Crate baml_sys 

BAML FFI bindings with runtime dynamic library loading.

This crate provides low-level FFI bindings to the BAML runtime library. The library is loaded dynamically at runtime using libloading.

Library Resolution

The library is searched in the following order:

1. Explicit path set via set_library_path()
2. BAML_LIBRARY_PATH environment variable
3. User cache directory (~/.cache/baml/libs/{VERSION}/)
4. Auto-download from GitHub releases (if download feature enabled)
5. System default paths (/usr/local/lib/, etc.)

Usage

Runtime Loading (Default)

use baml_sys::{get_symbols, version};

// Library is loaded on first access
let v = version()?;
println!("BAML version: {v}");

Build-time Hook

In your build.rs:

fn main() {
    // Ensure library is available before build completes
    let lib_path = baml_sys::ensure_library()
        .expect("Failed to find/download BAML library");
    println!("cargo:rerun-if-changed={}", lib_path.display());
}

Environment Variables

• BAML_LIBRARY_PATH: Explicit path to the library
• BAML_CACHE_DIR: Override cache directory location
• BAML_LIBRARY_DISABLE_DOWNLOAD: Set to “true” to disable auto-download

Structs

Buffer

Buffer returned from object operations.

Symbols

Loaded symbols from the dynamic library.

Enums

BamlSysError

Errors that can occur during library loading.

Constants

ENV_CACHE_DIR

Environment variable for cache directory override.

ENV_DISABLE_DOWNLOAD

Environment variable to disable automatic download.

ENV_LIBRARY_PATH

Environment variable for explicit library path.

VERSION

Package version from Cargo.toml (workspace).

Functions

call_function_from_c^⚠

Call a BAML function.

call_function_parse_from_c^⚠

Call a BAML function for parsing.

call_function_stream_from_c^⚠

Call a BAML function with streaming.

call_object_constructor^⚠

Call an object constructor.

call_object_method^⚠

Call an object method.

cancel_function_call^⚠

Cancel a function call.

create_baml_runtime^⚠

Create a new BAML runtime.

destroy_baml_runtime^⚠

Destroy a BAML runtime.

ensure_library

Ensure the library is available (for use in build.rs).

free_buffer^⚠

Free a buffer returned from object operations.

get_symbols

Get the loaded symbols, initializing if necessary.

invoke_runtime_cli^⚠

Invoke the runtime CLI.

library_path

Get the path to the loaded library.

register_callbacks^⚠

Register callbacks for FFI operations.

set_library_path

Set an explicit library path before initialization.

version

Get the BAML library version.

Type Aliases

CallbackFn

Callback function type for results.

OnTickCallbackFn

Callback function type for streaming ticks.

Result

Result type for baml-sys operations.