// Copyright 2025 Don MacAskill. Licensed under MIT or Apache-2.0.

//! FFI bindings for the Rust library

//!

//! This module provides a C-compatible interface for the Rust library, allowing

//! C programs to use the library's functionality.

#![cfg(all(

    feature = "ffi",

    any(target_arch = "aarch64", target_arch = "x86_64", target_arch = "x86")

))]

use crate::CrcAlgorithm;

use crate::CrcParams;

use crate::{get_calculator_target, Digest};

use std::collections::HashMap;

use std::collections::HashSet;

use std::ffi::CStr;

use std::os::raw::c_char;

use std::slice;

use std::sync::{Mutex, OnceLock};

static STRING_CACHE: OnceLock<Mutex<HashSet<&'static str>>> = OnceLock::new();

/// Error codes for FFI operations

#[repr(C)]

#[derive(Debug, Clone, Copy, PartialEq, Eq)]

pub enum CrcFastError {

    /// Operation completed successfully

    Success = 0,

    /// Lock was poisoned (thread panicked while holding lock)

    LockPoisoned = 1,

    /// Null pointer was passed where non-null required

    NullPointer = 2,

    /// Invalid key count for CRC parameters

    InvalidKeyCount = 3,

    /// Unsupported CRC width (must be 32 or 64)

    UnsupportedWidth = 4,

    /// Invalid UTF-8 string

    InvalidUtf8 = 5,

    /// File I/O error

    IoError = 6,

    /// Internal string conversion error

    StringConversionError = 7,

}

impl CrcFastError {

    /// Returns a static string describing the error

    fn message(&self) -> &'static str {

        match self {

            CrcFastError::Success => "Operation completed successfully",

            CrcFastError::LockPoisoned => "Lock was poisoned (thread panicked while holding lock)",

            CrcFastError::NullPointer => "Null pointer was passed where non-null required",

            CrcFastError::InvalidKeyCount => "Invalid key count for CRC parameters",

            CrcFastError::UnsupportedWidth => "Unsupported CRC width (must be 32 or 64)",

            CrcFastError::InvalidUtf8 => "Invalid UTF-8 string",

            CrcFastError::IoError => "File I/O error",

            CrcFastError::StringConversionError => "Internal string conversion error",

        }

    }

}

// Thread-local storage for the last error that occurred

thread_local! {

    static LAST_ERROR: std::cell::Cell<CrcFastError> = const { std::cell::Cell::new(CrcFastError::Success) };

}

/// Sets the thread-local last error

fn set_last_error(error: CrcFastError) {

    LAST_ERROR.with(|e| e.set(error));

}

/// Clears the thread-local last error (sets it to Success)

fn clear_last_error() {

    LAST_ERROR.with(|e| e.set(CrcFastError::Success));

}

// Global storage for stable key pointers to ensure they remain valid across FFI boundary

static STABLE_KEY_STORAGE: OnceLock<Mutex<HashMap<u64, Box<[u64]>>>> = OnceLock::new();

/// Creates a stable pointer to the keys for FFI usage.

/// The keys are stored in global memory to ensure the pointer remains valid.

/// Returns (pointer, count) on success, or (null, 0) on error.

/// Sets CrcFastError::LockPoisoned on lock failure.

fn create_stable_key_pointer(keys: &crate::CrcKeysStorage) -> (*const u64, u32) {

    let storage = STABLE_KEY_STORAGE.get_or_init(|| Mutex::new(HashMap::new()));

    // Create a unique hash for this key set to avoid duplicates

    let key_hash = match keys {

        crate::CrcKeysStorage::KeysFold256(keys) => {

            let mut hasher = std::collections::hash_map::DefaultHasher::new();

            use std::hash::{Hash, Hasher};

            keys.hash(&mut hasher);

            hasher.finish()

        }

        crate::CrcKeysStorage::KeysFutureTest(keys) => {

            let mut hasher = std::collections::hash_map::DefaultHasher::new();

            use std::hash::{Hash, Hasher};

            keys.hash(&mut hasher);

            hasher.finish()

        }

    };

    let mut storage_map = match storage.lock() {

        Ok(guard) => guard,

        Err(_) => {

            set_last_error(CrcFastError::LockPoisoned);

            return (std::ptr::null(), 0);

        }

    };

    // Check if we already have this key set stored

    if let Some(stored_keys) = storage_map.get(&key_hash) {

        return (stored_keys.as_ptr(), stored_keys.len() as u32);

    }

    // Store the keys in stable memory

    let key_vec: Vec<u64> = match keys {

        crate::CrcKeysStorage::KeysFold256(keys) => keys.to_vec(),

        crate::CrcKeysStorage::KeysFutureTest(keys) => keys.to_vec(),

    };

    let boxed_keys = key_vec.into_boxed_slice();

    let count = boxed_keys.len() as u32;

    storage_map.insert(key_hash, boxed_keys);

    let ptr = storage_map.get(&key_hash).expect("just inserted").as_ptr();

    (ptr, count)

}

/// A handle to the Digest object

#[repr(C)]

pub struct CrcFastDigestHandle(*mut Digest);

/// The supported CRC algorithms

#[repr(C)]

#[derive(Clone, Copy)]

pub enum CrcFastAlgorithm {

    // CrcCustom works with any supported widths (16, 32, 64)

    CrcCustom,

    Crc16Arc,

    Crc16Cdma2000,

    Crc16Cms,

    Crc16Dds110,

    Crc16DectR,

    Crc16DectX,

    Crc16Dnp,

    Crc16En13757,

    Crc16Genibus,

    Crc16Gsm,

    Crc16Ibm3740,

    Crc16IbmSdlc,

    Crc16IsoIec144433A,

    Crc16Kermit,

    Crc16Lj1200,

    Crc16M17,

    Crc16MaximDow,

    Crc16Mcrf4xx,

    Crc16Modbus,

    Crc16Nrsc5,

    Crc16OpensafetyA,

    Crc16OpensafetyB,

    Crc16Profibus,

    Crc16Riello,

    Crc16SpiFujitsu,

    Crc16T10Dif,

    Crc16Teledisk,

    Crc16Tms37157,

    Crc16Umts,

    Crc16Usb,

    Crc16Xmodem,

    Crc32Aixm,

    Crc32Autosar,

    Crc32Base91D,

    Crc32Bzip2,

    Crc32CdRomEdc,

    Crc32Cksum,

    Crc32Custom,

    Crc32Iscsi,

    Crc32IsoHdlc,

    Crc32Jamcrc,

    Crc32Mef,

    Crc32Mpeg2,

    Crc32Xfer,

    Crc64Custom,

    Crc64Ecma182,

    Crc64GoIso,

    Crc64Ms,

    Crc64Nvme,

    Crc64Redis,

    Crc64We,

    Crc64Xz,

}

// Convert from FFI enum to internal enum

#[allow(deprecated)]

impl From<CrcFastAlgorithm> for CrcAlgorithm {

    fn from(value: CrcFastAlgorithm) -> Self {

        match value {

            CrcFastAlgorithm::Crc16Arc => CrcAlgorithm::Crc16Arc,

            CrcFastAlgorithm::Crc16Cdma2000 => CrcAlgorithm::Crc16Cdma2000,

            CrcFastAlgorithm::Crc16Cms => CrcAlgorithm::Crc16Cms,

            CrcFastAlgorithm::Crc16Dds110 => CrcAlgorithm::Crc16Dds110,

            CrcFastAlgorithm::Crc16DectR => CrcAlgorithm::Crc16DectR,

            CrcFastAlgorithm::Crc16DectX => CrcAlgorithm::Crc16DectX,

            CrcFastAlgorithm::Crc16Dnp => CrcAlgorithm::Crc16Dnp,

            CrcFastAlgorithm::Crc16En13757 => CrcAlgorithm::Crc16En13757,

            CrcFastAlgorithm::Crc16Genibus => CrcAlgorithm::Crc16Genibus,

            CrcFastAlgorithm::Crc16Gsm => CrcAlgorithm::Crc16Gsm,

            CrcFastAlgorithm::Crc16Ibm3740 => CrcAlgorithm::Crc16Ibm3740,

            CrcFastAlgorithm::Crc16IbmSdlc => CrcAlgorithm::Crc16IbmSdlc,

            CrcFastAlgorithm::Crc16IsoIec144433A => CrcAlgorithm::Crc16IsoIec144433A,

            CrcFastAlgorithm::Crc16Kermit => CrcAlgorithm::Crc16Kermit,

            CrcFastAlgorithm::Crc16Lj1200 => CrcAlgorithm::Crc16Lj1200,

            CrcFastAlgorithm::Crc16M17 => CrcAlgorithm::Crc16M17,

            CrcFastAlgorithm::Crc16MaximDow => CrcAlgorithm::Crc16MaximDow,

            CrcFastAlgorithm::Crc16Mcrf4xx => CrcAlgorithm::Crc16Mcrf4xx,

            CrcFastAlgorithm::Crc16Modbus => CrcAlgorithm::Crc16Modbus,

            CrcFastAlgorithm::Crc16Nrsc5 => CrcAlgorithm::Crc16Nrsc5,

            CrcFastAlgorithm::Crc16OpensafetyA => CrcAlgorithm::Crc16OpensafetyA,

            CrcFastAlgorithm::Crc16OpensafetyB => CrcAlgorithm::Crc16OpensafetyB,

            CrcFastAlgorithm::Crc16Profibus => CrcAlgorithm::Crc16Profibus,

            CrcFastAlgorithm::Crc16Riello => CrcAlgorithm::Crc16Riello,

            CrcFastAlgorithm::Crc16SpiFujitsu => CrcAlgorithm::Crc16SpiFujitsu,

            CrcFastAlgorithm::Crc16T10Dif => CrcAlgorithm::Crc16T10Dif,

            CrcFastAlgorithm::Crc16Teledisk => CrcAlgorithm::Crc16Teledisk,

            CrcFastAlgorithm::Crc16Tms37157 => CrcAlgorithm::Crc16Tms37157,

            CrcFastAlgorithm::Crc16Umts => CrcAlgorithm::Crc16Umts,

            CrcFastAlgorithm::Crc16Usb => CrcAlgorithm::Crc16Usb,

            CrcFastAlgorithm::Crc16Xmodem => CrcAlgorithm::Crc16Xmodem,

            CrcFastAlgorithm::Crc32Aixm => CrcAlgorithm::Crc32Aixm,

            CrcFastAlgorithm::Crc32Autosar => CrcAlgorithm::Crc32Autosar,

            CrcFastAlgorithm::Crc32Base91D => CrcAlgorithm::Crc32Base91D,

            CrcFastAlgorithm::Crc32Bzip2 => CrcAlgorithm::Crc32Bzip2,

            CrcFastAlgorithm::Crc32CdRomEdc => CrcAlgorithm::Crc32CdRomEdc,

            CrcFastAlgorithm::Crc32Cksum => CrcAlgorithm::Crc32Cksum,

            CrcFastAlgorithm::Crc32Custom => CrcAlgorithm::Crc32Custom,

            CrcFastAlgorithm::Crc32Iscsi => CrcAlgorithm::Crc32Iscsi,

            CrcFastAlgorithm::Crc32IsoHdlc => CrcAlgorithm::Crc32IsoHdlc,

            CrcFastAlgorithm::Crc32Jamcrc => CrcAlgorithm::Crc32Jamcrc,

            CrcFastAlgorithm::Crc32Mef => CrcAlgorithm::Crc32Mef,

            CrcFastAlgorithm::Crc32Mpeg2 => CrcAlgorithm::Crc32Mpeg2,

            CrcFastAlgorithm::Crc32Xfer => CrcAlgorithm::Crc32Xfer,

            CrcFastAlgorithm::CrcCustom => CrcAlgorithm::CrcCustom,

            CrcFastAlgorithm::Crc64Custom => CrcAlgorithm::Crc64Custom,

            CrcFastAlgorithm::Crc64Ecma182 => CrcAlgorithm::Crc64Ecma182,

            CrcFastAlgorithm::Crc64GoIso => CrcAlgorithm::Crc64GoIso,

            CrcFastAlgorithm::Crc64Ms => CrcAlgorithm::Crc64Ms,

            CrcFastAlgorithm::Crc64Nvme => CrcAlgorithm::Crc64Nvme,

            CrcFastAlgorithm::Crc64Redis => CrcAlgorithm::Crc64Redis,

            CrcFastAlgorithm::Crc64We => CrcAlgorithm::Crc64We,

            CrcFastAlgorithm::Crc64Xz => CrcAlgorithm::Crc64Xz,

        }

    }

}

/// Gets the last error that occurred in the current thread

/// Returns CrcFastError::Success if no error has occurred

#[no_mangle]

pub extern "C" fn crc_fast_get_last_error() -> CrcFastError {

    LAST_ERROR.with(|e| e.get())

}

/// Clears the last error for the current thread

#[no_mangle]

pub extern "C" fn crc_fast_clear_error() {

    clear_last_error();

}

/// Gets a human-readable error message for the given error code

/// Returns a pointer to a static string (do not free)

#[no_mangle]

pub extern "C" fn crc_fast_error_message(error: CrcFastError) -> *const c_char {

    let message = error.message();

    // These are static strings, so we can safely return them as C strings

    // The strings are guaranteed to be valid UTF-8 and null-terminated

    match std::ffi::CString::new(message) {

        Ok(c_str) => {

            // Leak the string so it remains valid for the lifetime of the program

            // This is safe because error messages are static and small

            Box::leak(Box::new(c_str)).as_ptr()

        }

        Err(_) => std::ptr::null(),

    }

}

/// Custom CRC parameters

#[repr(C)]

pub struct CrcFastParams {

    pub algorithm: CrcFastAlgorithm,

    pub width: u8,

    pub poly: u64,

    pub init: u64,

    pub refin: bool,

    pub refout: bool,

    pub xorout: u64,

    pub check: u64,

    pub key_count: u32,

    pub keys: *const u64,

}

/// Fallible conversion from FFI struct to internal struct

/// Returns None if the parameters are invalid (unsupported key count)

fn try_params_from_ffi(value: &CrcFastParams) -> Option<CrcParams> {

    // Validate key pointer

    if value.keys.is_null() {

        return None;

    }

    // Convert C array back to appropriate CrcKeysStorage

    let keys = unsafe { std::slice::from_raw_parts(value.keys, value.key_count as usize) };

    let storage = match value.key_count {

        23 => match keys.try_into() {

            Ok(arr) => crate::CrcKeysStorage::from_keys_fold_256(arr),

            Err(_) => return None,

        },

        25 => match keys.try_into() {

            Ok(arr) => crate::CrcKeysStorage::from_keys_fold_future_test(arr),

            Err(_) => return None,

        },

        _ => return None, // Unsupported key count

    };

    // For reflected CRC-16, bit-reverse the init value for the SIMD algorithm

    let init_algorithm = if value.width == 16 && value.refin {

        (value.init as u16).reverse_bits() as u64

    } else {

        value.init

    };

    Some(CrcParams {

        algorithm: value.algorithm.into(),

        name: "custom", // C interface doesn't need the name field

        width: value.width,

        poly: value.poly,

        init: value.init,

        init_algorithm,

        refin: value.refin,

        refout: value.refout,

        xorout: value.xorout,

        check: value.check,

        keys: storage,

    })

}

// Convert from FFI struct to internal struct (legacy, may panic)

// For backwards compatibility, but prefer try_params_from_ffi

impl From<CrcFastParams> for CrcParams {

    fn from(value: CrcFastParams) -> Self {

        try_params_from_ffi(&value)

            .expect("Invalid CRC parameters: unsupported key count or null pointer")

    }

}

// Convert from internal struct to FFI struct

#[allow(deprecated)]

impl From<CrcParams> for CrcFastParams {

    fn from(params: CrcParams) -> Self {

        // Create stable key pointer for FFI usage

        let (keys_ptr, key_count) = create_stable_key_pointer(&params.keys);

        CrcFastParams {

            algorithm: match params.algorithm {

                CrcAlgorithm::Crc16Arc => CrcFastAlgorithm::Crc16Arc,

                CrcAlgorithm::Crc16Cdma2000 => CrcFastAlgorithm::Crc16Cdma2000,

                CrcAlgorithm::Crc16Cms => CrcFastAlgorithm::Crc16Cms,

                CrcAlgorithm::Crc16Dds110 => CrcFastAlgorithm::Crc16Dds110,

                CrcAlgorithm::Crc16DectR => CrcFastAlgorithm::Crc16DectR,

                CrcAlgorithm::Crc16DectX => CrcFastAlgorithm::Crc16DectX,

                CrcAlgorithm::Crc16Dnp => CrcFastAlgorithm::Crc16Dnp,

                CrcAlgorithm::Crc16En13757 => CrcFastAlgorithm::Crc16En13757,

                CrcAlgorithm::Crc16Genibus => CrcFastAlgorithm::Crc16Genibus,

                CrcAlgorithm::Crc16Gsm => CrcFastAlgorithm::Crc16Gsm,

                CrcAlgorithm::Crc16Ibm3740 => CrcFastAlgorithm::Crc16Ibm3740,

                CrcAlgorithm::Crc16IbmSdlc => CrcFastAlgorithm::Crc16IbmSdlc,

                CrcAlgorithm::Crc16IsoIec144433A => CrcFastAlgorithm::Crc16IsoIec144433A,

                CrcAlgorithm::Crc16Kermit => CrcFastAlgorithm::Crc16Kermit,

                CrcAlgorithm::Crc16Lj1200 => CrcFastAlgorithm::Crc16Lj1200,

                CrcAlgorithm::Crc16M17 => CrcFastAlgorithm::Crc16M17,

                CrcAlgorithm::Crc16MaximDow => CrcFastAlgorithm::Crc16MaximDow,

                CrcAlgorithm::Crc16Mcrf4xx => CrcFastAlgorithm::Crc16Mcrf4xx,

                CrcAlgorithm::Crc16Modbus => CrcFastAlgorithm::Crc16Modbus,

                CrcAlgorithm::Crc16Nrsc5 => CrcFastAlgorithm::Crc16Nrsc5,

                CrcAlgorithm::Crc16OpensafetyA => CrcFastAlgorithm::Crc16OpensafetyA,

                CrcAlgorithm::Crc16OpensafetyB => CrcFastAlgorithm::Crc16OpensafetyB,

                CrcAlgorithm::Crc16Profibus => CrcFastAlgorithm::Crc16Profibus,

                CrcAlgorithm::Crc16Riello => CrcFastAlgorithm::Crc16Riello,

                CrcAlgorithm::Crc16SpiFujitsu => CrcFastAlgorithm::Crc16SpiFujitsu,

                CrcAlgorithm::Crc16T10Dif => CrcFastAlgorithm::Crc16T10Dif,

                CrcAlgorithm::Crc16Teledisk => CrcFastAlgorithm::Crc16Teledisk,

                CrcAlgorithm::Crc16Tms37157 => CrcFastAlgorithm::Crc16Tms37157,

                CrcAlgorithm::Crc16Umts => CrcFastAlgorithm::Crc16Umts,

                CrcAlgorithm::Crc16Usb => CrcFastAlgorithm::Crc16Usb,

                CrcAlgorithm::Crc16Xmodem => CrcFastAlgorithm::Crc16Xmodem,

                CrcAlgorithm::Crc32Aixm => CrcFastAlgorithm::Crc32Aixm,

                CrcAlgorithm::Crc32Autosar => CrcFastAlgorithm::Crc32Autosar,

                CrcAlgorithm::Crc32Base91D => CrcFastAlgorithm::Crc32Base91D,

                CrcAlgorithm::Crc32Bzip2 => CrcFastAlgorithm::Crc32Bzip2,

                CrcAlgorithm::Crc32CdRomEdc => CrcFastAlgorithm::Crc32CdRomEdc,

                CrcAlgorithm::Crc32Cksum => CrcFastAlgorithm::Crc32Cksum,

                CrcAlgorithm::Crc32Custom => CrcFastAlgorithm::Crc32Custom,

                CrcAlgorithm::Crc32Iscsi => CrcFastAlgorithm::Crc32Iscsi,

                CrcAlgorithm::Crc32IsoHdlc => CrcFastAlgorithm::Crc32IsoHdlc,

                CrcAlgorithm::Crc32Jamcrc => CrcFastAlgorithm::Crc32Jamcrc,

                CrcAlgorithm::Crc32Mef => CrcFastAlgorithm::Crc32Mef,

                CrcAlgorithm::Crc32Mpeg2 => CrcFastAlgorithm::Crc32Mpeg2,

                CrcAlgorithm::Crc32Xfer => CrcFastAlgorithm::Crc32Xfer,

                CrcAlgorithm::CrcCustom => CrcFastAlgorithm::CrcCustom,

                CrcAlgorithm::Crc64Custom => CrcFastAlgorithm::Crc64Custom,

                CrcAlgorithm::Crc64Ecma182 => CrcFastAlgorithm::Crc64Ecma182,

                CrcAlgorithm::Crc64GoIso => CrcFastAlgorithm::Crc64GoIso,

                CrcAlgorithm::Crc64Ms => CrcFastAlgorithm::Crc64Ms,

                CrcAlgorithm::Crc64Nvme => CrcFastAlgorithm::Crc64Nvme,

                CrcAlgorithm::Crc64Redis => CrcFastAlgorithm::Crc64Redis,

                CrcAlgorithm::Crc64We => CrcFastAlgorithm::Crc64We,

                CrcAlgorithm::Crc64Xz => CrcFastAlgorithm::Crc64Xz,

            },

            width: params.width,

            poly: params.poly,

            init: params.init,

            refin: params.refin,

            refout: params.refout,

            xorout: params.xorout,

            check: params.check,

            key_count,

            keys: keys_ptr,

        }

    }

}

/// Creates a new Digest to compute CRC checksums using algorithm

#[no_mangle]

pub extern "C" fn crc_fast_digest_new(algorithm: CrcFastAlgorithm) -> *mut CrcFastDigestHandle {

    clear_last_error();

    let digest = Box::new(Digest::new(algorithm.into()));

    let handle = Box::new(CrcFastDigestHandle(Box::into_raw(digest)));

    Box::into_raw(handle)

}

/// Creates a new Digest with a custom initial state

#[no_mangle]

pub extern "C" fn crc_fast_digest_new_with_init_state(

    algorithm: CrcFastAlgorithm,

    init_state: u64,

) -> *mut CrcFastDigestHandle {

    clear_last_error();

    let digest = Box::new(Digest::new_with_init_state(algorithm.into(), init_state));

    let handle = Box::new(CrcFastDigestHandle(Box::into_raw(digest)));

    Box::into_raw(handle)

}

/// Creates a new Digest to compute CRC checksums using custom parameters

/// Returns NULL if parameters are invalid (invalid key count or null pointer)

/// Call crc_fast_get_last_error() to get the specific error code

#[no_mangle]

pub extern "C" fn crc_fast_digest_new_with_params(

    params: CrcFastParams,

) -> *mut CrcFastDigestHandle {

    clear_last_error();

    match try_params_from_ffi(&params) {

        Some(crc_params) => {

            let digest = Box::new(Digest::new_with_params(crc_params));

            let handle = Box::new(CrcFastDigestHandle(Box::into_raw(digest)));

            Box::into_raw(handle)

        }

        None => {

            // Set appropriate error based on the failure

            if params.keys.is_null() {

                set_last_error(CrcFastError::NullPointer);

            } else {

                set_last_error(CrcFastError::InvalidKeyCount);

            }

            std::ptr::null_mut()

        }

    }

}

/// Updates the Digest with data

#[no_mangle]

pub extern "C" fn crc_fast_digest_update(

    handle: *mut CrcFastDigestHandle,

    data: *const c_char,

    len: usize,

) {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return;

    }

    if data.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return;

    }

    clear_last_error();

    unsafe {

        let digest = &mut *(*handle).0;

        #[allow(clippy::unnecessary_cast)]

        let bytes = slice::from_raw_parts(data as *const u8, len);

        digest.update(bytes);

    }

}

/// Calculates the CRC checksum for data that's been written to the Digest

/// Returns 0 on error (e.g. null handle)

#[no_mangle]

pub extern "C" fn crc_fast_digest_finalize(handle: *mut CrcFastDigestHandle) -> u64 {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return 0;

    }

    clear_last_error();

    unsafe {

        let digest = &*(*handle).0;

        digest.finalize()

    }

}

/// Free the Digest resources without finalizing

#[no_mangle]

pub extern "C" fn crc_fast_digest_free(handle: *mut CrcFastDigestHandle) {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return;

    }

    clear_last_error();

    unsafe {

        let handle = Box::from_raw(handle);

        let _ = Box::from_raw(handle.0); // This drops the digest

    }

}

/// Reset the Digest state

#[no_mangle]

pub extern "C" fn crc_fast_digest_reset(handle: *mut CrcFastDigestHandle) {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return;

    }

    clear_last_error();

    unsafe {

        let digest = &mut *(*handle).0;

        digest.reset();

    }

}

/// Finalize and reset the Digest in one operation

/// Returns 0 on error (e.g. null handle)

#[no_mangle]

pub extern "C" fn crc_fast_digest_finalize_reset(handle: *mut CrcFastDigestHandle) -> u64 {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return 0;

    }

    clear_last_error();

    unsafe {

        let digest = &mut *(*handle).0;

        digest.finalize_reset()

    }

}

/// Combine two Digest checksums

#[no_mangle]

pub extern "C" fn crc_fast_digest_combine(

    handle1: *mut CrcFastDigestHandle,

    handle2: *mut CrcFastDigestHandle,

) {

    if handle1.is_null() || handle2.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return;

    }

    clear_last_error();

    unsafe {

        let digest1 = &mut *(*handle1).0;

        let digest2 = &*(*handle2).0;

        digest1.combine(digest2);

    }

}

/// Gets the amount of data processed by the Digest so far

/// Returns 0 on error (e.g. null handle)

#[no_mangle]

pub extern "C" fn crc_fast_digest_get_amount(handle: *mut CrcFastDigestHandle) -> u64 {

    if handle.is_null() {

        set_last_error(CrcFastError::NullPointer);

        return 0;

    }

    clear_last_error();

    unsafe {

        let digest = &*(*handle).0;

        digest.get_amount()

    }

}

/// Gets the current state of the Digest

/// Returns 0 on error (e.g. null handle)

#[no_mangle]

pub extern "C" fn crc_fast_digest_get_state(handle: *mut CrcFastDigestHandle) -> u64 {

    if handle.is_null() {