Simple brainfuck interpreter in C

brainfuck.c

#include <string.h>
#include <stdio.h>

#define MEM_SIZE 30000

char mem[MEM_SIZE] = {0};
char *memp = mem;

void bf_eval(char *code, int len, FILE *in, FILE *out)
{
    int ip = 0;

    while (ip < len) {
        switch (code[ip]) {
            case '+':
                ++*memp;
                break;
            case '-':
                --*memp;
                break;
            case '>':
                memp++;
                break;
            case '<':
                memp--;
                break;
            case '.':
                putc(*(int *)memp, out);
                break;
            case ',':
                *memp = getc(in);
                break;
            case '[':
                if (*memp == 0) {
                    int depth = 1;
                    while (depth != 0) {
                        ip++;
                        if (code[ip] == '[') {
                            depth++;
                        } else if (code[ip] == ']') {
                            depth--;
                        }
                    }
                }
                break;
            case ']':
                if (*memp != 0) {
                    int depth = 1;
                    while (depth != 0) {
                        ip--;
                        if (code[ip] == ']') {
                            depth++;
                        } else if (code[ip] == '[') {
                            depth--;
                        }
                    }
                }
                break;
        }

        ip++;
    }
}

int main(int argc, char *argv[])
{
    char *test_code = "+++>++>++>++>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++..";
    bf_eval(test_code, strlen(test_code), stdin, stdout);
    printf("\n----------\n");
    printf("mem[0]: %d\n", mem[0]);
    printf("mem[1]: %d\n", mem[1]);
    printf("mem[2]: %d\n", mem[2]);
    printf("mem[3]: %d\n", mem[3]);
    printf("\n----------\n");

    // reset memory pointer and memory
    memp = mem;
    memset(mem, 0, MEM_SIZE);

    char *hello_world = "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.";
    bf_eval(hello_world, strlen(hello_world), stdin, stdout);

    return 0;
}