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sms-part-3gpp: decode Unicode SMS with non-BMP code points

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Depsite 3GPP TS 23.038 specifies that Unicode SMS messages are encoded in
UCS-2, UTF-16 encoding is commonly used instead on many modern platforms to
allow encoding code points that fall outside the Basic Multilingual Plane
(BMP), such as Emoji. Most of the UCS-2 code points are identical to their
equivalent UTF-16 code points.  In UTF-16, non-BMP code points are encoded in a
pair of surrogate code points (i.e. a high surrogate in 0xD800..0xDBFF,
followed by a low surrogate in 0xDC00..0xDFFF). An isolated surrogate code
point has no general interpretation in UTF-16, but could be a valid (though
unmapped) code point in UCS-2.

This patch modifies the 3GPP SMS decoding to first try UTF-16BE and then fall
back to UCS-2BE on failure. If both fail, an empty string is returned
instead of a NULL pointer.
This commit is contained in:
Ben Chan
2017-12-15 00:45:12 -08:00
committed by Aleksander Morgado
parent c44b928206
commit e8bac6cb92
1 changed files with 22 additions and 2 deletions
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24
src/mm-sms-part-3gpp.c
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@@ -247,8 +247,28 @@ sms_decode_text (const guint8 *text, int len, MMSmsEncoding encoding, int bit_of
mm_dbg (" Got UTF-8 text: '%s'", utf8);
g_free (unpacked);
} else if (encoding == MM_SMS_ENCODING_UCS2) {
mm_dbg ("Converting SMS part text from UCS-2BE to UTF8...");
utf8 = g_convert ((char *) text, len, "UTF8", "UCS-2BE", NULL, NULL, NULL);
/* Despite 3GPP TS 23.038 specifies that Unicode SMS messages are
* encoded in UCS-2, UTF-16 encoding is commonly used instead on many
* modern platforms to allow encoding code points that fall outside the
* Basic Multilingual Plane (BMP), such as Emoji. Most of the UCS-2
* code points are identical to their equivalent UTF-16 code points.
* In UTF-16, non-BMP code points are encoded in a pair of surrogate
* code points (i.e. a high surrogate in 0xD800..0xDBFF, followed by a
* low surrogate in 0xDC00..0xDFFF). An isolated surrogate code point
* has no general interpretation in UTF-16, but could be a valid
* (though unmapped) code point in UCS-2. Here we first try to decode
* the SMS message in UTF-16BE, and if that fails, fall back to decode
* in UCS-2BE.
*/
mm_dbg ("Converting SMS part text from UTF16BE to UTF8...");
utf8 = g_convert ((const gchar *) text, len, "UTF8", "UTF16BE", NULL, NULL, NULL);
if (!utf8) {
mm_dbg ("Converting SMS part text from UCS-2BE to UTF8...");
utf8 = g_convert ((const gchar *) text, len, "UTF8", "UCS-2BE", NULL, NULL, NULL);
}
if (!utf8)
utf8 = g_strdup ("");
mm_dbg (" Got UTF-8 text: '%s'", utf8);
} else {
g_warn_if_reached ();