memoryRange.go

package izapple2

import (
	"fmt"
)

type memoryRange struct {
	base uint16
	data []uint8
	name string
}

type memoryRangeROM struct {
	memoryRange
	pageOffset uint16
	pages      uint8
}

func newMemoryRange(base uint16, data []uint8, name string) *memoryRange {
	var m memoryRange
	m.base = base
	m.data = data
	m.setBase(base)

	m.name = name
	return &m
}

func newMemoryRangeROM(base uint16, data []uint8, name string) *memoryRangeROM {
	return newMemoryRangePagedROM(base, data, name, 1)
}

func newMemoryRangePagedROM(base uint16, data []uint8, name string, pages uint8) *memoryRangeROM {
	var m memoryRangeROM
	m.base = base
	m.data = data
	m.name = name
	m.pages = pages
	return &m
}

func (m *memoryRange) setBase(base uint16) {
	m.base = base
}

func (m *memoryRange) peek(address uint16) uint8 {
	return m.data[address-m.base]
}

func (m *memoryRange) poke(address uint16, value uint8) {
	m.data[address-m.base] = value
}

func (m *memoryRange) subRange(a, b uint16) []uint8 {
	return m.data[a-m.base : b-m.base]
}

func (m *memoryRangeROM) setPage(page uint8) {
	pageSize := len(m.data) / int(m.pages)
	m.pageOffset = uint16(int(page%m.pages) * pageSize)
}

func (m *memoryRangeROM) getPage() uint8 {
	pageSize := len(m.data) / int(m.pages)
	return uint8(m.pageOffset / uint16(pageSize))
}

func (m *memoryRangeROM) peek(address uint16) uint8 {
	pos := address - m.base + m.pageOffset
	if pos >= uint16(len(m.data)) {
		return uint8(address) // Non existent memory
	}

	return m.data[pos]
}
func (m *memoryRangeROM) poke(address uint16, value uint8) {
	// Ignore
}

//lint:ignore U1000 this is used to write debug code
func identifyMemory(m memoryHandler) string {
	ram, ok := m.(*memoryRange)
	if ok {
		return fmt.Sprintf("RAM 0x%04x %s", ram.base, ram.name)
	}

	rom, ok := m.(*memoryRangeROM)
	if ok {
		return fmt.Sprintf("ROM 0x%04x %s", rom.base, rom.name)
	}

	return ("Unknown memory")
}