Small Brainfuck interpreter in C++

bf.cxx

#include <iostream>
#include <fstream>
#include <cstring>

namespace bfck {
    #define BRAINFUCK_ARRAY_SIZE 30000
    void interpretFile(const char *);
    void eval(int = 0);
    char bfa[BRAINFUCK_ARRAY_SIZE];
    int  bptr;
    std::string program;
}

int main(int argc, const char *argv[])
{
    argv++;
    while (--argc > 0) {
        bfck::interpretFile(*argv);
        argv++;
    }
    return 0;
}

using namespace std;

void bfck::interpretFile(const char *filename)
{
    ifstream file(filename);
    memset(bfck::bfa, 0, BRAINFUCK_ARRAY_SIZE);
    string line;
    while (getline(file, line)) {
        bfck::program += line;
    }
    file.close();
    bfck::eval();
}

void bfck::eval(int from)
{
    using bfck::bptr;
    using bfck::bfa;
    using bfck::program;

    bptr = 0;
    int pc = from;
    char ch;
    int l;

    while ((ch = program[pc]) != '\0') { 
        switch (ch) {
        case '[':
        if (bfa[bptr] == 0) {
            l = 1;
            while (l > 0 && program[pc] != '\0') {
                pc++;
                if (program[pc] == '[') {
                    l++;
                } else if (program[pc] == ']') {
                    l--;
                }
            }
        }
        break;

        case ']':
            l = 1;
            while (l > 0 && pc > 0) {
                pc--;
                if (program[pc] == '[') {
                    l--;
                } else if (program[pc] == ']') {
                    l++;
                }
            }
            pc--;
        break;

        case '>':
            if (bptr >= BRAINFUCK_ARRAY_SIZE)
                bptr = 0;
            else 
                bptr++;
        break;

        case '<':
            if (bptr <= 0)
                bptr = BRAINFUCK_ARRAY_SIZE-1;
            else 
                bptr--;
        break;

        case '+':
            bfa[bptr]++;
        break;

        case '-':
            bfa[bptr]--;
        break;

        case '.':
           printf("%c", bfa[bptr]);
        break;

        case ',':
           bfa[bptr] = getc(stdin);
        break;

        default: break;
        }
        pc++;
    }
}