const_str/__ctfe/
replace.rs

1#![allow(unsafe_code)]
2
3use crate::slice::advance;
4use crate::utf8::CharEncodeUtf8;
5
6use super::str::StrBuf;
7
8pub struct Replace<I, P, O>(pub I, pub P, pub O);
9
10impl Replace<&str, &str, &str> {
11    pub const fn output_len(&self) -> usize {
12        let Self(mut input, replace_from, replace_to) = *self;
13
14        if replace_from.is_empty() {
15            let input_chars = crate::utf8::str_count_chars(self.0);
16            input.len() + (input_chars + 1) * replace_to.len()
17        } else {
18            let mut ans = 0;
19            while let Some((pos, remain)) = crate::str::next_match(input, replace_from) {
20                ans += pos + replace_to.len();
21                input = remain;
22            }
23            ans += input.len();
24            ans
25        }
26    }
27
28    pub const fn const_eval<const N: usize>(&self) -> StrBuf<N> {
29        let Self(input, replace_from, replace_to) = *self;
30
31        let mut buf = [0; N];
32        let mut pos = 0;
33
34        macro_rules! push {
35            ($x: expr) => {{
36                buf[pos] = $x;
37                pos += 1;
38            }};
39        }
40
41        if replace_from.is_empty() {
42            let mut input = input.as_bytes();
43            let replace_to = replace_to.as_bytes();
44            loop {
45                let mut k = 0;
46                while k < replace_to.len() {
47                    push!(replace_to[k]);
48                    k += 1;
49                }
50
51                let count = match crate::utf8::next_char(input) {
52                    Some((_, count)) => count,
53                    None => break,
54                };
55
56                let mut i = 0;
57                while i < count {
58                    push!(input[i]);
59                    i += 1;
60                }
61
62                input = advance(input, count);
63            }
64        } else {
65            let mut input = input;
66            let replace_to = replace_to.as_bytes();
67
68            while let Some((pos, remain)) = crate::str::next_match(input, replace_from) {
69                let mut i = 0;
70                while i < pos {
71                    push!(input.as_bytes()[i]);
72                    i += 1;
73                }
74                let mut k = 0;
75                while k < replace_to.len() {
76                    push!(replace_to[k]);
77                    k += 1;
78                }
79                input = remain;
80            }
81
82            let input = input.as_bytes();
83            let mut i = 0;
84            while i < input.len() {
85                push!(input[i]);
86                i += 1;
87            }
88        }
89
90        assert!(pos == N);
91        unsafe { StrBuf::new_unchecked(buf) }
92    }
93}
94
95impl Replace<&str, char, &str> {
96    pub const fn output_len(&self) -> usize {
97        let ch = CharEncodeUtf8::new(self.1);
98        Replace(self.0, ch.as_str(), self.2).output_len()
99    }
100    pub const fn const_eval<const N: usize>(&self) -> StrBuf<N> {
101        let ch = CharEncodeUtf8::new(self.1);
102        Replace(self.0, ch.as_str(), self.2).const_eval()
103    }
104}
105
106/// Replaces all matches of a pattern with another string slice.
107///
108/// See [`str::replace`](https://doc.rust-lang.org/std/primitive.str.html#method.replace).
109///
110/// The pattern type must be one of
111///
112/// + [`&str`](str)
113/// + [`char`]
114///
115/// This macro is [const-context only](./index.html#const-context-only).
116///
117/// # Examples
118///
119/// ```
120/// assert_eq!("this is new", const_str::replace!("this is old", "old", "new"));
121/// ```
122///
123#[macro_export]
124macro_rules! replace {
125    ($s: expr, $from: expr, $to: expr) => {{
126        const OUTPUT_LEN: usize = $crate::__ctfe::Replace($s, $from, $to).output_len();
127        const OUTPUT_BUF: $crate::__ctfe::StrBuf<OUTPUT_LEN> =
128            $crate::__ctfe::Replace($s, $from, $to).const_eval();
129        OUTPUT_BUF.as_str()
130    }};
131}
132
133#[cfg(test)]
134mod tests {
135    use super::*;
136
137    #[test]
138    fn test_replace() {
139        macro_rules! testcase {
140            ($input: expr, $from: expr, $to: expr) => {{
141                const OUTPUT_LEN: usize = Replace($input, $from, $to).output_len();
142                const OUTPUT_BUF: StrBuf<OUTPUT_LEN> = Replace($input, $from, $to).const_eval();
143                const OUTPUT: &str = OUTPUT_BUF.as_str();
144
145                let ans = $input.replace($from, $to);
146                assert_eq!(OUTPUT, &*ans, "ans = {:?}", ans);
147                assert_eq!(OUTPUT_LEN, ans.len());
148            }};
149        }
150
151        testcase!("", "", "");
152        testcase!("", "", "a");
153        testcase!("", "a", "");
154        testcase!("", "a", "b");
155        testcase!("a", "", "b");
156        testcase!("asd", "", "b");
157        testcase!("aba", "a", "c");
158        testcase!("this is old", "old", "new");
159        testcase!("我", "", "1");
160        testcase!("我", "", "我");
161        testcase!("我", "我", "");
162        testcase!("aaaa", "aa", "bb");
163        testcase!("run / v4", " ", "");
164        testcase!("token", " ", "");
165        testcase!("v4 / udp", " ", "");
166        testcase!("v4 / upnp", "p", "");
167
168        testcase!("", 'a', "");
169        testcase!("", 'a', "b");
170        testcase!("aba", 'a', "c");
171        testcase!("run / v4", ' ', "");
172        testcase!("token", ' ', "");
173        testcase!("v4 / udp", ' ', "");
174        testcase!("我", '我', "");
175    }
176}
const_str/__ctfe/replace.rs

const_str/__ctfe/
replace.rs
