Ensure Buffer objects are returned by compression functions (#88)

Problem
=======

compression functions' return values are assumed to be Buffer objects.
However, in reality they could be non-Buffer objects and will results in
exceptions during reading/writing.
#72 

Solution
========

Detect the data type of the value from various compression libraries and
convert the value to Buffer object if necessary before returning.

Change summary:
---------------
Ensure Buffer objects are returned by compression functions

Steps to Verify:
----------------
As pointed out in the original issue, the problem can be reproduced
using the browser build of parquetjs to read a file with snappy
compression.

.gitignore

@@ -6,3 +6,4 @@ npm-debug.log
 dist
 !test/test-files/*.parquet
 examples/server/package-lock.json
+test/browser/*.js

esbuild.js

@@ -16,6 +16,21 @@ const baseConfig = {
     plugins: [compressionBrowserPlugin, wasmPlugin],
     target: "es2020"  // default
 };
+// configuration for generating test code in browser
+const testConfig = {
+    bundle: true,
+    entryPoints: ['test/browser/main.ts'],
+    define: {
+        "process.env.NODE_DEBUG": false,
+        "process.env.NODE_ENV": "\"production\"",
+        global: "window"
+    },
+    inject: ['./esbuild-shims.js'],
+    minify: false,
+    platform: 'browser',  // default
+    plugins: [compressionBrowserPlugin, wasmPlugin],
+    target: "es2020"  // default
+}
 const targets = [
     {
         ...baseConfig,
@@ -31,6 +46,11 @@ const targets = [
         ...baseConfig,
         format: "cjs",
         outfile: path.resolve(__dirname, "dist","browser","parquet.cjs.js"),
+    },
+    // Browser test code below
+    {
+        ...testConfig,
+        outfile: path.resolve(__dirname, "test","browser","main.js"),
     }
 ]
 Promise.all(targets.map(esbuild.build))

lib/browser/compression.js

@@ -29,15 +29,16 @@ async function deflate(method, value) {
 }
 
 function deflate_identity(value) {
-    return value;
+    return buffer_from_result(value);
 }
 
 function deflate_gzip(value) {
     return zlib.gzipSync(value);
 }
 
 function deflate_snappy(value) {
-    return snappy.compress(value);
+    const compressedValue = snappy.compress(value);
+    return buffer_from_result(compressedValue);
 }
 
 /**
@@ -52,15 +53,24 @@ async function inflate(method, value) {
 }
 
 function inflate_identity(value) {
-    return value;
+    return buffer_from_result(value);
 }
 
 function inflate_gzip(value) {
     return zlib.gunzipSync(value);
 }
 
 function inflate_snappy(value) {
-    return snappy.uncompress(value);
+    const uncompressedValue = snappy.uncompress(value);
+    return buffer_from_result(uncompressedValue);
+}
+
+function buffer_from_result(result) {
+    if (Buffer.isBuffer(result)) {
+        return result;
+    } else {
+        return Buffer.from(result);
+    }
 }
 
 exports.PARQUET_COMPRESSION_METHODS = PARQUET_COMPRESSION_METHODS

lib/compression.ts

@@ -9,8 +9,8 @@ type d_brotli = (value: Uint8Array ) => Promise<Buffer>
 
 interface PARQUET_COMPRESSION_METHODS {
   [key:string]: {
-      deflate: Function
-      inflate: Function
+    deflate: (value: any) => Buffer | Promise<Buffer>
+    inflate: (value: any) => Buffer | Promise<Buffer>
   }
 }
 // LZO compression is disabled. See: https://github.com/LibertyDSNP/parquetjs/issues/18
@@ -36,7 +36,7 @@ export const PARQUET_COMPRESSION_METHODS: PARQUET_COMPRESSION_METHODS = {
 /**
  * Deflate a value using compression method `method`
  */
-export async function deflate(method: string, value: unknown) {
+export async function deflate(method: string, value: unknown): Promise<Buffer> {
   if (!(method in PARQUET_COMPRESSION_METHODS)) {
     throw 'invalid compression method: ' + method;
   }
@@ -45,15 +45,16 @@ export async function deflate(method: string, value: unknown) {
 }
 
 function deflate_identity(value: ArrayBuffer | Buffer | Uint8Array) {
-  return value;
+  return buffer_from_result(value);
 }
 
 function deflate_gzip(value: ArrayBuffer | Buffer | string) {
   return zlib.gzipSync(value);
 }
 
 function deflate_snappy(value: ArrayBuffer | Buffer | Uint8Array) {
-  return snappy.compress(value);
+  const compressedValue = snappy.compress(value);
+  return buffer_from_result(compressedValue);
 }
 
 async function deflate_brotli(value: Uint8Array) {
@@ -70,29 +71,36 @@ async function deflate_brotli(value: Uint8Array) {
 /**
  * Inflate a value using compression method `method`
  */
-export async function inflate(method: string, value: unknown) {
+export async function inflate(method: string, value: unknown): Promise<Buffer> {
   if (!(method in PARQUET_COMPRESSION_METHODS)) {
     throw 'invalid compression method: ' + method;
   }
 
   return await PARQUET_COMPRESSION_METHODS[method].inflate(value);
 }
 
-function inflate_identity(value: ArrayBuffer | Buffer | Uint8Array) {
-  return value;
+async function inflate_identity(value: ArrayBuffer | Buffer | Uint8Array): Promise<Buffer> {
+  return buffer_from_result(value);
 }
 
-function inflate_gzip(value: Buffer | ArrayBuffer | string) {
+async function inflate_gzip(value: Buffer | ArrayBuffer | string) {
   return zlib.gunzipSync(value);
 }
 
 function inflate_snappy(value: ArrayBuffer | Buffer | Uint8Array) {
-  return snappy.uncompress(value);
+  const uncompressedValue = snappy.uncompress(value);
+  return buffer_from_result(uncompressedValue);
 }
 
 async function inflate_brotli(value: Uint8Array) {
   const uncompressedContent = await brotliDecompress(value)
   return Buffer.from(uncompressedContent);
 }
 
-
+function buffer_from_result(result: ArrayBuffer | Buffer | Uint8Array): Buffer {
+  if (Buffer.isBuffer(result)) {
+    return result;
+  } else {
+    return Buffer.from(result);
+  }
+}

package.json

@@ -62,7 +62,7 @@
     "build:browser": "node esbuild.js",
     "type": "tsc --noEmit",
     "lint": "echo 'Linting, it is on the TODO list...'",
-    "test": "mocha -r ts-node/register 'test/**/*.{js,ts}'",
+    "test": "mocha -r ts-node/register 'test/{,!(browser)/**}/*.{js,ts}'",
     "test:only": "mocha -r ts-node/register",
     "clean": "rm -Rf ./dist",
     "prepublishOnly": "npm run clean && npm run build:node && npm run build:types && npm run build:browser",

test/browser/index.html

@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <title>Mocha Tests</title>
+    <link rel="stylesheet" href="../../node_modules/mocha/mocha.css">
+</head>
+
+<body>
+    <div id="mocha"></div>
+    <script src="../../node_modules/mocha/mocha.js"></script>
+    <script src="../../node_modules/chai/chai.js"></script>
+    <script>mocha.setup('bdd')</script>
+
+    <!-- load code you want to test here -->
+    <script src="./main.js"></script>
+    <!-- load your test files here -->
+
+    <script>
+        mocha.run();
+    </script>
+</body>
+</html>

test/browser/main.ts

@@ -0,0 +1,24 @@
+import * as parquetjs from "../../dist/browser/parquet.esm";
+import { assert } from "chai";
+
+const buffer = require("buffer");
+
+describe("Browser tests", () => {
+  describe("reader", () => {
+    it("can read snappy compressed data", async () => {
+      // Data from test/test-files/snappy-compressed.parquet
+      const uint8Array = [80, 65, 82, 49, 21, 6, 21, 80, 21, 82, 92, 21, 8, 21, 0, 21, 8, 21, 0, 21, 0, 21, 0, 17, 28, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 22, 0, 22, 8, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 0, 0, 0, 40, 32, 5, 0, 0, 0, 104, 101, 108, 108, 111, 1, 9, 104, 119, 111, 114, 108, 100, 6, 0, 0, 0, 98, 97, 110, 97, 110, 97, 8, 0, 0, 0, 49, 112, 111, 97, 52, 98, 112, 102, 21, 12, 25, 37, 6, 0, 25, 24, 16, 99, 111, 109, 112, 114, 101, 115, 115, 101, 100, 83, 116, 114, 105, 110, 103, 21, 2, 22, 8, 22, 206, 1, 22, 206, 1, 38, 8, 60, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 22, 0, 22, 8, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 0, 0, 41, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 25, 24, 5, 119, 111, 114, 108, 100, 0, 25, 28, 22, 8, 21, 206, 1, 22, 0, 0, 0, 21, 2, 25, 44, 72, 4, 114, 111, 111, 116, 21, 2, 0, 21, 12, 37, 0, 24, 16, 99, 111, 109, 112, 114, 101, 115, 115, 101, 100, 83, 116, 114, 105, 110, 103, 37, 0, 0, 22, 8, 25, 28, 25, 28, 38, 214, 1, 28, 21, 12, 25, 37, 6, 0, 25, 24, 16, 99, 111, 109, 112, 114, 101, 115, 115, 101, 100, 83, 116, 114, 105, 110, 103, 21, 2, 22, 8, 22, 206, 1, 22, 206, 1, 38, 8, 60, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 22, 0, 22, 8, 24, 5, 119, 111, 114, 108, 100, 24, 8, 49, 112, 111, 97, 52, 98, 112, 102, 0, 0, 22, 154, 3, 21, 22, 22, 242, 2, 21, 40, 0, 22, 234, 2, 22, 8, 0, 25, 12, 24, 15, 64, 100, 115, 110, 112, 47, 112, 97, 114, 113, 117, 101, 116, 106, 115, 0, 163, 0, 0, 0, 80, 65, 82, 49];
+      const snappyCompressedBuffer = buffer.Buffer.from(uint8Array);
+      const reader = await parquetjs.ParquetReader.openBuffer(snappyCompressedBuffer);
+      const data: any[] = [];
+      for await (const record of reader) {
+        data.push(record);
+      }
+      assert.equal(data.length, 4);
+
+      after(async () => {
+        await reader.close();
+      })
+    });
+  });
+});