Neel/linkedlist

pkg/linkedlist/linkedlist.go

@@ -6,82 +6,82 @@ package linkedlist
 
 import (
 	"bytes"
+	"fmt"
 
 	"github.com/neelkshah/pandora/config"
 )
 
 // LinkedList is the data structure used for the hash table.
 type LinkedList struct {
-	head  *linkedListNode
-	tail  *linkedListNode
+	head  *Node
+	tail  *Node
 	count int
 }
 
-// linkedListNode is the data structure that forms the LinkedList.
-type linkedListNode struct {
-	values   []valueNode
-	nextNode *linkedListNode
+// Node is the data structure that forms the LinkedList.
+type Node struct {
+	Values   []valueNode
+	nextNode *Node
 }
 
-// valueNode contains a single value to be stored in the LinkedList.
+// ValueNode contains a single value to be stored in the LinkedList.
 type valueNode struct {
-	key   []byte
-	value []byte
+	Key   []byte
+	Value []byte
 }
 
-// CreateLinkedList returns a pointer to a new empty linked list instance.
-func CreateLinkedList() *LinkedList {
+// createImpl returns a pointer to a new empty linked list instance.
+func createImpl() *LinkedList {
 	linkedList := LinkedList{head: nil, tail: nil, count: 0}
 	return &linkedList
 }
 
-// Append appends a given value to the end of the referenced LinkedList instance.
-func (linkedList *LinkedList) Append(key []byte, value []byte) {
-	var newValue = valueNode{key: key, value: value}
+// AppendImpl appends a given value to the end of the referenced LinkedList instance.
+func (linkedList *LinkedList) appendImpl(key []byte, value []byte) {
+	var newValue = valueNode{Key: key, Value: value}
 	if linkedList.count == 0 {
-		var newNode = linkedListNode{values: []valueNode{newValue}, nextNode: nil}
+		var newNode = Node{Values: []valueNode{newValue}, nextNode: nil}
 		linkedList.head = &newNode
 		linkedList.tail = &newNode
 		linkedList.count = 1
 		return
 	}
 	var tailNode = linkedList.tail
-	if len(tailNode.values) < config.NODEFATNESS {
-		tailNode.values = append(tailNode.values, newValue)
+	if len(tailNode.Values) < config.NODEFATNESS {
+		tailNode.Values = append(tailNode.Values, newValue)
 	} else {
-		var newNode = linkedListNode{values: []valueNode{newValue}, nextNode: nil}
+		var newNode = Node{Values: []valueNode{newValue}, nextNode: nil}
 		tailNode.nextNode = &newNode
 		linkedList.tail = &newNode
 	}
 	linkedList.count++
 }
 
-// Get returns the values associate with the key.
-func (linkedList *LinkedList) Get(key []byte) ([][]byte, bool) {
+// GetImpl returns the values associate with the key.
+func (linkedList *LinkedList) getImpl(key []byte) ([][]byte, bool) {
 	if linkedList == nil || linkedList.head == nil {
 		return nil, true
 	}
 	var currentNode = linkedList.head
 	var result = make([][]byte, 0)
 	for {
 		if currentNode == nil {
-			break
+			return result, len(result) != 0
 		}
-		for _, vnode := range (*currentNode).values {
-			if bytes.Equal(vnode.key, key) {
-				result = append(result, vnode.value)
+		for _, vnode := range (*currentNode).Values {
+			if bytes.Equal(vnode.Key, key) {
+				result = append(result, vnode.Value)
 			}
 		}
 		currentNode = currentNode.nextNode
 	}
-	return result, false
 }
 
-// Delete deletes all key-value pairs having the key passed as parameter.
-// It returns the number of deleted pairs and a bool indicating occurrence of an error.
-func (linkedList *LinkedList) Delete(key []byte) (int, bool) {
+// DeleteImpl deletes all key-value pairs having the key passed as parameter.
+// It returns the number of deleted pairs and any error.
+func (linkedList *LinkedList) deleteImpl(key []byte) (int, error) {
 	if linkedList == nil || linkedList.head == nil {
-		return 0, true
+		return 0, fmt.Errorf("The linked list is empty")
 	}
 	var currentNode = linkedList.head
 	var count = 0
@@ -90,16 +90,16 @@ func (linkedList *LinkedList) Delete(key []byte) (int, bool) {
 		if currentNode == nil {
 			break
 		}
-		for _, vnode := range (*currentNode).values {
-			if !bytes.Equal(vnode.key, key) {
-				(*currentNode).values[k] = vnode
+		for _, vnode := range (*currentNode).Values {
+			if !bytes.Equal(vnode.Key, key) {
+				(*currentNode).Values[k] = vnode
 				k++
 				continue
 			}
 			count++
 		}
-		(*currentNode).values = (*currentNode).values[:k]
+		(*currentNode).Values = (*currentNode).Values[:k]
 		currentNode = currentNode.nextNode
 	}
-	return count, false
+	return count, nil
 }

pkg/linkedlist/linkedlist_api.go

@@ -0,0 +1,60 @@
+// Author: Neel Shah, 2020
+// linkedlist_api.go provides the API for the CRUD methods for the linked-list ADT
+// to be used as part of the hash table ADT.
+
+package linkedlist
+
+// CreateLinkedList returns a pointer to a new empty linked list instance.
+func CreateLinkedList() *LinkedList {
+	return createImpl()
+}
+
+// Append appends a key value pair to the linked list after checking their respective types.
+func (linkedlist *LinkedList) Append(iKey interface{}, iValue interface{}) error {
+
+	pair, conversionError := convert(iKey, iValue)
+
+	if conversionError != nil {
+		return conversionError
+	}
+
+	linkedlist.appendImpl(pair[0], pair[1])
+	return nil
+}
+
+// Get gets the value array of values associated with the passed key.
+func (linkedlist *LinkedList) Get(iKey interface{}) ([][]byte, bool, error) {
+
+	key, conversionError := convert(iKey)
+
+	if conversionError != nil {
+		return nil, false, conversionError
+	}
+
+	valueArray, found := linkedlist.getImpl(key[0])
+
+	return valueArray, found, nil
+}
+
+// Delete deletes the key-value pairs associated with the passed key. It returns the count of deleted pairs and any error.
+func (linkedlist *LinkedList) Delete(iKey interface{}) (int, error) {
+	key, conversionError := convert(iKey)
+
+	if conversionError != nil {
+		return 0, conversionError
+	}
+
+	deletedCount, deletionError := linkedlist.deleteImpl(key[0])
+
+	return deletedCount, deletionError
+}
+
+// Head returns the head node of the linked list.
+func (linkedlist *LinkedList) Head() *Node {
+	return linkedlist.head
+}
+
+// Next returns the next node in the linked list.
+func (node *Node) Next() *Node {
+	return node.nextNode
+}

pkg/linkedlist/linkedlist_test.go

@@ -25,89 +25,103 @@ func TestCreateLinkedList(t *testing.T) {
 // Test append function for single value append.
 func TestAppend(t *testing.T) {
 	var response = *CreateLinkedList()
-	response.Append([]byte("a"), helper.IntToByte(5))
-	if response.head == nil ||
+	appendError := response.Append("a", 5)
+	if appendError != nil ||
+		response.head == nil ||
 		response.tail == nil ||
 		response.count != 1 ||
 		response.head != response.tail ||
-		helper.ByteToInt(response.head.values[0].value) != 5 ||
-		len(response.head.values) != 1 {
-		t.Fail()
+		helper.ByteToInt(response.head.Values[0].Value) != 5 ||
+		len(response.head.Values) != 1 {
+		t.Fatalf("Failed to append single key-value pair to empty linked list.")
 	}
 }
 
 // Test whether fatness is maintained during append.
 func TestFatness(t *testing.T) {
-	var response = CreateLinkedList()
+	var list = CreateLinkedList()
 	var N = 3 * config.NODEFATNESS
 	for i := 1; i <= N; i++ {
-		var key = helper.IntToByte(rand.Uint64())
-		var value = helper.IntToByte(rand.Uint64())
-		response.Append(key, value)
+		var key = rand.Uint64()
+		var value = rand.Uint64()
+		if appendError := list.Append(key, value); appendError != nil {
+			t.Fatalf("Error in appending key-value pair %v, %v to linkedlist.\nInner error: %v", key, value, appendError)
+		}
 	}
-	var responselist = *response
+	var responselist = *list
 	if (responselist).count != 3*config.NODEFATNESS ||
 		responselist.head == responselist.tail ||
 		responselist.head == nil ||
 		responselist.tail == nil {
-		t.Fail()
+		t.Fatalf("Error in appending to fat nodes.")
 	}
 	var currentNode = *responselist.head
+	var i = 0
 	for {
-		if len(currentNode.values) != config.NODEFATNESS {
-			t.Fail()
+		if len(currentNode.Values) != config.NODEFATNESS {
+			t.Fatalf("Error in individual node fatness.")
 		}
+		i++
 		if currentNode.nextNode == nil {
-			return
+			break
 		}
 		currentNode = *currentNode.nextNode
 	}
+	if i != 3 {
+		t.Fatalf("Overall fatness not being maintained. Number of fat nodes != 3")
+	}
 }
 
 // Test get
 func TestGet(t *testing.T) {
-	var response = CreateLinkedList()
-	response.Append(helper.IntToByte(5), helper.IntToByte(7))
-	if result, isEmpty := response.Get(helper.IntToByte(5)); isEmpty == true || !bytes.Equal(result[0], helper.IntToByte(7)) {
-		t.Fail()
+	var list = CreateLinkedList()
+	if appendError := list.Append(5, 7); appendError != nil {
+		t.Fatalf("Error in appending key-value pair to linkedlist.\nInner error: %v", appendError)
 	}
-	if result, isEmpty := response.Get(helper.IntToByte(7)); isEmpty == true || len(result) != 0 {
-		t.Fail()
+	if result, found, _ := list.Get(5); !found || !bytes.Equal(result[0], helper.IntToByte(7)) {
+		t.Fatalf("Value present in linkedlist, but not found.")
+	}
+	if result, found, _ := list.Get(helper.IntToByte(7)); found || len(result) != 0 {
+		t.Fatalf("Value not present in linkedlist, returned as found.")
 	}
 }
 
 // Test get behaviour for an empty LinkedList instance
 func TestGetNilValidation(t *testing.T) {
 	var response = CreateLinkedList()
-	if result, isEmpty := response.Get(helper.IntToByte(5)); isEmpty == false || result != nil {
-		t.Fail()
+	if result, found, _ := response.Get(helper.IntToByte(5)); found || result != nil {
+		t.Fatalf("Getting values from empty linkedlist.")
 	}
 }
 
 // Test delete behaviour for an empty LinkedList instance
 func TestDeleteNilValidation(t *testing.T) {
 	var response = CreateLinkedList()
-	if count, isEmpty := response.Delete(helper.IntToByte(5)); isEmpty == false || count != 0 {
-		t.Fail()
+	if count, errorValue := response.Delete(helper.IntToByte(5)); errorValue == nil || count != 0 {
+		t.Fatalf("Deleting values from empty linkedlist.")
 	}
 }
 
 // Test deletion
 func TestDelete(t *testing.T) {
 	var response = CreateLinkedList()
 	for i := 1; i <= 5; i++ {
-		var key = helper.IntToByte(rand.Uint64())
-		var value = helper.IntToByte(rand.Uint64())
-		response.Append(key, value)
+		var key = rand.Uint64()
+		var value = rand.Uint64()
+		if appendResponse := response.Append(key, value); appendResponse != nil {
+			t.Fatalf("Error in appending key-value pair to linkedlist.")
+		}
 	}
-	response.Append(helper.IntToByte(5), helper.IntToByte(7))
+	response.Append(5, 7)
 	for i := 1; i <= 5; i++ {
-		var key = helper.IntToByte(rand.Uint64())
-		var value = helper.IntToByte(rand.Uint64())
-		response.Append(key, value)
+		var key = rand.Uint64()
+		var value = rand.Uint64()
+		if appendResponse := response.Append(key, value); appendResponse != nil {
+			t.Fatalf("Error in appending key-value pair to linkedlist.")
+		}
 	}
 
-	if count, status := response.Delete(helper.IntToByte(5)); count < 1 || status == true {
-		t.Fail()
+	if count, errorValue := response.Delete(5); count < 1 || errorValue != nil {
+		t.Fatalf("Error in deleting key-value pair.")
 	}
 }

pkg/linkedlist/utils.go

@@ -1,14 +1,18 @@
 package linkedlist
 
-import "fmt"
+import (
+	"fmt"
+
+	"github.com/neelkshah/pandora/pkg/helper"
+)
 
 // Print prints the contents of a LinkedList instance.
 func (linkedList *LinkedList) Print() {
 	fmt.Printf("Count of elements: %v\n", linkedList.count)
 	var currentNode = *linkedList.head
 	for {
-		for _, element := range currentNode.values {
-			fmt.Printf("%v, %v\t", element.key, element.value)
+		for _, element := range currentNode.Values {
+			fmt.Printf("%v, %v\t", element.Key, element.Value)
 		}
 		if currentNode.nextNode == nil {
 			return
@@ -17,3 +21,23 @@ func (linkedList *LinkedList) Print() {
 		fmt.Println()
 	}
 }
+
+// convert converts the given slice of values into a slice of byte slices.
+func convert(originalValues ...interface{}) ([][]byte, error) {
+	var values [][]byte
+
+	for _, originalValue := range originalValues {
+		switch keyType := originalValue.(type) {
+		case int:
+			values = append(values, helper.IntToByte(uint64(originalValue.(int))))
+		case uint64:
+			values = append(values, helper.IntToByte(originalValue.(uint64)))
+		case string:
+			values = append(values, []byte(originalValue.(string)))
+		default:
+			return nil, fmt.Errorf("%v is of invalid type %v", originalValue, keyType)
+		}
+	}
+
+	return values, nil
+}