I am looking for small assembler translator for a student project. The problem is so that it is necessary to translate small portions of assembler (AT&T) syntax into machine code (x86 and/or x86_64) on the fly. I don't want to reinvent the wheel so I will be grateful for any links to ready implementations. Preference will be given to lightweight library with simple interface.
Give FASM a look, although its a full assembler for x86 and x86_64, its opensource, which should easily allow you to integrate it, you can also have a look at GAS, which is also open source.
Finding an actual assembler library is gonna very difficult, as most are geared to JIT compilers, the best you'll find is asmjit.