虚拟并口仿真器

本文介绍了虚拟并口仿真器的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在我的计算机网络过程中，我们应该使用本地寄存器学习并行端口编程（如使用outportb像命令）。我没有并行端口（因为我住在2011年），但要练习的程序（我安装使用DOSBox中老TURBOC 3 IDE）。有rel=\"nofollow\">这计划模拟串口可模拟如

In my computer networks course we are supposed to learn parallel port programming by using the native registers (like using outportb like commands). I don't have a parallel port (because I live in 2011) but want to practice the programs (I installed the old turboc 3 IDE using dosbox). Is there a program which emulates parallel ports like this program emulates serial ports?

推荐答案

由于环境是假的，无论如何，也就是你没有一个实际的端口一起玩，你也可以同样模拟程序中的端口功能。

Since the environment is fake anyway, i.e. you don't have an actual port to play with, you could just as well emulate the port functionality in your program.

下面是如何使用的 结构化异常处理 （SEH）：

Here's how to do it in Windows using Structured Exception Handling (SEH):

// Filename: PortEmu.c // Compiled with Open Watcom 1.9 as: wcl386 PortEmu.c #include <windows.h> #include <stdio.h> #include <conio.h> // Port state. Holds the last value written by OUT. // IN reads from it. volatile UINT32 PortState = 0; UINT32 ReadPort(UINT16 PortNumber, UINT OperandSize) { UNREFERENCED_PARAMETER(PortNumber); switch (OperandSize) { default: case 8: return PortState & 0xFF; case 16: return PortState & 0xFFFF; case 32: return PortState; } } void WritePort(UINT16 PortNumber, UINT OperandSize, UINT32 Value) { UNREFERENCED_PARAMETER(PortNumber); switch (OperandSize) { default: case 8: PortState = (PortState & ~0xFF) | (Value & 0xFF); break; case 16: PortState = (PortState & ~0xFFFF) | (Value & 0xFFFF); break; case 32: PortState = Value; break; } } // Exception filter to emulate x86 IN and OUT instructions // in 32-bit Windows application. int IoExceptionFilter(LPEXCEPTION_POINTERS ep) { CONTEXT* c = ep->ContextRecord; UINT8* instr = (UINT8*)c->Eip; int OperandSizeIs16Bit = 0; switch (ep->ExceptionRecord->ExceptionCode) { case EXCEPTION_PRIV_INSTRUCTION: if (instr[0] == 0x66) { OperandSizeIs16Bit = 1; instr++; } switch (instr[0]) { case 0xE4: // IN AL, imm8 *(UINT8*)&c->Eax = ReadPort(instr[1], 8); c->Eip += 2 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xE5: // IN (E)AX, imm8 if (OperandSizeIs16Bit) *(UINT16*)&c->Eax = ReadPort(instr[1], 16); else c->Eax = ReadPort(instr[1], 32); c->Eip += 2 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xEC: // IN AL, DX *(UINT8*)&c->Eax = ReadPort((UINT16)c->Edx, 8); c->Eip += 1 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xED: // IN (E)AX, DX if (OperandSizeIs16Bit) *(UINT16*)&c->Eax = ReadPort((UINT16)c->Edx, 16); else c->Eax = ReadPort((UINT16)c->Edx, 32); c->Eip += 1 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xE6: // OUT imm8, AL WritePort(instr[1], 8, (UINT8)c->Eax); c->Eip += 2 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xE7: // OUT imm8, (E)AX if (OperandSizeIs16Bit) WritePort(instr[1], 16, (UINT16)c->Eax); else WritePort(instr[1], 32, c->Eax); c->Eip += 2 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xEE: // OUT DX, AL WritePort((UINT16)c->Edx, 8, (UINT8)c->Eax); c->Eip += 1 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; case 0xEF: // OUT DX, (E)AX if (OperandSizeIs16Bit) WritePort((UINT16)c->Edx, 16, (UINT16)c->Eax); else WritePort((UINT16)c->Edx, 32, c->Eax); c->Eip += 1 + OperandSizeIs16Bit; return EXCEPTION_CONTINUE_EXECUTION; default: return EXCEPTION_CONTINUE_SEARCH; } default: return EXCEPTION_CONTINUE_SEARCH; } } int main(void) { __try { outp(0x278, 0x00); printf("portb=0x%X\n", inp(0)); outp(0x278, 0x55); printf("portb=0x%X\n", inp(0)); outp(0x278, 0xFF); printf("portb=0x%X\n", inp(0)); outpw(0x278, 0xAAAA); printf("portw=0x%X\n", inpw(0)); outpd(0x278, 0x12345678); printf("portd=0x%X\n", inpd(0)); outpw(0x278, 0xAAAA); outp(0x278, 0x55); printf("portd=0x%X\n", inpd(0)); } __except(IoExceptionFilter(GetExceptionInformation())) { } return 0; }

输出：

C:\>PortEmu.exe portb=0x0 portb=0x55 portb=0xFF portw=0xAAAA portd=0x12345678 portd=0x1234AA55

只需改变实施 ReadPort（）和 WritePort（）做一些更有用或更符合打印机端口操作。

Just alter the implementation of ReadPort() and WritePort() to do something more useful or more in line with the printer port operation.