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Options may be ``true`` or ``false``, the default value is ``false``.
For example:
digest.base64_encode(string_variable,{nopad=true})
Returns a regular string from a base64 encoding.
Returns array of random bytes with length = integer.
Returns 32-bit checksum made with CRC32.
The ``crc32`` and ``crc32_update`` functions use the `Cyclic Redundancy Check <https://en.wikipedia.org/wiki/Cyclic_redundancy_check>`_ polynomial value: ``0x1EDC6F41`` / ``4812730177``. (Other settings are: input = reflected, output = reflected, initial value = 0xFFFFFFFF, final xor value = 0x0.) If it is necessary to be compatible with other checksum functions in other programming languages, ensure that the other functions use the same polynomial value.
For example, in Python, install the ``crcmod`` package and say:
>>> import crcmod
>>> fun = crcmod.mkCrcFun('4812730177')
>>> fun('string')
3304160206L
In Perl, install the ``Digest::CRC`` module and run the following code:
use Digest::CRC;
$d = Digest::CRC->new(width => 32, poly => 0x1EDC6F41, init => 0xFFFFFFFF, refin => 1, refout => 1);
$d->add('string');
print $d->digest;
(the expected output is 3304160206).
Initiates incremental crc32. See :ref:`incremental methods <digest-incremental_digests>` notes.
Returns a number made with consistent hash.
The guava function uses the `Consistent Hashing <https://en.wikipedia.org/wiki/Consistent_hashing>`_ algorithm of the Google guava library. The first parameter should be a hash code; the second parameter should be the number of buckets; the returned value will be an integer between 0 and the number of buckets. For example,
tarantool> digest.guava(10863919174838991, 11)
---
- 8
...
Returns 32-bit binary string = digest made with MurmurHash.
Initiates incremental MurmurHash. See :ref:`incremental methods <digest-incremental_digests>` notes. For example:
murmur.new({seed=0})
Incremental methods in the ``digest`` module
Suppose that a digest is done for a string 'A', then a new part 'B' is appended to the string, then a new digest is required. The new digest could be recomputed for the whole string 'AB', but it is faster to take what was computed before for 'A' and apply changes based on the new part 'B'. This is called multi-step or "incremental" digesting, which Tarantool supports with crc32 and with murmur...
digest = require('digest')

-- print crc32 of 'AB', with one step, then incrementally
print(digest.crc32('AB'))
c = digest.crc32.new()
c:update('A')
c:update('B')
print(c:result())

-- print murmur hash of 'AB', with one step, then incrementally
print(digest.murmur('AB'))
m = digest.murmur.new()
m:update('A')
m:update('B')
print(m:result())
Example
In the following example, the user creates two functions, ``password_insert()`` which inserts a `SHA-1 <https://en.wikipedia.org/wiki/Sha-1>`_ digest of the word "**^S^e^c^ret Wordpass**" into a tuple set, and ``password_check()`` which requires input of a password.
tarantool> digest = require('digest')
---
...
tarantool> function password_insert()
> box.space.tester:insert{1234, digest.sha1('^S^e^c^ret Wordpass')}
> return 'OK'
> end
---
...
tarantool> function password_check(password)
> local t = box.space.tester:select{12345}
> if digest.sha1(password) == t[2] then
> return 'Password is valid'
> else
> return 'Password is not valid'
> end
> end
---
...
tarantool> password_insert()
---
- 'OK'
...
If a later user calls the ``password_check()`` function and enters the wrong password, the result is an error.
tarantool> password_check('Secret Password')
---
- 'Password is not valid'
...

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testing_project / Documentation: reference/reference_lua/digest — English

tarantool> digest.guava(10863919174838991, 11)
---
- 8
...
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