Bit Fields tutorial
Suppose the source text looked like this:
We have a disassembly like this:
Let’s improve it by using bitfields. We first define a bitfield type by opening an enumeration window (menu View|Enumerations) where we press Ins to create a new object and make it a bitfield. The name given to the bitfield does not matter much. We press Ctrl-N to define the bitfield values.
The first bitfield mask is 3 (or 2 bits). The name of the mask is not used by IDA, it is intended as a memory helper. Out of the 4 values this field can take, we only define the first value, zero, and assign a name to it : OOFS_IFSIGN. If we want to define other values, within the fields limits, we just repeat the process. With some comments, the definition becomes
We switch to the disassembly window (or close the enumeration window with Alt-F3). Through the Edit|Operand types|Enum member menu we select the enum type we just defined and get this result…
That’s all folks !
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