WordPress custom class per page based on object name.

functions.php

<?php

add_filter('body_class', 'sf3_custom_body_class');
function sf3_custom_body_class($classes){
  global $post;
  $prefix = 'cpgname_'; //insert your own prefix

  if(isset($post->post_type)){ //if a post-type is required
    $prefix .= sprintf('%s_%s', $prefix, $post->post_type);
    // 'cpgname_page'
  }

  if(isset($post->post_name)){
    $classes[] = sprintf('%s_%s', $prefix, $post->post_name);
    // 'cpgname_page_contact-us'
  }

  return $classes;
}