Implementation:Fede1024 Rust rdkafka FFI Bindings

Knowledge Sources	Fede1024_Rust_rdkafka librdkafka API
Domains	FFI, Kafka_Protocol, Systems_Programming
Last Updated	2026-02-07 19:00 GMT

Overview

Auto-generated Rust FFI binding declarations for the entire librdkafka C API, providing raw extern function signatures, struct layouts, enum types, and constants required for all Kafka operations from Rust.

Description

The bindings module is generated by rust-bindgen (v0.72.1) from librdkafka's C headers (rdkafka.h and rdkafka_mock.h). It declares approximately 500+ extern "C" function prototypes, 80+ struct and enum type definitions, and numerous constants. Opaque C structs (e.g., rd_kafka_t, rd_kafka_conf_t) are represented as zero-sized marker types, while data-carrying structs (e.g., rd_kafka_message_t, rd_kafka_metadata_t) have full field layouts. This module is the foundational FFI layer through which every interaction with the native librdkafka library flows.

Usage

This module is used internally by the rdkafka-sys crate and re-exported at the crate root. End users of the higher-level rdkafka crate rarely interact with these bindings directly. Use this when you need raw access to librdkafka C functions not yet wrapped by the safe Rust API, or when implementing custom FFI extensions.

Code Reference

Source Location

• Repository: Fede1024_Rust_rdkafka
• File: rdkafka-sys/src/bindings.rs
• Lines: 1-3909

Signature

// Key opaque type aliases
pub type rd_kafka_t = rd_kafka_s;          // Kafka client handle
pub type rd_kafka_conf_t = rd_kafka_conf_s; // Configuration handle
pub type rd_kafka_topic_t = rd_kafka_topic_s; // Topic handle
pub type rd_kafka_queue_t = rd_kafka_queue_s; // Event queue handle

// Key data-carrying struct
#[repr(C)]
pub struct rd_kafka_message_s {
    pub err: rd_kafka_resp_err_t,
    pub rkt: *mut rd_kafka_topic_t,
    pub partition: i32,
    pub payload: *mut c_void,
    pub len: usize,
    pub key: *mut c_void,
    pub key_len: usize,
    pub offset: i64,
    pub _private: *mut c_void,
}

// Error code enum (~180 variants)
#[repr(u32)]
#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, TryFromPrimitive)]
pub enum rd_kafka_resp_err_t {
    RD_KAFKA_RESP_ERR__BEGIN = -200,
    RD_KAFKA_RESP_ERR_NO_ERROR = 0,
    // ... 180+ error codes
}

// Example extern functions
extern "C" {
    pub fn rd_kafka_version() -> c_int;
    pub fn rd_kafka_version_str() -> *const c_char;
    pub fn rd_kafka_new(
        type_: rd_kafka_type_t,
        conf: *mut rd_kafka_conf_t,
        errstr: *mut c_char,
        errstr_size: usize,
    ) -> *mut rd_kafka_t;
    pub fn rd_kafka_produce(
        rkt: *mut rd_kafka_topic_t,
        partition: i32,
        msgflags: c_int,
        payload: *mut c_void,
        len: usize,
        key: *const c_void,
        keylen: usize,
        msg_opaque: *mut c_void,
    ) -> c_int;
}

Import

use rdkafka_sys::*;
// or selectively:
use rdkafka_sys::bindings::{rd_kafka_t, rd_kafka_conf_t, rd_kafka_resp_err_t};

I/O Contract

Inputs

Name	Type	Required	Description
C header files	rdkafka.h, rdkafka_mock.h	Yes	Source headers for bindgen generation
librdkafka native library	Shared/static library	Yes	Linked at compile time via build.rs

Outputs

Name	Type	Description
Opaque type aliases	Rust type aliases	Zero-sized marker types for C handles (rd_kafka_t, rd_kafka_conf_t, etc.)
Data structs	#[repr(C)] structs	Memory-layout-compatible Rust structs (rd_kafka_message_t, rd_kafka_metadata_t, etc.)
Enum types	#[repr(u32/i32)] enums	C enum mappings (rd_kafka_resp_err_t, rd_kafka_type_t, etc.)
Extern functions	extern "C" fn	~500 function declarations for the full librdkafka API
Constants	pub const	Offset constants, message flags, event type flags, purge flags

Usage Examples

Checking librdkafka Version

use rdkafka_sys::bindings::{rd_kafka_version, rd_kafka_version_str};
use std::ffi::CStr;

fn check_version() {
    unsafe {
        let version_int = rd_kafka_version();
        let version_str = CStr::from_ptr(rd_kafka_version_str())
            .to_str()
            .unwrap();
        println!("librdkafka version: {} ({})", version_str, version_int);
    }
}

Using Offset Constants

use rdkafka_sys::{
    RD_KAFKA_OFFSET_BEGINNING,
    RD_KAFKA_OFFSET_END,
    RD_KAFKA_OFFSET_STORED,
};

// Start consuming from the beginning of a partition
let offset = RD_KAFKA_OFFSET_BEGINNING; // -2
// Start consuming from the end
let offset = RD_KAFKA_OFFSET_END; // -1
// Resume from the last stored offset
let offset = RD_KAFKA_OFFSET_STORED; // -1000

Related Pages

• Environment:Fede1024_Rust_rdkafka_Rust_Librdkafka_Build_Environment