[fpc-pascal] Is there some example of an FPC program for use in svn hook calls (email)?

[Bo Berglund]

On Thu, 14 Dec 2017 10:26:22 +0000, Mark Morgan Lloyd
<markMLl.fpc-pascal at telemetry.co.uk> wrote:

>On 14/12/17 10:00, Adriaan van Os wrote:
>> Bo Berglund wrote:
>>> Now I am looking at the same problem for svn and this time I need it> 
>>> to be cross-platform, hence using FPC.> Before I start on it myself I 
>>> wonder if someone here has already> written such a program for svn and 
>>> if so, if it is available as open> source?
>> I use sendmail <https://en.wikipedia.org/wiki/Sendmail> from FPC, using 
>> AssignStream, fpgeterrno and PClose. Haven't tried that on Windows though.
>
>With the caveat that while Sendmail is a well-respected MTA, many unix 
>systems also provide a sendmail command as a generic mailer. On Windows 
>Blat is an alternative.
But *sending email* is not the problem, I have done this in many
applications using Indy TIdSMTP. Instead it is getting data out oof
svn and formatting these in a friendly looking email to be sent....

Anyway I started on my own svn data collector and got stuck in a very
basic function...

I used the information in the wiki page below on how to execute a
command line program and retrieving its output data for processing.
Look at the section towards the bottom with subject "Reading large
output":
http://wiki.freepascal.org/Executing_External_Programs

To get the subversion commit data one has to use svnlook, which is a
command line program so I need to do this.

But when I use this approach I get no data at all, what could have
gone wrong here?

When I reach the end of the repeat loop there is no data at all to
process, i = 0!
But when I run the command on the command line manually I do get svn
data back.
So what did I do wrong when I used the wiki solution?

var
  //Command line parameters are:
  REPOS_PATH,         //Full path to repository
  REV,                //Revision number
  TXN_NAME:  string;  //Transaction name
  DataBuf,
  Parms:   TStringList;
  svncmd: string;
  SCD: TSvnCommitData;


function GetSvnData(Command: string; Parameters: TStringList; var
SvnData: TStringList): boolean;
{Command is the full path to the executable to run (<path>\svnlook.exe
or <path>/svnlook
Parameters contain the command line parameters. A typical parameter
set could be
 info
 -r
 2121
 <repository path on server>

 The result from the command will be stored into the SvnData
stringlist
 }
const
  BUF_SIZE = 2048; // Buffer size for reading the output in chunks
var
  AProcess     : TProcess;
  OutputStream : TStream;
  BytesRead    : longint;
  i: integer;
  Buffer       : array[1..BUF_SIZE] of byte;
begin
  Result := false;
  // Set up the process
  AProcess := TProcess.Create(nil);
  // Create a stream object to store the generated output in.
  OutputStream := TMemoryStream.Create;
  //Create the data buffer
  try
    AProcess.Executable := Command;

    // Process option poUsePipes has to be used so the output can be
captured.
    AProcess.Options := [poUsePipes];

    for i := 0 to Parameters.Count -1 do
      AProcess.Parameters.Add(Parameters[i]);

    i := 0;
    // Start the process (run the command)
    AProcess.Execute;

    // All generated output from AProcess is read in a loop until no
more data is available
    repeat
      // Get the new data from the process to a maximum of the buffer
size that was allocated.
      // Note that all read(...) calls will block except for the last
one, which returns 0 (zero).
      BytesRead := AProcess.Output.Read(Buffer, BUF_SIZE);

      // Add the bytes that were read to the stream for later usage
      OutputStream.Write(Buffer, BytesRead);
      Inc(i, BytesRead);
    until BytesRead = 0;  // Stop if no more data is available

    OutputStream.Position := 0; // Required to make sure all data is
copied from the start
    SvnData.LoadFromStream(OutputStream);
    Result := (i > 0); //(SvnData.Count > 0);
  finally
    OutputStream.Free;;
    AProcess.Free;
  end;

end;

begin
  //Check for the call parameters:
  if ParamCount() < 3 then
  begin
    Writeln('Call parameters missing!');
    exit;
  end;
  REPOS_PATH := ParamStr(1);
  REV := ParamStr(2);
  TXN_NAME := ParamStr(3);
  Parms := TStringList.Create;
  DataBuf := TStringList.Create;
  SCD := TSvnCommitData.Create;
  try
    // The commands for Windows and *nix are different hence the
$IFDEFs
    {$IFDEF Windows}
      svncmd := 'C:\Programs\Subversion\svnlook.exe';
    {$ENDIF Windows}
    {$IFDEF Unix}
      svncmd := '/usr/bin/svnlook';
    {$ENDIF Unix}
    //Build the call for svnlook
    {1. Get the starting information on the operation
        svnlook info -r <REV> <REPOS_PATH>
    }
    Parms.Add('info');
    Parms.Add('-r');
    Parms.Add('REV');
    Parms.Add('REPOS_PATH');
    if GetSvnData(svncmd, Parms, DataBuf) then
    begin
      SCD.UserName := DataBuf[0];
      SCD.CommitTime := DataBuf[1];
      SCD.Logmessage := DataBuf[3];
    end;
  finally
    SCD.Free;
    DataBuf.Free;
  end;
end.



-- 
Bo Berglund
Developer in Sweden