※ 引述《unixxxx (皓皓)》之铭言：
: 标题: Re: [讨论] 写三元判断式code review被打枪
: 时间: Sat Dec 17 03:51:38 2022
: 很多Javascript 高手都是用 switch 取代
"特定"情况下的确是好方式
举个例子 以前我在调校能时候有用过这种方式 这是c#的code部分节录
void Mem_w(ushort address, byte value)
{
if (address < 0x2000) NES_MEM[address & 0x7ff] = value;
else if (address < 0x4020) IO_write(address, value);
else if (address < 0x6000) MapperRouterW_ExpansionROM(address,value);
else if (address < 0x8000) MapperRouterW_RAM(address, value);
else MapperRouterW_PRG(address, value);
}
这个是一个非常频繁被呼叫的method 如果address 大于等于0x8000
其实前面就浪费好几次计算在判断式上
因此改成 功能上是相等的
static void Mem_w(ushort address, byte value)
{
switch (address & 0xf000)
{
case 0:
case 0x1000:
NES_MEM[address & 0x7ff] = value;
break;
case 0x2000:
case 0x3000:
case 0x4000:
IO_write(address, value);
break;
case 0x5000:
MapperObj.MapperW_ExpansionROM(address, value);
break;
case 0x6000:
case 0x7000:
MapperObj.MapperW_RAM(address, value);
break;
case 0x8000:
case 0x9000:
case 0xa000:
case 0xb000:
case 0xc000:
case 0xd000:
case 0xe000:
case 0xf000:
MapperObj.MapperW_PRG(address, value);
break;
}
}
但再简化快速下去还有大招
初始化执行一次就好
static void init_function()
{
mem_write_fun = new Action<ushort, byte>[0x10000];
for (int address = 0; address < 0x10000; address++)
{
if (address < 0x2000) mem_write_fun[address] =
new Action<ushort, byte>((addr, val) => { NES_MEM[addr & 0x7ff] = val; });
else if (address < 0x4020) mem_write_fun[address] =
new Action<ushort,byte>(IO_write);
else if (address < 0x6000) mem_write_fun[address] =
new Action<ushort, byte>(MapperObj.MapperW_ExpansionROM);
else if (address < 0x8000) mem_write_fun[address] =
new Action<ushort, byte>(MapperObj.MapperW_RAM);
else mem_write_fun[address] =
new Action<ushort, byte>(MapperObj.MapperW_PRG);
}
}
之后读取
[MethodImpl(MethodImplOptions.AggressiveInlining)]
static void Mem_w(ushort address, byte value)
{
mem_write_fun[address](address, value);
}
实际上跟switch原理很相似 但直接把mapper的实作 哪个address对应啥动作
直接写到记忆址array去了
我是不知道你所谓的javascript高手用switch替代判断式是碰到啥议题
但特定议题用改用switch 甚至自己刻死路由效能是会快非常多
以前有笔记在这边...
https://dotblogs.com.tw/enet/2017/01/21/emu_optimization_1