A brainfuck interpreter

In case you didn't know, there's an esoteric programming language named brainfuck. It is quite simple and I thought I should make an interpreter for it, in C. It is nowhere near the sub-200 bytes compilers others have made, but it's a good exercise. Well, here's my solution: /* A brainfuck intepreter written in C, complete with error checking so you don't hurt yourself while, uh, brainfucking. Nothing really special about the implementation and it is probably very poor performance-wise. Author: Felix Oghină License: (brain)fuck licenses! */ #include <stdio.h> #include <stdlib.h> #include <string.h> // by brainfuck standards (doesn't that sound funny?), the data pointer has // 30,000 bytes at its disposal, but I hate hard-coding such stuff. #define DATA_SIZE 30000 void usage() { puts( "Usage: brainfuck FILE\n" "If FILE is ommited or is '-', standard input is read" ); } int main(int argc, char **argv) { // used by the bf program unsigned char *dataptr = malloc(sizeof(char) * DATA_SIZE); // position of the data pointer unsigned int datapos = 0; // input file FILE *input; // level - deepness of brackets // i - uh, you need explanation for this one? unsigned int level, i; // we will read chars from the input into r unsigned char r; // determine input if (argc == 2) { if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0) { usage(); return EXIT_SUCCESS; } else { input = fopen(argv[1], "r"); if (input == NULL) { puts("Error opening input file"); return EXIT_FAILURE; } } } else { usage(); return EXIT_FAILURE; } // zero the data pointer for (i=0; i < DATA_SIZE; i++) { dataptr[i] = 0; } // start interpreting rewind(input); while (!feof(input)) { r = (unsigned char) fgetc(input); switch(r) { case '>': if (datapos < DATA_SIZE - 1) datapos++; else { puts("brainfuck error: pointer overflow"); return EXIT_FAILURE; } break; case '<': if (datapos > 0) datapos--; else { puts("brainfuck error: pointer underflow"); return EXIT_FAILURE; } break; case '+': dataptr[datapos]++; break; case '-': dataptr[datapos]--; break; case '.': putchar(dataptr[datapos]); break; case ',': dataptr[datapos] = getchar(); break; case '[': if (dataptr[datapos] == 0) { level = 1; while (level != 0) { r = (unsigned char) fgetc(input); if (r == '[') level ++; else if (r == ']') level --; } } break; case ']': if (dataptr[datapos] != 0) { level = 1; while (level != 0) { fseek(input, -2, SEEK_CUR); r = (unsigned char) fgetc(input); if (r == ']') level ++; else if (r == '[') level --; } } break; } } return EXIT_SUCCESS; }

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Well, guess it's time to fill up that swear jar now.