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Apache OpenDAL™ C Binding

A C binding for OpenDAL, giving C programs blocking access to S3, GCS, Azure Blob, the local filesystem, and 50+ more services through one API backed by the Rust core.

New to the model behind the API? Read Concepts first — service, operator, layer, operation are the same four ideas in every language.

Experimental

This binding is experimental and a work in progress. The API surface is limited, there are no pre-built packages, and breaking changes may occur between releases. It must be built from source.

Status​

Unreleased and experimental. The C binding exposes a blocking-only API generated via cbindgen from the Rust core. There is no async interface and no package registry distribution; you must compile the shared library yourself.

Capabilities​

  • Blocking operations — write, read, stat, delete, copy, rename, list, and create-dir through a single opendal_operator *.
  • Streaming reader and writer — opendal_reader and opendal_writer for chunk-at-a-time I/O with seek support on the reader.
  • All services via build flags — enable individual backends with -DFEATURES at CMake time.
  • C11 compatible — the header opendal.h requires C11 or later (and a C++14 compiler for the Rust-generated glue).
  • Explicit memory ownership — every heap-allocated value has a matching *_free function; results carry an opendal_error * that is NULL on success.

Building​

Requirements: a C11/C++14 compiler, CMake, and a Rust toolchain.

cd bindings/c
mkdir -p build && cd build

# Build with the default memory + fs services
cmake ..
make

# Enable additional services
cmake .. -DFEATURES="opendal/services-s3,opendal/services-gcs"
make

The shared library lands in ../../target/debug/ and the header is at bindings/c/include/opendal.h.

Next steps​

  1. Getting started — build an operator, write and read data, handle errors, and free resources.