src/librustc/util/common.rs

   1 // Copyright 2012-2014 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 #![allow(non_camel_case_types)]
  12
  13 use std::cell::{RefCell, Cell};
  14 use std::collections::HashMap;
  15 use std::collections::hash_state::HashState;
  16 use std::ffi::CString;
  17 use std::fmt::Debug;
  18 use std::hash::Hash;
  19 use std::iter::repeat;
  20 use std::path::Path;
  21 use std::time::Duration;
  22
  23 use syntax::ast;
  24 use syntax::visit;
  25 use syntax::visit::Visitor;
  26
  27 // The name of the associated type for `Fn` return types
  28 pub const FN_OUTPUT_NAME: &'static str = "Output";
  29
  30 // Useful type to use with `Result<>` indicate that an error has already
  31 // been reported to the user, so no need to continue checking.
  32 #[derive(Clone, Copy, Debug)]
  33 pub struct ErrorReported;
  34
  35 pub fn time<T, U, F>(do_it: bool, what: &str, u: U, f: F) -> T where
  36     F: FnOnce(U) -> T,
  37 {
  38     thread_local!(static DEPTH: Cell<usize> = Cell::new(0));
  39     if !do_it { return f(u); }
  40
  41     let old = DEPTH.with(|slot| {
  42         let r = slot.get();
  43         slot.set(r + 1);
  44         r
  45     });
  46
  47     let mut rv = None;
  48     let dur = {
  49         let ref mut rvp = rv;
  50
  51         Duration::span(move || {
  52             *rvp = Some(f(u))
  53         })
  54     };
  55     let rv = rv.unwrap();
  56
  57     // Hack up our own formatting for the duration to make it easier for scripts
  58     // to parse (always use the same number of decimal places and the same unit).
  59     const NANOS_PER_SEC: f64 = 1_000_000_000.0;
  60     let secs = dur.secs() as f64;
  61     let secs = secs + dur.extra_nanos() as f64 / NANOS_PER_SEC;
  62     println!("{}time: {:.3} \t{}", repeat("  ").take(old).collect::<String>(),
  63              secs, what);
  64
  65     DEPTH.with(|slot| slot.set(old));
  66
  67     rv
  68 }
  69
  70 pub fn indent<R, F>(op: F) -> R where
  71     R: Debug,
  72     F: FnOnce() -> R,
  73 {
  74     // Use in conjunction with the log post-processor like `src/etc/indenter`
  75     // to make debug output more readable.
  76     debug!(">>");
  77     let r = op();
  78     debug!("<< (Result = {:?})", r);
  79     r
  80 }
  81
  82 pub struct Indenter {
  83     _cannot_construct_outside_of_this_module: ()
  84 }
  85
  86 impl Drop for Indenter {
  87     fn drop(&mut self) { debug!("<<"); }
  88 }
  89
  90 pub fn indenter() -> Indenter {
  91     debug!(">>");
  92     Indenter { _cannot_construct_outside_of_this_module: () }
  93 }
  94
  95 struct LoopQueryVisitor<P> where P: FnMut(&ast::Expr_) -> bool {
  96     p: P,
  97     flag: bool,
  98 }
  99
 100 impl<'v, P> Visitor<'v> for LoopQueryVisitor<P> where P: FnMut(&ast::Expr_) -> bool {
 101     fn visit_expr(&mut self, e: &ast::Expr) {
 102         self.flag |= (self.p)(&e.node);
 103         match e.node {
 104           // Skip inner loops, since a break in the inner loop isn't a
 105           // break inside the outer loop
 106           ast::ExprLoop(..) | ast::ExprWhile(..) => {}
 107           _ => visit::walk_expr(self, e)
 108         }
 109     }
 110 }
 111
 112 // Takes a predicate p, returns true iff p is true for any subexpressions
 113 // of b -- skipping any inner loops (loop, while, loop_body)
 114 pub fn loop_query<P>(b: &ast::Block, p: P) -> bool where P: FnMut(&ast::Expr_) -> bool {
 115     let mut v = LoopQueryVisitor {
 116         p: p,
 117         flag: false,
 118     };
 119     visit::walk_block(&mut v, b);
 120     return v.flag;
 121 }
 122
 123 struct BlockQueryVisitor<P> where P: FnMut(&ast::Expr) -> bool {
 124     p: P,
 125     flag: bool,
 126 }
 127
 128 impl<'v, P> Visitor<'v> for BlockQueryVisitor<P> where P: FnMut(&ast::Expr) -> bool {
 129     fn visit_expr(&mut self, e: &ast::Expr) {
 130         self.flag |= (self.p)(e);
 131         visit::walk_expr(self, e)
 132     }
 133 }
 134
 135 // Takes a predicate p, returns true iff p is true for any subexpressions
 136 // of b -- skipping any inner loops (loop, while, loop_body)
 137 pub fn block_query<P>(b: &ast::Block, p: P) -> bool where P: FnMut(&ast::Expr) -> bool {
 138     let mut v = BlockQueryVisitor {
 139         p: p,
 140         flag: false,
 141     };
 142     visit::walk_block(&mut v, &*b);
 143     return v.flag;
 144 }
 145
 146 /// K: Eq + Hash<S>, V, S, H: Hasher<S>
 147 ///
 148 /// Determines whether there exists a path from `source` to `destination`.  The
 149 /// graph is defined by the `edges_map`, which maps from a node `S` to a list of
 150 /// its adjacent nodes `T`.
 151 ///
 152 /// Efficiency note: This is implemented in an inefficient way because it is
 153 /// typically invoked on very small graphs. If the graphs become larger, a more
 154 /// efficient graph representation and algorithm would probably be advised.
 155 pub fn can_reach<T, S>(edges_map: &HashMap<T, Vec<T>, S>, source: T,
 156                        destination: T) -> bool
 157     where S: HashState, T: Hash + Eq + Clone,
 158 {
 159     if source == destination {
 160         return true;
 161     }
 162
 163     // Do a little breadth-first-search here.  The `queue` list
 164     // doubles as a way to detect if we've seen a particular FR
 165     // before.  Note that we expect this graph to be an *extremely
 166     // shallow* tree.
 167     let mut queue = vec!(source);
 168     let mut i = 0;
 169     while i < queue.len() {
 170         match edges_map.get(&queue[i]) {
 171             Some(edges) => {
 172                 for target in edges {
 173                     if *target == destination {
 174                         return true;
 175                     }
 176
 177                     if !queue.iter().any(|x| x == target) {
 178                         queue.push((*target).clone());
 179                     }
 180                 }
 181             }
 182             None => {}
 183         }
 184         i += 1;
 185     }
 186     return false;
 187 }
 188
 189 /// Memoizes a one-argument closure using the given RefCell containing
 190 /// a type implementing MutableMap to serve as a cache.
 191 ///
 192 /// In the future the signature of this function is expected to be:
 193 /// ```
 194 /// pub fn memoized<T: Clone, U: Clone, M: MutableMap<T, U>>(
 195 ///    cache: &RefCell<M>,
 196 ///    f: &|T| -> U
 197 /// ) -> impl |T| -> U {
 198 /// ```
 199 /// but currently it is not possible.
 200 ///
 201 /// # Examples
 202 /// ```
 203 /// struct Context {
 204 ///    cache: RefCell<HashMap<usize, usize>>
 205 /// }
 206 ///
 207 /// fn factorial(ctxt: &Context, n: usize) -> usize {
 208 ///     memoized(&ctxt.cache, n, |n| match n {
 209 ///         0 | 1 => n,
 210 ///         _ => factorial(ctxt, n - 2) + factorial(ctxt, n - 1)
 211 ///     })
 212 /// }
 213 /// ```
 214 #[inline(always)]
 215 pub fn memoized<T, U, S, F>(cache: &RefCell<HashMap<T, U, S>>, arg: T, f: F) -> U
 216     where T: Clone + Hash + Eq,
 217           U: Clone,
 218           S: HashState,
 219           F: FnOnce(T) -> U,
 220 {
 221     let key = arg.clone();
 222     let result = cache.borrow().get(&key).cloned();
 223     match result {
 224         Some(result) => result,
 225         None => {
 226             let result = f(arg);
 227             cache.borrow_mut().insert(key, result.clone());
 228             result
 229         }
 230     }
 231 }
 232
 233 #[cfg(unix)]
 234 pub fn path2cstr(p: &Path) -> CString {
 235     use std::os::unix::prelude::*;
 236     use std::ffi::OsStr;
 237     let p: &OsStr = p.as_ref();
 238     CString::new(p.as_bytes()).unwrap()
 239 }
 240 #[cfg(windows)]
 241 pub fn path2cstr(p: &Path) -> CString {
 242     CString::new(p.to_str().unwrap()).unwrap()
 243 }