Create algorithm for converting binary data to base64 #756

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	// About base64: https://en.wikipedia.org/wiki/Base64

	/**
	* Converts an array of bytes to base64 encoding
	* @param {ArrayBuffer} binaryData An ArrayBuffer which represents an array of bytes
	* @returns {string} A string containing the base64 encoding of `binaryData`
	*/
	function bufferToBase64 (binaryData) {
	// The base64 encoding uses the following set of characters to encode any binary data as text
	const base64Table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
	// Every 3 bytes translates to 4 base64 characters, if we have less than 3 bytes we must append '=' chars as padding
	const padding = 3 - (binaryData.byteLength % 3)
	// Create an instance of Uint8Array, to read from the binaryData array buffer
	const byteView = new Uint8Array(binaryData)
	let result = ''

	// Loop through all bytes in the buffer, in increments of 3 bytes
	for (let i = 0; i < byteView.byteLength; i += 3) {
	// Get the index for the next 4 base64 chars
	const char1 = (byteView[i] & 252) >> 2
	const char2 = ((byteView[i] & 3) << 4) + ((byteView[i + 1] & 240) >> 4)
	const char3 = ((byteView[i + 1] & 15) << 2) + ((byteView[i + 2] & 192) >> 6)
	const char4 = byteView[i + 2] & 63

	result +=
	base64Table[char1] +
	base64Table[char2] +
	base64Table[char3] +
	base64Table[char4]
	}

	// Add padding '=' chars if needed
	if (padding !== 3) {
	const paddedResult = result.slice(0, result.length - padding) + '='.repeat(padding)
	return paddedResult
	}

	return result
	}

	export { bufferToBase64 }

24 changes: 24 additions & 0 deletions Conversions/test/ArrayBufferToBase64.test.js

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	import { bufferToBase64 } from '../ArrayBufferToBase64'
	import { TextEncoder } from 'util'

	describe('ArrayBufferToBase64', () => {
	it('should encode "Hello, world!" as "SGVsbG8sIHdvcmxkIQ=="', () => {
	const testString = 'Hello, world!'
	const encoder = new TextEncoder()
	const helloWorldBuffer = encoder.encode(testString)
	const result = bufferToBase64(helloWorldBuffer)
	expect(result).toBe('SGVsbG8sIHdvcmxkIQ==')
	})

	it('should encode binary buffer [55,23,177,234,68,26,90] as "Nxex6kQaWg=="', () => {
	const testBuffer = new Uint8Array([55, 23, 177, 234, 68, 26, 90])
	const result = bufferToBase64(testBuffer)
	expect(result).toBe('Nxex6kQaWg==')
	})

	it('should encode binary buffer [0,1,2,3,4,5,6,7,8,9] as "AAECAwQFBgcICQ=="', () => {
	const testBuffer = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
	const result = bufferToBase64(testBuffer)
	expect(result).toBe('AAECAwQFBgcICQ==')
	})
	})

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