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use alloc::{boxed::Box, vec, vec::Vec};
/// A set of "packed pair" test seeds. Each seed serves as the base for the
/// generation of many other tests. In essence, the seed captures the pair of
/// bytes we used for a predicate and first byte among our needle. The tests
/// generated from each seed essentially vary the length of the needle and
/// haystack, while using the rare/first byte configuration from the seed.
///
/// The purpose of this is to test many different needle/haystack lengths.
/// In particular, some of the vector optimizations might only have bugs
/// in haystacks of a certain size.
const SEEDS: &[Seed] = &[
// Why not use different 'first' bytes? It seemed like a good idea to be
// able to configure it, but when I wrote the test generator below, it
// didn't seem necessary to use for reasons that I forget.
Seed { first: b'x', index1: b'y', index2: b'z' },
Seed { first: b'x', index1: b'x', index2: b'z' },
Seed { first: b'x', index1: b'y', index2: b'x' },
Seed { first: b'x', index1: b'x', index2: b'x' },
Seed { first: b'x', index1: b'y', index2: b'y' },
];
/// Runs a host of "packed pair" search tests.
///
/// These tests specifically look for the occurrence of a possible substring
/// match based on a pair of bytes matching at the right offsets.
pub(crate) struct Runner {
fwd: Option<
Box<
dyn FnMut(&[u8], &[u8], u8, u8) -> Option<Option<usize>> + 'static,
>,
>,
}
impl Runner {
/// Create a new test runner for "packed pair" substring search.
pub(crate) fn new() -> Runner {
Runner { fwd: None }
}
/// Run all tests. This panics on the first failure.
///
/// If the implementation being tested returns `None` for a particular
/// haystack/needle combination, then that test is skipped.
///
/// This runs tests on both the forward and reverse implementations given.
/// If either (or both) are missing, then tests for that implementation are
/// skipped.
pub(crate) fn run(self) {
if let Some(mut fwd) = self.fwd {
for seed in SEEDS.iter() {
for t in seed.generate() {
match fwd(&t.haystack, &t.needle, t.index1, t.index2) {
None => continue,
Some(result) => {
assert_eq!(
t.fwd, result,
"FORWARD, needle: {:?}, haystack: {:?}, \
index1: {:?}, index2: {:?}",
t.needle, t.haystack, t.index1, t.index2,
)
}
}
}
}
}
}
/// Set the implementation for forward "packed pair" substring search.
///
/// If the closure returns `None`, then it is assumed that the given
/// test cannot be applied to the particular implementation and it is
/// skipped. For example, if a particular implementation only supports
/// needles or haystacks for some minimum length.
///
/// If this is not set, then forward "packed pair" search is not tested.
pub(crate) fn fwd(
mut self,
search: impl FnMut(&[u8], &[u8], u8, u8) -> Option<Option<usize>> + 'static,
) -> Runner {
self.fwd = Some(Box::new(search));
self
}
}
/// A test that represents the input and expected output to a "packed pair"
/// search function. The test should be able to run with any "packed pair"
/// implementation and get the expected output.
struct Test {
haystack: Vec<u8>,
needle: Vec<u8>,
index1: u8,
index2: u8,
fwd: Option<usize>,
}
impl Test {
/// Create a new "packed pair" test from a seed and some given offsets to
/// the pair of bytes to use as a predicate in the seed's needle.
///
/// If a valid test could not be constructed, then None is returned.
/// (Currently, we take the approach of massaging tests to be valid
/// instead of rejecting them outright.)
fn new(
seed: Seed,
index1: usize,
index2: usize,
haystack_len: usize,
needle_len: usize,
fwd: Option<usize>,
) -> Option<Test> {
let mut index1: u8 = index1.try_into().unwrap();
let mut index2: u8 = index2.try_into().unwrap();
// The '#' byte is never used in a haystack (unless we're expecting
// a match), while the '@' byte is never used in a needle.
let mut haystack = vec![b'@'; haystack_len];
let mut needle = vec![b'#'; needle_len];
needle[0] = seed.first;
needle[index1 as usize] = seed.index1;
needle[index2 as usize] = seed.index2;
// If we're expecting a match, then make sure the needle occurs
// in the haystack at the expected position.
if let Some(i) = fwd {
haystack[i..i + needle.len()].copy_from_slice(&needle);
}
// If the operations above lead to rare offsets pointing to the
// non-first occurrence of a byte, then adjust it. This might lead
// to redundant tests, but it's simpler than trying to change the
// generation process I think.
if let Some(i) = crate::memchr(seed.index1, &needle) {
index1 = u8::try_from(i).unwrap();
}
if let Some(i) = crate::memchr(seed.index2, &needle) {
index2 = u8::try_from(i).unwrap();
}
Some(Test { haystack, needle, index1, index2, fwd })
}
}
/// Data that describes a single prefilter test seed.
#[derive(Clone, Copy)]
struct Seed {
first: u8,
index1: u8,
index2: u8,
}
impl Seed {
const NEEDLE_LENGTH_LIMIT: usize = {
#[cfg(not(miri))]
{
33
}
#[cfg(miri)]
{
5
}
};
const HAYSTACK_LENGTH_LIMIT: usize = {
#[cfg(not(miri))]
{
65
}
#[cfg(miri)]
{
8
}
};
/// Generate a series of prefilter tests from this seed.
fn generate(self) -> impl Iterator<Item = Test> {
let len_start = 2;
// The iterator below generates *a lot* of tests. The number of
// tests was chosen somewhat empirically to be "bearable" when
// running the test suite.
//
// We use an iterator here because the collective haystacks of all
// these test cases add up to enough memory to OOM a conservative
// sandbox or a small laptop.
(len_start..=Seed::NEEDLE_LENGTH_LIMIT).flat_map(move |needle_len| {
let index_start = len_start - 1;
(index_start..needle_len).flat_map(move |index1| {
(index1..needle_len).flat_map(move |index2| {
(needle_len..=Seed::HAYSTACK_LENGTH_LIMIT).flat_map(
move |haystack_len| {
Test::new(
self,
index1,
index2,
haystack_len,
needle_len,
None,
)
.into_iter()
.chain(
(0..=(haystack_len - needle_len)).flat_map(
move |output| {
Test::new(
self,
index1,
index2,
haystack_len,
needle_len,
Some(output),
)
},
),
)
},
)
})
})
})
}
}