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/*
* MIT License
*
* Copyright (c) 2017 Michael VanOverbeek and ShiftOS devs
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ShiftOS.Engine
{
/// <summary>
/// Receives events from the interpreter.
/// </summary>
public interface IBFListener
{
void PointerMoved(ushort newval);
void IPtrMoved(int newval);
void MemChanged(ushort pos, byte newval);
void MemReset();
}
/// <summary>
/// Interprets Brainfuck code.
/// </summary>
public class BFInterpreter
{
private byte[] mem;
private ushort ptr;
private string prg;
private object lck;
private Stream str;
public IBFListener lst = null;
private static byte[] newline = Encoding.UTF8.GetBytes(Environment.NewLine);
public BFInterpreter(Stream io, IBFListener listener = null, string program = "")
{
lck = new object();
prg = program;
str = io;
Reset();
lst = listener;
}
public void Execute(string program, int offset = 0)
{
int c = 0;
lock (lck)
while (c < program.Length)
{
switch (program[c++])
{
case '<':
ptr--;
if (lst != null)
lst.PointerMoved(ptr);
break;
case '>':
ptr++;
if (lst != null)
lst.PointerMoved(ptr);
break;
case '+':
mem[ptr]++;
if (lst != null)
lst.MemChanged(ptr, mem[ptr]);
break;
case '-':
mem[ptr]--;
if (lst != null)
lst.MemChanged(ptr, mem[ptr]);
break;
case '.':
if (mem[ptr] == 10)
str.Write(newline, 0, newline.Length); // normalise newline
else
str.WriteByte(mem[ptr]);
break;
case ',':
mem[ptr] = (byte)str.ReadByte();
if (mem[ptr] == 13)
mem[ptr] = 10; // normalise newline
if (lst != null)
lst.MemChanged(ptr, mem[ptr]);
break;
case '[':
int b;
int oldc = c;
for (b = 1; b != 0 && c < program.Length; c++)
{
if (program[c] == '[')
b++;
else if (program[c] == ']')
b--;
}
if (b == 0)
{
string block = program.Substring(oldc, c - oldc - 1);
while (mem[ptr] != 0)
Execute(block, offset + oldc);
}
break;
case ']':
throw new Exception("Unbalanced brackets");
}
if (lst != null)
lst.IPtrMoved(offset + c);
}
}
public void Execute()
{
Execute(prg);
}
public void Reset()
{
lock (lck)
{
mem = new byte[30000];
ptr = 0;
if (lst != null)
{
lst.MemReset();
lst.PointerMoved(0);
}
}
}
}
}
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