custom_share.module

<?php
/*
 * Implements hook_ds_fields_info()
 */
function custom_share_ds_fields_info($entity_type) {
  $fields = array();
  
  $fields['social_share_button'] = array(
   'title' => t('DS THEME: Social share button'),
    'field_type' => DS_FIELD_TYPE_THEME,
    'ui_limit' => array('*|*'),
    'properties' => array(
      // In case the field_type is DS_FIELD_TYPE_THEME, you also
      // need to register these formatters as a theming function
      // since the key will be called with theme('function').
      // The value is the caption used in the selection config on Field UI.
      'formatters' => array(
        'social_share_button' => t('The social share in a dropdown button'),
        // 'social_share_inline' => t('The social share printed inline'),
      ),
    )
  );
  
  return array($entity_type => $fields);
}

/**
 * Implements hook_theme().
 */
function custom_share_theme($existing, $type, $theme, $path) {
  return array(
    'social_share_button' => array(
      'template' => 'templates/social-share-button',
    ),
  );
}

/**
 * Implements of hook_preprocess_hook()
 */
function custom_share_preprocess_social_share_button(&$vars) {

  // Add AddThis Javascript
  drupal_add_js('//s7.addthis.com/js/300/addthis_widget.js#pubid=xa-51d1983c58c1f351', 'external');

  $siteURL = 'http://' . $_SERVER['HTTP_HOST'];
  
  $data_share = '';
  
  $node_article = $vars['entity'];
  $node_id = $node_article->nid;
  $node_absolute_url = $siteURL . url('node/' . $node_id);
  $node_title = $node_article->title;
  $node_body = $node_article->body[LANGUAGE_NONE][0]['safe_value'];

  // Here I'm using the function of the nice module advanced_text_formatter 
  // https://drupal.org/project/advanced_text_formatter
  // to trim down the body for share description
  $trimmed_node_description = advanced_text_formatter_trim_text($node_body, array('html' => TRUE, 'max_length' => 200, 'word_boundary' => TRUE, 'ellipsis' => TRUE));

  // For addThis API documentation see
  // http://support.addthis.com/customer/portal/articles/1337989-overview
  $additional_parameters  = 'addthis:url="' . $node_absolute_url . '" ';
  $additional_parameters .= 'addthis:title="' . $node_title . '" ';
  $additional_parameters .= 'addthis:description="' . drupal_html_to_text($trimmed_node_description) . '"';

  // Add facebook like
  $data_share .= '<a class="addthis_button_facebook_like" fb:like:layout="button_count" ' . $additional_parameters . '></a>';
  // Add facebook send
  $data_share .= '<a class="addthis_button_facebook_send" ' . $additional_parameters . '></a>';
  // Addthis google+ button
  $data_share .= '<a class="addthis_button_google_plusone" g:plusone:size="medium" ' . $additional_parameters . '></a>';
  // Add tweet button
  $data_share .= '<a class="addthis_button_tweet" ' . $additional_parameters . '></a>';

  // Add to the DOM the object with sharing infos for each node
  drupal_add_js(array ('socialShare' => array( 'share-' . $node_id => $data_share ) ), 'setting');
  
  // Add the javascript for button interaction
  drupal_add_js(base_path() . drupal_get_path('module', 'custom_share') . '/share.js', 'file');
  // Add basic CSS styles
  drupal_add_css(base_path() . drupal_get_path('module', 'custom_share') . '/share.css', 'file');

}