#code by hengry My blog :http//:hyhgd.blog.51cto.com
proc Base64Decode {code} {
#Creat the Base64 Decoding table
     set Base64Table {
        A B C D E F G H I J K L M N O P
        Q R S T U V W X Y Z a b c d e f
        g h i j k l m n o p q r s t u v 
        w x y z 0 1 2 3 4 5 6 7 8 9 + /
        =
     }
     set i 0
     foreach byte $Base64Table {
         set DecodingBase64($byte) $i
         incr i 
     }


     set list [split $code ""]
     set length [llength $list]
     set DecodeList ""
     set Base64Code ""
     for {set i 0} {$i<$length} {incr i 4} {
                                 
          
            set BaseCode_0 $DecodingBase64([lindex $list $i])
            set BaseCode_1 $DecodingBase64([lindex $list $i+1])
            set BaseCode_2 $DecodingBase64([lindex $list $i+2])
            set BaseCode_3 $DecodingBase64([lindex $list $i+3])


           set code_16 [expr $BaseCode_0<<2]
           set code_78 [expr {$i+1<$length?[expr [expr $BaseCode_1>>4]&0x03]:0x00}]

#Add the first code
           lappend DecodeList [expr $code_16|$code_78]

           set code_14 [expr {$i+1<$length?[expr [expr $BaseCode_1<<4]&0xF0]:0x00}]
           if {$i+2>$length || [lindex $list $i+2]=={=}} {
                set code1 0x00
           } else {
                set code_58 [expr [expr $BaseCode_2>>2] &0x0F]
                set code1 [expr $code_14|$code_58]
#Add the second code
                if {$code1!=0x00} {
                    lappend DecodeList $code1
                }
                if {$i+2>$length || [lindex $list $i+2]=={=}} {
                set code2 0x00
                } else {
                     set code_12 [expr [expr $BaseCode_2<<6]&0xC0]
                }
                if {$i+3>$length || [lindex $list $i+3]=={=}} {
                     set code_38 0x00
                } else {
                     set code_38 [expr  $BaseCode_3&0x3F]
                }
                 set code2 [expr $code_12|$code_38]
                if {$code2!=0x00} {
                    lappend DecodeList $code2
                }
           }     
    }

#ASCIIDecoding
    set data {}
    foreach byte $DecodeList {
    append data [binary format c $byte]
    }
    return $data
}