Explore block module in Drupal

block.info is the block module description file and the "package" property tells us that block is Drupal core module and it can be configured by menu "admin/structure/block".
 
block.install is executed when block is installed. The purpose of this file is to create the necessary tables: block, block_custom, block_role
 
Table block is used to store the block information declared by code statements;
Table block_custom is used to store the block information created by administration inte易做图ce;
Table block_role is used to control the visibility of blocks.
The main logic are defined in the block.module file. Let us go around this file.There are lots of functions in block.module,but they can be categorized into two types: hook function and block module internal-used function.hook function includes block_menu, block_theme, block_theme_initialize, block_themes_enable.
Function block_menu:block configuration, block management, block list by theme
[html]   
  $default_theme = variable_get('theme_default', 'bartik');  
  $items['admin/structure/block'] = array(  
    'title' => 'Blocks',  
    'description' => 'Configure what block content appears in your site\'s sidebars and other regions.',  
    'page callback' => 'block_admin_display',  
    'page arguments' => array($default_theme),  
    'access arguments' => array('administer blocks'),  
    'file' => 'block.admin.inc',  
  );  
  $items['admin/structure/block/manage/%/%'] = array(  
    'title' => 'Configure block',  
    'page callback' => 'drupal_get_form',  
    'page arguments' => array('block_admin_configure', 4, 5),  
    'access arguments' => array('administer blocks'),  
    'file' => 'block.admin.inc',  
  );  
  $items['admin/structure/block/manage/%/%/configure'] = array(  
    'title' => 'Configure block',  
    'type' => MENU_DEFAULT_LOCAL_TASK,  
    'context' => MENU_CONTEXT_INLINE,  
  );  
  $items['admin/structure/block/manage/%/%/delete'] = array(  
    'title' => 'Delete block',  
    'page callback' => 'drupal_get_form',  
    'page arguments' => array('block_custom_block_delete', 4, 5),  
    'access arguments' => array('administer blocks'),  
    'type' => MENU_LOCAL_TASK,  
    'context' => MENU_CONTEXT_NONE,  
    'file' => 'block.admin.inc',  
  );  
  $items['admin/structure/block/add'] = array(  
    'title' => 'Add block',  
    'page callback' => 'drupal_get_form',  
    'page arguments' => array('block_add_block_form'),  
    'access arguments' => array('administer blocks'),  
    'type' => MENU_LOCAL_ACTION,  
    'file' => 'block.admin.inc',  
  );  
  foreach (list_themes() as $key => $theme) {  
    $items['admin/structure/block/list/' . $key] = array(  
      'title' => check_plain($theme->info['name']),  
      'page arguments' => array($key),  
      'type' => $key == $default_theme ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,  
      'weight' => $key == $default_theme ? -10 : 0,  
      'access callback' => '_block_themes_access',  
      'access arguments' => array($theme),  
      'file' => 'block.admin.inc',  
    );  
    if ($key != $default_theme) {  
      $items['admin/structure/block/list/' . $key . '/add'] = array(  
        'title' => 'Add block',  
        'page callback' => 'drupal_get_form',  
        'page arguments' => array('block_add_block_form'),  
        'access arguments' => array('administer blocks'),  
        'type' => MENU_LOCAL_ACTION,  
        'file' => 'block.admin.inc',  
      );  
    }  
    $items['admin/structure/block/demo/' . $key] = array(  
      'title' => check_plain($theme->info['name']),  
      'page callback' => 'block_admin_demo',  
      'page arguments' => array($key),  
      'type' => MENU_CALLBACK,  
      'access callback' => '_block_themes_access',  
      'access arguments' => array($theme),  
      'theme callback' => '_block_custom_theme',  
      'theme arguments' => array($key),  
      'file' => 'block.admin.inc',  
    );  
  }  
  return $items;  
}  
Function block_theme: offers two theme options: block is for front-end and block_admin_display_form is for administration inte易做图ce
[html]  
function block_theme() {  
  return array(  
    'block' => array(  
      'render element' => 'elements',  
      'template' => 'block',  
    ),  
    'block_admin_display_form' => array(  
      'template' => 'block-admin-display-form',  
      'file' => 'block.admin.inc',  
      'render element' => 'form',  
    ),  
  );  
}  
Function block_theme_initialize: assign the blocks to theme's regions<

补充：Web开发 , php ,