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Copy pathArrayBufferToBase64.js
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43 lines (37 loc) · 1.54 KB
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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 }