uint8_t buffer[] = {0x49, 0x90};
FdInstr instr;
// Decode from buffer into instr in 64-bit mode.
int ret = fd_decode(buffer, sizeof(buffer), 64, 0, &instr);
// ret<0 indicates an error, ret>0 the number of decoded bytes
// Relevant properties of instructions can now be queried using the FD_* macros.
// Or, we can format the instruction to a string buffer:
char fmtbuf[64];
fd_format(&instr, fmtbuf, sizeof(fmtbuf));
// fmtbuf now reads: "xchg r8, rax"