Initial C Bindings for Cosmos DB SDK for Rust

[analogrelay]

This PR ports over the initial C bindings, contributed by a partner team, to this repository.

The bindings are defined in the azure_data_cosmos_native crate, which builds libazurecosmos.a and libazurecosmos.so (and others on other platforms). That project also creates the azurecosmos.h header file.

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

azure_data_cosmos

[Copilot]

Pull Request Overview

This PR introduces C bindings for the Azure Cosmos DB SDK for Rust, allowing the SDK to be used from C and other languages. Key changes include:

• New FFI layer with runtime context, call context, and error handling infrastructure
• C bindings for CosmosClient, DatabaseClient, and ContainerClient
• Support for CRUD operations, queries, and resource management
• Auto-generated C header file (azurecosmos.h)
• Comprehensive C test suite covering CRUD operations, error handling, and memory management

Reviewed Changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/string.rs	String utilities and FFI string conversion helpers
src/runtime/tokio.rs	Tokio runtime wrapper for async operations
src/runtime/mod.rs	Runtime context FFI functions
src/options/mod.rs	Empty option structs for future extensibility
src/lib.rs	Main library entry, version function, and tracing setup
src/error.rs	Error types, codes, and conversion from Azure SDK errors
src/context.rs	Call context for FFI operations and helper macros
src/clients/mod.rs	Client module exports
src/clients/database_client.rs	Database operations FFI functions
src/clients/cosmos_client.rs	Cosmos client creation and database operations
src/clients/container_client.rs	Container and item operations FFI functions
include/azurecosmos.h	Auto-generated C header file
c_tests/*.c	C test suite for FFI functionality
build.rs	cbindgen configuration for header generation
Cargo.toml	Dependencies and features for native bindings
CMakeLists.txt	CMake build configuration for C tests

Comments suppressed due to low confidence (1)

sdk/cosmos/azure_data_cosmos_native/src/string.rs:37

• The safe_cstring_new function calls expect() which can panic, but this panic behavior is not documented. Add a # Panics section to the function documentation explaining when this function panics (when the string contains interior NUL bytes).

[Copilot]

Corrected comment from 'read database options' to 'delete database options'.

Suggested change

	// Placeholder for future read database options
	// Placeholder for future delete database options

[Copilot]

Corrected comment from 'read container options' to 'delete container options'.

Suggested change

	// Placeholder for future read container options
	// Placeholder for future delete container options

[Copilot]

The partition_key is already converted to String on line 161. This .to_string() call creates an unnecessary allocation. Use partition_key directly instead of creating pk.

Suggested change

	let pk = partition_key.to_string();
	container.replace_item(pk, item_id, raw_value, None).await?;
	container.replace_item(partition_key, item_id, raw_value, None).await?;

[Copilot]

The cosmos_call_context_create function expects a pointer to CallContextOptions as its second parameter (const struct cosmos_call_context_options *options), but false (a boolean literal) is being passed instead. This should either be NULL or a pointer to a properly initialized cosmos_call_context_options struct with include_error_details set to false.

Suggested change

	cosmos_call_context *ctx = cosmos_call_context_create(runtime, false);
	struct cosmos_call_context_options options = { 0 };
	options.include_error_details = false;
	cosmos_call_context *ctx = cosmos_call_context_create(runtime, &options);

[Copilot]

The project() command should be called before cmake_minimum_required() according to CMake best practices. While this code moves project() after cmake_minimum_required() (which is correct), the version 4.1 appears incorrect as CMake versions follow a 3.x numbering scheme. This should likely be VERSION 3.1 or higher.

Suggested change

	cmake_minimum_required(VERSION 4.1)
	cmake_minimum_required(VERSION 3.15)