Regex Expressions
Currently there is no regex support in Zig, so the best way to go is binding with Posix's regex.h.
Interop with C is easy in Zig, but since translate-c doesn't support bitfields, we can't use regex_t directly. So here we create a static C library first, providing two functions:
regex_t* alloc_regex_t(void);
void free_regex_t(regex_t* ptr);
regex_t* is a pointer, it has fixed size, so we can use it directly in Zig.
const std = @import("std");
const print = std.debug.print;
const c = @cImport({
@cInclude("regex.h");
// This is our static library.
@cInclude("regex_slim.h");
});
const Regex = struct {
inner: *c.regex_t,
fn init(pattern: [:0]const u8) !Regex {
const inner = c.alloc_regex_t().?;
if (0 != c.regcomp(inner, pattern, c.REG_NEWLINE | c.REG_EXTENDED)) {
return error.compile;
}
return .{
.inner = inner,
};
}
fn deinit(self: Regex) void {
c.free_regex_t(self.inner);
}
fn matches(self: Regex, input: [:0]const u8) bool {
const match_size = 1;
var pmatch: [match_size]c.regmatch_t = undefined;
return 0 == c.regexec(self.inner, input, match_size, &pmatch, 0);
}
fn exec(self: Regex, input: [:0]const u8) !void {
const match_size = 1;
var pmatch: [match_size]c.regmatch_t = undefined;
var i: usize = 0;
var string = input;
const expected = [_][]const u8{ "John Do", "John Foo" };
while (true) {
if (0 != c.regexec(self.inner, string, match_size, &pmatch, 0)) {
break;
}
const slice = string[@as(usize, @intCast(pmatch[0].rm_so))..@as(usize, @intCast(pmatch[0].rm_eo))];
try std.testing.expectEqualStrings(expected[i], slice);
string = string[@intCast(pmatch[0].rm_eo)..];
i += 1;
}
try std.testing.expectEqual(i, 2);
}
};
pub fn main() !void {
{
const regex = try Regex.init("[ab]c");
defer regex.deinit();
try std.testing.expect(regex.matches("bc"));
try std.testing.expect(!regex.matches("cc"));
}
{
const regex = try Regex.init("John.*o");
defer regex.deinit();
try regex.exec(
\\ 1) John Driverhacker;
\\ 2) John Doe;
\\ 3) John Foo;
\\
);
}
}