(VB.NET) Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks.

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Dim crypt As New Chilkat.Crypt2
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"

Dim bd As New Chilkat.BinData

Dim s As String = "The quick brown fox jumped over the lazy dog." & vbCrLf

' Accumulate the text in a StringBuilder.  We'll demonstrate hashing the text in chunks,
' and then also hashing the entire text at once to show the results are the same.

bd.AppendString(s,"utf-8")
Dim success As Boolean = crypt.HashBeginString(s)

Dim i As Integer = 0
While i < 200
    bd.AppendString(s,"utf-8")
    crypt.HashMoreString(s)
    i = i + 1
End While

' Get the hash in base64 format.
crypt.EncodingMode = "base64"

Dim encodedHash As String = crypt.HashFinalENC()
Debug.WriteLine("Hash computed in chunks: " & encodedHash)

' Let's alternatively compute the hash of the entire amount of data at once,
' to show the hash computation is the same:
encodedHash = crypt.HashBdENC(bd)
Debug.WriteLine("Hash computed in 1 step: " & encodedHash)


' Output:

' Hash computed in chunks: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=
' Hash computed in 1 step: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=