This is the smallest x86 parser that I could make.
It supports full Pentium 4 instruction set (standard, FPU, MMX, SSE, SSE2).
It supports undocumented encodings like 82 00-FFh and F6/F7 xx001xxxxb).
It checks for instructions that are too long to execute (more than 15 bytes).
It is only 339 bytes long (198 bytes code, 141 bytes data).

Call with esi -> pointer to instruction to query.
Returns eax -> length of that instruction.  All other registers preserved.
Carry is set in case of error (invalid instruction, too long, etc).
eax is unpredictable value in that case.

rgb/29A jan 2003
iam_rgb@hotmail.com