schematic-kafka/dist/kafka-helper.js

Encode and decode kafka messages with Confluent Schema Registry (pure typescript implementation)

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.kafkaDecode = exports.kafkaEncode = void 0;
/**
 * Prefix kafka message with the correct preamble for the given schema id
 * @param {Buffer} encodedMessage already encoded message
 * @param {number} schemaId
 * @returns {Buffer}
 */
const kafkaEncode = (schemaId, encodedMessage) => {
    if (!(encodedMessage instanceof Buffer)) {
        throw new Error("encoded message must be of type Buffer");
    }
    // Allocate buffer for encoded kafka event (1 byte preable + 4 byte messageid + sizeof(encodedMessage))
    const message = Buffer.alloc(encodedMessage.length + 5);
    message.writeUInt8(0);
    message.writeUInt32BE(schemaId, 1);
    encodedMessage.copy(message, 5);
    return message;
};
exports.kafkaEncode = kafkaEncode;
/**
 * Decode the schema preamble and return schemaId anf payload
 * @param {Buffer} rawMessage Unencoded message from kafka event
 * @returns schemaId and unencoded payload
 */
const kafkaDecode = (rawMessage) => {
    if (rawMessage.readUInt8(0) !== 0) {
        // throw new Error(`Missing schema preamble.`)
        return { payload: rawMessage };
    }
    const schemaId = rawMessage.readUInt32BE(1);
    const payload = rawMessage.slice(5);
    return { schemaId, payload };
};
exports.kafkaDecode = kafkaDecode;
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