@softchef/cdk-iot-device-management
Version:
IoT device management is composed of things, thing types, thing groups, jobs, files API services. The constructs can be used independently, that are based on full-managed service to create an API Gateway & Lambda function.
35 lines (34 loc) • 2.05 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.splitMessage = void 0;
const crc32_1 = require("@aws-crypto/crc32");
const PRELUDE_MEMBER_LENGTH = 4;
const PRELUDE_LENGTH = PRELUDE_MEMBER_LENGTH * 2;
const CHECKSUM_LENGTH = 4;
const MINIMUM_MESSAGE_LENGTH = PRELUDE_LENGTH + CHECKSUM_LENGTH * 2;
function splitMessage({ byteLength, byteOffset, buffer }) {
if (byteLength < MINIMUM_MESSAGE_LENGTH) {
throw new Error("Provided message too short to accommodate event stream message overhead");
}
const view = new DataView(buffer, byteOffset, byteLength);
const messageLength = view.getUint32(0, false);
if (byteLength !== messageLength) {
throw new Error("Reported message length does not match received message length");
}
const headerLength = view.getUint32(PRELUDE_MEMBER_LENGTH, false);
const expectedPreludeChecksum = view.getUint32(PRELUDE_LENGTH, false);
const expectedMessageChecksum = view.getUint32(byteLength - CHECKSUM_LENGTH, false);
const checksummer = new crc32_1.Crc32().update(new Uint8Array(buffer, byteOffset, PRELUDE_LENGTH));
if (expectedPreludeChecksum !== checksummer.digest()) {
throw new Error(`The prelude checksum specified in the message (${expectedPreludeChecksum}) does not match the calculated CRC32 checksum (${checksummer.digest()})`);
}
checksummer.update(new Uint8Array(buffer, byteOffset + PRELUDE_LENGTH, byteLength - (PRELUDE_LENGTH + CHECKSUM_LENGTH)));
if (expectedMessageChecksum !== checksummer.digest()) {
throw new Error(`The message checksum (${checksummer.digest()}) did not match the expected value of ${expectedMessageChecksum}`);
}
return {
headers: new DataView(buffer, byteOffset + PRELUDE_LENGTH + CHECKSUM_LENGTH, headerLength),
body: new Uint8Array(buffer, byteOffset + PRELUDE_LENGTH + CHECKSUM_LENGTH + headerLength, messageLength - headerLength - (PRELUDE_LENGTH + CHECKSUM_LENGTH + CHECKSUM_LENGTH)),
};
}
exports.splitMessage = splitMessage;