Fully functional brainfuck evaluator

c/meltdown.c

@@ -0,0 +1,74 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+uint16_t compile(const char *prog, uint8_t *tape, uint16_t tape_len, uint8_t **idx, uint8_t eval) {
+  uint16_t elapsed = 1;
+
+  while(*prog) {
+    uint16_t traveled = 1;
+
+    if(eval && *prog == '>') {
+      if(*idx == tape + tape_len) {
+        *idx = tape;
+      } else {
+        *idx += 1;
+      }
+    } else if(eval && *prog == '<') {
+      if(*idx == tape) {
+        *idx = tape + tape_len;
+      } else {
+        *idx -= 1;
+      }
+    } else if(eval && *prog == '+') {
+      if(**idx == (2 << 7) - 1) {
+        **idx = 0;
+      } else {
+        **idx += 1;
+      }
+    } else if(eval && *prog == '-') {
+      if(**idx == 0) {
+        **idx = (2 << 7) - 1;
+      } else {
+        **idx -= 1;
+      }
+    } else if(eval && *prog == '.') {
+      putchar(**idx);
+    } else if(eval && *prog == ',') {
+      **idx = getchar();
+    } else if(*prog == '[') {
+      uint8_t should_eval = **idx > 0;
+
+      if(!eval) {
+        should_eval = 0;
+      }
+
+      traveled = compile(prog + 1, tape, tape_len, idx, should_eval);
+    } else if(*prog == ']') {
+      if(**idx > 0) {
+        return 0;
+      } else {
+        return elapsed + 1;
+      }
+    }
+
+    elapsed += traveled;
+    prog += traveled;
+  }
+
+  return 0;
+}
+
+int main(int argc, char **argv) {
+  if(argc != 2) {
+    return 1;
+  }
+
+  const char *prog = argv[1];
+  uint8_t tape[30000] = { 0 };
+  uint16_t tape_len = sizeof(tape);
+  uint8_t *idx = tape;
+  uint8_t eval = 1;
+
+  compile(prog, tape, tape_len, &idx, eval);
+}