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```{index} single: algorithm; Digest::SHA function
```
```{index} single: Digest::SHA::algorithm; Perl function
```

# algorithm

Return the algorithm code of a `Digest::SHA` object.

The code is the same integer you can pass to `new`: `1`, `224`, `256`,
`384`, `512`, `512224`, or `512256`. Useful when a function receives a
`Digest::SHA` object from elsewhere and needs to act differently based
on which variant it is.

## Synopsis

```perl
my $code = $sha->algorithm;
```

## What you get back

An integer in the set `{1, 224, 256, 384, 512, 512224, 512256}`.

## Examples

```perl
my $sha = Digest::SHA->new("SHA-256");
print $sha->algorithm;   # 256
```

```perl
my $sha = Digest::SHA->new("SHA-512/224");
print $sha->algorithm;   # 512224
```

```perl

## Dispatch on algorithm:

my $code = $sha->algorithm;
my $name = $code == 1 ? "SHA-1" : "SHA-$code";
```

## Edge cases

- Called on a non-`Digest::SHA` object, returns `undef`.

## Differences from upstream

Fully compatible with upstream `Digest::SHA` {{ upstream.Digest_SHA }}.

## See also

- `hashsize` — digest length in bits for this algorithm.
- `new` — accepts the values returned here as its algorithm argument.