APR provide member function for implement read and write file.Apr_xml.h,Apr_xml.cpp,ReadXML.cpp.Three file for read and lock file.APR have member function for show status "apr_status_t".If programs can read and lock data,It's return zero value.See below for example.

From

Read and lock step by

apr_file_open( &fp, fName, APR_READ,
APR_OS_DEFAULT,
mp ))

If you observe APR_READ macro,It's can change to write step by "APR_WRITE".
Reference : APR tutorial

After read about SAX,DOM concept about XML.DOM using pointers are pointer in data.DOM read all data in file before process data in file.SAX using concept read direction data in file.SAX appropriate of big data in file.
Short note for implement manage file with APR and DOM.

Simple using DOM Parser.
APR read,write lock file.

After read APR concepts.APR is able to execute programs in various OS.After compile code in Fedora distros for test completable with OS.One problem from develop using APR for manage thread in programs.If you write code delete memory,But APR allocator memory by you don't know about that.Some case you delete memory,but APR doesn't delete memory that.- -".Good choice about APR.Developing project with APR.Programs implement by APR can port to other OS.
I have written a few code in C++ concept.Source code depends on Codepad: APRImplement.cpp,APRImplement.h.Two sources run by Scons in config for building code.You can see old source wrote by C in array-simple.c.Other tutorial libapr can see on link here.See picture below for result after insert to stack.

From chatsiri.com

It's title of API for implementing programs.You can see topic about APR from link above.