B4X

Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks. B4X

Dim success As Boolean = False

Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"

Dim bd As ChilkatBinData
bd.Initialize

Dim s As String = "The quick brown fox jumped over the lazy dog." & Chr(13) & Chr(10)

'  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")
success = crypt.HashBeginString(s)

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

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

Dim encodedHash As String = crypt.HashFinalENC
Log("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)
Log("Hash computed in 1 step: " & encodedHash)

'  Output:

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