daydream

A small matrix web client written in rust
git clone git://archive.git.mtrnord.blog/daydream-mx/daydream.git
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string_utils.rs (1482B)

      1 use std::ops::{Bound, RangeBounds};
      2 
      3 pub trait StringUtils {
      4     fn substring(&self, start: usize, len: usize) -> &str;
      5     fn slice(&self, range: impl RangeBounds<usize>) -> &str;
      6 }
      7 
      8 impl StringUtils for str {
      9     fn substring(&self, start: usize, len: usize) -> &str {
     10         let mut char_pos = 0;
     11         let mut byte_start = 0;
     12         let mut it = self.chars();
     13         loop {
     14             if char_pos == start {
     15                 break;
     16             }
     17             if let Some(c) = it.next() {
     18                 char_pos += 1;
     19                 byte_start += c.len_utf8();
     20             } else {
     21                 break;
     22             }
     23         }
     24         char_pos = 0;
     25         let mut byte_end = byte_start;
     26         loop {
     27             if char_pos == len {
     28                 break;
     29             }
     30             if let Some(c) = it.next() {
     31                 char_pos += 1;
     32                 byte_end += c.len_utf8();
     33             } else {
     34                 break;
     35             }
     36         }
     37         &self[byte_start..byte_end]
     38     }
     39     fn slice(&self, range: impl RangeBounds<usize>) -> &str {
     40         let start = match range.start_bound() {
     41             Bound::Included(bound) | Bound::Excluded(bound) => *bound,
     42             Bound::Unbounded => 0,
     43         };
     44         let len = match range.end_bound() {
     45             Bound::Included(bound) => *bound + 1,
     46             Bound::Excluded(bound) => *bound,
     47             Bound::Unbounded => self.len(),
     48         } - start;
     49         self.substring(start, len)
     50     }
     51 }