Some weird test cases

[mstevens]

Hi,

I was investigating some slow performance and found a couple of weird test cases which I don't think are my original problem but definitely are interesting:

func TestNullByteMatcher(t *testing.T) {
    fmt.Printf("\ntesting in simple case...\n")
    m := NewMatcher()
    words := []string{
        "she", "he", "her", "hers",
    }
    for i, word := range words {
        m.Insert([]byte(word), i)
    }
    m.Cedar().DumpGraph("trie.gv")
    m.Compile()
    m.DumpGraph("dfa.gv")
    seq := []byte("he\x000")
    fmt.Printf("searching %s\n", string(seq))
    resp := m.Match(seq)
    for resp.HasNext() {
        items := resp.NextMatchItem(seq)
        for _, itr := range items {
            key := m.Key(seq, itr)
            fmt.Printf("key:%s value:%d\n", key, itr.Value.(int))
        }
    }
    resp.Release()
}

Fails with:

--- FAIL: TestNullByteMatcher (0.00s)
panic: runtime error: index out of range [-1] [recovered]
	panic: runtime error: index out of range [-1]

goroutine 5 [running]:
testing.tRunner.func1.2({0x100ead7a0, 0x140000160d8})
	/usr/local/go/src/testing/testing.go:1632 +0x1bc
testing.tRunner.func1()
	/usr/local/go/src/testing/testing.go:1635 +0x334
panic({0x100ead7a0?, 0x140000160d8?})
	/usr/local/go/src/runtime/panic.go:785 +0x124
github.com/iohub/ahocorasick.(*Cedar).child(...)
	/Users/michaelstevens/ahocorasick/cedar.go:307
github.com/iohub/ahocorasick.(*Cedar).hasLabel(...)
	/Users/michaelstevens/ahocorasick/cedar.go:302
github.com/iohub/ahocorasick.(*Matcher).Match(0x1400002d940, {0x1400000e728, 0x4, 0xd?})
	/Users/michaelstevens/ahocorasick/acmatcher.go:158 +0x304
github.com/iohub/ahocorasick.TestNullByteMatcher(0x14000077380?)
	/Users/michaelstevens/ahocorasick/matcher_test.go:22 +0x234
testing.tRunner(0x14000077380, 0x100ebbe30)
	/usr/local/go/src/testing/testing.go:1690 +0xe4
created by testing.(*T).Run in goroutine 1
	/usr/local/go/src/testing/testing.go:1743 +0x314
exit status 2

and

func TestOneByte(t *testing.T) {
    m := NewMatcher()
    words := []string{
        "\x01",
    }
    for i, word := range words {
        m.Insert([]byte(word), i)
    }
    m.Compile()
    seq := []byte("\x01")
    resp := m.Match(seq)
    for resp.HasNext() {
        items := resp.NextMatchItem(seq)
        for _, itr := range items {
            key := m.Key(seq, itr)
            fmt.Printf("key:%s value:%d\n", key, itr.Value.(int))
        }
    }
    resp.Release()
}

seems to do an infinite loop in resp.NextMatchItem and the test never completes.