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: dpapi.rs
    path of file: ./repos/habitat/components/core/src/crypto
    
    the code of the file until where you have to start completion: use crate::error::{Error,
                   Result
    
pub fn encrypt(secret: String) -> Result<String> {
    unsafe {
        let mut secret_bytes = secret.into_bytes();
        let mut in_blob = CRYPTOAPI_BLOB { cbData: secret_bytes.len() as DWORD,
                                           pbData: secret_bytes.as_mut_ptr(), };
        let mut out_blob = CRYPTOAPI_BLOB { cbData: 0,
                                            pbData: ptr::null_mut(), };
        let mut entropy = ptr::null_mut();
        let mut blob: CRYPTOAPI_BLOB = mem::zeroed::<CRYPTOAPI_BLOB>();
        let mut complexity_vec = COMPLEXITY.to_vec();
        if !complexity_vec.is_empty() {
            blob.cbData = complexity_vec.len() as DWORD;
            blob.pbData = complexity_vec.as_mut_ptr();
            entropy = &mut blob;
        }
        let ret = dpapi::CryptProtectData(&mut in_blob,
                                          ptr::null(),
                                          entropy,
                                          ptr::null_mut(),
                                          ptr::null_mut(),
                                          4, // CRYPTPROTECT_LOCAL_MACHINE
                                          &mut out_blob);
        if ret == 0 {
            return Err(Error::CryptProtectDataFailed(format!(
                "Failed to encrypt secret: {}",
                io::Error::last_os_error()
            )));
        }
        let sz = out_blob.cbData as usize;
        let mut dst: Vec<u8> = vec![0; sz];
        dst.set_len(sz);
        ptr::copy(out_blob.pbData, dst.as_mut_ptr(), sz);
        Ok(crate::base64::encode(&dst))
    }
}