NAME

       Encode::GSM0338 -- ETSI GSM 03.38 Encoding

SYNOPSIS

         use Encode qw/encode decode/;
         $gsm0338 = encode("gsm0338", $unicode); # loads Encode::GSM0338 implicitly
         $unicode = decode("gsm0338", $gsm0338); # ditto

DESCRIPTION

       GSM0338 is for GSM handsets. Though it shares alphanumerals with ASCII, control character
       ranges and other parts are mapped very differently, mainly to store Greek characters.
       There are also escape sequences (starting with 0x1B) to cover e.g. the Euro sign.

       This was once handled by Encode::Bytes but because of all those unusual specifications,
       Encode 2.20 has relocated the support to this module.

       This module implements only GSM 7 bit Default Alphabet and GSM 7 bit default alphabet
       extension table according to standard 3GPP TS 23.038 version 16. Therefore National
       Language Single Shift and National Language Locking Shift are not implemented nor
       supported.

   Septets
       This modules operates with octets (like any other Encode module) and not with packed
       septets (unlike other GSM standards). Therefore for processing binary SMS or parts of GSM
       TPDU payload (3GPP TS 23.040) it is needed to do conversion between octets and packed
       septets. For this purpose perl's "pack" and "unpack" functions may be useful:

         $bytes = substr(pack('(b*)*', unpack '(A7)*', unpack 'b*', $septets), 0, $num_of_septets);
         $unicode = decode('GSM0338', $bytes);

         $bytes = encode('GSM0338', $unicode);
         $septets = pack 'b*', join '', map { substr $_, 0, 7 } unpack '(A8)*', unpack 'b*', $bytes;
         $num_of_septets = length $bytes;

       Please note that for correct decoding of packed septets it is required to know number of
       septets packed in binary buffer as binary buffer is always padded with zero bits and 7
       zero bits represents character "@". Number of septets is also stored in TPDU payload when
       dealing with 3GPP TS 23.040.

BUGS

       Encode::GSM0338 2.7 and older versions (part of Encode 3.06) incorrectly handled zero
       bytes (character "@"). This was fixed in Encode::GSM0338 version 2.8 (part of Encode
       3.07).

SEE ALSO

       3GPP TS 23.038 <https://www.3gpp.org/dynareport/23038.htm>

       ETSI TS 123 038 V16.0.0 (2020-07)
       <https://www.etsi.org/deliver/etsi_ts/123000_123099/123038/16.00.00_60/ts_123038v160000p.pdf>

       Encode