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

# newSHA

Construct a fresh `Digest::SHA` object for the given algorithm number.

Low-level constructor that takes an algorithm code directly. Most code
calls `new` instead; `newSHA` is the path that the XS layer exposes and
that `new` eventually delegates to. Valid algorithm codes are `1`, `224`,
`256`, `384`, `512`, `512224`, and `512256`. Any other value returns
`undef` instead of croaking.

## Synopsis

```perl
my $sha = Digest::SHA::newSHA("Digest::SHA", 256);
```

## What you get back

A blessed `Digest::SHA` object, ready to accept `add`, `addfile`, or
`digest` calls. Returns `undef` on an unknown algorithm code.

## Examples

```perl
my $sha = Digest::SHA::newSHA("Digest::SHA", 512);
$sha->add("hello");
print $sha->hexdigest;
```

```perl
my $bad = Digest::SHA::newSHA("Digest::SHA", 999);
print defined $bad ? "ok" : "undef"; # undef
```

## Edge cases

- Missing algorithm or missing class name croaks with a usage error.
- Unknown algorithm code returns `undef`; check the return value before
  using it.

## Differences from upstream

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

## See also

- `new` — higher-level constructor that accepts strings like `"SHA-256"`.
- `clone` — copy an existing context instead of starting over.
- `reset` — reinitialise an existing object, optionally switching algorithm.