mirror of
https://github.com/uuid-rs/uuid.git
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Improve encode
This commit is contained in:
Nugine
parent
c98c7ff5dd
commit
19b838619c
195
src/fmt.rs
195
src/fmt.rs
@ -112,9 +112,7 @@ impl Uuid {
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#[inline]
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pub fn as_hyphenated(&self) -> &Hyphenated {
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// SAFETY: `Uuid` and `Hyphenated` have the same ABI
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unsafe {
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&*(self as *const Uuid as *const Hyphenated)
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}
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unsafe { &*(self as *const Uuid as *const Hyphenated) }
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}
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/// Get a [`Simple`] formatter.
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@ -131,9 +129,7 @@ impl Uuid {
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#[inline]
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pub fn as_simple(&self) -> &Simple {
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// SAFETY: `Uuid` and `Simple` have the same ABI
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unsafe {
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&*(self as *const Uuid as *const Simple)
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}
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unsafe { &*(self as *const Uuid as *const Simple) }
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}
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/// Get a [`Urn`] formatter.
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@ -152,9 +148,7 @@ impl Uuid {
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#[inline]
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pub fn as_urn(&self) -> &Urn {
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// SAFETY: `Uuid` and `Urn` have the same ABI
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unsafe {
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&*(self as *const Uuid as *const Urn)
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}
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unsafe { &*(self as *const Uuid as *const Urn) }
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}
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/// Get a [`Braced`] formatter.
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@ -173,9 +167,7 @@ impl Uuid {
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#[inline]
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pub fn as_braced(&self) -> &Braced {
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// SAFETY: `Uuid` and `Braced` have the same ABI
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unsafe {
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&*(self as *const Uuid as *const Braced)
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}
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unsafe { &*(self as *const Uuid as *const Braced) }
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}
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}
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@ -187,58 +179,109 @@ const LOWER: [u8; 16] = [
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b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9', b'a', b'b',
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b'c', b'd', b'e', b'f',
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];
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/// The segments of a UUID's [u8; 16] corresponding to each group.
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const BYTE_POSITIONS: [usize; 6] = [0, 4, 6, 8, 10, 16];
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/// The locations that hyphens are written into the buffer, after each
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/// group.
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const HYPHEN_POSITIONS: [usize; 4] = [8, 13, 18, 23];
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/// Encodes the `uuid` possibly with hyphens, and possibly in upper
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/// case, to full_buffer[start..] and returns the str sliced from
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/// full_buffer[..start + encoded_length].
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///
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/// The `start` parameter allows writing a prefix (such as
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/// "urn:uuid:") to the buffer that's included in the final encoded
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/// UUID.
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#[allow(clippy::needless_range_loop)]
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fn encode<'a>(
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full_buffer: &'a mut [u8],
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start: usize,
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trailing: usize,
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uuid: &Uuid,
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hyphens: bool,
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upper: bool,
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) -> &'a mut str {
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let len = if hyphens { 36 } else { 32 };
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{
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let buffer = &mut full_buffer[start..start + len];
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let bytes = uuid.as_bytes();
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let hex = if upper { &UPPER } else { &LOWER };
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for group in 0..5 {
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// If we're writing hyphens, we need to shift the output
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// location along by how many of them have been written
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// before this point. That's exactly the (0-indexed) group
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// number.
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let hyphens_before = if hyphens { group } else { 0 };
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for idx in BYTE_POSITIONS[group]..BYTE_POSITIONS[group + 1] {
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let b = bytes[idx];
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let out_idx = hyphens_before + 2 * idx;
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buffer[out_idx] = hex[(b >> 4) as usize];
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buffer[out_idx + 1] = hex[(b & 0b1111) as usize];
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}
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if group != 4 && hyphens {
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buffer[HYPHEN_POSITIONS[group]] = b'-';
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}
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}
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#[inline]
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const fn format_simple(src: &[u8; 16], upper: bool) -> [u8; 32] {
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let lut = if upper { &UPPER } else { &LOWER };
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let mut dst = [0; 32];
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let mut i = 0;
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while i < 16 {
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let x = src[i];
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dst[i * 2] = lut[(x >> 4) as usize];
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dst[i * 2 + 1] = lut[(x & 0x0f) as usize];
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i += 1;
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}
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dst
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}
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str::from_utf8_mut(&mut full_buffer[..start + len + trailing])
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.expect("found non-ASCII output characters while encoding a UUID")
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#[inline]
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const fn format_hyphenated(src: &[u8; 16], upper: bool) -> [u8; 36] {
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let lut = if upper { &UPPER } else { &LOWER };
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let groups = [(0, 8), (9, 13), (14, 18), (19, 23), (24, 36)];
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let mut dst = [0; 36];
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let mut group_idx = 0;
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let mut i = 0;
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while group_idx < 5 {
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let (start, end) = groups[group_idx];
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let mut j = start;
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while j < end {
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let x = src[i];
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i += 1;
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dst[j] = lut[(x >> 4) as usize];
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dst[j + 1] = lut[(x & 0x0f) as usize];
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j += 2;
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}
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if group_idx < 4 {
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dst[end] = b'-';
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}
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group_idx += 1;
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}
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dst
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}
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#[inline]
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fn encode_simple<'b>(
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src: &[u8; 16],
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buffer: &'b mut [u8],
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upper: bool,
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) -> &'b mut str {
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const LEN: usize = 32;
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let buf = &mut buffer[..LEN];
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unsafe {
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let dst = buf.as_mut_ptr();
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core::ptr::write(dst.cast(), format_simple(src, upper));
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core::str::from_utf8_unchecked_mut(buf) // SAFETY: ascii encoding
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}
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}
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#[inline]
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fn encode_hyphenated<'b>(
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src: &[u8; 16],
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buffer: &'b mut [u8],
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upper: bool,
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) -> &'b mut str {
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const LEN: usize = 36;
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let buf = &mut buffer[..LEN];
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unsafe {
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let dst = buf.as_mut_ptr();
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core::ptr::write(dst.cast(), format_hyphenated(src, upper));
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core::str::from_utf8_unchecked_mut(buf) // SAFETY: ascii encoding
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}
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}
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#[inline]
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fn encode_braced<'b>(
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src: &[u8; 16],
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buffer: &'b mut [u8],
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upper: bool,
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) -> &'b mut str {
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const LEN: usize = 38;
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let buf = &mut buffer[..LEN];
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buf[0] = b'{';
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buf[LEN - 1] = b'}';
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unsafe {
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let dst = buf.as_mut_ptr().add(1);
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core::ptr::write(dst.cast(), format_hyphenated(src, upper));
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core::str::from_utf8_unchecked_mut(buf) // SAFETY: ascii encoding
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}
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}
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#[inline]
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fn encode_urn<'b>(
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src: &[u8; 16],
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buffer: &'b mut [u8],
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upper: bool,
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) -> &'b mut str {
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const LEN: usize = 45;
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let buf = &mut buffer[..LEN];
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buf[..9].copy_from_slice(b"urn:uuid:");
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unsafe {
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let dst = buf.as_mut_ptr().add(9);
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core::ptr::write(dst.cast(), format_hyphenated(src, upper));
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core::str::from_utf8_unchecked_mut(buf) // SAFETY: ascii encoding
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}
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}
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impl Hyphenated {
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@ -301,8 +344,9 @@ impl Hyphenated {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_lower<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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encode(buffer, 0, 0, &self.0, true, false)
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encode_hyphenated(self.0.as_bytes(), buffer, false)
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}
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/// Writes the [`Uuid`] as an upper-case hyphenated string to
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@ -351,8 +395,9 @@ impl Hyphenated {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_upper<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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encode(buffer, 0, 0, &self.0, true, true)
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encode_hyphenated(self.0.as_bytes(), buffer, true)
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}
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/// Get a reference to the underlying [`Uuid`].
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@ -444,10 +489,9 @@ impl Braced {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_lower<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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buffer[0] = b'{';
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buffer[37] = b'}';
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encode(buffer, 1, 1, &self.0, true, false)
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encode_braced(self.0.as_bytes(), buffer, false)
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}
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/// Writes the [`Uuid`] as an upper-case hyphenated string surrounded by
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@ -496,10 +540,9 @@ impl Braced {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_upper<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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buffer[0] = b'{';
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buffer[37] = b'}';
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encode(buffer, 1, 1, &self.0, true, true)
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encode_braced(self.0.as_bytes(), buffer, true)
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}
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/// Get a reference to the underlying [`Uuid`].
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@ -592,8 +635,9 @@ impl Simple {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_lower<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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encode(buffer, 0, 0, &self.0, false, false)
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encode_simple(self.0.as_bytes(), buffer, false)
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}
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/// Writes the [`Uuid`] as an upper-case simple string to `buffer`,
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@ -639,8 +683,9 @@ impl Simple {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_upper<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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encode(buffer, 0, 0, &self.0, false, true)
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encode_simple(self.0.as_bytes(), buffer, true)
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}
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/// Get a reference to the underlying [`Uuid`].
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@ -735,9 +780,9 @@ impl Urn {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_lower<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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buffer[..9].copy_from_slice(b"urn:uuid:");
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encode(buffer, 9, 0, &self.0, true, false)
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encode_urn(self.0.as_bytes(), buffer, false)
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}
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/// Writes the [`Uuid`] as an upper-case URN string to
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@ -788,9 +833,9 @@ impl Urn {
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/// }
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/// ```
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/// */
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#[inline]
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pub fn encode_upper<'buf>(&self, buffer: &'buf mut [u8]) -> &'buf mut str {
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buffer[..9].copy_from_slice(b"urn:uuid:");
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encode(buffer, 9, 0, &self.0, true, true)
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encode_urn(self.0.as_bytes(), buffer, true)
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}
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/// Get a reference to the underlying [`Uuid`].
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