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dbaee198e6
This function predates the hex_util module. If there were hex_util, I would add it there.
104 lines
2.8 KiB
Rust
104 lines
2.8 KiB
Rust
// Copyright 2023 The Jujutsu Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#![allow(missing_docs)]
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fn to_reverse_hex_digit(b: u8) -> Option<u8> {
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let value = match b {
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b'0'..=b'9' => b - b'0',
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b'A'..=b'F' => b - b'A' + 10,
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b'a'..=b'f' => b - b'a' + 10,
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_ => return None,
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};
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Some(b'z' - value)
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}
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fn to_forward_hex_digit(b: u8) -> Option<u8> {
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let value = match b {
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b'k'..=b'z' => b'z' - b,
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b'K'..=b'Z' => b'Z' - b,
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_ => return None,
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};
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if value < 10 {
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Some(b'0' + value)
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} else {
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Some(b'a' + value - 10)
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}
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}
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pub fn to_forward_hex(reverse_hex: &str) -> Option<String> {
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reverse_hex
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.bytes()
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.map(|b| to_forward_hex_digit(b).map(char::from))
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.collect()
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}
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pub fn to_reverse_hex(forward_hex: &str) -> Option<String> {
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forward_hex
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.bytes()
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.map(|b| to_reverse_hex_digit(b).map(char::from))
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.collect()
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}
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/// Calculates common prefix length of two bytes. The length to be returned is
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/// a number of hexadecimal digits.
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pub fn common_hex_len(bytes_a: &[u8], bytes_b: &[u8]) -> usize {
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iter_half_bytes(bytes_a)
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.zip(iter_half_bytes(bytes_b))
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.take_while(|(a, b)| a == b)
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.count()
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}
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fn iter_half_bytes(bytes: &[u8]) -> impl ExactSizeIterator<Item = u8> + '_ {
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(0..bytes.len() * 2).map(|i| {
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let v = bytes[i / 2];
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if i & 1 == 0 {
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v >> 4
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} else {
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v & 0xf
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}
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})
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}
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#[cfg(test)]
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_reverse_hex() {
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// Empty string
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assert_eq!(to_reverse_hex(""), Some("".to_string()));
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assert_eq!(to_forward_hex(""), Some("".to_string()));
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// Single digit
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assert_eq!(to_reverse_hex("0"), Some("z".to_string()));
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assert_eq!(to_forward_hex("z"), Some("0".to_string()));
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// All digits
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assert_eq!(
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to_reverse_hex("0123456789abcdefABCDEF"),
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Some("zyxwvutsrqponmlkponmlk".to_string())
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);
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assert_eq!(
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to_forward_hex("zyxwvutsrqponmlkPONMLK"),
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Some("0123456789abcdefabcdef".to_string())
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);
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// Invalid digit
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assert_eq!(to_reverse_hex("g"), None);
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assert_eq!(to_forward_hex("j"), None);
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}
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}
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