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import * as zlib from 'zlib';
import { LEGACY_HELLO_COMMAND } from '../../constants';
import { getSnappy, getZstdLibrary, type SnappyLib, type ZStandard } from '../../deps';
import { MongoDecompressionError, MongoInvalidArgumentError } from '../../error';
import {
type MessageHeader,
OpCompressedRequest,
OpMsgResponse,
OpReply,
type WriteProtocolMessageType
} from '../commands';
import { OP_COMPRESSED, OP_MSG } from './constants';
/** @public */
export const Compressor = Object.freeze({
none: 0,
snappy: 1,
zlib: 2,
zstd: 3
} as const);
/** @public */
export type Compressor = (typeof Compressor)[CompressorName];
/** @public */
export type CompressorName = keyof typeof Compressor;
export const uncompressibleCommands = new Set([
LEGACY_HELLO_COMMAND,
'saslStart',
'saslContinue',
'getnonce',
'authenticate',
'createUser',
'updateUser',
'copydbSaslStart',
'copydbgetnonce',
'copydb'
]);
const ZSTD_COMPRESSION_LEVEL = 3;
const zlibInflate = promisify(zlib.inflate.bind(zlib));
const zlibDeflate = promisify(zlib.deflate.bind(zlib));
let zstd: ZStandard;
let Snappy: SnappyLib | null = null;
function loadSnappy() {
Eif (Snappy == null) {
const snappyImport = getSnappy();
Iif ('kModuleError' in snappyImport) {
throw snappyImport.kModuleError;
}
Snappy = snappyImport;
}
return Snappy;
}
// Facilitate compressing a message using an agreed compressor
export async function compress(
options: { zlibCompressionLevel: number; agreedCompressor: CompressorName },
dataToBeCompressed: Buffer
): Promise<Buffer> {
const zlibOptions = {} as zlib.ZlibOptions;
switch (options.agreedCompressor) {
case 'snappy': {
Snappy ??= loadSnappy();
return await Snappy.compress(dataToBeCompressed);
}
case 'zstd': {
loadZstd();
Iif ('kModuleError' in zstd) {
throw zstd['kModuleError'];
}
return await zstd.compress(dataToBeCompressed, ZSTD_COMPRESSION_LEVEL);
}
case 'zlib': {
Eif (options.zlibCompressionLevel) {
zlibOptions.level = options.zlibCompressionLevel;
}
return await zlibDeflate(dataToBeCompressed, zlibOptions);
}
default: {
throw new MongoInvalidArgumentError(
`Unknown compressor ${options.agreedCompressor} failed to compress`
);
}
}
}
// Decompress a message using the given compressor
export async function decompress(compressorID: number, compressedData: Buffer): Promise<Buffer> {
Iif (
compressorID !== Compressor.snappy &&
compressorID !== Compressor.zstd &&
compressorID !== Compressor.zlib &&
compressorID !== Compressor.none
) {
throw new MongoDecompressionError(
`Server sent message compressed using an unsupported compressor. (Received compressor ID ${compressorID})`
);
}
switch (compressorID) {
case Compressor.snappy: {
Snappy ??= loadSnappy();
return await Snappy.uncompress(compressedData, { asBuffer: true });
}
case Compressor.zstd: {
loadZstd();
Iif ('kModuleError' in zstd) {
throw zstd['kModuleError'];
}
return await zstd.decompress(compressedData);
}
case Compressor.zlib: {
return await zlibInflate(compressedData);
}
default: {
return compressedData;
}
}
}
/**
* Load ZStandard if it is not already set.
*/
function loadZstd() {
if (!zstd) {
zstd = getZstdLibrary();
}
}
const MESSAGE_HEADER_SIZE = 16;
/**
* @internal
*
* Compresses an OP_MSG or OP_QUERY message, if compression is configured. This method
* also serializes the command to BSON.
*/
export async function compressCommand(
command: WriteProtocolMessageType,
description: { agreedCompressor?: CompressorName; zlibCompressionLevel?: number }
): Promise<Buffer> {
const finalCommand =
description.agreedCompressor === 'none' || !OpCompressedRequest.canCompress(command)
? command
: new OpCompressedRequest(command, {
agreedCompressor: description.agreedCompressor ?? 'none',
zlibCompressionLevel: description.zlibCompressionLevel ?? 0
});
const data = await finalCommand.toBin();
return Buffer.concat(data);
}
/**
* @internal
*
* Decompresses an OP_MSG or OP_QUERY response from the server, if compression is configured.
*
* This method does not parse the response's BSON.
*/
export async function decompressResponse(message: Buffer): Promise<OpMsgResponse | OpReply> {
const messageHeader: MessageHeader = {
length: message.readInt32LE(0),
requestId: message.readInt32LE(4),
responseTo: message.readInt32LE(8),
opCode: message.readInt32LE(12)
};
if (messageHeader.opCode !== OP_COMPRESSED) {
const ResponseType = messageHeader.opCode === OP_MSG ? OpMsgResponse : OpReply;
const messageBody = message.subarray(MESSAGE_HEADER_SIZE);
return new ResponseType(message, messageHeader, messageBody);
}
const header: MessageHeader = {
...messageHeader,
fromCompressed: true,
opCode: message.readInt32LE(MESSAGE_HEADER_SIZE),
length: message.readInt32LE(MESSAGE_HEADER_SIZE + 4)
};
const compressorID = message[MESSAGE_HEADER_SIZE + 8];
const compressedBuffer = message.slice(MESSAGE_HEADER_SIZE + 9);
// recalculate based on wrapped opcode
const ResponseType = header.opCode === OP_MSG ? OpMsgResponse : OpReply;
const messageBody = await decompress(compressorID, compressedBuffer);
Iif (messageBody.length !== header.length) {
throw new MongoDecompressionError('Message body and message header must be the same length');
}
return new ResponseType(message, header, messageBody);
}
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