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// Brainfuck Interpreter
// Reads program from stdin, interprets and outputs to stdout.
//
// Main optimization targets:
// jump table, inline variables, etc.
int program_length = 0;
int program[65536] = {};
int tape[65536] = {};
int input[65536] = {};
int input_length = 0;
int output[65536] = {};
int output_length = 0;
int get_bf_char() {
int get = getch();
while (get != 62 && get != 60 && get != 43 && get != 45 && get != 91 &&
get != 93 && get != 46 && get != 44 && get != 35) {
get = getch();
}
return get;
}
void read_program() {
int get = get_bf_char();
while (get != 35) {
program[program_length] = get;
get = get_bf_char();
program_length = program_length + 1;
}
// read input
// input starts with an `i`
int verify = getch();
if (verify != 105) {
return;
}
// and a length
input_length = getint();
// and a random char
getch();
int i = 0;
while (i < input_length) {
input[i] = getch();
i = i + 1;
}
}
void run_program() {
int ip = 0;
int read_head = 0;
int input_head = 0;
int return_address[512] = {};
int return_address_top = 0;
output_length = 0;
while (ip < program_length) {
int code = program[ip];
if (code == 62) {
read_head = read_head + 1;
} else if (code == 60) {
read_head = read_head - 1;
} else if (code == 43) {
tape[read_head] = tape[read_head] + 1;
} else if (code == 45) {
tape[read_head] = tape[read_head] - 1;
} else if (code == 91) {
int val = tape[read_head];
if (val != 0) {
return_address[return_address_top] = ip;
return_address_top = return_address_top + 1;
} else {
// find the matching ]
int loop = 1;
while (loop > 0) {
ip = ip + 1;
if (program[ip] == 93) {
loop = loop - 1;
}
if (program[ip] == 91) {
loop = loop + 1;
}
}
}
} else if (code == 93) {
int val = tape[read_head];
if (val == 0) {
return_address_top = return_address_top - 1;
} else {
ip = return_address[return_address_top - 1];
}
} else if (code == 46) {
output[output_length] = tape[read_head];
output_length = output_length + 1;
} else if (code == 44) {
if (input_head >= input_length) {
tape[read_head] = 0;
} else {
tape[read_head] = input[input_head];
input_head = input_head + 1;
}
}
ip = ip + 1;
}
}
void output_() {
int i = 0;
while (i < output_length) {
putch(output[i]);
i = i + 1;
}
}
int main() {
read_program();
starttime();
run_program();
stoptime();
output_();
return 0;
}
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