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Posted to github@arrow.apache.org by "eerhardt (via GitHub)" <gi...@apache.org> on 2023/06/01 21:00:56 UTC
[GitHub] [arrow-adbc] eerhardt commented on a diff in pull request #697: feat(csharp): adding C# functionality
eerhardt commented on code in PR #697:
URL: https://github.com/apache/arrow-adbc/pull/697#discussion_r1213675613
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csharp/src/Apache.Arrow.Adbc/Interop/LoadDriver.cs:
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@@ -0,0 +1,508 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml.Linq;
+using Apache.Arrow.Adbc.Core;
+using Apache.Arrow.C;
+using Apache.Arrow.Ipc;
+using Apache.Arrow.Types;
+using Microsoft.Win32.SafeHandles;
+
+#if NETSTANDARD
+using Apache.Arrow.Adbc.Extensions;
+#endif
+
+namespace Apache.Arrow.Adbc.Interop
+{
+ public delegate byte AdbcDriverInit(int version, ref NativeAdbcDriver driver, ref NativeAdbcError error);
+
+ /// <summary>
+ /// Class for working with loading drivers from files
+ /// </summary>
+ public static class LoadDriver
+ {
+ private const string driverInit = "AdbcDriverInit";
+
+ class NativeDriver
+ {
+ public SafeHandle driverHandle;
+ public NativeAdbcDriver driver;
+ }
+
+ /// <summary>
+ /// Class used for Mac interoperability
+ /// </summary>
+ static class MacInterop
+ {
+ const string libdl = "libdl.dylib";
+
+ [DllImport(libdl)]
+ static extern SafeLibraryHandle dlopen(string fileName, int flags);
+
+ [DllImport(libdl)]
+ static extern IntPtr dlsym(SafeHandle libraryHandle, string symbol);
+
+ [DllImport(libdl)]
+ static extern int dlclose(IntPtr handle);
+
+ sealed class SafeLibraryHandle : SafeHandleZeroOrMinusOneIsInvalid
+ {
+ SafeLibraryHandle() : base(true) { }
+
+ protected override bool ReleaseHandle()
+ {
+ return dlclose(handle) == 0;
+ }
+ }
+
+ public static NativeDriver GetDriver(string file)
+ {
+ SafeHandle library = dlopen(file, 2); // TODO: find a symbol for 2
+ IntPtr symbol = dlsym(library, "AdbcDriverInit");
+ AdbcDriverInit init = Marshal.GetDelegateForFunctionPointer<AdbcDriverInit>(symbol);
+ NativeAdbcDriver driver = new NativeAdbcDriver();
+ NativeAdbcError error = new NativeAdbcError();
+ byte result = init(1000000, ref driver, ref error);
+ return new NativeDriver { driverHandle = library, driver = driver };
+ }
+ }
+
+ /// <summary>
+ /// Class used for Windows interoperability
+ /// </summary>
+ static class WindowsInterop
+ {
+ const string kernel32 = "kernel32.dll";
+
+ [DllImport(kernel32)]
+ [return: MarshalAs(UnmanagedType.Bool)]
+ static extern bool FreeLibrary(IntPtr libraryHandle);
+
+ [DllImport(kernel32, CharSet = CharSet.Ansi, BestFitMapping = false, ThrowOnUnmappableChar = true)]
+ static extern IntPtr GetProcAddress(SafeHandle libraryHandle, string functionName);
+
+ [DllImport(kernel32, CharSet = CharSet.Unicode, SetLastError = true)]
+ static extern SafeLibraryHandle LoadLibraryEx(string fileName, IntPtr hFile, uint flags);
+
+ sealed class SafeLibraryHandle : SafeHandleZeroOrMinusOneIsInvalid
+ {
+ SafeLibraryHandle() : base(true) { }
+
+ protected override bool ReleaseHandle()
+ {
+ return FreeLibrary(handle);
+ }
+ }
+
+ public static NativeDriver GetDriver(string file)
+ {
+ SafeHandle library = LoadLibraryEx(file, IntPtr.Zero, 0x1100);
+ IntPtr symbol = GetProcAddress(library, "AdbcDriverInit");
+ AdbcDriverInit init = Marshal.GetDelegateForFunctionPointer<AdbcDriverInit>(symbol);
+ NativeAdbcDriver driver = new NativeAdbcDriver();
+ NativeAdbcError error = new NativeAdbcError();
+ byte result = init(1000000, ref driver, ref error);
+ return new NativeDriver { /* driverHandle = library, */ driver = driver };
+ }
+ }
+
+ /// <summary>
+ /// Loads an <see cref="AdbcDriver"/> from the file system.
+ /// </summary>
+ /// <param name="file">The path to the file</param>
+ /// <returns></returns>
+ public static AdbcDriver Load(string file)
+ {
+ if (file[0] == '/')
+ {
+ return new AdbcDriverNative(MacInterop.GetDriver(file).driver);
+ }
+ else
+ {
+ return new AdbcDriverNative(WindowsInterop.GetDriver(file).driver);
+ }
+ }
+
+ /// <summary>
+ /// Native implementation of <see cref="AdbcDriver"/>
+ /// </summary>
+ sealed class AdbcDriverNative : AdbcDriver
+ {
+ private NativeAdbcDriver _nativeDriver;
+
+ public AdbcDriverNative(NativeAdbcDriver nativeDriver)
+ {
+ _nativeDriver = nativeDriver;
+ }
+
+ /// <summary>
+ /// Opens a database
+ /// </summary>
+ /// <param name="parameters"></param>
+ /// <returns></returns>
+ public unsafe override AdbcDatabase Open(Dictionary<string, string> parameters)
+ {
+ NativeAdbcDatabase nativeDatabase = new NativeAdbcDatabase();
+ using (ErrorHelper error = new ErrorHelper())
+ {
+ error.Call(
+ Marshal.GetDelegateForFunctionPointer<DatabaseFn>((IntPtr)_nativeDriver.DatabaseNew),
+ ref nativeDatabase);
+
+ DatabaseSetOption setOption = Marshal.GetDelegateForFunctionPointer<DatabaseSetOption>((IntPtr)_nativeDriver.DatabaseSetOption);
+ if (parameters != null)
+ {
+ foreach (KeyValuePair<string, string> pair in parameters)
+ {
+ error.Call(setOption, ref nativeDatabase, pair.Key, pair.Value);
+ }
+ }
+ error.Call(Marshal.GetDelegateForFunctionPointer<DatabaseFn>((IntPtr)_nativeDriver.DatabaseInit), ref nativeDatabase);
+ }
+
+ return new AdbcDatabaseNative(_nativeDriver, nativeDatabase);
+ }
+
+ public unsafe override void Dispose()
+ {
+ if (_nativeDriver.release != null)
+ {
+ using (ErrorHelper error = new ErrorHelper())
+ {
+ try
+ {
+ error.Call(Marshal.GetDelegateForFunctionPointer<DriverRelease>((IntPtr)_nativeDriver.release), ref _nativeDriver);
Review Comment:
You don't need to / shouldn't use `Marshal.GetDelegateForFunctionPointer` here. Instead you can invoke the function like:
```C#
fixed (NativeAdbcDriver* driver = &nativeDriver)
{
_nativeDriver.release(driver);
}
```
You'll probably have to rewrite your ErrorHelper for a new pattern. But there's no reason to allocate a managed object (a Delegate) just to call this function - or any native function.
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