libgrust/libproc_macro/token_stream.rs

   1 // Copyright (C) 2023-2024 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU Proc Macro Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // Under Section 7 of GPL version 3, you are granted additional
  15 // permissions described in the GCC Runtime Library Exception, version
  16 // 3.1, as published by the Free Software Foundation.
  17
  18 // You should have received a copy of the GNU General Public License and
  19 // a copy of the GCC Runtime Library Exception along with this program;
  20 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  21 // <http://www.gnu.org/licenses/>.
  22
  23 //! Public implementation details for the `TokenStream` type, such as iterators.
  24 use bridge;
  25 use std::convert::TryInto;
  26
  27 use TokenStream;
  28 use TokenTree;
  29
  30 /// An iterator over [`TokenStream`]'s [`TokenTree`]s.
  31 #[derive(Clone)]
  32 pub struct IntoIter {
  33     current: *const bridge::token_stream::TokenTree,
  34     end: *const bridge::token_stream::TokenTree,
  35 }
  36
  37 impl Iterator for IntoIter {
  38     type Item = TokenTree;
  39
  40     fn next(&mut self) -> Option<TokenTree> {
  41         if self.current == self.end {
  42             None
  43         } else {
  44             let result = self.current;
  45             self.current = unsafe { self.current.add(1) };
  46             Some(unsafe { std::ptr::read(result) }.into())
  47         }
  48     }
  49
  50     fn size_hint(&self) -> (usize, Option<usize>) {
  51         // TODO: I'm not a fan of those casts, once #![feature(ptr_sub_ptr)]
  52         // is implemented we may replace this line by the following:
  53         // self.end.sub_ptr(self.current)
  54         let remaining = self.end as usize - self.current as usize;
  55         (remaining, Some(remaining))
  56     }
  57
  58     fn count(self) -> usize {
  59         self.end as usize - self.current as usize
  60     }
  61 }
  62
  63 impl IntoIterator for TokenStream {
  64     type Item = TokenTree;
  65     type IntoIter = IntoIter;
  66
  67     fn into_iter(self) -> IntoIter {
  68         let capacity = self.0.size.try_into().unwrap();
  69         IntoIter {
  70             current: self.0.data,
  71             end: unsafe { self.0.data.add(capacity) },
  72         }
  73     }
  74 }