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; By Hroudtwolf
; 2009-09-03 (ISO 8601)
; PureBasic 4.4x
; Linux, Windows, OS X

EnableExplicit

; ***********************************************************************************
; Simple dataset structure for accessing strictly on ASCII character
; independent by character encoding mode. 
; ***********************************************************************************
Structure ASCII
	a.a
EndStructure

; ***********************************************************************************
; Public function.
; ***********************************************************************************
; Parameters:
; 		*ptrData		-	Pointer the the datablock which you want to encode.
;		nSize			-	Size of the datablock in bytes.
;
; Description:
; 		Use it to encode data to Base64 string.
;
; Return:
; 		Base64 string on success.
; ***********************************************************************************
Procedure.s Base64_Encode ( *ptrData.ASCII , nSize.i )
	Static 		Dim 	cLockUp		.c ( 64 )
	Static 				blInit		.i
	Static 				nI				.i
	Protected			*ptrEnd					= *ptrData + nSize
	Protected 	Dim	bInput		.b ( 3 )
	Protected 	Dim	cOutput		.a ( 4 )
	Protected			sOutput		.s
	Protected			nBlockSize	.i
	
	If Not ( blInit )
		blInit = #True

		; Creating static look up table.
		CopyMemory ( @ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" , @ cLockUp ( 0 ) , 64 * SizeOf ( CHARACTER ) )
	EndIf
	
	While ( *ptrData < *ptrEnd )
		nBlockSize = 0
		; Filling input table.
		For nI = 0 To 2
			If ( *ptrData < *ptrEnd )
				nBlockSize + 1
				bInput ( nI ) = *ptrData\a
				*ptrData + SizeOf ( ASCII )
			Else
				bInput ( nI ) = 0
			EndIf
		Next nI
		
		; Encoding of 3 bytes to 4 6-bit characters.
		If ( nBlockSize )
			cOutput ( 0 ) = cLockUp ( bInput ( 0 ) >> 2 )
			cOutput ( 1 ) = cLockUp ( ( ( bInput ( 0 ) & $03 ) << 4)  | ( ( bInput ( 1 ) & $f0 ) >> 4 ) )
			
			If ( nSize > 1 )
				cOutput ( 2 ) = cLockUp ( ( ( bInput ( 1 ) & $0f ) << 2 ) | ( ( bInput ( 2 ) & $c0 ) >> 6 ) )
			Else
				cOutput ( 2 ) = '='
			EndIf 
			
			If ( nSize > 2 )
				cOutput ( 3 ) = cLockUp ( bInput ( 2 ) & $3f )
			Else
				cOutput ( 3 ) = '='
			EndIf
			For nI = 0 To 3 
				sOutput + Chr ( cOutput ( nI ) )
			Next nI
		EndIf
	Wend
	
	ProcedureReturn sOutput
EndProcedure

; ***********************************************************************************
; Public function.
; ***********************************************************************************
; Parameters:
; 		sInput		-	Input base64 string.
;
; Description:
; 		Use it to decode a base64 string to binary data.
; 		Warning!!! You are full accountability about the returned datablock.
;
; Return:
; 		Pointer to a decoded memory block on success. Otherwise NULL.
; ***********************************************************************************
Procedure.i Base64_Decode ( sInput.s )
	Static 		Dim 	cLockUp			.c ( 81 )
	Static 				blInit			.i
	Protected			*ptrData			.CHARACTER 	= @ sInput
	Protected			nSize				.i				= Len ( sInput ) + 1
	Protected			*ptrEnd							= *ptrData + ( nSize * SizeOf ( CHARACTER ) )
	Protected			nValue			.b
	Protected			nPartSize		.f				= ( nSize - ( nSize / 3.333 ) ) * SizeOf ( CHARACTER ) 
	Protected			*ptrOutput		.BYTE			= AllocateMemory ( Int ( nPartSize ) )
	Protected			*ptrOutputStart				= *ptrOutput
	Protected 	Dim	cInput			.a ( 4 )
	Protected 	Dim	bOutput			.b ( 3 )
	Protected			nBlockSize		.i
	Protected			nI					.i
 
	If Not ( *ptrData )
		ProcedureReturn #Null
	EndIf

	If Not blInit
		blInit = #True
		
		; Creating static look up table.
		CopyMemory ( @ "|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\]^_`abcdefghijklmnopq" , @ cLockUp ( 0 ) , 80 * SizeOf ( CHARACTER ) )
	EndIf
	
	While ( *ptrData < *ptrEnd )
		
		nBlockSize = 0
		
		For nI = 0 To 3
			If ( *ptrData < *ptrEnd )
				nValue = 0
				While ( *ptrData < *ptrEnd And Not nValue )
					; Reading a character from base64 string.
					nValue = *ptrData\c : *ptrData + SizeOf ( CHARACTER )
			 
			 		; Adjust of the lookup value.
					If ( nValue < 43 Or nValue > 122 )
						nValue = 0
					Else
						nValue = cLockUp ( nValue - 43 )
					EndIf

					; Detecting the end of the input.							
					If ( nValue = '$' )
				  		nValue = 0 
				   Else
				    	nValue = nValue - 61
				   EndIf
 
				Wend
	 			
	 			; Filling input table.
				If ( *ptrData < *ptrEnd )
					nBlockSize + 1
		 
					If ( nValue )
						cInput ( nI ) = nValue - 1
					EndIf 
				EndIf					
			Else
				Break
			EndIf	
		
		Next nI
		  
		; Decoding of 4 6-bit characters to 3 bytes.  
		If nBlockSize 
			bOutput ( 0 ) = ( cInput ( 0 ) << 2 | cInput ( 1 ) >> 4 ) 
			bOutput ( 1 ) = ( cInput ( 1 ) << 4 | cInput ( 2 ) >> 2 )
			bOutput ( 2 ) = ( ( ( cInput ( 2 ) << 6 ) & $C0 ) | cInput ( 3 ) )
			nI = 0
			; Writting of the decoded byte to the output buffer.
			While ( nI < ( nBlockSize - 1 ) )
				*ptrOutput\b = bOutput ( nI ) 
				*ptrOutput	 + SizeOf ( BYTE )
				nI				 + 1
			Wend
		EndIf
	Wend
	
	ProcedureReturn *ptrOutputStart
EndProcedure

;--- Test

Define.s sInput	= "Feel the pure power! PureBasic."
Define.i	nInput	= StringByteLength ( sInput )
Define.s sBase64 


sBase64 = Base64_Encode ( @ sInput , nInput )

Debug "Encoded: " + sBase64
Debug "Decoded:" + PeekS ( Base64_Decode ( sBase64 ) , nInput )