drupal/core/modules/number/number.module

<?php

/**
 * @file
 * Defines numeric field types.
 */

use Drupal\Core\Entity\EntityInterface;

/**
 * Implements hook_help().
 */
function number_help($path, $arg) {
  switch ($path) {
    case 'admin/help#number':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Number module defines various numeric field types for the Field module. Numbers can be in integer, decimal, or floating-point form, and they can be formatted when displayed. Number fields can be limited to a specific set of input values or to a range of values. See the <a href="@field-help">Field module help page</a> for more information about fields.', array('@field-help' => url('admin/help/field'))) . '</p>';
      return $output;
  }
}

/**
 * Implements hook_field_info().
 */
function number_field_info() {
  return array(
    'number_integer' => array(
      'label' => t('Integer'),
      'description' => t('This field stores a number in the database as an integer.'),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_integer',
      'field item class' => '\Drupal\number\Type\IntegerItem',
    ),
    'number_decimal' => array(
      'label' => t('Decimal'),
      'description' => t('This field stores a number in the database in a fixed decimal format.'),
      'settings' => array('precision' => 10, 'scale' => 2),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_decimal',
      'field item class' => '\Drupal\number\Type\DecimalItem',
    ),
    'number_float' => array(
      'label' => t('Float'),
      'description' => t('This field stores a number in the database in a floating point format.'),
      'instance_settings' => array('min' => '', 'max' => '', 'prefix' => '', 'suffix' => ''),
      'default_widget' => 'number',
      'default_formatter' => 'number_decimal',
      'field item class' => '\Drupal\number\Type\FloatItem',
    ),
  );
}

/**
 * Implements hook_field_settings_form().
 */
function number_field_settings_form($field, $instance, $has_data) {
  $settings = $field['settings'];
  $form = array();

  if ($field['type'] == 'number_decimal') {
    $form['precision'] = array(
      '#type' => 'select',
      '#title' => t('Precision'),
      '#options' => drupal_map_assoc(range(10, 32)),
      '#default_value' => $settings['precision'],
      '#description' => t('The total number of digits to store in the database, including those to the right of the decimal.'),
      '#disabled' => $has_data,
    );
    $form['scale'] = array(
      '#type' => 'select',
      '#title' => t('Scale'),
      '#options' => drupal_map_assoc(range(0, 10)),
      '#default_value' => $settings['scale'],
      '#description' => t('The number of digits to the right of the decimal.'),
      '#disabled' => $has_data,
    );
  }

  return $form;
}

/**
 * Implements hook_field_instance_settings_form().
 */
function number_field_instance_settings_form($field, $instance) {
  $settings = $instance['settings'];

  $form['min'] = array(
    '#type' => 'textfield',
    '#title' => t('Minimum'),
    '#default_value' => $settings['min'],
    '#description' => t('The minimum value that should be allowed in this field. Leave blank for no minimum.'),
    '#element_validate' => array('form_validate_number'),
  );
  $form['max'] = array(
    '#type' => 'textfield',
    '#title' => t('Maximum'),
    '#default_value' => $settings['max'],
    '#description' => t('The maximum value that should be allowed in this field. Leave blank for no maximum.'),
    '#element_validate' => array('form_validate_number'),
  );
  $form['prefix'] = array(
    '#type' => 'textfield',
    '#title' => t('Prefix'),
    '#default_value' => $settings['prefix'],
    '#size' => 60,
    '#description' => t("Define a string that should be prefixed to the value, like '$ ' or '&euro; '. Leave blank for none. Separate singular and plural values with a pipe ('pound|pounds')."),
  );
  $form['suffix'] = array(
    '#type' => 'textfield',
    '#title' => t('Suffix'),
    '#default_value' => $settings['suffix'],
    '#size' => 60,
    '#description' => t("Define a string that should be suffixed to the value, like ' m', ' kb/s'. Leave blank for none. Separate singular and plural values with a pipe ('pound|pounds')."),
  );

  return $form;
}

/**
 * Implements hook_field_validate().
 *
 * Possible error codes:
 * - number_min: The value is less than the allowed minimum value.
 * - number_max: The value is greater than the allowed maximum value.
 */
function number_field_validate(EntityInterface $entity = NULL, $field, $instance, $langcode, $items, &$errors) {
  foreach ($items as $delta => $item) {
    if ($item['value'] != '') {
      if (is_numeric($instance['settings']['min']) && $item['value'] < $instance['settings']['min']) {
        $errors[$field['field_name']][$langcode][$delta][] = array(
          'error' => 'number_min',
          'message' => t('%name: the value may be no less than %min.', array('%name' => $instance['label'], '%min' => $instance['settings']['min'])),
        );
      }
      if (is_numeric($instance['settings']['max']) && $item['value'] > $instance['settings']['max']) {
        $errors[$field['field_name']][$langcode][$delta][] = array(
          'error' => 'number_max',
          'message' => t('%name: the value may be no greater than %max.', array('%name' => $instance['label'], '%max' => $instance['settings']['max'])),
        );
      }
    }
  }
}

/**
 * Implements hook_field_presave().
 */
function number_field_presave(EntityInterface $entity, $field, $instance, $langcode, &$items) {
  if ($field['type'] == 'number_decimal') {
    // Let PHP round the value to ensure consistent behavior across storage
    // backends.
    foreach ($items as $delta => $item) {
      if (isset($item['value'])) {
        $items[$delta]['value'] = round($item['value'], $field['settings']['scale']);
      }
    }
  }
}

/**
 * Implements hook_field_is_empty().
 */
function number_field_is_empty($item, $field) {
  if (empty($item['value']) && (string) $item['value'] !== '0') {
    return TRUE;
  }
  return FALSE;
}