src/vs/base/common/hash.ts/StringSHA1/digest
class StringSHA1:	public digest(): string {
		if (!this._finished) {
			this._finished = true;
			if (this._leftoverHighSurrogate) {
				// illegal => unicode replacement character
				this._leftoverHighSurrogate = 0;
				this._buffLen = this._push(this._buff, this._buffLen, SHA1Constant.UNICODE_REPLACEMENT);
			}
			this._totalLen += this._buffLen;
			this._wrapUp();
		}

		return toHexString(this._h0) + toHexString(this._h1) + toHexString(this._h2) + toHexString(this._h3) + toHexString(this._h4);
	}