[C]Brainfuck Interpreter - Printable Version

Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MEMORY_SIZE 30000

int files = 0;
char ** filelist = 0;
FILE * file = 0;
char * program = 0;
char memory[MEMORY_SIZE];

void print_guide(char * runname);
int file_is_alive(char * name);
void add_file_tolist(char * name);
int decent_character(char character);
int load_program(char * name);
int check_syntax(char * name);
void run_program(char * name);
void endfunction();

int main(int number_of_arguments, char **arguments)
{
    int i;

    atexit(endfunction);

    if (number_of_arguments < 2) {
        print_guide(arguments[0]);
        return EXIT_FAILURE;
    }

    for (i = 1; i < number_of_arguments; ++i) {
        if (file_is_alive(arguments[i])) {
            add_file_tolist(arguments[i]);
        }
        else {
            printf("Error! File %s was not found or it's unable to open!\n", arguments[i]);
            print_guide(arguments[0]);
            return EXIT_FAILURE;
        }
    }

    for (i = 0; i < files; ++i) {
        if (load_program(filelist[i])
        && check_syntax(filelist[i])) {
            run_program(filelist[i]);
        }
    }

    return EXIT_SUCCESS;
}

void print_guide(char * runname)
{
    printf("Brainfuck-compiler 0.1\nAction: %s files\n", runname);
}

int file_is_alive(char * name)
{
    file = fopen(name, "r");
    if (!file) {
        return 0;
    }
    fclose(file);
    return 1;
}

void add_file_tolist(char * name)
{
    /* Expand the list */
    ++files;
    filelist = (char**)realloc(filelist, files * sizeof(char*));
    if (!filelist) {
        printf("Program ran out of memory when creating the file list!\n");
        exit(EXIT_FAILURE);
    }

    /* Allocate memory and put the file name into there */
    filelist[files - 1] = (char*) malloc(strlen(name) + 1);
    if (!filelist[files - 1]) {
        printf("Program ran out of memory when creating the file list!\n");
        exit(EXIT_FAILURE);
    }
    strcpy(filelist[files - 1], name);
}

int decent_character(char character)
{
    if (character == '<') return 1;
    if (character == '>') return 1;
    if (character == '+') return 1;
    if (character == '-') return 1;
    if (character == '.') return 1;
    if (character == ',') return 1;
    if (character == '[') return 1;
    if (character == ']') return 1;
    return 0;
}

int load_program(char * name)
{
    size_t size;
    int i, j;

    file = fopen(name, "r");

    if (!file) {
        printf("Error! File '%s' couldn't be opened!\n", name);
        exit(EXIT_FAILURE);
    }

    /* Measure the file */
    fseek(file, 0, SEEK_END);
    size = ftell(file);
    fseek(file, 0, SEEK_SET);

    /* Release the old code and allocate new */
    if (program) {
        free(program);
    }
    program = (char*)malloc(size + 1);
    if (!program) {
        printf("Error! For the program in the file '%s' was not derived memory.", name);
        exit(EXIT_FAILURE);
    }

    /* Read the whole file */
    if (fread(program, size, 1, file) != 1) {
        printf("Error! File '%s' couldn't be opened!\n", name);
        exit(EXIT_FAILURE);
    }
    program[size] = 0;

    /* Delete characters which are not part of the program */
    for (i = j = 0; program[i] != 0; ++i) {
        if (decent_character(program[i])) {
            program[j] = program[i];
            ++j;
        }
    }
    program[j] = 0;

    return 1;
}

int check_syntax(char * name)
{
    int i, brackets;

    if (!program) {
        return 0;
    }

    /* Count that there are enough brackets for both ways */
    for (i = brackets = 0; program[i] != 0; ++i) {
        if (program[i] == '[') {
            ++brackets;
        }
        else if (program[i] == ']') {
            --brackets;
        }
    }

    if (brackets != 0) {
        printf("There is error in the syntax of the file '%s'!\n", name);
    }

    return brackets == 0;
}

void run_program(char * name)
{
    int position = 0, brackets;
    char *pointer = memory;

    if (!program) {
        return;
    }

    printf("Run '%s'\n", name);

    /* Reset the memory */
    memset(memory, 0, MEMORY_SIZE);

    /* In the end of the text, there is 'zeromark', repeat until that */
    while (program[position] != 0) {
        switch (program[position]) {
            case '>':
                ++pointer;
                break;

            case '<':
                --pointer;
                break;

            case '+':
                ++*pointer;
                break;

            case '-':
                --*pointer;
                break;

            case '.':
                putchar(*pointer);
                fflush(stdout);
                break;

            case ',':
                *pointer = getchar();
                break;

            case '[':
                if (*pointer == 0) {
                    /* Get equivalent closing bracket */
                    brackets = 1;
                    while (brackets) {
                        ++position;
                        if (program[position] == '[') {
                            ++brackets;
                        }
                        else if (program[position] == ']') {
                            --brackets;
                        }
                    }
                }
                break;

            case ']':
                if (*pointer != 0) {
                    /* Get equilevant starting bracket */
                    brackets = 1;
                    while (brackets) {
                        --position;
                        if (program[position] == ']') {
                            ++brackets;
                        }
                        else if (program[position] == '[') {
                            --brackets;
                        }
                    }
                }
                break;
        }
        /* To the next character in the code */
        ++position;
    }
    printf("\nThe end.\n");
}

void endfunction()
{
    int i;
    if (filelist) {
        for (i = 0; i < files; ++i) {
            if (filelist[i]) {
                free(filelist[i]);
            }
        }

        free(filelist);
    }

    if (program) {
        free(program);
    }

    if (file) {
        fclose(file);
    }
}