VBScript

Example: Hash Text in Chunks

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

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

set crypt = CreateObject("Chilkat.Crypt2")
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"

set bd = CreateObject("Chilkat.BinData")

s = "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.

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

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

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

encodedHash = crypt.HashFinalENC()
outFile.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)
outFile.WriteLine("Hash computed in 1 step: " & encodedHash)

' Output:

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

outFile.Close