Parsing BLOB object present in iPhone SMS database

I am developing an Android application to update iOS SMS database. I found that in iOS, MMS body (i.e.text of MMS and other information) is stored in BLOB object.

Sample BLOB object extracted from the database:

        streamtypedÅËÑ@ÑÑÑNSMutableAttributedStringÑÑNSAttributedStringÑÑNSObject
    ÖíÑÑÑNSMutableStringÑÑNSStringïÑ+ÔøºMerry 
    ChristmasÜÑiIíÑÑÑNSDictionaryïÑiíÑòò”__kIMFileTransferGUIDAttributeNameÜíÑòò$D060412D-D6A2-472D-9552-
0ACCDED7E9B5ÜíÑòò__kIMMessagePartAttributeNameÜíÑÑÑNSNumberÑÑNSValueïÑ*Ñõ
õÜÜôíÑöõíÑòò__kIMMessagePartAttributeNameÜíÑüû°õÜÜÜ

My aim is to update the text of the above BLOB object from “Merry Christmas” to “Happy new year”. I found that when I simply replace the text, the MMS body is not visible on the target iOS device (after inserting database to the iOS device). But I found that if I replace the string “Merry Christmas” with other string having the same length, it works properly and MMS body is visible with the updated text on the iOS device.

I have the following questions.

1. How to parse such type of BLOB objects to understand its details?
2. I think the BLOB objects contain information about the length of the text present in MMS. Which fields in the above BLOB object can possibly store information about the length?

3. Is “streamtype” a file type? (As the BLOB object starts with that string) If yes, how to parse such type of files?

   I’d appreciate any suggestions on this issue. Thank you in advance.