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206 lines
4.4 KiB
206 lines
4.4 KiB
4 years ago
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use std::borrow::Borrow;
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use std::cmp::Ordering;
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4 years ago
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use std::convert::TryFrom;
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4 years ago
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use std::convert::TryInto;
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use std::error::Error;
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use std::fmt;
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use std::hash::{Hash, Hasher};
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use std::ops::Deref;
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use std::str;
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use std::str::{FromStr, Utf8Error};
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/// A small inline string
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#[derive(Clone, Copy, Default)]
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#[repr(transparent)]
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pub struct SmallString {
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inner: [u8; 16],
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}
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impl SmallString {
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#[inline]
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pub const fn new() -> Self {
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Self { inner: [0; 16] }
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}
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#[inline]
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pub fn from_utf8(bytes: &[u8]) -> Result<SmallString, BadSmallStringError> {
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Self::from_str(str::from_utf8(bytes).map_err(BadSmallStringError::BadUtf8)?)
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}
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#[inline]
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pub fn from_be_bytes(bytes: [u8; 16]) -> Result<SmallString, BadSmallStringError> {
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// We check that it is valid UTF-8
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str::from_utf8(&bytes.as_ref()[..bytes[15].into()])
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.map_err(BadSmallStringError::BadUtf8)?;
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Ok(Self { inner: bytes })
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}
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#[inline]
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pub fn len(&self) -> usize {
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self.inner[15].into()
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}
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#[inline]
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pub fn is_empty(&self) -> bool {
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self.len() == 0
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}
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#[inline]
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#[allow(unsafe_code)]
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pub fn as_str(&self) -> &str {
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unsafe {
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// safe because we ensured it in constructors
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str::from_utf8_unchecked(self.as_bytes())
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}
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}
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#[inline]
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pub fn as_bytes(&self) -> &[u8] {
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&self.inner[..self.len()]
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}
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#[inline]
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pub fn to_be_bytes(self) -> [u8; 16] {
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self.inner
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}
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}
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impl Deref for SmallString {
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type Target = str;
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#[inline]
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fn deref(&self) -> &str {
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self.as_str()
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}
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}
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impl AsRef<str> for SmallString {
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#[inline]
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fn as_ref(&self) -> &str {
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self.as_str()
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}
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}
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impl Borrow<str> for SmallString {
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#[inline]
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fn borrow(&self) -> &str {
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self.as_str()
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}
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}
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impl fmt::Debug for SmallString {
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#[inline]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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self.as_str().fmt(f)
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}
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}
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impl fmt::Display for SmallString {
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#[inline]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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self.as_str().fmt(f)
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}
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}
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impl PartialEq for SmallString {
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#[inline]
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fn eq(&self, other: &Self) -> bool {
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self.as_str().eq(other.deref())
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}
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}
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impl Eq for SmallString {}
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impl PartialOrd for SmallString {
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#[inline]
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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self.as_str().partial_cmp(other.as_str())
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}
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}
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impl Ord for SmallString {
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#[inline]
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fn cmp(&self, other: &Self) -> Ordering {
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self.as_str().cmp(other.as_str())
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}
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}
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impl Hash for SmallString {
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#[inline]
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fn hash<H: Hasher>(&self, state: &mut H) {
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self.as_str().hash(state)
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}
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}
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impl From<SmallString> for String {
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#[inline]
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fn from(value: SmallString) -> Self {
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value.as_str().into()
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}
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}
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impl<'a> From<&'a SmallString> for &'a str {
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#[inline]
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fn from(value: &'a SmallString) -> Self {
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value.as_str()
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}
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}
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impl FromStr for SmallString {
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type Err = BadSmallStringError;
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#[inline]
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fn from_str(value: &str) -> Result<Self, BadSmallStringError> {
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if value.len() <= 15 {
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let mut inner = [0; 16];
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inner[..value.len()].copy_from_slice(value.as_bytes());
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inner[15] = value
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.len()
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.try_into()
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.map_err(|_| BadSmallStringError::TooLong(value.len()))?;
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Ok(Self { inner })
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} else {
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Err(BadSmallStringError::TooLong(value.len()))
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}
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}
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}
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impl<'a> TryFrom<&'a str> for SmallString {
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type Error = BadSmallStringError;
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#[inline]
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fn try_from(value: &'a str) -> Result<Self, BadSmallStringError> {
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Self::from_str(value)
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}
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}
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#[derive(Debug, Clone, Copy)]
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pub enum BadSmallStringError {
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TooLong(usize),
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BadUtf8(Utf8Error),
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}
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impl fmt::Display for BadSmallStringError {
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#[inline]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::TooLong(v) => write!(
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f,
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"small strings could only contain at most 15 characters, found {}",
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v
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),
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Self::BadUtf8(e) => e.fmt(f),
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}
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}
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}
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impl Error for BadSmallStringError {
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#[inline]
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fn source(&self) -> Option<&(dyn Error + 'static)> {
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match self {
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Self::TooLong(_) => None,
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Self::BadUtf8(e) => Some(e),
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}
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}
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}
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