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Add log2 and log10 to NonZeroU* #92956

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Jan 18, 2022
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Add log2 and log10 to NonZeroU* #92956

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43 changes: 21 additions & 22 deletions library/core/src/num/int_log10.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
mod unchecked {
/// These functions compute the integer logarithm of their type, assuming
/// that someone has already checked that the the value is strictly positive.

// 0 < val <= u8::MAX
#[inline]
pub const fn u8(val: u8) -> u32 {
Expand Down Expand Up @@ -89,6 +91,24 @@ mod unchecked {
log + u64(val as u64)
}

#[cfg(target_pointer_width = "16")]
#[inline]
pub const fn usize(val: usize) -> u32 {
u16(val as _)
}

#[cfg(target_pointer_width = "32")]
#[inline]
pub const fn usize(val: usize) -> u32 {
u32(val as _)
}

#[cfg(target_pointer_width = "64")]
#[inline]
pub const fn usize(val: usize) -> u32 {
u64(val as _)
}

// 0 < val <= i8::MAX
#[inline]
pub const fn i8(val: i8) -> u32 {
Expand Down Expand Up @@ -118,24 +138,3 @@ mod unchecked {
pub const fn i128(val: i128) -> u32 {
u128(val as u128)
}
}

macro_rules! impl_checked {
($T:ident) => {
#[inline]
pub const fn $T(val: $T) -> Option<u32> {
if val > 0 { Some(unchecked::$T(val)) } else { None }
}
};
}

impl_checked! { u8 }
impl_checked! { u16 }
impl_checked! { u32 }
impl_checked! { u64 }
impl_checked! { u128 }
impl_checked! { i8 }
impl_checked! { i16 }
impl_checked! { i32 }
impl_checked! { i64 }
impl_checked! { i128 }
6 changes: 5 additions & 1 deletion library/core/src/num/int_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2362,7 +2362,11 @@ macro_rules! int_impl {
without modifying the original"]
#[inline]
pub const fn checked_log10(self) -> Option<u32> {
int_log10::$ActualT(self as $ActualT)
if self > 0 {
Some(int_log10::$ActualT(self as $ActualT))
} else {
None
}
}

/// Computes the absolute value of `self`.
Expand Down
16 changes: 8 additions & 8 deletions library/core/src/num/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,7 @@ const ASCII_CASE_MASK: u8 = 0b0010_0000;

#[lang = "u8"]
impl u8 {
uint_impl! { u8, u8, i8, 8, 255, 2, "0x82", "0xa", "0x12", "0x12", "0x48", "[0x12]",
uint_impl! { u8, u8, i8, NonZeroU8, 8, 255, 2, "0x82", "0xa", "0x12", "0x12", "0x48", "[0x12]",
"[0x12]", "", "" }
widening_impl! { u8, u16, 8, unsigned }

Expand Down Expand Up @@ -813,21 +813,21 @@ impl u8 {

#[lang = "u16"]
impl u16 {
uint_impl! { u16, u16, i16, 16, 65535, 4, "0xa003", "0x3a", "0x1234", "0x3412", "0x2c48",
uint_impl! { u16, u16, i16, NonZeroU16, 16, 65535, 4, "0xa003", "0x3a", "0x1234", "0x3412", "0x2c48",
"[0x34, 0x12]", "[0x12, 0x34]", "", "" }
widening_impl! { u16, u32, 16, unsigned }
}

#[lang = "u32"]
impl u32 {
uint_impl! { u32, u32, i32, 32, 4294967295, 8, "0x10000b3", "0xb301", "0x12345678",
uint_impl! { u32, u32, i32, NonZeroU32, 32, 4294967295, 8, "0x10000b3", "0xb301", "0x12345678",
"0x78563412", "0x1e6a2c48", "[0x78, 0x56, 0x34, 0x12]", "[0x12, 0x34, 0x56, 0x78]", "", "" }
widening_impl! { u32, u64, 32, unsigned }
}

#[lang = "u64"]
impl u64 {
uint_impl! { u64, u64, i64, 64, 18446744073709551615, 12, "0xaa00000000006e1", "0x6e10aa",
uint_impl! { u64, u64, i64, NonZeroU64, 64, 18446744073709551615, 12, "0xaa00000000006e1", "0x6e10aa",
"0x1234567890123456", "0x5634129078563412", "0x6a2c48091e6a2c48",
"[0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]",
Expand All @@ -837,7 +837,7 @@ impl u64 {

#[lang = "u128"]
impl u128 {
uint_impl! { u128, u128, i128, 128, 340282366920938463463374607431768211455, 16,
uint_impl! { u128, u128, i128, NonZeroU128, 128, 340282366920938463463374607431768211455, 16,
"0x13f40000000000000000000000004f76", "0x4f7613f4", "0x12345678901234567890123456789012",
"0x12907856341290785634129078563412", "0x48091e6a2c48091e6a2c48091e6a2c48",
"[0x12, 0x90, 0x78, 0x56, 0x34, 0x12, 0x90, 0x78, \
Expand All @@ -850,15 +850,15 @@ impl u128 {
#[cfg(target_pointer_width = "16")]
#[lang = "usize"]
impl usize {
uint_impl! { usize, u16, isize, 16, 65535, 4, "0xa003", "0x3a", "0x1234", "0x3412", "0x2c48",
uint_impl! { usize, u16, isize, NonZeroUsize, 16, 65535, 4, "0xa003", "0x3a", "0x1234", "0x3412", "0x2c48",
"[0x34, 0x12]", "[0x12, 0x34]",
usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
widening_impl! { usize, u32, 16, unsigned }
}
#[cfg(target_pointer_width = "32")]
#[lang = "usize"]
impl usize {
uint_impl! { usize, u32, isize, 32, 4294967295, 8, "0x10000b3", "0xb301", "0x12345678",
uint_impl! { usize, u32, isize, NonZeroUsize, 32, 4294967295, 8, "0x10000b3", "0xb301", "0x12345678",
"0x78563412", "0x1e6a2c48", "[0x78, 0x56, 0x34, 0x12]", "[0x12, 0x34, 0x56, 0x78]",
usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
widening_impl! { usize, u64, 32, unsigned }
Expand All @@ -867,7 +867,7 @@ impl usize {
#[cfg(target_pointer_width = "64")]
#[lang = "usize"]
impl usize {
uint_impl! { usize, u64, isize, 64, 18446744073709551615, 12, "0xaa00000000006e1", "0x6e10aa",
uint_impl! { usize, u64, isize, NonZeroUsize, 64, 18446744073709551615, 12, "0xaa00000000006e1", "0x6e10aa",
"0x1234567890123456", "0x5634129078563412", "0x6a2c48091e6a2c48",
"[0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]",
Expand Down
52 changes: 51 additions & 1 deletion library/core/src/num/nonzero.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -302,7 +302,7 @@ nonzero_integers_div! {

// A bunch of methods for unsigned nonzero types only.
macro_rules! nonzero_unsigned_operations {
( $( $Ty: ident($Int: ty); )+ ) => {
( $( $Ty: ident($Int: ident); )+ ) => {
$(
impl $Ty {
/// Add an unsigned integer to a non-zero value.
Expand Down Expand Up @@ -442,6 +442,56 @@ macro_rules! nonzero_unsigned_operations {
None
}
}

/// Returns the base 2 logarithm of the number, rounded down.
///
/// This is the same operation as
#[doc = concat!("[`", stringify!($Int), "::log2`],")]
/// except that it has no failure cases to worry about
/// since this value can never be zero.
///
/// # Examples
///
/// ```
/// #![feature(int_log)]
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
///
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(7).unwrap().log2(), 2);")]
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(8).unwrap().log2(), 3);")]
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(9).unwrap().log2(), 3);")]
/// ```
#[unstable(feature = "int_log", issue = "70887")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn log2(self) -> u32 {
<$Int>::BITS - 1 - self.leading_zeros()
}

/// Returns the base 10 logarithm of the number, rounded down.
///
/// This is the same operation as
#[doc = concat!("[`", stringify!($Int), "::log10`],")]
/// except that it has no failure cases to worry about
/// since this value can never be zero.
///
/// # Examples
///
/// ```
/// #![feature(int_log)]
#[doc = concat!("# use std::num::", stringify!($Ty), ";")]
///
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(99).unwrap().log10(), 1);")]
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(100).unwrap().log10(), 2);")]
#[doc = concat!("assert_eq!(", stringify!($Ty), "::new(101).unwrap().log10(), 2);")]
/// ```
#[unstable(feature = "int_log", issue = "70887")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn log10(self) -> u32 {
super::int_log10::$Int(self.0)
}
}
)+
}
Expand Down
17 changes: 10 additions & 7 deletions library/core/src/num/uint_macros.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
macro_rules! uint_impl {
($SelfT:ty, $ActualT:ident, $SignedT:ident, $BITS:expr, $MaxV:expr,
($SelfT:ty, $ActualT:ident, $SignedT:ident, $NonZeroT:ident,
$BITS:expr, $MaxV:expr,
$rot:expr, $rot_op:expr, $rot_result:expr, $swap_op:expr, $swapped:expr,
$reversed:expr, $le_bytes:expr, $be_bytes:expr,
$to_xe_bytes_doc:expr, $from_xe_bytes_doc:expr) => {
Expand Down Expand Up @@ -839,12 +840,10 @@ macro_rules! uint_impl {
without modifying the original"]
#[inline]
pub const fn checked_log2(self) -> Option<u32> {
if self <= 0 {
None
if let Some(x) = <$NonZeroT>::new(self) {
Some(x.log2())
} else {
// SAFETY: We just checked that this number is positive
let log = (Self::BITS - 1) - unsafe { intrinsics::ctlz_nonzero(self) as u32 };
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One fewer unsafe, as a bonus.

Some(log)
None
}
}

Expand All @@ -863,7 +862,11 @@ macro_rules! uint_impl {
without modifying the original"]
#[inline]
pub const fn checked_log10(self) -> Option<u32> {
int_log10::$ActualT(self as $ActualT)
if let Some(x) = <$NonZeroT>::new(self) {
Some(x.log10())
} else {
None
}
}

/// Checked negation. Computes `-self`, returning `None` unless `self ==
Expand Down