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How to perform Base64 encoding/decoding using Cryptography API Functions

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#DEFINE CRYPT_STRING_BASE64 0x0001
#DEFINE CRYPT_STRING_NOCRLF 0x40000000
#DEFINE CRYPT_STRING_NOCR 0x80000000

DO declare

LOCAL cBuffer, cEncoded, cDecoded

TEXT TO cBuffer NOSHOW
Base cryptographic functions provide the most flexible means 
of developing cryptography applications. All communication 
with a cryptographic service provider (CSP) occurs through 
these functions.

A CSP is an independent module that performs all cryptographic 
operations. At least one CSP is required with each application 
that uses cryptographic functions. A single application can 
occasionally use more than one CSP.
ENDTEXT

cEncoded = ToBase64(m.cBuffer)
? cEncoded

cDecoded = FromBase64(cEncoded)
? cDecoded

* end of main

FUNCTION ToBase64(cSrc)
    LOCAL nFlags, nBufsize, cDst
    nFlags=CRYPT_STRING_BASE64

    nBufsize=0
    = CryptBinaryToString(@cSrc, LEN(cSrc),;
        m.nFlags, NULL, @nBufsize)

    cDst = REPLICATE(CHR(0), m.nBufsize)
    IF CryptBinaryToString(@cSrc, LEN(cSrc), m.nFlags,;
        @cDst, @nBufsize) = 0
        RETURN ""
    ENDIF
RETURN cDst

FUNCTION FromBase64(cSrc)
    LOCAL nFlags, nBufsize, cDst
    nFlags=CRYPT_STRING_BASE64

    nBufsize=0
    = CryptStringToBinary(@cSrc, LEN(m.cSrc),;
        nFlags, NULL, @nBufsize, 0,0)

    cDst = REPLICATE(CHR(0), m.nBufsize)
    IF CryptStringToBinary(@cSrc, LEN(m.cSrc),;
        nFlags, @cDst, @nBufsize, 0,0) = 0
        RETURN ""
    ENDIF
RETURN m.cDst

PROCEDURE declare
    DECLARE INTEGER CryptBinaryToString IN Crypt32;
        STRING @pbBinary, LONG cbBinary, LONG dwFlags,;
        STRING @pszString, LONG @pcchString

    DECLARE INTEGER CryptStringToBinary IN crypt32;
        STRING @pszString, LONG cchString, LONG dwFlags,;
        STRING @pbBinary, LONG @pcbBinary,;
        LONG pdwSkip, LONG pdwFlags

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1750 bytes  
Created: 2001-08-03 12:00:00  
Modified: 2010-04-08 11:20:04  
Visits in 7 days: 66  
Listed functions:
CryptBinaryToString
CryptStringToBinary
Printer friendly API declarations
My comment:
In VFP8 base64 conversion is normally performed with STRCONV().

In my tests, API routines presented on this page encoded and decoded strings approximately 2 times faster than STRCONV() did -- on 100K cycles 3.7 seconds vs. 7.7 seconds.

This is an output from call to CryptBinaryToString with dwFlags set to CRYPT_STRING_HEXASCIIADDR (0x000b). Can make a good starting point for programming a simple binary viewer.


* * *
From Burkhard Stiller`s VFP Blog:
Another way to encode and store picture-data inside your classes -- relates to base64 encoding, and is an interesting piece of code by itself.
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