /* non empty match? */
      src = e;  /* skip it */
    else if (src < ms.src_end)
      luaL_addchar(&b, *src++);
    else break;
    if (anchor) break;
  }
  luaL_addlstring(&b, src, ms.src_end-src);
  luaL_pushresult(&b);
  lua_pushinteger(L, n);  /* number of substitutions */
  return 2;
}

/* }====================================================== */