#!/usr/bin/env awk

function shift( array, \

                junk, elm0, l )

{

  elm0 = array[0]

  for ( l = 0; l < asorti( array, junk ) - 1; l++ )

    array[l] = array[l+1];

  delete array[l]

  return elm0

}

function init_cpp_src_line()

{

  logical_line = ""

  delete break_pos 

}

function shift_valid_bp( array, \

                         junk, elm )

{

  elm = -1

  if ( 0 < asorti( array, junk ) )

    do {

      elm = shift( array )

    } while ( 0 > elm );

  return elm

}

function check_cpp_src_line_break_pos( \

                                       i, junk )

{

  printf( "break_pos:" )

  for ( i = 0; i < asorti( break_pos, junk ); i++ )

    printf( " %d", break_pos[i] );

  printf( "\n" )

}

function check_cpp_src_line()

{

  printf( "logical_line[%s]\n", logical_line )

  check_cpp_src_line_break_pos()

}

function append_line( phys_line, \

                      filt_line, bp_len )

{

  filt_line = phys_line

  sub( /\\$/, " ", filt_line )

  logical_line    = logical_line filt_line

  bp_len = asorti( break_pos, junk )

  break_pos[bp_len] = length( logical_line ) - 1

}

function print_line( \

                     c0, c1, i, junk, part_str )

{

  c0 = 0

  while( asorti( break_pos, junk ) > 1 )

  {

    if ( ( c1 = shift_valid_bp( break_pos ) ) < 1 )

    {

      part_str = substr( logical_line, c0 + 1 )

      printf( "%s\n", part_str )

      return

    }

    part_str = substr( logical_line, c0 + 1, c1 - c0 + 1 )

    gsub( / $/, "\\", part_str )

    printf( "%s\n", part_str )

    c0 = c1 + 1

  }

  part_str = substr( logical_line, c0 + 1 )

  printf( "%s\n", part_str )

}

function shrink_spaces( pos, \

                        tail, removed_length, k )

{

  tail = substr( logical_line, pos )

  sub( /^[ \t]+/, " ", tail )

  removed_length = length( logical_line ) - pos - length( tail ) + 1

  logical_line = substr( logical_line, 0, pos - 1 ) tail

  for ( k = 0; k < asorti( break_pos, junk ); k++ )

    if ( ( pos + removed_length ) <= break_pos[k] )

      break_pos[k] = break_pos[k] - removed_length;

    else if ( pos <= break_pos[k] )

      break_pos[k] = -1;

  return removed_length

}

function shrink_spaces_to_linebreak( pos, \

                                     junk, part_str, removed_length, i )

{

  for ( i = 0; i < asorti( break_pos, junk ) && break_pos[i] < pos ; i++ )

    ;

  if ( break_pos[i] < 1 ) 

    return;

  part_str = substr( logical_line, pos, break_pos[i] - pos + 1 )

  sub( /^[ \t]+/, " ", part_str )

  removed_length = ( break_pos[i] - pos + 1 ) - length( part_str )

  tail = substr( logical_line, pos + removed_length )

  logical_line = substr( logical_line, 0, pos - 1 ) tail

  for ( ; i < asorti( break_pos, junk ); i++ )

    break_pos[i] -= removed_length;

  return removed_length

}

function delete_linebreaks_in_2nd_token( \

                                           tail, paren_depth, junk, i, j, k, l )

{

  if ( logical_line ~ /^[ \t]*#[ \t]*define[ \t]+[0-9A-Za-z_]+\(/ )

  {

    tail = logical_line

    sub( /^[ \t]*#[ \t]*define[ \t]+[0-9A-Za-z_]+/, "", tail )

    paren_depth = 0

    l = 0

    i = length( logical_line ) - length( tail ) + 1 # seek to the 1st op paren

    j = i

    do {

      if ( substr( logical_line, j, 2 ) ~ /[ \t][ \t]/ )

        l = shrink_spaces( j );

      else if ( substr( logical_line, j, 1 ) == "(" )

        paren_depth += 1;

      else if ( substr( logical_line, j, 1 ) == ")" )

        paren_depth -= 1;

      j += 1

    } while ( j < length( logical_line ) && paren_depth != 0 )

    for ( k = 0; k < asorti( break_pos, junk ); k++ )

      if ( i <= break_pos[k] && break_pos[k] < j )

        break_pos[k] = -1;

    if ( l > 0 )

      shrink_spaces_to_linebreak( j );

  }

}

BEGIN{

  init_cpp_src_line()

}

{

  append_line( $0 )

  if ( $0 !~ /\\$/ )

  {

    delete_linebreaks_in_2nd_token()

    print_line()

    init_cpp_src_line()

  }

}

END{

  if ( 0 < length( logical_line ) )

  {

    delete_linebreaks_in_2nd_token()

    print_line()

  }

}