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/**
* Convert from a Base64URL-encoded string to an Array Buffer. Best used when converting a
* credential ID from a JSON string to an ArrayBuffer, like in allowCredentials or
* excludeCredentials
*
* Helper method to compliment `bufferToBase64URLString`
*/
export function base64URLStringToBuffer(base64URLString: string): ArrayBuffer {
// Convert from Base64URL to Base64
const base64 = base64URLString.replace(/-/g, "+").replace(/_/g, "/");
/**
* Pad with '=' until it's a multiple of four
* (4 - (85 % 4 = 1) = 3) % 4 = 3 padding
* (4 - (86 % 4 = 2) = 2) % 4 = 2 padding
* (4 - (87 % 4 = 3) = 1) % 4 = 1 padding
* (4 - (88 % 4 = 0) = 4) % 4 = 0 padding
*/
const padLength = (4 - (base64.length % 4)) % 4;
const padded = base64.padEnd(base64.length + padLength, "=");
// Convert to a binary string
const binary = atob(padded);
// Convert binary string to buffer
const buffer = new ArrayBuffer(binary.length);
const bytes = new Uint8Array(buffer);
for (let i = 0; i < binary.length; i++) {
bytes[i] = binary.charCodeAt(i);
}
return buffer;
}
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