Decoding i386 opcodes to instructions

I'm trying to Is there any good resource available to learn 'decoding' of i386 opcodes开发者_开发问答? Most of the websites talk about how to encode instructions, but I don't find anywhere something telling as to how to decode opcodes to instructions.

I've looked at the source code of some disassemblers, but I want some documentation as to how to decode opcodes to instructions.

Thanks and Regards,

Hrishikesh Murali

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Read the processor manuals, they have it described, though maybe not in complete details:

1. Intel Manuals, in particular see Chapter 2 in Volume 2A and Appendix A in Volume 2B.
2. AMD Manuals, see Programmer's Manual Volume 3.

See also How to interpret the opcode manually?

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if you want to lean at a more programmatic level, olly's old disasm engine is a very simple disassembler to learn from (written in C), and if you want to cover the more recent opcodes (and hidden/aliased opcodes), bea-engine is a great open-source disassem engine.