qfall_math/integer_mod_q/modulus/
to_string.rs

1// Copyright © 2023 Marcel Luca Schmidt, Marvin Beckmann
2//
3// This file is part of qFALL-math.
4//
5// qFALL-math is free software: you can redistribute it and/or modify it under
6// the terms of the Mozilla Public License Version 2.0 as published by the
7// Mozilla Foundation. See <https://mozilla.org/en-US/MPL/2.0/>.
8
9//! This module contains all options to convert a modulus of type
10//! [`Modulus`] into a [`String`].
11//!
12//! This includes the [`Display`](std::fmt::Display) trait.
13
14use super::Modulus;
15use crate::macros::for_others::implement_for_owned;
16use core::fmt;
17use flint_sys::fmpz::fmpz_get_str;
18use std::{ffi::CStr, ptr::null_mut};
19
20impl From<&Modulus> for String {
21    /// Converts a [`Modulus`] into its [`String`] representation.
22    ///
23    /// Parameters:
24    /// - `value`: specifies the modulus that will be represented as a [`String`]
25    ///
26    /// Returns a [`String`].
27    ///
28    /// # Examples
29    /// ```
30    /// use qfall_math::integer_mod_q::Modulus;
31    /// use std::str::FromStr;
32    /// let modulus = Modulus::from_str("6").unwrap();
33    ///
34    /// let string: String = modulus.into();
35    /// ```
36    fn from(value: &Modulus) -> Self {
37        value.to_string()
38    }
39}
40
41implement_for_owned!(Modulus, String, From);
42
43impl fmt::Display for Modulus {
44    /// Allows to convert a modulus of type [`Modulus`] into a [`String`].
45    ///
46    /// # Examples
47    /// ```
48    /// use qfall_math::integer_mod_q::Modulus;
49    /// use std::str::FromStr;
50    /// use core::fmt;
51    ///
52    /// let modulus = Modulus::from(42);
53    /// println!("{modulus}");
54    /// ```
55    ///
56    /// ```
57    /// use qfall_math::integer_mod_q::Modulus;
58    /// use std::str::FromStr;
59    ///
60    /// let modulus = Modulus::from(42);
61    /// let modulus_string = modulus.to_string();
62    /// ```
63    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
64        // we have to access modulus.n[0] manually because there is no dedicated
65        // method in FLINT
66        let c_str_ptr = unsafe { fmpz_get_str(null_mut(), 10, &self.modulus.n[0]) };
67
68        // we expect c_str_ptr to be reference a real value, hence get_str returns an
69        // actual value, hence a simple unwrap should be sufficient and we do not have
70        // to consider an exception
71        //
72        // c_string should not be null either, since we call this method on an
73        // instantiated object
74        let msg = "We expect the pointer to point to a real value and the c_string 
75        not to be null.  This error occurs if the provided string does not have UTF-8 format.";
76        let return_str = unsafe { CStr::from_ptr(c_str_ptr).to_str().expect(msg).to_owned() };
77
78        unsafe { libc::free(c_str_ptr as *mut libc::c_void) };
79
80        write!(f, "{return_str}")
81    }
82}
83
84#[cfg(test)]
85mod test_to_string {
86    use crate::integer_mod_q::Modulus;
87    use std::str::FromStr;
88
89    /// Tests whether a large modulus works in a roundtrip
90    #[test]
91    fn working_large() {
92        let cmp_str = "1".repeat(65);
93        let cmp = Modulus::from_str(&cmp_str).unwrap();
94
95        assert_eq!(cmp_str, cmp.to_string());
96    }
97
98    /// Tests whether a positive modulus works in a roundtrip
99    #[test]
100    fn working_positive() {
101        let cmp_str = "42";
102        let cmp = Modulus::from_str(cmp_str).unwrap();
103
104        assert_eq!(cmp_str, cmp.to_string());
105    }
106
107    /// Tests whether a modulus that is created using a string, returns a
108    /// string that can be used to create a [`Modulus`]
109    #[test]
110    fn working_use_result_of_to_string_as_input() {
111        let cmp_str = "42";
112        let cmp = Modulus::from_str(cmp_str).unwrap();
113
114        let cmp_str_2 = cmp.to_string();
115
116        assert!(Modulus::from_str(&cmp_str_2).is_ok());
117    }
118
119    /// Ensures that the `Into<String>` trait works properly
120    #[test]
121    fn into_works_properly() {
122        let cmp = "6";
123        let modulus = Modulus::from_str(cmp).unwrap();
124
125        let string: String = modulus.clone().into();
126        let borrowed_string: String = (&modulus).into();
127
128        assert_eq!(cmp, string);
129        assert_eq!(cmp, borrowed_string);
130    }
131}
qfall_math/integer_mod_q/modulus/to_string.rs

qfall_math/integer_mod_q/modulus/
to_string.rs
