subcoding/gen/operand.go

package gen

import "math/rand"

import "github.com/firestuff/subcoding/vm"

func randOperand(prog *vm.Program, t vm.OperandNumericType) *vm.Operand {
	for {
		op := &vm.Operand{
			Type: randOperandType(),
		}

		switch op.Type {
		case vm.GlobalMemoryIndex:
			op.Value = RandBiasedUint64n(prog.GlobalMemorySize)

		case vm.FunctionMemoryIndex:
			op.Value = RandBiasedUint64n(prog.FunctionMemorySize)

		case vm.Literal:
			switch t {
			case vm.OperandUnsigned:
				op.Value = RandBiasedUint64()

			case vm.OperandSigned:
				op.Value = RandBiasedInt64()

			case vm.OperandSignedOrUnsigned:
				op.Value = RandBiasedUSint64()

			case vm.OperandReference:
				// Invalid. Roll the dice again.
				continue
			}
		}

		return op
	}
}

var operandTypes = []vm.OperandType{
	vm.Literal,
	vm.FunctionMemoryIndex,
	vm.GlobalMemoryIndex,
}

func randOperandType() vm.OperandType {
	// Uniform distribution
	return operandTypes[rand.Intn(len(operandTypes))]
}