# Asp Programming Code Examples

## Asp > Mathematics Code Examples

### Base 64 Encode - Decode

``` Base 64 Encode - Decode Const sBASE_64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/ ' --------------------------------------- Function Base64decode(ByVal asContents) Dim lsResult Dim lnPosition Dim lsGroup64, lsGroupBinary Dim Char1, Char2, Char3, Char4 Dim Byte1, Byte2, Byte3 If Len(asContents) Mod 4 > 0 Then asContents = asContents & String(4 - (Len(asContents) Mod 4), " ") lsResult = "" For lnPosition = 1 To Len(asContents) Step 4 lsGroupBinary = "" lsGroup64 = Mid(asContents, lnPosition, 4) Char1 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 1, 1)) - 1 Char2 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 2, 1)) - 1 Char3 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 3, 1)) - 1 Char4 = InStr(sBASE_64_CHARACTERS, Mid(lsGroup64, 4, 1)) - 1 Byte1 = Chr(((Char2 And 48) 16) Or (Char1 * 4) And &HFF) Byte2 = lsGroupBinary & Chr(((Char3 And 60) 4) Or (Char2 * 16) And &HFF) Byte3 = Chr((((Char3 And 3) * 64) And &HFF) Or (Char4 And 63)) lsGroupBinary = Byte1 & Byte2 & Byte3 lsResult = lsResult + lsGroupBinary Next Base64decode = lsResult End Function ' -------------------------------------- Function Base64encode(ByVal asContents) Dim lnPosition Dim lsResult Dim Char1 Dim Char2 Dim Char3 Dim Char4 Dim Byte1 Dim Byte2 Dim Byte3 Dim SaveBits1 Dim SaveBits2 Dim lsGroupBinary Dim lsGroup64 If Len(asContents) Mod 3 > 0 Then asContents = asContents & String(3 - (Len(asContents) Mod 3), " ") lsResult = "" For lnPosition = 1 To Len(asContents) Step 3 lsGroup64 = "" lsGroupBinary = Mid(asContents, lnPosition, 3) Byte1 = Asc(Mid(lsGroupBinary, 1, 1)): SaveBits1 = Byte1 And 3 Byte2 = Asc(Mid(lsGroupBinary, 2, 1)): SaveBits2 = Byte2 And 15 Byte3 = Asc(Mid(lsGroupBinary, 3, 1)) Char1 = Mid(sBASE_64_CHARACTERS, ((Byte1 And 252) 4) + 1, 1) Char2 = Mid(sBASE_64_CHARACTERS, (((Byte2 And 240) 16) Or (SaveBits1 * 16) And &HFF) + 1, 1) Char3 = Mid(sBASE_64_CHARACTERS, (((Byte3 And 192) 64) Or (SaveBits2 * 4) And &HFF) + 1, 1) Char4 = Mid(sBASE_64_CHARACTERS, (Byte3 And 63) + 1, 1) lsGroup64 = Char1 & Char2 & Char3 & Char4 lsResult = lsResult + lsGroup64 Next Base64encode = lsResult End Function ```