#include <petsc/private/viewerimpl.h>  /*I "petscviewer.h" I*/

/*@C
   PetscViewerGetSubViewer - Creates a new PetscViewer (same type as the old)
    that lives on a subcommunicator

    Collective on PetscViewer

   Input Parameter:
.  viewer - the PetscViewer to be reproduced

   Output Parameter:
.  outviewer - new PetscViewer

   Level: advanced

   Notes:
    Call PetscViewerRestoreSubViewer() to return this PetscViewer, NOT PetscViewerDestroy()

     This is most commonly used to view a sequential object that is part of a
    parallel object. For example block Jacobi PC view could use this to obtain a
    PetscViewer that is used with the sequential KSP on one block of the preconditioner.

   Concepts: PetscViewer^sequential version

.seealso: PetscViewerSocketOpen(), PetscViewerASCIIOpen(), PetscViewerDrawOpen(), PetscViewerRestoreSubViewer()
@*/
PetscErrorCode  PetscViewerGetSubViewer(PetscViewer viewer,MPI_Comm comm,PetscViewer *outviewer)
{
  PetscErrorCode ierr;
  PetscMPIInt    size;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,1);
  PetscValidPointer(outviewer,2);
  ierr = MPI_Comm_size(PetscObjectComm((PetscObject)viewer),&size);CHKERRQ(ierr);
  if (size == 1) {
    ierr       = PetscObjectReference((PetscObject)viewer);CHKERRQ(ierr);
    *outviewer = viewer;
  } else if (viewer->ops->getsubviewer) {
    ierr = (*viewer->ops->getsubviewer)(viewer,comm,outviewer);CHKERRQ(ierr);
  } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_SUP,"Cannot get SubViewer PetscViewer for type %s",((PetscObject)viewer)->type_name);
  ierr = PetscViewerASCIIPushSynchronized(viewer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*@C
   PetscViewerRestoreSubViewer - Restores a new PetscViewer obtained with PetscViewerGetSubViewer().

    Collective on PetscViewer

   Input Parameters:
+  viewer - the PetscViewer that was reproduced
-  outviewer - new PetscViewer

   Level: advanced

   Notes:
    Call PetscViewerGetSubViewer() to get this PetscViewer, NOT PetscViewerCreate()

.seealso: PetscViewerSocketOpen(), PetscViewerASCIIOpen(), PetscViewerDrawOpen(), PetscViewerGetSubViewer()
@*/
PetscErrorCode  PetscViewerRestoreSubViewer(PetscViewer viewer,MPI_Comm comm,PetscViewer *outviewer)
{
  PetscErrorCode ierr;
  PetscMPIInt    size;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,1);

  ierr = MPI_Comm_size(PetscObjectComm((PetscObject)viewer),&size);CHKERRQ(ierr);
  if (size == 1) {
    ierr = PetscObjectDereference((PetscObject)viewer);CHKERRQ(ierr);
    if (outviewer) *outviewer = NULL;
  } else if (viewer->ops->restoresubviewer) {
    ierr = (*viewer->ops->restoresubviewer)(viewer,comm,outviewer);CHKERRQ(ierr);
  }
  ierr = PetscViewerASCIIPopSynchronized(viewer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}