Merge remote-tracking branch 'origin' into feat/get-no-error

## Description

Currently, the errors are not sentinel, and so are hard to test for. This PR makes sure hash collision errors are accounted for.

## Changes

- Add `ErrBadHash`. Happens when there are too many collisions for an item to be added.

### Design Decisions

- Chose to name `ErrBadHash` over `ErrCycle` because the feedbach that the user should be given is to evaluate their hash functions. Cycle collision is a bit esoteric.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #19
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

cuckoo_fuzz_test.go

@@ -73,16 +73,16 @@ func FuzzInsertLookup(f *testing.F) {
 
 				delete(expected, step.key)
 
-				_, err = actual.Get(step.key)
-				assert.Error(err)
+				_, ok := actual.Get(step.key)
+				assert.False(ok)
 			} else {
 				err := actual.Put(step.key, step.value)
 				assert.NoError(err)
 
 				expected[step.key] = step.value
 
-				found, err := actual.Get(step.key)
-				assert.NoError(err)
+				found, ok := actual.Get(step.key)
+				assert.True(ok)
 				assert.Equal(step.value, found)
 			}
 

cuckoo_test.go

@@ -108,12 +108,12 @@ func TestGetMany(t *testing.T) {
 	}
 
 	for i := range 2_000 {
-		value, err := table.Get(i)
+		value, ok := table.Get(i)
 		if i < 1_000 {
-			assert.NoError(err)
+			assert.True(ok)
 			assert.Equal(value, true)
 		} else {
-			assert.Error(err)
+			assert.False(ok)
 		}
 	}
 }

doc_example_test.go

@@ -14,19 +14,19 @@ func Example_basic() {
 		fmt.Println("Put error:", err)
 	}
 
-	if item, err := table.Get(1); err != nil {
-		fmt.Println("Error:", err)
+	if item, ok := table.Get(1); !ok {
+		fmt.Println("Not Found 1!")
 	} else {
 		fmt.Println("Found 1:", item)
 	}
 
-	if item, err := table.Get(0); err != nil {
-		fmt.Println("Error:", err)
+	if item, ok := table.Get(0); !ok {
+		fmt.Println("Not Found 0!")
 	} else {
 		fmt.Println("Found 0:", item)
 	}
 
 	// Output:
 	// Found 1: Hello, World!
-	// Error: key '0' not found
+	// Not Found 0!
 }

table.go

@@ -1,12 +1,21 @@
 package cuckoo
 
 import (
+	"errors"
 	"fmt"
 	"iter"
 	"math/bits"
 	"strings"
 )
 
+// ErrBadHash occurs when the hashes given to a [Table] cause too many key
+// collisions. Try rebuilding the table using:
+//
+//  1. Different hash seeds. Equal seeds produce equal hash functions, which
+//     always cycle.
+//  2. A different [Hash] algorithm.
+var ErrBadHash = errors.New("bad hash")
+
 // A Table is hash table that uses cuckoo hashing to resolve collision. Create
 // one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
 // [NewCustomTable].
@@ -86,24 +95,23 @@ func (t *Table[K, V]) shrink() error {
 	return t.resize(t.bucketA.capacity / t.growthFactor)
 }
 
-// Get fetches the value for a key in the [Table]. Returns an error if no value
-// is found.
-func (t Table[K, V]) Get(key K) (value V, err error) {
+// Get fetches the value for a key in the [Table].
+func (t Table[K, V]) Get(key K) (value V, ok bool) {
 	if item, ok := t.bucketA.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
 	if item, ok := t.bucketB.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
-	return value, fmt.Errorf("key '%v' not found", key)
+	return
 }
 
 // Has returns true if a key has a value in the table.
 func (t Table[K, V]) Has(key K) (exists bool) {
-	_, err := t.Get(key)
-	return err == nil
+	_, exists = t.Get(key)
+	return
 }
 
 // Put sets the value for a key. Returns error if its value cannot be set.
@@ -128,7 +136,7 @@ func (t *Table[K, V]) Put(key K, value V) (err error) {
 	}
 
 	if t.load() < t.minLoadFactor {
-		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
+		return fmt.Errorf("hash functions produced a cycle at load %d/%d: %w", t.Size(), t.TotalCapacity(), ErrBadHash)
 	}
 
 	if err := t.grow(); err != nil {