71 lines
2.1 KiB
JavaScript
71 lines
2.1 KiB
JavaScript
var util = require('../core').util;
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var toBuffer = require('./to-buffer').toBuffer;
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// All prelude components are unsigned, 32-bit integers
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var PRELUDE_MEMBER_LENGTH = 4;
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// The prelude consists of two components
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var PRELUDE_LENGTH = PRELUDE_MEMBER_LENGTH * 2;
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// Checksums are always CRC32 hashes.
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var CHECKSUM_LENGTH = 4;
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// Messages must include a full prelude, a prelude checksum, and a message checksum
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var MINIMUM_MESSAGE_LENGTH = PRELUDE_LENGTH + CHECKSUM_LENGTH * 2;
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/**
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* @api private
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*
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* @param {Buffer} message
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*/
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function splitMessage(message) {
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if (!util.Buffer.isBuffer(message)) message = toBuffer(message);
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if (message.length < MINIMUM_MESSAGE_LENGTH) {
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throw new Error('Provided message too short to accommodate event stream message overhead');
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}
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if (message.length !== message.readUInt32BE(0)) {
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throw new Error('Reported message length does not match received message length');
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}
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var expectedPreludeChecksum = message.readUInt32BE(PRELUDE_LENGTH);
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if (
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expectedPreludeChecksum !== util.crypto.crc32(
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message.slice(0, PRELUDE_LENGTH)
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)
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) {
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throw new Error(
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'The prelude checksum specified in the message (' +
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expectedPreludeChecksum +
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') does not match the calculated CRC32 checksum.'
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);
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}
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var expectedMessageChecksum = message.readUInt32BE(message.length - CHECKSUM_LENGTH);
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if (
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expectedMessageChecksum !== util.crypto.crc32(
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message.slice(0, message.length - CHECKSUM_LENGTH)
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)
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) {
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throw new Error(
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'The message checksum did not match the expected value of ' +
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expectedMessageChecksum
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);
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}
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var headersStart = PRELUDE_LENGTH + CHECKSUM_LENGTH;
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var headersEnd = headersStart + message.readUInt32BE(PRELUDE_MEMBER_LENGTH);
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return {
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headers: message.slice(headersStart, headersEnd),
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body: message.slice(headersEnd, message.length - CHECKSUM_LENGTH),
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};
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}
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/**
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* @api private
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*/
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module.exports = {
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splitMessage: splitMessage
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};
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