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Diffstat (limited to '')
-rw-r--r-- | vendor/ryu/src/common.rs | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/vendor/ryu/src/common.rs b/vendor/ryu/src/common.rs new file mode 100644 index 000000000..9613036a2 --- /dev/null +++ b/vendor/ryu/src/common.rs @@ -0,0 +1,95 @@ +// Translated from C to Rust. The original C code can be found at +// https://github.com/ulfjack/ryu and carries the following license: +// +// Copyright 2018 Ulf Adams +// +// The contents of this file may be used under the terms of the Apache License, +// Version 2.0. +// +// (See accompanying file LICENSE-Apache or copy at +// http://www.apache.org/licenses/LICENSE-2.0) +// +// Alternatively, the contents of this file may be used under the terms of +// the Boost Software License, Version 1.0. +// (See accompanying file LICENSE-Boost or copy at +// https://www.boost.org/LICENSE_1_0.txt) +// +// Unless required by applicable law or agreed to in writing, this software +// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. + +// Returns the number of decimal digits in v, which must not contain more than 9 +// digits. +#[cfg_attr(feature = "no-panic", inline)] +pub fn decimal_length9(v: u32) -> u32 { + // Function precondition: v is not a 10-digit number. + // (f2s: 9 digits are sufficient for round-tripping.) + debug_assert!(v < 1000000000); + + if v >= 100000000 { + 9 + } else if v >= 10000000 { + 8 + } else if v >= 1000000 { + 7 + } else if v >= 100000 { + 6 + } else if v >= 10000 { + 5 + } else if v >= 1000 { + 4 + } else if v >= 100 { + 3 + } else if v >= 10 { + 2 + } else { + 1 + } +} + +// Returns e == 0 ? 1 : [log_2(5^e)]; requires 0 <= e <= 3528. +#[cfg_attr(feature = "no-panic", inline)] +#[allow(dead_code)] +pub fn log2_pow5(e: i32) -> i32 /* or u32 -> u32 */ { + // This approximation works up to the point that the multiplication + // overflows at e = 3529. If the multiplication were done in 64 bits, it + // would fail at 5^4004 which is just greater than 2^9297. + debug_assert!(e >= 0); + debug_assert!(e <= 3528); + ((e as u32 * 1217359) >> 19) as i32 +} + +// Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528. +#[cfg_attr(feature = "no-panic", inline)] +pub fn pow5bits(e: i32) -> i32 /* or u32 -> u32 */ { + // This approximation works up to the point that the multiplication + // overflows at e = 3529. If the multiplication were done in 64 bits, it + // would fail at 5^4004 which is just greater than 2^9297. + debug_assert!(e >= 0); + debug_assert!(e <= 3528); + (((e as u32 * 1217359) >> 19) + 1) as i32 +} + +#[cfg_attr(feature = "no-panic", inline)] +#[allow(dead_code)] +pub fn ceil_log2_pow5(e: i32) -> i32 /* or u32 -> u32 */ { + log2_pow5(e) + 1 +} + +// Returns floor(log_10(2^e)); requires 0 <= e <= 1650. +#[cfg_attr(feature = "no-panic", inline)] +pub fn log10_pow2(e: i32) -> u32 /* or u32 -> u32 */ { + // The first value this approximation fails for is 2^1651 which is just greater than 10^297. + debug_assert!(e >= 0); + debug_assert!(e <= 1650); + (e as u32 * 78913) >> 18 +} + +// Returns floor(log_10(5^e)); requires 0 <= e <= 2620. +#[cfg_attr(feature = "no-panic", inline)] +pub fn log10_pow5(e: i32) -> u32 /* or u32 -> u32 */ { + // The first value this approximation fails for is 5^2621 which is just greater than 10^1832. + debug_assert!(e >= 0); + debug_assert!(e <= 2620); + (e as u32 * 732923) >> 20 +} |