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Move length to the start of buffer
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@DoumanAsh
DoumanAsh committed Nov 15, 2024
1 parent 33ba0f1 commit 2edf508
Showing 1 changed file with 37 additions and 30 deletions.
67 changes: 37 additions & 30 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -76,18 +76,18 @@ pub const fn capacity(desired: usize) -> usize {
///
///const CONST_STR: MyStr = MyStr::new().and("hello").and(" ").and("world");
///
///assert_eq!(CONST_STR.len(), "hello world".len());
///assert_eq!(CONST_STR.len(), "hello world".len(), "Length should be 11 characters");
///assert_eq!(CONST_STR, "hello world");
///
///assert_eq!(MyStr::capacity(), mem::size_of::<String>());
///assert_eq!(MyStr::capacity(), mem::size_of::<String>(), "Should be equal to size of String");
///
///let text: MyStr = "test".try_into().expect("To fit string");
///assert_eq!("test", text);
///assert_eq!(text, "test");
///let mut text = MyStr::new();
///let _ = write!(text, "test {}", "hello world");
///assert_eq!(text.as_str(), "test hello world");
///assert_eq!(text.remaining(), MyStr::capacity() - "test hello world".len());
///assert_eq!(text.remaining(), MyStr::capacity() - "test hello world".len(), "Should modify length");
///
///assert_eq!(text.push_str(" or maybe not"), 8); //Overflow!
///assert_eq!(text.as_str(), "test hello world or mayb");
Expand All @@ -105,16 +105,19 @@ pub struct StrBuf<const N: usize> {
}

impl<const N: usize> StrBuf<N> {
const CAPACITY: usize = if N == 0 {
N
///Length of bytes used to store buffer's length
const LEN_OFFSET: usize = if N == 0 {
0
} else if N <= CAPACITY_U8 {
N - 1
1
} else if N <= CAPACITY_U16 {
N - 2
2
} else {
N - mem::size_of::<usize>()
mem::size_of::<usize>()
};

const CAPACITY: usize = N - Self::LEN_OFFSET;

#[inline]
///Creates new instance
pub const fn new() -> Self {
Expand Down Expand Up @@ -142,9 +145,9 @@ impl<const N: usize> StrBuf<N> {
let mut idx = 0;
let mut storage = [mem::MaybeUninit::<u8>::uninit(); N];

assert!(text.len() <= Self::CAPACITY, "Text cannot fit static storage");
debug_assert!(text.len() <= Self::CAPACITY, "Text cannot fit static storage");
while idx < text.len() {
storage[idx] = mem::MaybeUninit::new(text.as_bytes()[idx]);
storage[Self::LEN_OFFSET + idx] = mem::MaybeUninit::new(text.as_bytes()[idx]);
idx += 1;
}

Expand All @@ -166,7 +169,7 @@ impl<const N: usize> StrBuf<N> {
#[inline(always)]
///Reads byte at `idx`.
pub const unsafe fn get_unchecked(&self, idx: usize) -> u8 {
self.inner[idx].assume_init()
self.inner[Self::LEN_OFFSET + idx].assume_init()
}

#[inline]
Expand All @@ -184,13 +187,17 @@ impl<const N: usize> StrBuf<N> {
#[inline]
///Returns pointer to the beginning of underlying buffer
pub const fn as_ptr(&self) -> *const u8 {
self.inner.as_ptr() as _
unsafe {
self.inner.as_ptr().add(Self::LEN_OFFSET) as _
}
}

#[inline]
///Returns pointer to the beginning of underlying buffer
pub fn as_mut_ptr(&mut self) -> *mut u8 {
self.inner.as_mut_ptr() as *mut u8
unsafe {
self.inner.as_mut_ptr().add(Self::LEN_OFFSET) as *mut u8
}
}

#[inline]
Expand Down Expand Up @@ -233,7 +240,7 @@ impl<const N: usize> StrBuf<N> {
///Returns mutable slice with unwritten parts of the buffer.
pub fn as_write_slice(&mut self) -> &mut [mem::MaybeUninit<u8>] {
let len = self.len();
&mut self.inner[len..]
&mut self.inner[Self::LEN_OFFSET + len..]
}

#[inline(always)]
Expand Down Expand Up @@ -277,15 +284,15 @@ impl<const N: usize> StrBuf<N> {
0
} else if N <= CAPACITY_U8 {
unsafe {
self.inner[Self::CAPACITY].assume_init() as _
self.inner[0].assume_init() as _
}
} else if N <= CAPACITY_U16 {
unsafe {
u16::from_ne_bytes([self.inner[Self::CAPACITY].assume_init(), self.inner[Self::CAPACITY + 1].assume_init()]) as _
u16::from_ne_bytes(*(self.inner.as_ptr() as *const [u8; mem::size_of::<u16>()])) as usize
}
} else {
unsafe {
usize::from_ne_bytes(*(self.inner.as_ptr().add(Self::CAPACITY) as *const [u8; mem::size_of::<usize>()]))
usize::from_ne_bytes(*(self.inner.as_ptr() as *const [u8; mem::size_of::<usize>()]))
}
}
}
Expand All @@ -296,16 +303,16 @@ impl<const N: usize> StrBuf<N> {
if N == 0 {
//no length
} else if N <= CAPACITY_U8 {
self.inner[Self::CAPACITY] = mem::MaybeUninit::new(len as _);
self.inner[0] = mem::MaybeUninit::new(len as _);
} else if N <= CAPACITY_U16 {
let len = (len as u16).to_ne_bytes();
self.inner[Self::CAPACITY] = mem::MaybeUninit::new(len[0]);
self.inner[Self::CAPACITY + 1] = mem::MaybeUninit::new(len[1]);
self.inner[0] = mem::MaybeUninit::new(len[0]);
self.inner[1] = mem::MaybeUninit::new(len[1]);
} else {
let len = len.to_ne_bytes();
let mut idx = 0;
loop {
self.inner[Self::CAPACITY + idx] = mem::MaybeUninit::new(len[idx]);
self.inner[idx] = mem::MaybeUninit::new(len[idx]);
idx = idx.saturating_add(1);
if idx >= len.len() {
break;
Expand All @@ -322,15 +329,15 @@ impl<const N: usize> StrBuf<N> {
if N == 0 {
//No length
} else if N <= CAPACITY_U8 {
self.inner[Self::CAPACITY] = mem::MaybeUninit::new(len as _);
self.inner[0] = mem::MaybeUninit::new(len as _);
} else if N <= CAPACITY_U16 {
let len = (len as u16).to_ne_bytes();
self.inner[Self::CAPACITY] = mem::MaybeUninit::new(len[0]);
self.inner[Self::CAPACITY + 1] = mem::MaybeUninit::new(len[1]);
self.inner[0] = mem::MaybeUninit::new(len[0]);
self.inner[1] = mem::MaybeUninit::new(len[1]);
} else {
let len = len.to_ne_bytes();
unsafe {
let ptr = self.inner.as_mut_ptr().add(Self::CAPACITY);
let ptr = self.inner.as_mut_ptr();
ptr::copy_nonoverlapping(len.as_ptr(), ptr as *mut _, mem::size_of::<usize>());
}
}
Expand Down Expand Up @@ -387,7 +394,7 @@ impl<const N: usize> StrBuf<N> {
let mut idx = 0;
let cursor = self.len();
while idx < bytes.len() {
self.inner[cursor + idx] = mem::MaybeUninit::new(bytes[idx]);
self.inner[Self::LEN_OFFSET + cursor + idx] = mem::MaybeUninit::new(bytes[idx]);
idx += 1;
}
self.const_set_len(cursor + bytes.len())
Expand All @@ -406,8 +413,8 @@ impl<const N: usize> StrBuf<N> {
#[inline(always)]
///Modifies this string to convert all its characters into ASCII lower case equivalent
pub const fn into_ascii_lowercase(mut self) -> Self {
let len = self.len();
let mut idx = 0;
let len = Self::LEN_OFFSET + self.len();
let mut idx = Self::LEN_OFFSET;
loop {
if idx >= len {
break;
Expand All @@ -432,8 +439,8 @@ impl<const N: usize> StrBuf<N> {
#[inline(always)]
///Modifies this string to convert all its characters into ASCII upper case equivalent
pub const fn into_ascii_uppercase(mut self) -> Self {
let len = self.len();
let mut idx = 0;
let len = Self::LEN_OFFSET + self.len();
let mut idx = Self::LEN_OFFSET;
loop {
if idx >= len {
break;
Expand Down

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