<!-- GENERATED by docs/sphinx/bin/02-reference from Digest/SHA.rs (xs_putstate). Do not edit. -->

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

# putstate

Restore a `Digest::SHA` object's state from a packed binary string.

The inverse of `_getstate`. Validates the length of the supplied blob
against the receiver's algorithm and rewrites the internal hash state
in place. After a successful `_putstate`, feeding more data with `add`
continues the hash as if no break had occurred.

The receiver's algorithm is **not** changed by this call; it must
already match the algorithm the blob was produced under.

## Synopsis

```perl
$sha->_putstate($blob);
```

## What you get back

The receiver on success, `undef` on failure (invalid length or bad
object).

## Examples

```perl
my $a = Digest::SHA->new(256);
$a->add("first half");
my $blob = $a->_getstate;

my $b = Digest::SHA->new(256);
$b->_putstate($blob) or die "restore failed";
$b->add("second half");
print $b->hexdigest;
```

```perl

## Round-trip through a file:

open my $in, "<", "hash.state" or die $!;
binmode $in;
my $blob = do { local $/; <$in> };
my $sha = Digest::SHA->new(256);
$sha->_putstate($blob);
```

## Edge cases

- Blob length must match the receiver's algorithm (116 vs 212 bytes);
  a mismatch returns `undef`.
- Called on a non-`Digest::SHA` object, returns `undef`.

## Differences from upstream

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

## See also

- `_getstate` — produces the blob consumed here.
- `putstate` — text-based restore that also creates new objects.
- `load` — text-based file-loading counterpart.