B4X

Compress and Encrypt a Large File (Low and Constant Memory Footprint)

See more Compression Examples

Demonstrates how to compress and encrypt a large file such that the memory footprint remains low and constant.

Note: This example requires Chilkat v9.5.0.99 or greater.

B4X

Dim success As Boolean = False

'  This example assumes the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

Dim compress As ChilkatCompression
compress.Initialize("compress")
compress.Algorithm = "deflate"

'  Set encryption params.
'  The possible values are the same as for the corresponding properties in the Chilkat Crypt2 class/object.
'  The encoded IV and Key must be specified as hex.
Dim json As ChilkatJsonObject
json.Initialize
json.UpdateString("cryptAlgorithm", "aes")
json.UpdateString("cipherMode", "cbc")
json.UpdateInt("keyLength", 128)
json.UpdateInt("paddingScheme", 0)
json.UpdateString("encodedIV", "000102030405060708090A0B0C0D0E0F")
json.UpdateString("encodedKey", "000102030405060708090A0B0C0D0E0F")

'  Do file-to-file compression+encryption in a single call.
Dim inPath As String = "qa_data/largeFile.dat"
Dim outPath As String = "c:/temp/qa_output/compressed_encrypted.dat"
success = compress.CompressEncryptFile(json, inPath, outPath)
If success = False Then
    Log(compress.LastErrorText)
    Return
End If


'  We can do file-to-file decrypt/decompress like this:
Dim inPath2 As String = outPath
Dim outPath2 As String = "c:/temp/qa_output/restored.dat"
success = compress.DecryptDecompressFile(json, inPath2, outPath2)
If success = False Then
    Log(compress.LastErrorText)
    Return
End If


'  Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")
crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 128
crypt.PaddingScheme = 0
crypt.SetEncodedIV("000102030405060708090A0B0C0D0E0F", "hex")
crypt.SetEncodedKey("000102030405060708090A0B0C0D0E0F", "hex")

Dim decryptedPath As String = "c:/temp/qa_output/decrypted.dat"
success = crypt.CkDecryptFile(inPath2, decryptedPath)
If success = False Then
    Log(crypt.LastErrorText)
    Return
End If


Dim outPath3 As String = "c:/temp/qa_output/restored_in_two_steps.dat"
success = compress.DecompressFile(decryptedPath, outPath3)
If success = False Then
    Log(compress.LastErrorText)
    Return
End If


Log("Success.")