Here is example code on how my reWIP / enhanced DBO2X (and OBJ) app reads in DBO files and grabs the information needed to rebuild X/OBJ formats. Note: not all codes have been implemented here as it's still being tested / debugged thoroughly.
The idea is you grab an embedded DBO code and validate it. If it's a valid code then grab the data by advancing the pBuffer forward. The DBOPTR is the pointer to the DBO in memory. So you can use ALLOC, memblocks or banks. ALLOC memory is quite slow when having to read in the DBO data and "POKE" each byte to allocated memory. As far as I know there is no make memory from file, but I could be wrong (hmmm will double check just so I'm not going crazy).