aargonian/BFInterpreter
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This commit is contained in:
Aaron Helton
2022-05-28 21:46:43 -04:00
commit 9c952e65ca
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.gitignore vendored Normal file
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#Ignore IDE
.idea/
cmake-build*/

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CMakeLists.txt Normal file
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cmake_minimum_required(VERSION 3.22)
project(BrainfuckInterpretter)
set(CMAKE_CXX_STANDARD 14)
add_executable(BrainfuckInterpretter main.cpp)

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main.cpp Normal file
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#include <iostream>
#include <string>
#define MAX_MEMORY_SIZE 30000
#define RETURN_SUCCESS 0
#define RETURN_INVALID_MEMORY_ADDRESS 1
#define RETURN_INVALID_INSTRUCTION 2
class BFMachine
{
public:
BFMachine();
~BFMachine();
void load(const char *instructions);
int execute();
void reset();
private:
uint8_t* memory;
const char *program{};
size_t programIndex{};
size_t dataIndex{};
int error{};
void increment();
void decrement();
void incrementDataPointer();
void decrementDataPointer();
void printByte();
void readByte();
};
BFMachine::BFMachine()
{
this->memory = new uint8_t[MAX_MEMORY_SIZE];
this->reset();
}
BFMachine::~BFMachine()
{
delete[] memory;
memory = nullptr;
}
void BFMachine::load(const char *instructions)
{
this->program = instructions;
}
void BFMachine::reset()
{
memset(this->memory, 0, sizeof(uint8_t)*MAX_MEMORY_SIZE);
this->dataIndex = 0;
this->programIndex = 0;
this->program = nullptr;
this->error = RETURN_SUCCESS;
}
int BFMachine::execute()
{
if(!this->program)
return RETURN_SUCCESS;
while(this->error == RETURN_SUCCESS && program[programIndex] != '\0')
{
unsigned char command = program[programIndex];
switch(command)
{
case '>': incrementDataPointer(); break;
case '<': decrementDataPointer(); break;
case '+': increment(); break;
case '-': decrement(); break;
case '.': printByte(); break;
case ',': readByte(); break;
case '[':
if(this->memory[this->dataIndex] == 0)
{
uint8_t depth = 1;
while(this->program[programIndex] != ']' || depth != 0)
{
programIndex++;
if(program[programIndex] == '\0')
{
this->error = RETURN_INVALID_INSTRUCTION;
break;
}
if(program[programIndex] == '[')
depth++;
if(program[programIndex] == ']')
depth--;
}
}
break;
case ']':
if(this->memory[this->dataIndex] != 0)
{
uint8_t depth = 1;
while(this->program[programIndex] != '[' || depth != 0)
{
if(programIndex == 0)
{
this->error = RETURN_INVALID_INSTRUCTION;
break;
}
programIndex--;
if(program[programIndex] == '[')
depth--;
if(program[programIndex] == ']')
depth++;
}
}
break;
default:
break;
}
programIndex++;
}
return this->error;
}
void BFMachine::increment()
{
this->memory[this->dataIndex]++;
}
void BFMachine::decrement()
{
this->memory[this->dataIndex]--;
}
void BFMachine::incrementDataPointer()
{
this->dataIndex++;
if(this->dataIndex >= MAX_MEMORY_SIZE)
{
this->error = RETURN_INVALID_MEMORY_ADDRESS;
}
}
void BFMachine::decrementDataPointer()
{
if(this->dataIndex == 0)
{
this->error = RETURN_INVALID_MEMORY_ADDRESS;
return;
}
this->dataIndex--;
}
void BFMachine::printByte()
{
auto c = reinterpret_cast<unsigned char>(this->memory[this->dataIndex]);
std::cout << c;
}
void BFMachine::readByte()
{
unsigned char c;
std::cin >> c;
this->memory[this->dataIndex] = reinterpret_cast<uint8_t>(c);
}
int main()
{
BFMachine machine;
const char* instructions =
"[ This program prints \"Hello World!\" and a newline to the screen, its\n"
" length is 106 active command characters. [It is not the shortest.]\n"
"\n"
" This loop is an \"initial comment loop\", a simple way of adding a comment\n"
" to a BF program such that you don't have to worry about any command\n"
" characters. Any \".\", \",\", \"+\", \"-\", \"<\" and \">\" characters are simply\n"
" ignored, the \"[\" and \"]\" characters just have to be balanced. This\n"
" loop and the commands it contains are ignored because the current cell\n"
" defaults to a value of 0; the 0 value causes this loop to be skipped.\n"
"]\n"
"++++++++ Set Cell #0 to 8\n"
"[\n"
" >++++ Add 4 to Cell #1; this will always set Cell #1 to 4\n"
" [ as the cell will be cleared by the loop\n"
" >++ Add 2 to Cell #2\n"
" >+++ Add 3 to Cell #3\n"
" >+++ Add 3 to Cell #4\n"
" >+ Add 1 to Cell #5\n"
" <<<<- Decrement the loop counter in Cell #1\n"
" ] Loop until Cell #1 is zero; number of iterations is 4\n"
" >+ Add 1 to Cell #2\n"
" >+ Add 1 to Cell #3\n"
" >- Subtract 1 from Cell #4\n"
" >>+ Add 1 to Cell #6\n"
" [<] Move back to the first zero cell you find; this will\n"
" be Cell #1 which was cleared by the previous loop\n"
" <- Decrement the loop Counter in Cell #0\n"
"] Loop until Cell #0 is zero; number of iterations is 8\n"
"\n"
"The result of this is:\n"
"Cell no : 0 1 2 3 4 5 6\n"
"Contents: 0 0 72 104 88 32 8\n"
"Pointer : ^\n"
"\n"
">>. Cell #2 has value 72 which is 'H'\n"
">---. Subtract 3 from Cell #3 to get 101 which is 'e'\n"
"+++++++..+++. Likewise for 'llo' from Cell #3\n"
">>. Cell #5 is 32 for the space\n"
"<-. Subtract 1 from Cell #4 for 87 to give a 'W'\n"
"<. Cell #3 was set to 'o' from the end of 'Hello'\n"
"+++.------.--------. Cell #3 for 'rl' and 'd'\n"
">>+. Add 1 to Cell #5 gives us an exclamation point\n"
">++. And finally a newline from Cell #6";
machine.load(instructions);
int ret = machine.execute();
if(ret != 0)
{
std::cout << "An error occurred. Error is: ";
switch(ret)
{
case RETURN_INVALID_INSTRUCTION:
std::cout << "Invalid Instruction"; break;
case RETURN_INVALID_MEMORY_ADDRESS:
std::cout << "Invalid Memory Access"; break;
default:
std::cout << "Unknown Error"; break;
}
std::cout << std::endl;
std::cout.flush();
}
return ret;
}