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Add log2
and log10
to NonZeroU*
#92956
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Original file line number | Diff line number | Diff line change |
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@@ -1,141 +1,140 @@ | ||
mod unchecked { | ||
// 0 < val <= u8::MAX | ||
#[inline] | ||
pub const fn u8(val: u8) -> u32 { | ||
let val = val as u32; | ||
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// For better performance, avoid branches by assembling the solution | ||
// in the bits above the low 8 bits. | ||
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// Adding c1 to val gives 10 in the top bits for val < 10, 11 for val >= 10 | ||
const C1: u32 = 0b11_00000000 - 10; // 758 | ||
// Adding c2 to val gives 01 in the top bits for val < 100, 10 for val >= 100 | ||
const C2: u32 = 0b10_00000000 - 100; // 412 | ||
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// Value of top bits: | ||
// +c1 +c2 1&2 | ||
// 0..=9 10 01 00 = 0 | ||
// 10..=99 11 01 01 = 1 | ||
// 100..=255 11 10 10 = 2 | ||
((val + C1) & (val + C2)) >> 8 | ||
} | ||
/// These functions compute the integer logarithm of their type, assuming | ||
/// that someone has already checked that the the value is strictly positive. | ||
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// 0 < val <= u8::MAX | ||
#[inline] | ||
pub const fn u8(val: u8) -> u32 { | ||
let val = val as u32; | ||
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// For better performance, avoid branches by assembling the solution | ||
// in the bits above the low 8 bits. | ||
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// Adding c1 to val gives 10 in the top bits for val < 10, 11 for val >= 10 | ||
const C1: u32 = 0b11_00000000 - 10; // 758 | ||
// Adding c2 to val gives 01 in the top bits for val < 100, 10 for val >= 100 | ||
const C2: u32 = 0b10_00000000 - 100; // 412 | ||
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// Value of top bits: | ||
// +c1 +c2 1&2 | ||
// 0..=9 10 01 00 = 0 | ||
// 10..=99 11 01 01 = 1 | ||
// 100..=255 11 10 10 = 2 | ||
((val + C1) & (val + C2)) >> 8 | ||
} | ||
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// 0 < val < 100_000 | ||
#[inline] | ||
const fn less_than_5(val: u32) -> u32 { | ||
// Similar to u8, when adding one of these constants to val, | ||
// we get two possible bit patterns above the low 17 bits, | ||
// depending on whether val is below or above the threshold. | ||
const C1: u32 = 0b011_00000000000000000 - 10; // 393206 | ||
const C2: u32 = 0b100_00000000000000000 - 100; // 524188 | ||
const C3: u32 = 0b111_00000000000000000 - 1000; // 916504 | ||
const C4: u32 = 0b100_00000000000000000 - 10000; // 514288 | ||
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// Value of top bits: | ||
// +c1 +c2 1&2 +c3 +c4 3&4 ^ | ||
// 0..=9 010 011 010 110 011 010 000 = 0 | ||
// 10..=99 011 011 011 110 011 010 001 = 1 | ||
// 100..=999 011 100 000 110 011 010 010 = 2 | ||
// 1000..=9999 011 100 000 111 011 011 011 = 3 | ||
// 10000..=99999 011 100 000 111 100 100 100 = 4 | ||
(((val + C1) & (val + C2)) ^ ((val + C3) & (val + C4))) >> 17 | ||
} | ||
// 0 < val < 100_000 | ||
#[inline] | ||
const fn less_than_5(val: u32) -> u32 { | ||
// Similar to u8, when adding one of these constants to val, | ||
// we get two possible bit patterns above the low 17 bits, | ||
// depending on whether val is below or above the threshold. | ||
const C1: u32 = 0b011_00000000000000000 - 10; // 393206 | ||
const C2: u32 = 0b100_00000000000000000 - 100; // 524188 | ||
const C3: u32 = 0b111_00000000000000000 - 1000; // 916504 | ||
const C4: u32 = 0b100_00000000000000000 - 10000; // 514288 | ||
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||
// Value of top bits: | ||
// +c1 +c2 1&2 +c3 +c4 3&4 ^ | ||
// 0..=9 010 011 010 110 011 010 000 = 0 | ||
// 10..=99 011 011 011 110 011 010 001 = 1 | ||
// 100..=999 011 100 000 110 011 010 010 = 2 | ||
// 1000..=9999 011 100 000 111 011 011 011 = 3 | ||
// 10000..=99999 011 100 000 111 100 100 100 = 4 | ||
(((val + C1) & (val + C2)) ^ ((val + C3) & (val + C4))) >> 17 | ||
} | ||
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// 0 < val <= u16::MAX | ||
#[inline] | ||
pub const fn u16(val: u16) -> u32 { | ||
less_than_5(val as u32) | ||
} | ||
// 0 < val <= u16::MAX | ||
#[inline] | ||
pub const fn u16(val: u16) -> u32 { | ||
less_than_5(val as u32) | ||
} | ||
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// 0 < val <= u32::MAX | ||
#[inline] | ||
pub const fn u32(mut val: u32) -> u32 { | ||
let mut log = 0; | ||
if val >= 100_000 { | ||
val /= 100_000; | ||
log += 5; | ||
} | ||
log + less_than_5(val) | ||
// 0 < val <= u32::MAX | ||
#[inline] | ||
pub const fn u32(mut val: u32) -> u32 { | ||
let mut log = 0; | ||
if val >= 100_000 { | ||
val /= 100_000; | ||
log += 5; | ||
} | ||
log + less_than_5(val) | ||
} | ||
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||
// 0 < val <= u64::MAX | ||
#[inline] | ||
pub const fn u64(mut val: u64) -> u32 { | ||
let mut log = 0; | ||
if val >= 10_000_000_000 { | ||
val /= 10_000_000_000; | ||
log += 10; | ||
} | ||
if val >= 100_000 { | ||
val /= 100_000; | ||
log += 5; | ||
} | ||
log + less_than_5(val as u32) | ||
// 0 < val <= u64::MAX | ||
#[inline] | ||
pub const fn u64(mut val: u64) -> u32 { | ||
let mut log = 0; | ||
if val >= 10_000_000_000 { | ||
val /= 10_000_000_000; | ||
log += 10; | ||
} | ||
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// 0 < val <= u128::MAX | ||
#[inline] | ||
pub const fn u128(mut val: u128) -> u32 { | ||
let mut log = 0; | ||
if val >= 100_000_000_000_000_000_000_000_000_000_000 { | ||
val /= 100_000_000_000_000_000_000_000_000_000_000; | ||
log += 32; | ||
return log + u32(val as u32); | ||
} | ||
if val >= 10_000_000_000_000_000 { | ||
val /= 10_000_000_000_000_000; | ||
log += 16; | ||
} | ||
log + u64(val as u64) | ||
if val >= 100_000 { | ||
val /= 100_000; | ||
log += 5; | ||
} | ||
log + less_than_5(val as u32) | ||
} | ||
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// 0 < val <= i8::MAX | ||
#[inline] | ||
pub const fn i8(val: i8) -> u32 { | ||
u8(val as u8) | ||
// 0 < val <= u128::MAX | ||
#[inline] | ||
pub const fn u128(mut val: u128) -> u32 { | ||
let mut log = 0; | ||
if val >= 100_000_000_000_000_000_000_000_000_000_000 { | ||
val /= 100_000_000_000_000_000_000_000_000_000_000; | ||
log += 32; | ||
return log + u32(val as u32); | ||
} | ||
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// 0 < val <= i16::MAX | ||
#[inline] | ||
pub const fn i16(val: i16) -> u32 { | ||
u16(val as u16) | ||
if val >= 10_000_000_000_000_000 { | ||
val /= 10_000_000_000_000_000; | ||
log += 16; | ||
} | ||
log + u64(val as u64) | ||
} | ||
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// 0 < val <= i32::MAX | ||
#[inline] | ||
pub const fn i32(val: i32) -> u32 { | ||
u32(val as u32) | ||
} | ||
#[cfg(target_pointer_width = "16")] | ||
#[inline] | ||
pub const fn usize(val: usize) -> u32 { | ||
u16(val as _) | ||
} | ||
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// 0 < val <= i64::MAX | ||
#[inline] | ||
pub const fn i64(val: i64) -> u32 { | ||
u64(val as u64) | ||
} | ||
#[cfg(target_pointer_width = "32")] | ||
#[inline] | ||
pub const fn usize(val: usize) -> u32 { | ||
u32(val as _) | ||
} | ||
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// 0 < val <= i128::MAX | ||
#[inline] | ||
pub const fn i128(val: i128) -> u32 { | ||
u128(val as u128) | ||
} | ||
#[cfg(target_pointer_width = "64")] | ||
#[inline] | ||
pub const fn usize(val: usize) -> u32 { | ||
u64(val as _) | ||
} | ||
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// 0 < val <= i8::MAX | ||
#[inline] | ||
pub const fn i8(val: i8) -> u32 { | ||
u8(val as u8) | ||
} | ||
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macro_rules! impl_checked { | ||
($T:ident) => { | ||
#[inline] | ||
pub const fn $T(val: $T) -> Option<u32> { | ||
if val > 0 { Some(unchecked::$T(val)) } else { None } | ||
} | ||
}; | ||
// 0 < val <= i16::MAX | ||
#[inline] | ||
pub const fn i16(val: i16) -> u32 { | ||
u16(val as u16) | ||
} | ||
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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 } | ||
// 0 < val <= i32::MAX | ||
#[inline] | ||
pub const fn i32(val: i32) -> u32 { | ||
u32(val as u32) | ||
} | ||
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// 0 < val <= i64::MAX | ||
#[inline] | ||
pub const fn i64(val: i64) -> u32 { | ||
u64(val as u64) | ||
} | ||
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// 0 < val <= i128::MAX | ||
#[inline] | ||
pub const fn i128(val: i128) -> u32 { | ||
u128(val as u128) | ||
} |
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These are unchanged, just de-indented. You might want to use ignore whitespace mode to review.