58 lines
1.5 KiB
Rust
58 lines
1.5 KiB
Rust
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pub struct SinglePattern {
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seq: &'static [u8],
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table: Vec<usize>,
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}
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impl SinglePattern {
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pub fn new(seq: &'static [u8]) -> SinglePattern {
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let mut max_prefix_len = 0usize;
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let mut table = vec![0usize; seq.len()];
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let mut i = 1;
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while i < seq.len() {
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if seq[i] == seq[max_prefix_len] {
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max_prefix_len += 1;
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table[i] = max_prefix_len;
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i += 1;
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} else {
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if max_prefix_len != 0 {
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max_prefix_len = table[max_prefix_len - 1];
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} else {
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table[i] = 0;
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i += 1;
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};
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};
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};
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SinglePattern {
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seq,
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table,
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}
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}
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pub fn match_against(&self, haystack: &[u8]) -> Option<usize> {
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let mut hay_idx = 0usize;
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let mut pat_idx = 0usize;
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while hay_idx < haystack.len() {
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if self.seq[pat_idx] == haystack[hay_idx] {
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pat_idx += 1;
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hay_idx += 1;
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};
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if pat_idx == self.seq.len() {
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return Some(hay_idx - pat_idx);
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};
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if hay_idx < haystack.len() && self.seq[pat_idx] != haystack[hay_idx] {
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if pat_idx != 0 {
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pat_idx = self.table[pat_idx - 1];
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} else {
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hay_idx += 1;
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};
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};
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};
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None
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}
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}
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