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Implement functions for searching bytesets #15
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| use memchr::{memchr, memchr2, memchr3, memrchr, memrchr2, memrchr3}; | ||
| mod scalar; | ||
|
|
||
| #[inline] | ||
| fn build_table(byteset: &[u8]) -> [u8; 256] { | ||
| let mut table = [0u8; 256]; | ||
| for &b in byteset { | ||
| table[b as usize] = 1; | ||
| } | ||
| table | ||
| } | ||
|
|
||
| #[inline] | ||
| pub(crate) fn find(haystack: &[u8], byteset: &[u8]) -> Option<usize> { | ||
| match byteset.len() { | ||
| 0 => return None, | ||
| 1 => memchr(byteset[0], haystack), | ||
| 2 => memchr2(byteset[0], byteset[1], haystack), | ||
| 3 => memchr3(byteset[0], byteset[1], byteset[2], haystack), | ||
| _ => { | ||
| let table = build_table(byteset); | ||
| scalar::forward_search_bytes(haystack, |b| table[b as usize] != 0) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[inline] | ||
| pub(crate) fn rfind(haystack: &[u8], byteset: &[u8]) -> Option<usize> { | ||
| match byteset.len() { | ||
| 0 => return None, | ||
| 1 => memrchr(byteset[0], haystack), | ||
| 2 => memrchr2(byteset[0], byteset[1], haystack), | ||
| 3 => memrchr3(byteset[0], byteset[1], byteset[2], haystack), | ||
| _ => { | ||
| let table = build_table(byteset); | ||
| scalar::reverse_search_bytes(haystack, |b| table[b as usize] != 0) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[inline] | ||
| pub(crate) fn find_not(haystack: &[u8], byteset: &[u8]) -> Option<usize> { | ||
| if haystack.is_empty() { | ||
| return None; | ||
| } | ||
| match byteset.len() { | ||
| 0 => return Some(0), | ||
| 1 => scalar::inv_memchr(byteset[0], haystack), | ||
| 2 => scalar::forward_search_bytes(haystack, |b| { | ||
| b != byteset[0] && b != byteset[1] | ||
| }), | ||
| 3 => scalar::forward_search_bytes(haystack, |b| { | ||
| b != byteset[0] && b != byteset[1] && b != byteset[2] | ||
| }), | ||
| _ => { | ||
| let table = build_table(byteset); | ||
| scalar::forward_search_bytes(haystack, |b| table[b as usize] == 0) | ||
| } | ||
| } | ||
| } | ||
| #[inline] | ||
| pub(crate) fn rfind_not(haystack: &[u8], byteset: &[u8]) -> Option<usize> { | ||
| if haystack.is_empty() { | ||
| return None; | ||
| } | ||
| match byteset.len() { | ||
| 0 => return Some(haystack.len() - 1), | ||
| 1 => scalar::inv_memrchr(byteset[0], haystack), | ||
| 2 => scalar::reverse_search_bytes(haystack, |b| { | ||
| b != byteset[0] && b != byteset[1] | ||
| }), | ||
| 3 => scalar::reverse_search_bytes(haystack, |b| { | ||
| b != byteset[0] && b != byteset[1] && b != byteset[2] | ||
| }), | ||
| _ => { | ||
| let table = build_table(byteset); | ||
| scalar::reverse_search_bytes(haystack, |b| table[b as usize] == 0) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
|
|
||
| quickcheck! { | ||
| fn qc_byteset_forward_matches_naive( | ||
| haystack: Vec<u8>, | ||
| needles: Vec<u8> | ||
| ) -> bool { | ||
| super::find(&haystack, &needles) | ||
| == haystack.iter().position(|b| needles.contains(b)) | ||
| } | ||
| fn qc_byteset_backwards_matches_naive( | ||
| haystack: Vec<u8>, | ||
| needles: Vec<u8> | ||
| ) -> bool { | ||
| super::rfind(&haystack, &needles) | ||
| == haystack.iter().rposition(|b| needles.contains(b)) | ||
| } | ||
| fn qc_byteset_forward_not_matches_naive( | ||
| haystack: Vec<u8>, | ||
| needles: Vec<u8> | ||
| ) -> bool { | ||
| super::find_not(&haystack, &needles) | ||
| == haystack.iter().position(|b| !needles.contains(b)) | ||
| } | ||
| fn qc_byteset_backwards_not_matches_naive( | ||
| haystack: Vec<u8>, | ||
| needles: Vec<u8> | ||
| ) -> bool { | ||
| super::rfind_not(&haystack, &needles) | ||
| == haystack.iter().rposition(|b| !needles.contains(b)) | ||
| } | ||
| } | ||
| } | ||
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I kind of feel like this might not be enough test coverage. Most of the code here is simple enough that I'd probably be okay with it, but the
inv_memchr1function is not as simple and probably deserves more testing. A particularly important part of testing code likeinv_memchr1is to make sure all offsets are tested, which is what the memchr crate does: https://github.com/BurntSushi/rust-memchr/blob/665fffcc9506ac1cd93339470d2ca4b018e648c6/src/tests/mod.rs#L353-L374I realize this is perhaps more work than you wanted to take on. I would totally be okay with leaving the extra tests out of this PR, but I'd probably insist on dropping
inv_memchr1in addition to that. (You could just throw it up into another PR without tests, and I'd be happy to add tests to it later when I get a chance. It's up to you and your time/desire budget. :-))There was a problem hiding this comment.
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Adding more tests doesn't bother me, I was just being lazy.
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I've added what I think amounts to equivalent tests to what you have for memchr 1 byte, although it's possible it's still not ideal, let me know.