simplify, use CStr to hopefully handle i8/u8 nonsense

use std::ffi::c_void;

use std::ffi::{c_void, CStr};

use std::ptr;

use crate::error::ErrorStack;

use crate::{cvt, cvt_p};

struct EvpKdf {

    kdf: *mut ffi::EVP_KDF,

}

struct EvpKdf(*mut ffi::EVP_KDF);

impl Drop for EvpKdf {

    fn drop(&mut self) {

        unsafe {

            ffi::EVP_KDF_free(self.kdf);

            ffi::EVP_KDF_free(self.0);

        }

    }

}

struct EvpKdfCtx {

    ctx: *mut ffi::EVP_KDF_CTX,

}

struct EvpKdfCtx(*mut ffi::EVP_KDF_CTX);

impl Drop for EvpKdfCtx {

    fn drop(&mut self) {

        unsafe {

            ffi::EVP_KDF_CTX_free(self.ctx);

            ffi::EVP_KDF_CTX_free(self.0);

        }

    }

}

        let param_end = ffi::OSSL_PARAM_construct_end();

        params.push(param_end);

        let argon2id = CStr::from_bytes_with_nul(b"ARGON2ID\0").unwrap();

        let argon2_p = cvt_p(ffi::EVP_KDF_fetch(

            ptr::null_mut(),

            b"ARGON2ID\0".as_ptr() as *const i8,

            argon2id.as_ptr(),

            ptr::null(),

        ))?;

        let argon2 = EvpKdf { kdf: argon2_p };

        let ctx_p = cvt_p(ffi::EVP_KDF_CTX_new(argon2.kdf))?;

        let ctx = EvpKdfCtx { ctx: ctx_p };

        let argon2 = EvpKdf(argon2_p);

        let ctx_p = cvt_p(ffi::EVP_KDF_CTX_new(argon2.0))?;

        let ctx = EvpKdfCtx(ctx_p);

        cvt(ffi::EVP_KDF_derive(

            ctx.ctx,

            ctx.0,

            out.as_mut_ptr(),

            out.len(),

            params.as_ptr(),