Builds

NuGet

Longtail C# Bindings

This project generates cross platform C# bindings for Dan Engelbrecht longtail library. longtail.

How to

BuildTool

Run the entire build pipeline to sync with the latest version of Longtail. Delete the LONGTAIL_VERSION file in the root folder of the repo to force the pipeline to run.

.\build.ps1     # windows
./build.sh      # mac/linux

Current status

Version 0.4.2 of longtail - 0.4.2

Implemented

• Generates bindings for all structs, enums, functions, function pointers
• Supports .NET 8.0-preview on platforms Linux, MacOS(arm64) and Windows x64
• Automatic documentation for function pointers with the original names of parameters

Working on

• Copy the comments from the API functions and generate C# comments in the LongtailLibrary.cs file
• Managed abstrations (hide all unsafe code behind easy to use managed functions and classes)
• Task based interfaces for IStorage and IBlockStore (will probably be named IAsyncBlockStore and IAsyncStorage) for easy .NET IO (which is mostly async code).
• More tests for both CodeGen and Longtail

Known issues

• Currently using type ulong for size_t. This works but it's not correct, it should be nuint (or UIntPtr in older versions of .NET)
• Hardcoded paths for longtail inside code gen (can be overriden with calling the project with arguments)
• Some pointer references does not have a fixed size, so we can't convert them to a managed safe type in an easy way. (will continue to investigate that)
• Some APIs have not been implemented as managed functions yet.

Comments on function pointers might be a bit different from original. This happens because it binds the type to the parent.

// The comment
// int Longtail_BlockStore_PreflightGetFunc(struct Longtail_BlockStoreAPI* block_store_api, unsigned int block_count, const unsigned long long int* block_hashes, struct Longtail_AsyncPreflightStartedAPI* optional_async_complete_api)

// The c# code
public delegate* unmanaged[Cdecl]<Longtail_BlockStoreAPI*, uint, ulong*, Longtail_AsyncPreflightStartedAPI*, int> PreflightGet;

// The original function pointer
typedef int (*Longtail_BlockStore_PreflightGetFunc)(struct Longtail_BlockStoreAPI* block_store_api, uint32_t block_count, const TLongtail_Hash* block_hashes, struct Longtail_AsyncPreflightStartedAPI* optional_async_complete_api);

Project structure

src/BuildTool

• Tool to update dll/so files and run the code gen on the latest version from github.

src/CodeGen

• Parser, bindings, type handling etc

src/Longtail

• Extensions and helpers for the generated bindings. These are updated manually.

src/Longtail/Generated

• Longtail.cs contains all structs, enums etc
• LongtailLibrary.cs contains all the longtail functions found in longtail.h (and all other h files in the repo)

samples/LongtailSample01

• Full upsync and downsync sample with a FileSystem block store.