Xbase++

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.

Xbase++

LOCAL nSuccess
LOCAL oCompress
LOCAL oJson
LOCAL cInPath
LOCAL cOutPath
LOCAL cInPath2
LOCAL cOutPath2
LOCAL oCrypt
LOCAL cDecryptedPath
LOCAL cOutPath3

nSuccess := 0

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

oCompress := CreateObject("Chilkat.Compression")
oCompress: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.
oJson := CreateObject("Chilkat.JsonObject")
oJson:UpdateString("cryptAlgorithm", "aes")
oJson:UpdateString("cipherMode", "cbc")
oJson:UpdateInt("keyLength", 128)
oJson:UpdateInt("paddingScheme", 0)
oJson:UpdateString("encodedIV", "000102030405060708090A0B0C0D0E0F")
oJson:UpdateString("encodedKey", "000102030405060708090A0B0C0D0E0F")

//  Do file-to-file compression+encryption in a single call.
cInPath := "qa_data/largeFile.dat"
cOutPath := "c:/temp/qa_output/compressed_encrypted.dat"
nSuccess := oCompress:CompressEncryptFile(oJson, cInPath, cOutPath)
IF (nSuccess == 0)
    ? oCompress:LastErrorText
    oCompress:destroy()
    oJson:destroy()
    RETURN
ENDIF

//  We can do file-to-file decrypt/decompress like this:
cInPath2 := cOutPath
cOutPath2 := "c:/temp/qa_output/restored.dat"
nSuccess := oCompress:DecryptDecompressFile(oJson, cInPath2, cOutPath2)
IF (nSuccess == 0)
    ? oCompress:LastErrorText
    oCompress:destroy()
    oJson:destroy()
    RETURN
ENDIF

//  Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
oCrypt := CreateObject("Chilkat.Crypt2")
oCrypt:CryptAlgorithm := "aes"
oCrypt:CipherMode := "cbc"
oCrypt:KeyLength := 128
oCrypt:PaddingScheme := 0
oCrypt:SetEncodedIV("000102030405060708090A0B0C0D0E0F", "hex")
oCrypt:SetEncodedKey("000102030405060708090A0B0C0D0E0F", "hex")

cDecryptedPath := "c:/temp/qa_output/decrypted.dat"
nSuccess := oCrypt:CkDecryptFile(cInPath2, cDecryptedPath)
IF (nSuccess == 0)
    ? oCrypt:LastErrorText
    oCompress:destroy()
    oJson:destroy()
    oCrypt:destroy()
    RETURN
ENDIF

cOutPath3 := "c:/temp/qa_output/restored_in_two_steps.dat"
nSuccess := oCompress:DecompressFile(cDecryptedPath, cOutPath3)
IF (nSuccess == 0)
    ? oCompress:LastErrorText
    oCompress:destroy()
    oJson:destroy()
    oCrypt:destroy()
    RETURN
ENDIF

? "Success."

oCompress:destroy()
oJson:destroy()
oCrypt:destroy()