Base64 encoded String to binary file

Question

I have a Base64 encoded String that contains PDF data. Using the EncdDecd unit I can decode the String to a Byte Array.

This is where I am having trouble: I tried saving the characters to a String but once it hits a zero value (ASCII = 0 or #0 or $00) the String no longer appends. Example:

uses
  EncdDecd;
var
  EncodedString : String;
  Report : String;
  Base64Bytes: TBytes; // contains the binary data
begin
  Base64Bytes := DecodeBase64(EncodedString);
  for I := 0 to Length(Base64Bytes) - 1 do
    begin
      Report := Report + Chr(Base64Bytes[I]);
    end;

Writing to a text file seems to work better but after renaming it to .PDF the file does not open correctly.

How can I write to a binary file in Delphi? Or even save the data to a stream? Basically I am just trying to take the encoded String and save it to a PDF/binary file, or display the PDF in Delphi.

I have looked around quite a bit and found a possible solution in Saving a Base64 string to disk as a binary using Delphi 2007 but is there another way?

Duplicate of Saving a Base64 string to disk as a binary using Delphi 2007. I don't see what new information you're requesting here. If you just want additional options, they belong as answers to the original question, not this duplicate. — Rob Kennedy
– Rob Kennedy, Commented Oct 31, 2011 at 16:41
what have you tried? what was the problem? How do you "append" the string? please post your code using "EncdDecd namespace". Also, how do you change a text file to a pdf? again post your code. There are many ways in Delphi to transform a string and save it in binary. The link you posted is quite a compact code to do it. — PA.
– PA., Commented Oct 31, 2011 at 16:45

David Heffernan · Accepted Answer · 2011-10-31 17:25:59Z

9

This should do it:

procedure DecodeBaseToFile(const FileName: string; 
  const EncodedString: AnsiString);
var
  bytes: TBytes;
  Stream: TFileStream;
begin
  bytes := DecodeBase64(EncodedString);
  Stream := TFileStream.Create(FileName, fmCreate);
  try
    if bytes<>nil then
      Stream.WriteBuffer(bytes[0], Length(bytes));
  finally
    Stream.Free;
  end;
end;

Note: I have only compiled this in my head.

answered Oct 31, 2011 at 17:25

David Heffernan

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5 Comments

Remy Lebeau Over a year ago

@Trevor: you can alternatively use a TByteStream instead. It is a TMemoryStream descendant, so it has a SaveToFile() method available. That way, you don't have to instantiate TFileStream manually.

Marjan Venema Over a year ago

@Trevor: upvoted it for you, but you'll have to accept it as the answer yourself (check mark underneath the up/down vote arrows).

Márcio Rossato Over a year ago

I created a empty unit, in uses need uses System.Classes, System.SysUtils, synacode, IdCoder, IdCoderMIME; and I need change the line Decodebase64 to bytes := TIdDecoderMIME.DecodeBytes(EncodedString);

David Heffernan Over a year ago

@MárcioRossato That's using a different base64 encoder

Márcio Rossato Over a year ago

yes, I need change because I have not found the correct uses.

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