src/librustc_const_math/us.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use syntax::ast;
  12 use super::err::*;
  13
  14 /// Depending on the target only one variant is ever used in a compilation.
  15 /// Anything else is an error. This invariant is checked at several locations
  16 #[derive(Copy, Clone, Debug, RustcEncodable, RustcDecodable, Hash, Eq, PartialEq)]
  17 pub enum ConstUsize {
  18     Us32(u32),
  19     Us64(u64),
  20 }
  21 pub use self::ConstUsize::*;
  22
  23 impl ConstUsize {
  24     pub fn as_u64(self, target_uint_ty: ast::UintTy) -> u64 {
  25         match (self, target_uint_ty) {
  26             (Us32(i), ast::UintTy::U32) => i as u64,
  27             (Us64(i), ast::UintTy::U64) => i,
  28             _ => panic!("got invalid usize size for target"),
  29         }
  30     }
  31     pub fn new(i: u64, target_uint_ty: ast::UintTy) -> Result<Self, ConstMathErr> {
  32         match target_uint_ty {
  33             ast::UintTy::U32 if i as u32 as u64 == i => Ok(Us32(i as u32)),
  34             ast::UintTy::U32 => Err(ULitOutOfRange(ast::UintTy::Us)),
  35             ast::UintTy::U64 => Ok(Us64(i)),
  36             _ => unreachable!(),
  37         }
  38     }
  39 }