You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: secure_message_sign_verify_rsa.rs
    path of file: ./repos/themis/benches/themis/benches
    
    the code of the file until where you have to start completion: // Copyright 2020 Cossack Labs Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#![allow(clippy::needless_borrow)]

use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};

use libthemis_sys::{
    themis_secure_message_sign, themis_secure_message_verify, THEMIS_BUFFER_TOO_SMALL,
    THEMIS_SUCCESS,
};
use themis::{keygen::gen_rsa_key_pair, secure_message::SecureSign};

const KB: usize = 1024;
const MB: usize = 1024 * KB;
#[allow(clippy::identity_op)]
const MESSAGE_SIZES: &[usize] = &[
    16,     // UUID
    32,     // SymmetricKey
    64,     // cache line (and close to EcdsaPrivateKey)
    256,    // RsaPrivateKey
    4 * KB, // memory page
    16 * KB,
    64 * KB,
    1 * MB, // L2 cache
    2 * MB,
    4 * MB,
];

pub fn signing(c: &mut Criterion) {
    let (private, _) = gen_rsa_key_pair().split();
    let private = private.as_ref();

    // Allocate buffer large enough for maximum test
    let mut signature = vec![0; 10 * MB];

    let mut group = c.benchmark_group("Sec
    
pub fn signing(c: &mut Criterion) {
    let (private, _) = gen_rsa_key_pair().split();
    let private = private.as_ref();

    // Allocate buffer large enough for maximum test
    let mut signature = vec![0; 10 * MB];

    let mut group = c.benchmark_group("Secure Message signing - RSA");
    for message_size in MESSAGE_SIZES {
        group.throughput(Throughput::Bytes(*message_size as u64));
        group.bench_with_input(
            BenchmarkId::from_parameter(pretty(*message_size)),
            message_size,
            |b, &size| {
                let message = vec![0; size];

                b.iter(|| {
                    let mut signature_size = 0;

                    let res = unsafe {
                        themis_secure_message_sign(
                            private.as_ptr(),
                            private.len(),
                            message.as_ptr(),
                            message.len(),
                            std::ptr::null_mut(),
                            &mut signature_size,
                        )
                    };
                    assert_eq!(res, THEMIS_BUFFER_TOO_SMALL as i32);
                    assert!(signature_size <= signature.len());

                    let res = unsafe {
                        themis_secure_message_sign(
                            private.as_ptr(),
                            private.len(),
                            message.as_ptr(),
                            message.len(),
                            signature.as_mut_ptr(),
                            &mut signature_size,
                        )
                    };
                    assert_eq!(res, THEMIS_SUCCESS as i32);
                });
            },
        );
    }
    group.finish();
}