Delphi: How to calculate the SHA hash of a large file

Question

Hi I need to generate a SHA over a 5 Gig file

Do you know of a non string based Delphi library that can do this ?

Answer 1

@Davy Landman, thank you, your answer really helped me out. This is the code I ended up using:

function HashFileSHA256(const fileName: String): String;
var
  sha256: TDCP_sha256;
  buffer: array[0..1024*1024] of byte;
  i, bytesRead: Integer;
  streamIn: TFileStream;
  hashBuf: array[0..31] of byte;
begin
  // Initialization
  Result := '';
  streamIn := TFileStream.Create(fileName, fmOpenRead);
  sha256 := TDCP_sha256.Create(nil);
  for i:=0 to Sizeof(buffer) do
    buffer[i] := 0;
  for i:=0 to Sizeof(hashBuf) do
    hashBuf[i] := 0;
  bytesRead := -1;

  // Compute
  try
    sha256.Init;
    while bytesRead <> 0 do
    begin
      bytesRead := streamIn.Read(buffer[0], Sizeof(buffer));
      sha256.Update(buffer[0], bytesRead);
    end;
    sha256.Final(hashBuf);
    for I := 0 to 31 do
      Result := Result + IntToHex(hashBuf[i], 2);
  finally
    streamIn.Free;
    sha256.Free;
  end;

  Result := LowerCase(Result);
end;

P.S.: I am a total beginner with Pascal, so this code most likely sucks. But I tested it on the MSYS2 installer and was able to verify the hash, so that's nice.