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<?php
/**
* Class capable of encoding GSM 03.38 default alphabet and packing octets into septets as described by GSM 03.38.
* Based on mapping: http://www.unicode.org/Public/MAPPINGS/ETSI/GSM0338.TXT
*
* Copyright (C) 2011 OnlineCity
* Licensed under the MIT license, which can be read at: http://www.opensource.org/licenses/mit-license.php
* @author hd@onlinecity.dk
*/
class GsmEncoder
{
/**
* Encode an UTF-8 string into GSM 03.38
* Since UTF-8 is largely ASCII compatible, and GSM 03.38 is somewhat compatible, unnecessary conversions are removed.
* Specials chars such as € can be encoded by using an escape char \x1B in front of a backwards compatible (similar) char.
* UTF-8 chars which doesn't have a GSM 03.38 equivalent is replaced with a question mark.
* UTF-8 continuation bytes (\x08-\xBF) are replaced when encountered in their valid places, but
* any continuation bytes outside of a valid UTF-8 sequence is not processed.
*
* @param string $string
* @return string
*/
public static function utf8_to_gsm0338($string)
{
$dict = array(
'@' => "\x00", '£' => "\x01", '$' => "\x02", '¥' => "\x03", 'è' => "\x04", 'é' => "\x05", 'ù' => "\x06", 'ì' => "\x07", 'ò' => "\x08", 'Ç' => "\x09", 'Ø' => "\x0B", 'ø' => "\x0C", 'Å' => "\x0E", 'å' => "\x0F",
'Δ' => "\x10", '_' => "\x11", 'Φ' => "\x12", 'Γ' => "\x13", 'Λ' => "\x14", 'Ω' => "\x15", 'Π' => "\x16", 'Ψ' => "\x17", 'Σ' => "\x18", 'Θ' => "\x19", 'Ξ' => "\x1A", 'Æ' => "\x1C", 'æ' => "\x1D", 'ß' => "\x1E", 'É' => "\x1F",
// all \x2? removed
// all \x3? removed
// all \x4? removed
'Ä' => "\x5B", 'Ö' => "\x5C", 'Ñ' => "\x5D", 'Ü' => "\x5E", '§' => "\x5F",
'¿' => "\x60",
'ä' => "\x7B", 'ö' => "\x7C", 'ñ' => "\x7D", 'ü' => "\x7E", 'à' => "\x7F",
'^' => "\x1B\x14", '{' => "\x1B\x28", '}' => "\x1B\x29", '\\' => "\x1B\x2F", '[' => "\x1B\x3C", '~' => "\x1B\x3D", ']' => "\x1B\x3E", '|' => "\x1B\x40", '' => "\x1B\x65"
);
$converted = strtr($string, $dict);
// Replace unconverted UTF-8 chars from codepages U+0080-U+07FF, U+0080-U+FFFF and U+010000-U+10FFFF with a single ?
return preg_replace('/([\\xC0-\\xDF].)|([\\xE0-\\xEF]..)|([\\xF0-\\xFF]...)/m','?',$converted);
}
/**
* Count the number of GSM 03.38 chars a conversion would contain.
* It's about 3 times faster to count than convert and do strlen() if conversion is not required.
*
* @param string $utf8String
* @return integer
*/
public static function countGsm0338Length($utf8String)
{
$len = mb_strlen($utf8String,'utf-8');
$len += preg_match_all('/[\\^{}\\\~€|\\[\\]]/mu',$utf8String,$m);
return $len;
}
/**
* Pack an 8-bit string into 7-bit GSM format
* Returns the packed string in binary format
*
* @param string $data
* @return string
*/
public static function pack7bit($data)
{
$l = strlen($data);
$currentByte = 0;
$offset = 0;
$packed = '';
for ($i = 0; $i < $l; $i++) {
// cap off any excess bytes
$septet = ord($data[$i]) & 0x7f;
// append the septet and then cap off excess bytes
$currentByte |= ($septet << $offset) & 0xff;
// update offset
$offset += 7;
if ($offset > 7) {
// the current byte is full, add it to the encoded data.
$packed .= chr($currentByte);
// shift left and append the left shifted septet to the current byte
$currentByte = $septet = $septet >> (7 - ($offset - 8 ));
// update offset
$offset -= 8; // 7 - (7 - ($offset - 8))
}
}
if ($currentByte > 0) $packed .= chr($currentByte); // append the last byte
return $packed;
}
}
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