Press n or j to go to the next uncovered block, b, p or k for the previous block.
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import Action from '@/components/hashes/HashTableVerticalActions';
import Color from '@/utils/Color';
/**
* Bucket
* @param {number} localDepth
* @param {number} bucketSize
* @param {number} directoryKey
* @constructor
*/
function Bucket(localDepth, bucketSize, directoryKey) {
this.localDepth = localDepth;
this.elements = new Array(bucketSize);
this.key = directoryKey;
}
export default class ExtendibleHashing extends HashStructure {
/**
* ?
* @type {number}
*/
globalDepth;
/**
* The Hash Table consists of a list of DataBlocks that hold the values.
* @type {Bucket[]}
*/
directory;
/**
* Number of elements within a Bucket
* @type {number}
*/
MAX_BUCKET_SIZE;
/**
* Initialize an empty hash table.
* @param {number} bucketSize
*/
init(bucketSize) {
const steps = [];
this.globalDepth = 1;
this.MAX_BUCKET_SIZE = bucketSize;
this.directory = [];
// Initially, every index shall reference its own personal Bucket, thus
// localDepth = globalDepth for all DataBlocks.
for (let address = 0; address < 2 ** this.globalDepth; address += 1) {
this.directory[address] = new Bucket(this.globalDepth, this.MAX_BUCKET_SIZE, address);
}
this.visualizeCreateTable(steps);
this.visualizeUpdateInfoBoxes(steps, `Table initialized with bucket size: ${this.MAX_BUCKET_SIZE}`);
return steps;
}
/**
* Generates a hash value for a given key using a bitmask.
* @param {number} key - The key to be hashed.
* @param {number} globalDepth - The global depth for creating the bitmask.
* @returns {number} - The hashed value.
*/
hash(key, globalDepth) {
// The bitmask is created to consist of <globalDepth> 1s.
const bitMask = (2 ** globalDepth) - 1; // Sum of 2^x series: 1 + 2 + 4 ...
// Retain only the rightmost <globalDepth> bits using bitwise AND.
// eslint-disable-next-line no-bitwise
const result = key & bitMask;
return result;
}
/**
* Insert a value into the hash table.
* @param value
* @returns {steps[]} - The steps of the visualization.
*/
insert(value) {
let inserted = false;
const steps = [];
while (!inserted) {
const ADDRESS = this.hash(value, this.globalDepth);
this.visualizeHashCalculation(steps, value, ADDRESS, 'insert');
// 1) Add value
let freeElementIndex;
for (let i = 0; i < this.MAX_BUCKET_SIZE; i += 1) {
if (this.directory[ADDRESS].elements[i] === value) {
freeElementIndex = i;
inserted = true;
break;
}
if (freeElementIndex === undefined && this.directory[ADDRESS].elements[i] === undefined) {
// Remember the first free slot
freeElementIndex = i;
}
// Insert value in a free slot
if (i === (this.MAX_BUCKET_SIZE - 1) && freeElementIndex !== undefined) {
this.directory[ADDRESS].elements[freeElementIndex] = value;
inserted = true;
break;
}
}
if (inserted) {
this.visualizeHighlightCell(steps, ADDRESS, 'green');
this.visualizeHighlightCell(steps, ADDRESS, 'green', 'buckets', freeElementIndex);
this.visualizeInsert(steps, value, ADDRESS, freeElementIndex);
this.visualizeHighlightCell(steps, ADDRESS, 'base', 'buckets', freeElementIndex);
this.visualizeHighlightCell(steps, ADDRESS, 'base');
break;
}
this.visualizeHighlightCell(steps, ADDRESS, 'red');
// not inserted, overflow, split!
if (this.directory[ADDRESS].localDepth < this.globalDepth) {
// if localDepth < globalDepth: split the Bucket
this.visualizeHighlightBucketRow(steps, 'yellow', ADDRESS);
let haveToShiftKeys = false;
const KEY_TO_SPLIT = this.directory[ADDRESS].key;
const OLD_POINTS_LIST = this.directory.map((bucket) => bucket.key);
// Save old Bucket elements
const copyOfOldElements = [...this.directory[ADDRESS].elements];
const oldElements = this.directory[ADDRESS].elements;
// increase localDepth for the bucket and its references
this.directory[ADDRESS].localDepth += 1;
// create a new Bucket
this.directory[ADDRESS] = new Bucket(this.directory[ADDRESS].localDepth,
this.MAX_BUCKET_SIZE, ADDRESS);
// check if the pointers need to be updated
// because a new bucket has been created at this position.
if (KEY_TO_SPLIT === ADDRESS) {
haveToShiftKeys = true;
}
// Move oldElements to new Bucket if necessary (???)
let freePosNew = 0;
// loop over old elements
for (let i = 0; i < this.MAX_BUCKET_SIZE; i += 1) {
const newAddress = this.hash(oldElements[i], this.directory[ADDRESS].localDepth);
if (newAddress === ADDRESS) {
this.directory[ADDRESS].elements[freePosNew] = oldElements[i];
freePosNew += 1;
oldElements[i] = undefined;
}
}
if (haveToShiftKeys === true) {
for (let directoryIndex = KEY_TO_SPLIT + 1; directoryIndex < this.directory.length; directoryIndex += 1) {
if (this.directory[directoryIndex].key === KEY_TO_SPLIT) {
this.directory[directoryIndex].key = directoryIndex;
this.visualizeSplitting(steps, OLD_POINTS_LIST, copyOfOldElements,
ADDRESS, directoryIndex, haveToShiftKeys);
this.visualizeHighlightBucketRow(steps, 'base', ADDRESS, directoryIndex);
break;
}
}
} else {
this.visualizeSplitting(steps, OLD_POINTS_LIST, copyOfOldElements,
ADDRESS, KEY_TO_SPLIT, haveToShiftKeys);
this.visualizeHighlightBucketRow(steps, 'base', ADDRESS, KEY_TO_SPLIT);
}
// expanded, try to insert in next iteration
} else if (this.directory[ADDRESS].localDepth === this.globalDepth) {
// if localDepth == globalDepth: Expand Index
// Double the size of the Bucket array and point the new fields to the
// old ones sequentially from 0 to the last field of the "old" array
const directoryLengthOld = this.directory.length;
for (let i = directoryLengthOld; i < 2 * directoryLengthOld; i += 1) {
// Assign references from bucket
this.directory[i] = this.directory[i - directoryLengthOld];
}
this.globalDepth += 1;
// expanded, try to insert in next iteration
this.visualizeIncreaseDirectoryTable(steps, ADDRESS);
}
}
return steps;
}
/**
* Search the given value in the hash table.
* @param value
*/
search(value) {
const steps = [];
const ADDRESS = this.hash(value, this.globalDepth);
this.visualizeHashCalculation(steps, value, ADDRESS, 'search');
this.visualizeHighlightCell(steps, ADDRESS, 'green');
let found = false;
for (let i = 0; i < this.directory[ADDRESS].elements.length; i += 1) {
if (this.directory[ADDRESS].elements[i] === value) {
found = true;
this.visualizeHighlightCell(steps, ADDRESS, 'green', 'buckets', i);
this.visualizeHighlightCell(steps, ADDRESS, 'base', 'buckets', i);
break;
}
this.visualizeHighlightCell(steps, ADDRESS, 'red', 'buckets', i);
this.visualizeHighlightCell(steps, ADDRESS, 'base', 'buckets', i);
}
if (found) {
this.visualizeUpdateInfoBoxes(steps, `Value: ${value} was found`);
this.visualizeHighlightCell(steps, ADDRESS, 'base');
} else {
this.visualizeUpdateInfoBoxes(steps, `Value: ${value} was not found`);
this.visualizeHighlightCell(steps, ADDRESS, 'red');
this.visualizeHighlightCell(steps, ADDRESS, 'base');
}
return steps;
}
/**
* Remove the given value from the hash table.
* @param value
*/
remove(value) {
const steps = [];
const ADDRESS = this.hash(value, this.globalDepth);
this.visualizeHashCalculation(steps, value, ADDRESS, 'remove');
this.visualizeHighlightCell(steps, ADDRESS, 'green');
let removed = false;
for (let i = 0; i < this.directory[ADDRESS].elements.length; i += 1) {
if (this.directory[ADDRESS].elements[i] === value) {
this.directory[ADDRESS].elements[i] = undefined;
this.visualizeHighlightCell(steps, ADDRESS, 'green', 'buckets', i);
this.visualizeRemove(steps, value, ADDRESS, i);
this.visualizeHighlightCell(steps, ADDRESS, 'base', 'buckets', i);
removed = true;
break;
}
this.visualizeHighlightCell(steps, ADDRESS, 'red', 'buckets', i);
this.visualizeHighlightCell(steps, ADDRESS, 'base', 'buckets', i);
}
if (removed) {
this.visualizeUpdateInfoBoxes(steps, `Value: ${value} was removed`);
this.visualizeHighlightCell(steps, ADDRESS, 'base');
// removed
} else {
this.visualizeUpdateInfoBoxes(steps, `Value: ${value} to remove was not found`);
this.visualizeHighlightCell(steps, ADDRESS, 'red');
this.visualizeHighlightCell(steps, ADDRESS, 'base');
}
return steps;
}
visualizeCreateTable(steps) {
const indexes = [];
const maxBinaryLength = this.directory.length - 1;
const maxBits = maxBinaryLength.toString(2).length;
for (let i = 0; i < this.directory.length; i += 1) {
indexes.push(i.toString(2)
.padStart(maxBits, '0'));
}
steps.push({
do: [
{
action: Action.CREATE_LIST,
rows: this.directory.length,
cols: this.MAX_BUCKET_SIZE,
globalDepth: this.globalDepth,
pointsMap: this.directory.map((bucket) => bucket.key),
},
{
action: Action.SET_ROW_VALUE,
bucketIndexes: indexes,
},
],
undo: [
{
action: Action.DELETE_LIST,
},
{
action: Action.SET_ROW_VALUE,
bucketIndexes: indexes,
},
],
});
return steps;
}
visualizeUpdateInfoBoxes(steps, text) {
steps.push({
do: [{
action: Action.UPDATE_INFO_BOX,
bucketSize: this.MAX_BUCKET_SIZE,
infoText: text,
}],
undo: [{
action: Action.UPDATE_INFO_BOX,
bucketSize: this.MAX_BUCKET_SIZE,
infoText: '',
}],
});
return steps;
}
visualizeHashCalculation(steps, value, addressDecimal, action) {
let text;
switch (action) {
case 'insert':
text = `Inserting Value: ${value}`;
break;
case 'search':
text = `Searching for Value: ${value}`;
break;
case 'remove':
text = `Removing Value: ${value}`;
break;
default:
}
const binaryValue = value.toString(2);
const addressBinary = addressDecimal.toString(2)
.padStart(this.globalDepth, '0');
steps.push({
do: [
{
action: Action.SET_HASH_CALCULATION,
value,
binaryValue,
addressBinary,
},
{
action: Action.UPDATE_INFO_BOX,
infoText: text,
bucketSize: null,
},
],
undo: [
{
action: Action.SET_HASH_CALCULATION,
value: null,
},
{
action: Action.UPDATE_INFO_BOX,
infoText: '',
bucketSize: null,
},
],
});
return steps;
}
visualizeInsert(steps, value, directoryIndex, bucketIndex) {
steps.push({
do: [
{
action: Action.INSERT_VALUE_AT_POS,
value,
row: this.directory[directoryIndex].key,
col: bucketIndex,
},
],
undo: [{
action: Action.REMOVE_VALUE_AT_POS,
row: this.directory[directoryIndex].key,
col: bucketIndex,
}],
});
return steps;
}
visualizeRemove(steps, oldValue, address, bucketIndex) {
steps.push({
do: [{
action: Action.REMOVE_VALUE_AT_POS,
row: this.directory[address].key,
col: bucketIndex,
}],
undo: [{
action: Action.INSERT_VALUE_AT_POS,
value: oldValue,
row: this.directory[address].key,
col: bucketIndex,
}],
});
return steps;
}
visualizeHighlightCell(steps, directoryIndex, color, table = 'directory', column = 0) {
let selectedColor;
switch (color) {
case 'red':
selectedColor = Color.HASH_COLLISION;
break;
case 'green':
selectedColor = Color.HASH_INSERT_SEARCH_COMPLETED;
break;
case 'base':
selectedColor = Color.BASE_COLOR_HASH_TABLE;
break;
default:
}
steps.push({
do: [{
action: Action.SET_ROW_COLOR,
rowType: table,
row: directoryIndex,
pointToRow: this.directory[directoryIndex].key,
col: column,
color: selectedColor,
}],
undo: [{
action: Action.SET_ROW_COLOR,
rowType: table,
row: directoryIndex,
pointToRow: this.directory[directoryIndex].key,
col: column,
color: Color.BASE_COLOR_HASH_TABLE,
}],
});
return steps;
}
visualizeHighlightBucketRow(steps, color, directoryIndexFirst, directoryIndexSecond = null) {
const pointToRowMap = [];
if (directoryIndexSecond === null) {
pointToRowMap.push(this.directory[directoryIndexFirst].key);
} else {
pointToRowMap.push(this.directory[directoryIndexFirst].key);
pointToRowMap.push(this.directory[directoryIndexSecond].key);
}
let selectedColor;
switch (color) {
case 'yellow':
selectedColor = Color.HASH_COMPARE;
break;
case 'base':
selectedColor = Color.BASE_COLOR_HASH_TABLE;
break;
default:
}
steps.push({
do: [
{
action: Action.HIGHLIGHT_BUCKET_ROW,
pointToRowMap: pointToRowMap,
color: selectedColor,
},
{
action: Action.UPDATE_INFO_BOX,
infoText: 'Splitting Bucket because localDepth < globalDepth',
bucketSize: null,
},
],
undo: [
{
action: Action.HIGHLIGHT_BUCKET_ROW,
rowType: 'directory',
pointToRowMap: pointToRowMap,
color: Color.BASE_COLOR_HASH_TABLE,
},
{
action: Action.UPDATE_INFO_BOX,
infoText: '',
bucketSize: null,
},
],
});
return steps;
}
visualizeIncreaseDirectoryTable(steps, directoryIndex) {
const indexes = [];
const shorterIndexes = [];
const maxBinaryLength = this.directory.length - 1;
const maxBits = maxBinaryLength.toString(2).length;
for (let i = 0; i < this.directory.length; i += 1) {
indexes.push(i.toString(2)
.padStart(maxBits, '0'));
}
for (let i = 0; i < this.directory.length / 2; i += 1) {
shorterIndexes.push(i.toString(2)
.padStart(maxBits - 1, '0'));
}
steps[steps.length - 1].do.push({
action: Action.UPDATE_INFO_BOX,
infoText: 'Expanding Directory because localDepth == globalDepth',
bucketSize: null,
});
steps[steps.length - 1].undo.push({
action: Action.UPDATE_INFO_BOX,
infoText: '',
bucketSize: null,
});
steps.push({
do: [
{
action: Action.ADD_DIRECTORY_ENTRY,
rows: this.directory.length,
globalDepth: this.globalDepth,
pointsMap: this.directory.map((bucket) => bucket.key),
},
{
action: Action.SET_ROW_COLOR,
rowType: 'directory',
row: directoryIndex,
color: Color.BASE_COLOR_HASH_TABLE,
},
{
action: Action.ADD_BUCKETS,
rows: this.directory.length,
},
{
action: Action.SET_ROW_VALUE,
bucketIndexes: indexes,
},
],
undo: [
{
action: Action.REMOVE_DIRECTORY_ENTRY,
globalDepth: this.globalDepth - 1,
rows: this.directory.length / 2,
},
{
action: Action.SET_ROW_COLOR,
rowType: 'directory',
row: directoryIndex,
color: Color.HASH_COLLISION,
},
{
action: Action.REMOVE_BUCKETS,
rows: this.directory.length / 2,
},
{
action: Action.SET_ROW_VALUE,
bucketIndexes: shorterIndexes,
},
],
});
return steps;
}
visualizeSplitting(steps, oldPointsList, oldElements,
directoryIndex, splitDirectoryIndex, haveToShiftKeys) {
const pointToRowMap = [];
if (haveToShiftKeys === true) {
pointToRowMap.push(this.directory[splitDirectoryIndex].key);
} else {
pointToRowMap.push(this.directory[directoryIndex].key);
}
let oldLocalDepth = this.directory[directoryIndex].localDepth;
oldLocalDepth -= 1;
steps.push({
do: [
{
action: Action.UPDATE_LINK_AT_POS,
pointsMap: this.directory.map((bucket) => bucket.key),
},
{
action: Action.UPDATE_VALUES_OF_ROW,
row: directoryIndex,
localDepth: this.directory[directoryIndex].localDepth,
values: [...this.directory[directoryIndex].elements],
},
{
action: Action.UPDATE_VALUES_OF_ROW,
row: splitDirectoryIndex,
localDepth: this.directory[splitDirectoryIndex].localDepth,
values: [...this.directory[splitDirectoryIndex].elements],
},
{
action: Action.HIGHLIGHT_BUCKET_ROW,
pointToRowMap: pointToRowMap,
color: Color.HASH_COMPARE,
},
{
action: Action.SET_ROW_COLOR,
rowType: 'directory',
row: directoryIndex,
color: Color.BASE_COLOR_HASH_TABLE,
},
],
undo: [
{
action: Action.UPDATE_LINK_AT_POS,
pointsMap: oldPointsList,
},
{
action: Action.UPDATE_VALUES_OF_ROW,
row: directoryIndex,
localDepth: oldLocalDepth,
values: oldElements,
},
{
action: Action.UPDATE_VALUES_OF_ROW,
row: splitDirectoryIndex,
localDepth: oldLocalDepth,
values: oldElements,
},
{
action: Action.HIGHLIGHT_BUCKET_ROW,
pointToRowMap: pointToRowMap,
color: Color.BASE_COLOR_HASH_TABLE,
},
{
action: Action.SET_ROW_COLOR,
rowType: 'directory',
row: directoryIndex,
color: Color.HASH_COLLISION,
},
],
});
return steps;
}
}
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