flow like the river

VISUALIZACION/node_modules/mongodb/lib/cmap/wire_protocol/compression.js

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+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.decompress = exports.compress = exports.uncompressibleCommands = exports.Compressor = void 0;
+const util_1 = require("util");
+const zlib = require("zlib");
+const constants_1 = require("../../constants");
+const deps_1 = require("../../deps");
+const error_1 = require("../../error");
+/** @public */
+exports.Compressor = Object.freeze({
+    none: 0,
+    snappy: 1,
+    zlib: 2,
+    zstd: 3
+});
+exports.uncompressibleCommands = new Set([
+    constants_1.LEGACY_HELLO_COMMAND,
+    'saslStart',
+    'saslContinue',
+    'getnonce',
+    'authenticate',
+    'createUser',
+    'updateUser',
+    'copydbSaslStart',
+    'copydbgetnonce',
+    'copydb'
+]);
+const ZSTD_COMPRESSION_LEVEL = 3;
+const zlibInflate = (0, util_1.promisify)(zlib.inflate.bind(zlib));
+const zlibDeflate = (0, util_1.promisify)(zlib.deflate.bind(zlib));
+let zstd;
+let Snappy = null;
+function loadSnappy() {
+    if (Snappy == null) {
+        const snappyImport = (0, deps_1.getSnappy)();
+        if ('kModuleError' in snappyImport) {
+            throw snappyImport.kModuleError;
+        }
+        Snappy = snappyImport;
+    }
+    return Snappy;
+}
+// Facilitate compressing a message using an agreed compressor
+async function compress(options, dataToBeCompressed) {
+    const zlibOptions = {};
+    switch (options.agreedCompressor) {
+        case 'snappy': {
+            Snappy ?? (Snappy = loadSnappy());
+            return Snappy.compress(dataToBeCompressed);
+        }
+        case 'zstd': {
+            loadZstd();
+            if ('kModuleError' in zstd) {
+                throw zstd['kModuleError'];
+            }
+            return zstd.compress(dataToBeCompressed, ZSTD_COMPRESSION_LEVEL);
+        }
+        case 'zlib': {
+            if (options.zlibCompressionLevel) {
+                zlibOptions.level = options.zlibCompressionLevel;
+            }
+            return zlibDeflate(dataToBeCompressed, zlibOptions);
+        }
+        default: {
+            throw new error_1.MongoInvalidArgumentError(`Unknown compressor ${options.agreedCompressor} failed to compress`);
+        }
+    }
+}
+exports.compress = compress;
+// Decompress a message using the given compressor
+async function decompress(compressorID, compressedData) {
+    if (compressorID !== exports.Compressor.snappy &&
+        compressorID !== exports.Compressor.zstd &&
+        compressorID !== exports.Compressor.zlib &&
+        compressorID !== exports.Compressor.none) {
+        throw new error_1.MongoDecompressionError(`Server sent message compressed using an unsupported compressor. (Received compressor ID ${compressorID})`);
+    }
+    switch (compressorID) {
+        case exports.Compressor.snappy: {
+            Snappy ?? (Snappy = loadSnappy());
+            return Snappy.uncompress(compressedData, { asBuffer: true });
+        }
+        case exports.Compressor.zstd: {
+            loadZstd();
+            if ('kModuleError' in zstd) {
+                throw zstd['kModuleError'];
+            }
+            return zstd.decompress(compressedData);
+        }
+        case exports.Compressor.zlib: {
+            return zlibInflate(compressedData);
+        }
+        default: {
+            return compressedData;
+        }
+    }
+}
+exports.decompress = decompress;
+/**
+ * Load ZStandard if it is not already set.
+ */
+function loadZstd() {
+    if (!zstd) {
+        zstd = (0, deps_1.getZstdLibrary)();
+    }
+}
+//# sourceMappingURL=compression.js.map