A proc macro regex library to match an arbitrary string or byte array to a regular expression.
Add this to your Cargo.toml:
toml
[dependencies]
proc-macro-regex = "~1.1.0"
The macro regex! creates a function of the given name which takes a string or byte array and
returns true if the argument matches the regex, otherwise false.
```rust
use procmacroregex::regex;
/// Create the function with the signature: /// fn regexemail(s: &str) -> bool; regex!(regexemail "^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$");
fn main () { println!("Returns true == {}", regexemail("example@example.org")); println!("Returns false == {}", regexemail("example.example.org")); } ```
The given regex works the same as in the regex crate. If the ^
is at the beginning of the regex and $ at the end then the whole string is checked, otherwise is
check if the string contains the regex.
The macro creates a deterministic finite automaton (DFA), which parse the given input. Depending on the size of the DFA or the character of the regex, a lookup table or a code base implementation (binary search) is generated. If the size of the lookup table would be bigger than 65536 bytes (can be changed) then a code base implementation (binary search) is used. Additionally, if the regex contains any Unicode (no ASCII) character then a code base implementation (binary search) is used, too.
The following macro generates the following code:
rust
regex!(example_1 "abc");
Generates:
rust
fn example_1(s: &str) -> bool {
static TABLE: [[u8; 256]; 3usize] = [ ... ];
let mut state = 0;
for c in s.bytes() {
state = TABLE[state as usize][c as usize];
if state == u8::MAX {
return true;
}
}
false
}
To tell the macro that the lookup table is not allowed to be bigger than 256 bytes, a third
argument can be given. Therefore, a code base implementation (binary search) of the DFA is
generated.
rust
regex!(example_2 "abc" 256);
Generates:
rust
fn example_2(s: &str) -> bool {
let mut state = 0;
for c in s.bytes() {
state = if state < 1usize {
match c {
97u8 => 1usize,
_ => 0usize,
}
} else {
if state == 1usize {
match c {
97u8 => 1usize,
98u8 => 2usize,
_ => 0usize,
}
} else {
match c {
97u8 => 1usize,
99u8 => return true,
_ => 0usize,
}
}
};
}
false
}
To change the visibility of the function, add the keywords at the beginning of the arguments.
rust
regex!(pub example_2 "abc" 256);
Generates:
rust
pub fn example_3(s: &str) -> bool {
// same as in example_1 (see above)
}
To parse a byte array instead of string, pass a byte string.
rust
regex!(example_4 b"abc");
Generates:
rust
fn example_4(s: &[u8]) -> bool {
// same as in example_1 (see above)
}
The generated code should work with #![no_std], too.
Advantages: * Compile-time (no runtime initialization, no lazy-static) * Generated code that does not contain any dependencies * No heap allocation * Approximately 12%-68% faster for no trivia regex [^1]
because the [regex](https://crates.io/crates/regex) library uses
[aho-corasick](https://crates.io/crates/aho-corasick/). (See Performance)
Disadvantages: * Currently, no group captures * No runtime regex generation
This is the performance comparison between this crate and the regex crate. If you want to test it
by yourself, run cargo bench --bench compare.
| Name | proc-macro-regex | regex | Result |
|--------|--------------:|-------------:|--------:|
| E-Mail | 743.95 MiB/s | 441.67 MiB/s | 68.44 % |
| URL | 584.62 MiB/s | 519.00 MiB/s | 12.64 % |
| IPv6 | 746.92 MiB/s | 473.38 MiB/s | 57.78 % |
This was compiled with rustc 1.53.0-nightly (392ba2ba1 2021-04-17).
This project is licensed under the BSD-3-Clause license.
Any contribution intentionally submitted for inclusion in proc-macro-regex by you, shall
be licensed as BSD-3-Clause, without any additional
terms or conditions.