Sup*_*tar 4 java parsing esoteric-languages brainfuck
我正在尝试用Java编写一个可以读取,编译和运行brainfuck源文件的程序(.bf).我已经让它与维基百科的Hello World示例一起工作得很好,但它打破了ROT13的例子(声称]它在实际匹配时达到了无与伦比的效果).
实际的解析器代码都写在一个.JAVA文件中,但它的核心(实际的brainfuck解析器和运行代码)在下面的方法中,doNow(char).以下是变量的含义:cells是要运行的字符数组(char[]); pointer是指向array(short)中的地址的Java变通方法; PC是程序计数器(int),并且loopStack是对应于[s(基本上是a short[])的地址堆栈.这些不是问题,因为它们在Hello World测试中工作得很好.采取输入的方法自动过滤掉多余的字符,我确认它可以从调试检查中完美地工作.
为什么这个解析器不运行ROT 13代码？
我的解析器,用Java编写
/** The array of data */
private byte[] cells = new byte[Short.MAX_VALUE];
/** The pointer that is manipulated by the user or program */
private short pointer = 0;
/** The program counter, to run compiled programs */
private int PC = 0;
/** The compiled commands */
private ArrayPP<Character> commandBuffer = new ArrayPP<>();
/** The stack of locations of loop brackets ({@code [}) in the command buffer */
private ArrayPP<Short> loopStack = new ArrayPP<>();//ArrayPP is my proprietary augmented array object, which also functions as a perfectly working stack.
public int doNow(char command) throws IOException
{
PC++;
switch (command)
{
case '>':
return ++pointer;
case '<':
return --pointer;
case '+':
return ++cells[pointer];
case '-':
return --cells[pointer];
case '.':
System.out.print((char)cells[pointer]);
return 0;
case ',':
return cells[pointer] = (byte)System.in.read();
case '[':
if (cells[pointer] == 0)//If we're ready to skip this conditional
{
int oldPC = PC;
try
{
while (getCompiledCommand(PC) != ']')//Find the matching ]
PC++;
PC++;//Now that we're at the ], skip over it to the next command
}
catch (ArrayIndexOutOfBoundsException e)
{
throw new NullPointerException("Unmatched '[' at " + oldPC);//If we try to reference a command outside the buffer
}
}
else//if we want to enter this conditional
loopStack.push(PC - 1);//Add the location of this conditional to the list of conditionals which we are in
return PC;
case ']':
try
{
return PC = loopStack.pop();//Move us to the matching [ and remove it from the list of conditionals we're in
}
catch (ArrayIndexOutOfBoundsException e)
{
throw new NullPointerException("Unmatched ] at " + PC);//If the loop stack is empty
}
default:
throw new AssertionError(command + " is not a valid command.");
}
}
public char getCompiledCommand(int commandIndex)
{
return commandBuffer.get(commandIndex);//Look into the buffer of precompiled commands and fetch the one at the given index
}
Hello World示例(完美运行)
+++++ +++++ initialize counter (cell #0) to 10
[ use loop to set the next four cells to 70/100/30/10
> +++++ ++ add 7 to cell #1
> +++++ +++++ add 10 to cell #2
> +++ add 3 to cell #3
> + add 1 to cell #4
<<<< - decrement counter (cell #0)
]
> ++ . print 'H'
> + . print 'e'
+++++ ++ . print 'l'
. print 'l'
+++ . print 'o'
> ++ . print ' '
<< +++++ +++++ +++++ . print 'W'
> . print 'o'
+++ . print 'r'
----- - . print 'l'
----- --- . print 'd'
> + . print '!'
> . print '\n'
ROT 13示例(我的测试控制台输入是M.在几次循环迭代后中断命令54)
-,+[ Read first character and start outer character reading loop
-[ Skip forward if character is 0
>>++++[>++++++++<-] Set up divisor (32) for division loop
(MEMORY LAYOUT: dividend copy remainder divisor quotient zero zero)
<+<-[ Set up dividend (x minus 1) and enter division loop
>+>+>-[>>>] Increase copy and remainder / reduce divisor / Normal case: skip forward
<[[>+<-]>>+>] Special case: move remainder back to divisor and increase quotient
<<<<<- Decrement dividend
] End division loop
]>>>[-]+ End skip loop; zero former divisor and reuse space for a flag
>--[-[<->+++[-]]]<[ Zero that flag unless quotient was 2 or 3; zero quotient; check flag
++++++++++++<[ If flag then set up divisor (13) for second division loop
(MEMORY LAYOUT: zero copy dividend divisor remainder quotient zero zero)
>-[>+>>] Reduce divisor; Normal case: increase remainder
>[+[<+>-]>+>>] Special case: increase remainder / move it back to divisor / increase quotient
<<<<<- Decrease dividend
] End division loop
>>[<+>-] Add remainder back to divisor to get a useful 13
>[ Skip forward if quotient was 0
-[ Decrement quotient and skip forward if quotient was 1
-<<[-]>> Zero quotient and divisor if quotient was 2
]<<[<<->>-]>> Zero divisor and subtract 13 from copy if quotient was 1
]<<[<<+>>-] Zero divisor and add 13 to copy if quotient was 0
] End outer skip loop (jump to here if ((character minus 1)/32) was not 2 or 3)
<[-] Clear remainder from first division if second division was skipped
<.[-] Output ROT13ed character from copy and clear it
<-,+ Read next character
] End character reading loop
说清楚,这是它打破的地方:
>[+[<+>-]>+>>] Special case: increase remainder / move it back to divisor / increase quotient
^