Brainfuck parser in C using seeks.

brainfuck.c

#include <stdio.h>
#include <stdlib.h>

static char *ptr;

int do_command(const char command, FILE *pFile)
{
	char c;
	int pos;

	switch (command)
	{
		case '>':
			++ptr; // Move to next cell
		break;
		
		case '<':
			--ptr; // Move to previous cell
		break;

		case '+':
			++*ptr; // Increment cell
		break;

		case '-':
			--*ptr; // Decrement cell
		break;

		case '.':
			putchar(*ptr); // Print character
		break;

		case '[':
			pos = ftell(pFile); // Get position of [

			// Perform the loop the times defined in the current cell
			while (*ptr) 
			{
				fseek(pFile, pos, SEEK_SET); // Reset seek to the [
				c = getc(pFile); // Get the character

				while (c != ']' && c != EOF) // While it's not end of the loop nor end of file
				{
					do_command(c, pFile); // Execute commands
					c = getc(pFile); // Get the next character
				}
			}
		break;
	}
}

int parse_source(const char *source)
{
	char command; // Stores each command
	FILE *pFile = fopen(source, "r");

	if (pFile) // If we were able to open the file
	{
		while ((command = getc(pFile)) != EOF) // For each character in file
		{
			do_command(command, pFile); // Execute command
		}
	}
	else
	{
		puts("Not able to open file.");
	}

	fclose(pFile);
}

int main(int argc, const char *argv[])
{
	int memory[9001]; // Make array to store values in
	ptr = &memory; // Put it into the global pointer

	parse_source(argv[1]); // Parse the source file defined in argument
	return 0;
}