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node_modules/mysql2/lib/compressed_protocol.js

@@ -0,0 +1,127 @@
+'use strict';
+
+// connection mixins
+// implementation of http://dev.mysql.com/doc/internals/en/compression.html
+
+const zlib = require('zlib');
+const PacketParser = require('./packet_parser.js');
+
+function handleCompressedPacket(packet) {
+  // eslint-disable-next-line consistent-this, no-invalid-this
+  const connection = this;
+  const deflatedLength = packet.readInt24();
+  const body = packet.readBuffer();
+
+  if (deflatedLength !== 0) {
+    connection.inflateQueue.push(task => {
+      zlib.inflate(body, (err, data) => {
+        if (err) {
+          connection._handleNetworkError(err);
+          return;
+        }
+        connection._bumpCompressedSequenceId(packet.numPackets);
+        connection._inflatedPacketsParser.execute(data);
+        task.done();
+      });
+    });
+  } else {
+    connection.inflateQueue.push(task => {
+      connection._bumpCompressedSequenceId(packet.numPackets);
+      connection._inflatedPacketsParser.execute(body);
+      task.done();
+    });
+  }
+}
+
+function writeCompressed(buffer) {
+  // http://dev.mysql.com/doc/internals/en/example-several-mysql-packets.html
+  // note: sending a MySQL Packet of the size 2^24−5 to 2^24−1 via compression
+  // leads to at least one extra compressed packet.
+  // (this is because "length of the packet before compression" need to fit
+  // into 3 byte unsigned int. "length of the packet before compression" includes
+  // 4 byte packet header, hence 2^24−5)
+  const MAX_COMPRESSED_LENGTH = 16777210;
+  let start;
+  if (buffer.length > MAX_COMPRESSED_LENGTH) {
+    for (start = 0; start < buffer.length; start += MAX_COMPRESSED_LENGTH) {
+      writeCompressed.call(
+        // eslint-disable-next-line no-invalid-this
+        this,
+        buffer.slice(start, start + MAX_COMPRESSED_LENGTH)
+      );
+    }
+    return;
+  }
+
+  // eslint-disable-next-line no-invalid-this, consistent-this
+  const connection = this;
+
+  let packetLen = buffer.length;
+  const compressHeader = Buffer.allocUnsafe(7);
+
+  // seqqueue is used here because zlib async execution is routed via thread pool
+  // internally and when we have multiple compressed packets arriving we need
+  // to assemble uncompressed result sequentially
+  (function(seqId) {
+    connection.deflateQueue.push(task => {
+      zlib.deflate(buffer, (err, compressed) => {
+        if (err) {
+          connection._handleFatalError(err);
+          return;
+        }
+        let compressedLength = compressed.length;
+
+        if (compressedLength < packetLen) {
+          compressHeader.writeUInt8(compressedLength & 0xff, 0);
+          compressHeader.writeUInt16LE(compressedLength >> 8, 1);
+          compressHeader.writeUInt8(seqId, 3);
+          compressHeader.writeUInt8(packetLen & 0xff, 4);
+          compressHeader.writeUInt16LE(packetLen >> 8, 5);
+          connection.writeUncompressed(compressHeader);
+          connection.writeUncompressed(compressed);
+        } else {
+          // http://dev.mysql.com/doc/internals/en/uncompressed-payload.html
+          // To send an uncompressed payload:
+          //   - set length of payload before compression to 0
+          //   - the compressed payload contains the uncompressed payload instead.
+          compressedLength = packetLen;
+          packetLen = 0;
+          compressHeader.writeUInt8(compressedLength & 0xff, 0);
+          compressHeader.writeUInt16LE(compressedLength >> 8, 1);
+          compressHeader.writeUInt8(seqId, 3);
+          compressHeader.writeUInt8(packetLen & 0xff, 4);
+          compressHeader.writeUInt16LE(packetLen >> 8, 5);
+          connection.writeUncompressed(compressHeader);
+          connection.writeUncompressed(buffer);
+        }
+        task.done();
+      });
+    });
+  })(connection.compressedSequenceId);
+  connection._bumpCompressedSequenceId(1);
+}
+
+function enableCompression(connection) {
+  connection._lastWrittenPacketId = 0;
+  connection._lastReceivedPacketId = 0;
+
+  connection._handleCompressedPacket = handleCompressedPacket;
+  connection._inflatedPacketsParser = new PacketParser(p => {
+    connection.handlePacket(p);
+  }, 4);
+  connection._inflatedPacketsParser._lastPacket = 0;
+  connection.packetParser = new PacketParser(packet => {
+    connection._handleCompressedPacket(packet);
+  }, 7);
+
+  connection.writeUncompressed = connection.write;
+  connection.write = writeCompressed;
+
+  const seqqueue = require('seq-queue');
+  connection.inflateQueue = seqqueue.createQueue();
+  connection.deflateQueue = seqqueue.createQueue();
+}
+
+module.exports = {
+  enableCompression: enableCompression
+};