71 lines
1.9 KiB
Rust
71 lines
1.9 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/// Convert unsigned integers into a string representation with some base.
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/// Bases up to and including 36 can be used for case-insensitive things.
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use std::str;
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pub const MAX_BASE: usize = 64;
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pub const ALPHANUMERIC_ONLY: usize = 62;
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pub const CASE_INSENSITIVE: usize = 36;
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const BASE_64: &'static [u8; MAX_BASE as usize] =
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b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
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#[inline]
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pub fn push_str(mut n: u128, base: usize, output: &mut String) {
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debug_assert!(base >= 2 && base <= MAX_BASE);
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let mut s = [0u8; 128];
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let mut index = 0;
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let base = base as u128;
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loop {
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s[index] = BASE_64[(n % base) as usize];
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index += 1;
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n /= base;
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if n == 0 {
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break;
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}
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}
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&mut s[0..index].reverse();
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output.push_str(str::from_utf8(&s[0..index]).unwrap());
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}
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#[inline]
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pub fn encode(n: u128, base: usize) -> String {
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let mut s = String::new();
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push_str(n, base, &mut s);
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s
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}
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#[test]
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fn test_encode() {
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fn test(n: u128, base: usize) {
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assert_eq!(Ok(n), u128::from_str_radix(&encode(n, base), base as u32));
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}
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for base in 2..37 {
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test(0, base);
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test(1, base);
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test(35, base);
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test(36, base);
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test(37, base);
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test(u64::max_value() as u128, base);
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test(u128::max_value(), base);
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for i in 0 .. 1_000 {
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test(i * 983, base);
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}
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}
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}
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