mirror of https://github.com/rust-lang/rust
111 lines
2.5 KiB
Rust
111 lines
2.5 KiB
Rust
/// Converts 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::ascii;
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use std::fmt;
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#[cfg(test)]
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mod tests;
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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: [ascii::Char; MAX_BASE] = {
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let bytes = b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
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let Some(ascii) = bytes.as_ascii() else { panic!() };
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*ascii
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};
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pub struct BaseNString {
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start: usize,
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buf: [ascii::Char; 128],
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}
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impl std::ops::Deref for BaseNString {
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type Target = str;
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fn deref(&self) -> &str {
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self.buf[self.start..].as_str()
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}
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}
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impl AsRef<str> for BaseNString {
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fn as_ref(&self) -> &str {
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self.buf[self.start..].as_str()
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}
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}
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impl fmt::Display for BaseNString {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.write_str(self)
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}
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}
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// This trait just lets us reserve the exact right amount of space when doing fixed-length
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// case-insensitve encoding. Add any impls you need.
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pub trait ToBaseN: Into<u128> {
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fn encoded_len(base: usize) -> usize;
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fn to_base_fixed_len(self, base: usize) -> BaseNString {
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let mut encoded = self.to_base(base);
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encoded.start = encoded.buf.len() - Self::encoded_len(base);
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encoded
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}
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fn to_base(self, base: usize) -> BaseNString {
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let mut output = [ascii::Char::Digit0; 128];
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let mut n: u128 = self.into();
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let mut index = output.len();
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loop {
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index -= 1;
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output[index] = BASE_64[(n % base as u128) as usize];
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n /= base as u128;
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if n == 0 {
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break;
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}
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}
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assert_eq!(n, 0);
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BaseNString { start: index, buf: output }
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}
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}
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impl ToBaseN for u128 {
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fn encoded_len(base: usize) -> usize {
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let mut max = u128::MAX;
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let mut len = 0;
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while max > 0 {
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len += 1;
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max /= base as u128;
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}
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len
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}
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}
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impl ToBaseN for u64 {
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fn encoded_len(base: usize) -> usize {
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let mut max = u64::MAX;
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let mut len = 0;
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while max > 0 {
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len += 1;
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max /= base as u64;
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}
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len
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}
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}
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impl ToBaseN for u32 {
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fn encoded_len(base: usize) -> usize {
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let mut max = u32::MAX;
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let mut len = 0;
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while max > 0 {
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len += 1;
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max /= base as u32;
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}
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len
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}
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}
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