[2023/07/04 Updated: To fix error due to recent change on Split function]
In previous post, I showed how to convert a base using multiple conversion tables.
As an application of this technique, I will show the encoding plain text to Base64 and decoding Base64.
Char() function
To make conversion table, I have used Char() function in Power Apps which converts decimal number to ASCII character.
Char(65) --> "A"
With help of Sequence() function, conversion table between decimal number and character is written as
AddColumns(Sequence(2^8,1),"char",Char(Value))
This returns a table like
| Value | char |
|---|---|
| 65 | A |
| 66 | B |
| 67 | C |
| 68 | D |
Translate decimal to binary
As I have shown previous post, conversion between different bases can be easily achieved by replacing them with binaries once. (Char --> Decimal --> Binary --> Base64)
Decimal to Binary translation is not required table, but done by following formula:
With(
{
number:41,
place:6
},
Concat(Sequence(place,place,-1),
Text(
If(
(Mod(number,Power(2,Value))>=Power(2,Value-1))&&(Mod(number,Power(2,Value))<Power(2,Value)),
1,
0
)
)
)
)
Encode plain text to Base64
Combining them, Power Apps formula to encode plain text to Base64 is written as
With({
InputText:"Happy Holidays",
AsciiTable:AddColumns(Sequence(2^8,1),"char",Char(Value)),
B64ToBin:
Table(
{b64:"A",bin:"000000"},
{b64:"B",bin:"000001"},
{b64:"C",bin:"000010"},
{b64:"D",bin:"000011"},
{b64:"E",bin:"000100"},
{b64:"F",bin:"000101"},
{b64:"G",bin:"000110"},
{b64:"H",bin:"000111"},
{b64:"I",bin:"001000"},
{b64:"J",bin:"001001"},
{b64:"K",bin:"001010"},
{b64:"L",bin:"001011"},
{b64:"M",bin:"001100"},
{b64:"N",bin:"001101"},
{b64:"O",bin:"001110"},
{b64:"P",bin:"001111"},
{b64:"Q",bin:"010000"},
{b64:"R",bin:"010001"},
{b64:"S",bin:"010010"},
{b64:"T",bin:"010011"},
{b64:"U",bin:"010100"},
{b64:"V",bin:"010101"},
{b64:"W",bin:"010110"},
{b64:"X",bin:"010111"},
{b64:"Y",bin:"011000"},
{b64:"Z",bin:"011001"},
{b64:"a",bin:"011010"},
{b64:"b",bin:"011011"},
{b64:"c",bin:"011100"},
{b64:"d",bin:"011101"},
{b64:"e",bin:"011110"},
{b64:"f",bin:"011111"},
{b64:"g",bin:"100000"},
{b64:"h",bin:"100001"},
{b64:"i",bin:"100010"},
{b64:"j",bin:"100011"},
{b64:"k",bin:"100100"},
{b64:"l",bin:"100101"},
{b64:"m",bin:"100110"},
{b64:"n",bin:"100111"},
{b64:"o",bin:"101000"},
{b64:"p",bin:"101001"},
{b64:"q",bin:"101010"},
{b64:"r",bin:"101011"},
{b64:"s",bin:"101100"},
{b64:"t",bin:"101101"},
{b64:"u",bin:"101110"},
{b64:"v",bin:"101111"},
{b64:"w",bin:"110000"},
{b64:"x",bin:"110001"},
{b64:"y",bin:"110010"},
{b64:"z",bin:"110011"},
{b64:"0",bin:"110100"},
{b64:"1",bin:"110101"},
{b64:"2",bin:"110110"},
{b64:"3",bin:"110111"},
{b64:"4",bin:"111000"},
{b64:"5",bin:"111001"},
{b64:"6",bin:"111010"},
{b64:"7",bin:"111011"},
{b64:"8",bin:"111100"},
{b64:"9",bin:"111101"},
{b64:"+",bin:"111110"},
{b64:"/",bin:"111111"}
)},
With({
BinRep:
Concat(
AddColumns(ForAll(Split(InputText,""), {Result: ThisRecord.Value}),"dec",LookUp(AsciiTable,char=Result).Value),//Convert text to Ascii character code (decimal)
Concat(Sequence(8,8,-1),Text(If(And(Mod(dec,Power(2,Value))>=Power(2,Value-1),Mod(dec,Power(2,Value))<Power(2,Value)),1,0)))&"","")//Convert decimal to binary
},
With({b64string:Concat(
Sequence(
RoundUp(Len(BinRep)/6,0),0),
LookUp(
B64ToBin,
bin=Mid(BinRep&Left("000000",6-Mod(Len(BinRep),6)),6*Value+1,6) //Left("000000"....) is padding right with zero
).b64&"",
""
)},
b64string&Left("====",Mod(4-Mod(Len(b64string),4),4))//Convert binary to base64
)
)
)
It returns "SGFwcHkgSG9saWRheXM=".
Decode Base64
Decoding Base64 string will be done by opposite procedure. (Base64 ---> Binary --> Decimal --> Char)
I'll skip the detail but formula to decode Base64 is
With({
InputB64:"SGFwcHkgSG9saWRheXM=",
B64ToBin:
Table(
{b64:"A",bin:"000000"},
{b64:"B",bin:"000001"},
{b64:"C",bin:"000010"},
{b64:"D",bin:"000011"},
{b64:"E",bin:"000100"},
{b64:"F",bin:"000101"},
{b64:"G",bin:"000110"},
{b64:"H",bin:"000111"},
{b64:"I",bin:"001000"},
{b64:"J",bin:"001001"},
{b64:"K",bin:"001010"},
{b64:"L",bin:"001011"},
{b64:"M",bin:"001100"},
{b64:"N",bin:"001101"},
{b64:"O",bin:"001110"},
{b64:"P",bin:"001111"},
{b64:"Q",bin:"010000"},
{b64:"R",bin:"010001"},
{b64:"S",bin:"010010"},
{b64:"T",bin:"010011"},
{b64:"U",bin:"010100"},
{b64:"V",bin:"010101"},
{b64:"W",bin:"010110"},
{b64:"X",bin:"010111"},
{b64:"Y",bin:"011000"},
{b64:"Z",bin:"011001"},
{b64:"a",bin:"011010"},
{b64:"b",bin:"011011"},
{b64:"c",bin:"011100"},
{b64:"d",bin:"011101"},
{b64:"e",bin:"011110"},
{b64:"f",bin:"011111"},
{b64:"g",bin:"100000"},
{b64:"h",bin:"100001"},
{b64:"i",bin:"100010"},
{b64:"j",bin:"100011"},
{b64:"k",bin:"100100"},
{b64:"l",bin:"100101"},
{b64:"m",bin:"100110"},
{b64:"n",bin:"100111"},
{b64:"o",bin:"101000"},
{b64:"p",bin:"101001"},
{b64:"q",bin:"101010"},
{b64:"r",bin:"101011"},
{b64:"s",bin:"101100"},
{b64:"t",bin:"101101"},
{b64:"u",bin:"101110"},
{b64:"v",bin:"101111"},
{b64:"w",bin:"110000"},
{b64:"x",bin:"110001"},
{b64:"y",bin:"110010"},
{b64:"z",bin:"110011"},
{b64:"0",bin:"110100"},
{b64:"1",bin:"110101"},
{b64:"2",bin:"110110"},
{b64:"3",bin:"110111"},
{b64:"4",bin:"111000"},
{b64:"5",bin:"111001"},
{b64:"6",bin:"111010"},
{b64:"7",bin:"111011"},
{b64:"8",bin:"111100"},
{b64:"9",bin:"111101"},
{b64:"+",bin:"111110"},
{b64:"/",bin:"111111"}
)},
With({
BinRep:Concat(AddColumns(ForAll(Split(InputB64,""), {Result: ThisRecord.Value}),"Bin",LookUp(B64ToBin,b64=Result).bin),Bin,"")//Convert base64 string to binary representation
},
With({binArray:
AddColumns(Sequence(
RoundUp(Len(BinRep)/8,0),0),
"bin",
Mid(BinRep&Left("00000000",Mod(8-Mod(Len(BinRep),8),8)),8*Value+1,8)
)},
Concat(binArray,
If(Sum(AddColumns(Sequence(8,8,-1),"dec",Power(2,Value-1)*Value(Mid(bin,8-Value+1,1))),dec)>0,Char(Sum(AddColumns(Sequence(8,8,-1),"dec",Power(2,Value-1)*Value(Mid(bin,8-Value+1,1))),dec)),"")&"","")
) //Convert each 8bits binary to Char
)
)
Sample App
You can download sample app from community library :)
Happy Holidays!
