User:Katharine Berry/Scripts/Brainfsck
Pandorabot | Rotating Online Status | SPD Viewer | Brainfsck Interpreter | Force Reload
Contents
About
This script interprets the incredibly useless (but Turing-Complete) Brainfsck language.
Usage
Place the script in a prim. Place a notecard containing the program in the same prim. Say "run Program Name" to start it.
If it states that it is awaiting input, provide input on channel 2 (e.g. by saying "/2 11"). It only listens to the owner.
Script
// LSL brainfsck interpreter v1.0.
// Copyright (c) 2007, Katharine Schomer
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Katharine Schomer nor the names of any contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY KATHARINE SCHOMER ``AS IS'' AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL KATHARINE SCHOMER BE LIABLE FOR ANY
// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Settings
integer STRIP_COMMENTS = FALSE; // If TRUE, comments will be removed while loading. If FALSE, comments are ignored while running.
// Brainfsck VM
list gBytes = [];
integer gPointer = 0;
string gInputBuffer = "";
string gOutputBuffer = "";
string gProgramCommands = "";
list gLoopPoints = [];
integer gCurrentVal = 0;
integer gCurrentInstruction = 0;
// Interpreter stuff
string ASCII_CHARSET = "§§§§§§§§§§\n§§§§§§§§§§§§§§§§§§§§§ !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
string VALID_COMMANDS = "[].,+-<>"; // # is also valid, but isn't included here.
string gProgram = "";
integer gLine = 0;
key gDataserverKey = NULL_KEY;
integer gArraySize = 0;
// Functions
integer GetArrayLength()
{
return llGetListLength(gBytes);
}
integer GetCurrentCellValue()
{
return llList2Integer(gBytes,gPointer);
}
SetCurrentCellValue(integer value)
{
gBytes = llListReplaceList(gBytes,[value],gPointer,gPointer);
}
string chr(integer c)
{
return llGetSubString(ASCII_CHARSET,c,c);
}
integer ord(string c)
{
return llSubStringIndex(ASCII_CHARSET,c);
}
RunProgram()
{
integer i;
integer length = llStringLength(gProgramCommands);
llSay(0,"Entering program flow at instruction "+(string)gCurrentInstruction);
for(i = gCurrentInstruction; i < length; ++i)
{
string command = llGetSubString(gProgramCommands,i,i);
if(command == ">")
{
SetCurrentCellValue(gCurrentVal);
++gPointer;
gCurrentVal = GetCurrentCellValue();
}
else if(command == "<")
{
SetCurrentCellValue(gCurrentVal);
--gPointer;
gCurrentVal = GetCurrentCellValue();
}
else if(command == "+")
{
++gCurrentVal;
}
else if(command == "-")
{
--gCurrentVal;
}
else if(command == ".")
{
if(gCurrentVal == 10)
{
llSay(0,gOutputBuffer);
gOutputBuffer = "";
}
else
{
gOutputBuffer += chr(gCurrentVal);
}
}
else if(command == ",")
{
if(gInputBuffer == "")
{
gCurrentInstruction = i;
llSay(0,"Awaiting input: ");
return;
}
else
{
gCurrentVal = ord(llGetSubString(gInputBuffer,0,0));
if(gCurrentVal == 0) gInputBuffer = "";
else gInputBuffer = llDeleteSubString(gInputBuffer,0,0);
}
}
else if(command == "[")
{
if(gCurrentVal != 0)
{
gLoopPoints = (gLoopPoints = []) + gLoopPoints + [i];
}
else
{
integer depth = 1;
while(i != -1 && depth)
{
command = llGetSubString(gProgramCommands,++i,i);
if(command == "[")
{
++depth;
}
else if(command == "]")
{
--depth;
}
}
if(command != "]")
{
llSay(0,"FATAL ERROR: Missing ]. Terminating program.");
llResetScript();
}
}
}
else if(command == "]")
{
integer len = llGetListLength(gLoopPoints);
if(len == 0)
{
llSay(0,"FATAL ERROR: Encountered ] at "+(string)i+" without leading [. Terminating program.");
llResetScript();
}
i = llList2Integer(gLoopPoints, -1) - 1;
gLoopPoints = llDeleteSubList(gLoopPoints, -1,-1);
}
else if(command == "#")
{
llSay(0,"gPointer = "+(string)gPointer+" | gCurrentVal = "+(string)gCurrentVal+" | gInputBuffer = \""+(string)gInputBuffer+"\" | gOutputBuffer = \""+(string)gOutputBuffer+"\"");
llSay(0,"gLoopPoints = ["+llList2CSV(gLoopPoints)+"]");
llSay(0,"gBytes = ["+llList2CSV(gBytes)+"]");
}
}
if(gOutputBuffer != "")
{
llSay(0,gOutputBuffer);
}
llSay(0,"Program execution complete.");
llResetScript();
}
default
{
state_entry()
{
llSay(0,"Initialising...");
if(ord("\n") != 10 || chr(10) != "\n" || ord("P") != 80 || chr(80) != "P")
{
llSay(0,"Failed system test: ASCII table inaccurate.");
return;
}
for(gPointer = 0; gPointer < 125; ++gPointer)
{
gBytes = (gBytes = [])+gBytes+[0,0];
gArraySize += 8;
}
gPointer = 0;
gDataserverKey = NULL_KEY;
gLine = 0;
gProgram = "";
llSay(0,"Ready. BF VM: 250 bytes free. LSL VM: "+(string)llGetFreeMemory()+" bytes free.");
llListen(0,"",llGetOwner(),"");
}
listen(integer channel, string name, key id, string message)
{
if(llGetSubString(message,0,3) == "run ")
{
string program = llGetSubString(message,4,-1);
if(llGetInventoryType(program) == INVENTORY_NOTECARD)
{
gProgram = program;
state loading;
}
else
{
llSay(0,"Could not load "+program+"!");
}
}
}
}
state loading
{
state_entry()
{
llSay(0,"Loading and preprocessing "+gProgram+"...");
gProgramCommands = "";
gDataserverKey = llGetNotecardLine(gProgram,gLine++);
}
dataserver(key id, string data)
{
if(id != gDataserverKey) return;
if(data == EOF)
{
llSay(0,"Loaded program ("+(string)llStringLength(gProgramCommands)+" bytes); starting interpreter.");
state running;
return;
}
data = llStringTrim(data,STRING_TRIM);
if(STRIP_COMMENTS)
{
integer i;
integer length = llStringLength(data);
for(i = 0; i < length; ++i)
{
string char = llGetSubString(data,i,i);
if(~llSubStringIndex(VALID_COMMANDS,char))
{
gProgramCommands += char;
}
}
}
else
{
gProgramCommands += data;
}
gDataserverKey = llGetNotecardLine(gProgram,gLine++);
}
}
state running
{
state_entry()
{
llSay(0,"Setting up input stream...");
llListen(2,"",llGetOwner(),"");
llSay(0,"I/O ready. Beginning execution now.");
gCurrentInstruction = 0;
RunProgram();
}
listen(integer channel, string name, key id, string message)
{
if(message == "EOF")
{
gInputBuffer += "§";
}
else
{
gInputBuffer += message+"\n";
}
RunProgram();
}
}
Hello, World!
This is a nicely commented "Hello world!" in Brainfsck, courtesy Wikipedia. Please note that it takes about a minute to run.
++++++++++ [>+++++++>++++++++++>+++>+<<<<-] The initial loop to set up useful values in the array >++. Print 'H' >+. Print 'e' +++++++. Print 'l' . Print 'l' +++. Print 'o' >++. Print ' ' <<+++++++++++++++. Print 'W' >. Print 'o' +++. Print 'r' ------. Print 'l' --------. Print 'd' >+. Print '!' >. Print newline
Flaws
- The original compiler had 30,000 bytes of memory. Due to technical restrictions, this version has 250. (Could be raised to ~1000 at the expense of some speed)
- Due to Second Life limitations, input is line-at-a-time. All input will have a trailing "\n" (ASCII code 10) added to the end. For an EOF, either say "EOF" or "§".
- Bounds checks, which were originally implemented, were removed for speed reasons.
- It's inherently slow anyway, given it runs a highly inefficient language on a slow virtual machine.
