void ComputeHeader()
{
int offset = 0;
var instructions = body.instructions;
var items = instructions.items;
var count = instructions.size;
var stack_size = 0;
var max_stack = 0;
Dictionary<Instruction, int> stack_sizes = null;
if (body.HasExceptionHandlers)
ComputeExceptionHandlerStackSize (ref stack_sizes);
for (int i = 0; i < count; i++) {
var instruction = items [i];
instruction.offset = offset;
offset += instruction.GetSize ();
ComputeStackSize (instruction, ref stack_sizes, ref stack_size, ref max_stack);
}
body.code_size = offset;
body.max_stack_size = max_stack;
}