function mime_header_encode in Drupal 4

Same name and namespace in other branches

1. 5 includes/unicode.inc \mime_header_encode()
2. 6 includes/unicode.inc \mime_header_encode()
3. 7 includes/unicode.inc \mime_header_encode()

Encodes MIME/HTTP header values that contain non-ASCII, UTF-8 encoded characters.

For example, mime_header_encode('tést.txt') returns "=?UTF-8?B?dMOpc3QudHh0?=".

See http://www.rfc-editor.org/rfc/rfc2047.txt for more information.

Notes:

• Only encode strings that contain non-ASCII characters.
• We progressively cut-off a chunk with truncate_utf8(). This is to ensure each chunk starts and ends on a character boundary.
• Using \n as the chunk separator may cause problems on some systems and may have to be changed to \r\n or \r.

3 calls to mime_header_encode()

upload_download in modules/upload.module

upload_file_download in modules/upload.module

user_mail in modules/user.module

Send an e-mail message, using Drupal variables and default settings. More information in the <a href="http://php.net/manual/en/function.mail.php">PHP function reference for mail()</a>

File

includes/unicode.inc, line 224

Code

function mime_header_encode($string) {
  if (preg_match('/[^\\x20-\\x7E]/', $string)) {
    $chunk_size = 47;

    // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
    $len = strlen($string);
    $output = '';
    while ($len > 0) {
      $chunk = truncate_utf8($string, $chunk_size);
      $output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\n";
      $c = strlen($chunk);
      $string = substr($string, $c);
      $len -= $c;
    }
    return trim($output);
  }
  return $string;
}