How to use CRC structs in `std.hash`?

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1

I noticed that in the source code for zig that there are some predefined CRC structs in (zig/lib/std/hash/crc.zig). I wrote a small test program to try to use them, but they don’t seem to be available in the way that I was expecting.

Compiling with 0.17.0-dev.1426+58a94eaae. I don’t really care about GSM, just an example.

const std = @import("std");

pub fn main() void {
    const data = "Hello, GSM!";
    const result = std.hash.Crc3Gsm.hash(data);
    std.debug.print("CRC-3 GSM: {x}\n", .{result});
}

test.zig:5:29: error: root source file struct 'hash' has no member named 'Crc3Gsm'
    const result = std.hash.Crc3Gsm.hash(data);
2

Use std.hash.crc.@"CRC-3/GSM".

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3

The name string identifier syntax. As @rosew0od noted, you must reference it in quotations with @ prefix, e.g. @"identifier with spaces or other non-standard characters".

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4

Ok, trying to understand how that trick works.
I did a search for “CRC-3/GSM” in the source, and it only shows up as a test label in zig/lib/std/hash/crc/test.zig. Where in the codebase does “CRC-3/GSM” get attached to that particular struct?

NM, I think it is “zig/tools/crc/catalog.txt” … and something must process that file.

5

It is in defined in the source code, specifically in std.hash.crc.zig. It happens to be the first thing defined in the file.

Guessing by Andrew’s latest commit message of “restore auto-generated status”, I assume the file is indeed generated at some point, though I haven’t spent any time investigating.

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