ODF standard and the code - EasyHack
Open Document Format (ODF) is a standard (ISO/IEC 26300) and native file format that LibreOffice uses. OASIS developed this file format based on the file format of StarOffice, the ancestor of LibreOffice.
To understand the ODF standard, working with the LibreOffice code and fixing a small bug is enlightening. Here we discuss a related EasyHack.
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Basically, LibreOffice handles the Open Document format by opening the zip file using the zip parser and the deflate algorithm, and then parses the XML files inside it using libxml2 library.