Simple Fast Brainfuck Interpreter

#include <stdio.h>

#define SIZE 30000
#define INDEX (SIZE - 1)

int main(int argc, char *argv[])
{
    if(argc < 2) return 1; // Need a file!
    FILE *file = fopen(argv[1], "r");
    if(!file) return 1;

    char array[SIZE];
    char *ptr = array;
    long int depth = 0;

    while(!feof(file))
    {
        char curr = fgetc(file);
        long int currDepth = depth;
        switch(curr)
        {
            case '>' : ptr = ptr == array + INDEX ? array : ptr + 1; break;
            case '<' : ptr = ptr == array ? array + INDEX : ptr - 1; break;
            case '+' : ++(*ptr); break;
            case '-' : --(*ptr); break;
            case '.' : putchar(*ptr); break;
            case ',' : while((*ptr = getchar()) == '\n'); break;
            case '[' : ++depth; if(!*ptr) while(depth > currDepth) switch(curr = fgetc(file))
            {
                case '[' : ++depth; break;
                case ']' : --depth; break;
            }
            break;
            case ']' : --depth; if(*ptr) while(depth < currDepth)
            {
                fseek(file, -2, SEEK_CUR);
                switch(curr = fgetc(file))
                {
                    case '[' : ++depth; break;
                    case ']' : --depth; break;
                }
            }
            break;
        }
    }

    fclose(file);
    putchar('\n');
    return 0;
}