Vendor things

third-party/vendor/num-bigint/benches/shootout-pidigits.rs

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+// The Computer Language Benchmarks Game
+// http://benchmarksgame.alioth.debian.org/
+//
+// contributed by the Rust Project Developers
+
+// Copyright (c) 2013-2014 The Rust Project Developers
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//
+// - Redistributions of source code must retain the above copyright
+//   notice, this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+//   notice, this list of conditions and the following disclaimer in
+//   the documentation and/or other materials provided with the
+//   distribution.
+//
+// - Neither the name of "The Computer Language Benchmarks Game" nor
+//   the name of "The Computer Language Shootout Benchmarks" nor the
+//   names of its contributors may be used to endorse or promote
+//   products derived from this software without specific prior
+//   written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+// OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use std::io;
+use std::str::FromStr;
+
+use num_bigint::BigInt;
+use num_integer::Integer;
+use num_traits::{FromPrimitive, One, ToPrimitive, Zero};
+
+struct Context {
+    numer: BigInt,
+    accum: BigInt,
+    denom: BigInt,
+}
+
+impl Context {
+    fn new() -> Context {
+        Context {
+            numer: One::one(),
+            accum: Zero::zero(),
+            denom: One::one(),
+        }
+    }
+
+    fn from_i32(i: i32) -> BigInt {
+        FromPrimitive::from_i32(i).unwrap()
+    }
+
+    fn extract_digit(&self) -> i32 {
+        if self.numer > self.accum {
+            return -1;
+        }
+        let (q, r) = (&self.numer * Context::from_i32(3) + &self.accum).div_rem(&self.denom);
+        if r + &self.numer >= self.denom {
+            return -1;
+        }
+        q.to_i32().unwrap()
+    }
+
+    fn next_term(&mut self, k: i32) {
+        let y2 = Context::from_i32(k * 2 + 1);
+        self.accum = (&self.accum + (&self.numer << 1)) * &y2;
+        self.numer = &self.numer * Context::from_i32(k);
+        self.denom = &self.denom * y2;
+    }
+
+    fn eliminate_digit(&mut self, d: i32) {
+        let d = Context::from_i32(d);
+        let ten = Context::from_i32(10);
+        self.accum = (&self.accum - &self.denom * d) * &ten;
+        self.numer = &self.numer * ten;
+    }
+}
+
+fn pidigits(n: isize, out: &mut dyn io::Write) -> io::Result<()> {
+    let mut k = 0;
+    let mut context = Context::new();
+
+    for i in 1..=n {
+        let mut d;
+        loop {
+            k += 1;
+            context.next_term(k);
+            d = context.extract_digit();
+            if d != -1 {
+                break;
+            }
+        }
+
+        write!(out, "{}", d)?;
+        if i % 10 == 0 {
+            writeln!(out, "\t:{}", i)?;
+        }
+
+        context.eliminate_digit(d);
+    }
+
+    let m = n % 10;
+    if m != 0 {
+        for _ in m..10 {
+            write!(out, " ")?;
+        }
+        writeln!(out, "\t:{}", n)?;
+    }
+    Ok(())
+}
+
+const DEFAULT_DIGITS: isize = 512;
+
+fn main() {
+    let args = std::env::args().collect::<Vec<_>>();
+    let n = if args.len() < 2 {
+        DEFAULT_DIGITS
+    } else if args[1] == "--bench" {
+        return pidigits(DEFAULT_DIGITS, &mut std::io::sink()).unwrap();
+    } else {
+        FromStr::from_str(&args[1]).unwrap()
+    };
+    pidigits(n, &mut std::io::stdout()).unwrap();
+}