128 lines
4.4 KiB
JavaScript
128 lines
4.4 KiB
JavaScript
'use strict';
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// connection mixins
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// implementation of http://dev.mysql.com/doc/internals/en/compression.html
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const zlib = require('zlib');
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const PacketParser = require('./packet_parser.js');
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function handleCompressedPacket(packet) {
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// eslint-disable-next-line consistent-this, no-invalid-this
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const connection = this;
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const deflatedLength = packet.readInt24();
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const body = packet.readBuffer();
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if (deflatedLength !== 0) {
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connection.inflateQueue.push((task) => {
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zlib.inflate(body, (err, data) => {
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if (err) {
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connection._handleNetworkError(err);
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return;
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}
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connection._bumpCompressedSequenceId(packet.numPackets);
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connection._inflatedPacketsParser.execute(data);
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task.done();
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});
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});
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} else {
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connection.inflateQueue.push((task) => {
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connection._bumpCompressedSequenceId(packet.numPackets);
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connection._inflatedPacketsParser.execute(body);
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task.done();
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});
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}
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}
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function writeCompressed(buffer) {
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// http://dev.mysql.com/doc/internals/en/example-several-mysql-packets.html
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// note: sending a MySQL Packet of the size 2^24−5 to 2^24−1 via compression
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// leads to at least one extra compressed packet.
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// (this is because "length of the packet before compression" need to fit
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// into 3 byte unsigned int. "length of the packet before compression" includes
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// 4 byte packet header, hence 2^24−5)
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const MAX_COMPRESSED_LENGTH = 16777210;
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let start;
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if (buffer.length > MAX_COMPRESSED_LENGTH) {
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for (start = 0; start < buffer.length; start += MAX_COMPRESSED_LENGTH) {
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writeCompressed.call(
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// eslint-disable-next-line no-invalid-this
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this,
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buffer.slice(start, start + MAX_COMPRESSED_LENGTH)
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);
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}
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return;
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}
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// eslint-disable-next-line no-invalid-this, consistent-this
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const connection = this;
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let packetLen = buffer.length;
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const compressHeader = Buffer.allocUnsafe(7);
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// seqqueue is used here because zlib async execution is routed via thread pool
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// internally and when we have multiple compressed packets arriving we need
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// to assemble uncompressed result sequentially
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(function (seqId) {
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connection.deflateQueue.push((task) => {
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zlib.deflate(buffer, (err, compressed) => {
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if (err) {
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connection._handleFatalError(err);
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return;
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}
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let compressedLength = compressed.length;
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if (compressedLength < packetLen) {
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compressHeader.writeUInt8(compressedLength & 0xff, 0);
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compressHeader.writeUInt16LE(compressedLength >> 8, 1);
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compressHeader.writeUInt8(seqId, 3);
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compressHeader.writeUInt8(packetLen & 0xff, 4);
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compressHeader.writeUInt16LE(packetLen >> 8, 5);
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connection.writeUncompressed(compressHeader);
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connection.writeUncompressed(compressed);
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} else {
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// http://dev.mysql.com/doc/internals/en/uncompressed-payload.html
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// To send an uncompressed payload:
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// - set length of payload before compression to 0
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// - the compressed payload contains the uncompressed payload instead.
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compressedLength = packetLen;
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packetLen = 0;
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compressHeader.writeUInt8(compressedLength & 0xff, 0);
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compressHeader.writeUInt16LE(compressedLength >> 8, 1);
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compressHeader.writeUInt8(seqId, 3);
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compressHeader.writeUInt8(packetLen & 0xff, 4);
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compressHeader.writeUInt16LE(packetLen >> 8, 5);
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connection.writeUncompressed(compressHeader);
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connection.writeUncompressed(buffer);
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}
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task.done();
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});
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});
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})(connection.compressedSequenceId);
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connection._bumpCompressedSequenceId(1);
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}
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function enableCompression(connection) {
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connection._lastWrittenPacketId = 0;
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connection._lastReceivedPacketId = 0;
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connection._handleCompressedPacket = handleCompressedPacket;
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connection._inflatedPacketsParser = new PacketParser((p) => {
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connection.handlePacket(p);
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}, 4);
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connection._inflatedPacketsParser._lastPacket = 0;
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connection.packetParser = new PacketParser((packet) => {
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connection._handleCompressedPacket(packet);
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}, 7);
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connection.writeUncompressed = connection.write;
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connection.write = writeCompressed;
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const seqqueue = require('seq-queue');
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connection.inflateQueue = seqqueue.createQueue();
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connection.deflateQueue = seqqueue.createQueue();
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}
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module.exports = {
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enableCompression: enableCompression,
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};
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