so uint32_t generates a 32 bit variable anywhere stdint.h is supported.
for implementing the file-to-file mode it's enough to make a quick modification to the code using fgetc in UNLZSS_CGET and fputc in UNLZSS_CPUT and using FILE instead of in, out and their relative sizes.
I linked that code only as example of what worked here in my quick tests so that then you could do your tests and use a similar code which works better for your needs.
uhmmm I don't have understood this.Yes, I think so... It is abstracted from 3D-Gamestudio ACKNEX.DLL.