Initial commit: implementation of the Universal Machine

um.c

@@ -0,0 +1,149 @@
+#include "uthash.h"
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+struct array {
+  uint32_t id;
+  uint32_t *arr;
+  uint32_t size;
+  UT_hash_handle hh;
+};
+
+void allocate_array(struct array **arrays, uint32_t next_id, uint32_t size) {
+  struct array *a;
+  a = malloc(sizeof(struct array));
+  a->id = next_id;
+  a->arr = calloc(size, sizeof(uint32_t));
+  a->size = size;
+  HASH_ADD(hh, *arrays, id, sizeof(uint32_t), a);
+}
+
+struct array *get_array(struct array *arrays, uint32_t id) {
+  struct array *a;
+  HASH_FIND(hh, arrays, &id, sizeof(uint32_t), a);
+  return a;
+}
+
+void free_array(struct array **arrays, uint32_t id) {
+  struct array *a;
+  HASH_FIND(hh, *arrays, &id, sizeof(uint32_t), a);
+  HASH_DEL(*arrays, a);
+  free(a->arr);
+  free(a);
+}
+
+int main(int argc, char **argv) {
+  if (argc < 2) {
+    fprintf(stderr, "Usage: %s <program>\n", argv[0]);
+    return EXIT_SUCCESS;
+  }
+
+  struct stat file_stat;
+  if (stat(argv[1], &file_stat) == -1) {
+    fprintf(stderr, "Could not stat file %s\n", argv[1]);
+    return EXIT_FAILURE;
+  }
+
+  FILE *fp = fopen(argv[1], "rb");
+  if (fp == NULL) {
+    fprintf(stderr, "Could not open file %s\n", argv[1]);
+    return EXIT_FAILURE;
+  }
+
+  uint32_t *program = malloc(file_stat.st_size);
+
+  int c = 0;
+  size_t n = -1;
+  int i = 0;
+  while ((c = fgetc(fp)) != EOF) {
+    if (i == 0) {
+      n++;
+      program[n] = c;
+    } else {
+      program[n] = (program[n] << 8) | c;
+    }
+    i = (i + 1) % 4;
+  }
+  fclose(fp);
+
+  uint32_t reg[8] = {0};       // registers
+  struct array *arrays = NULL; // arrays of platters
+  uint32_t next_id = 1;        // next free index available for a new array
+
+  size_t pc = 0;
+  for (;;) {
+    uint32_t opcode = program[pc] >> 28;
+    uint32_t c = program[pc] & 7;
+    uint32_t b = (program[pc] >> 3) & 7;
+    uint32_t a = (program[pc] >> 6) & 7;
+    /* printf("\n%zu: %u (op=%u, a=%u, b=%u, c=%u)\n", pc, program[pc], opcode, a, b, c); */
+    /* printf("reg[a] = %u, reg[b] = %u, reg[c] = %u\n", reg[a], reg[b], reg[c]); */
+    pc++;
+    switch (opcode) {
+    case 0:
+      if (reg[c]) {
+        reg[a] = reg[b];
+      }
+      break;
+    case 1: {
+      uint32_t *arr = reg[b] ? get_array(arrays, reg[b])->arr : program;
+      reg[a] = arr[reg[c]];
+      break;
+    }
+    case 2: {
+      uint32_t *arr = reg[a] ? get_array(arrays, reg[a])->arr : program;
+      arr[reg[b]] = reg[c];
+      break;
+    }
+    case 3:
+      reg[a] = reg[b] + reg[c];
+      break;
+    case 4:
+      reg[a] = reg[b] * reg[c];
+      break;
+    case 5:
+      reg[a] = reg[b] / reg[c];
+      break;
+    case 6:
+      reg[a] = (~reg[b]) | (~reg[c]);
+      break;
+    case 7:
+      return EXIT_SUCCESS;
+    case 8:
+      allocate_array(&arrays, next_id, reg[c]);
+      reg[b] = next_id;
+      next_id++;
+      break;
+    case 9:
+      free_array(&arrays, reg[c]);
+      break;
+    case 10:
+      putchar(reg[c]);
+      break;
+    case 11:
+      reg[c] = getchar();
+      break;
+    case 12: {
+      if (reg[b]) {
+        free(program);
+        struct array *arr = get_array(arrays, reg[b]);
+        program = malloc(arr->size * sizeof(uint32_t));
+        memcpy(program, arr->arr, arr->size * sizeof(uint32_t));
+      }
+      pc = reg[c];
+      break;
+    }
+    case 13:
+      a = (program[pc - 1] >> 25) & 7;
+      reg[a] = program[pc - 1] & 0x1FFFFFF;
+      break;
+    }
+  }
+  free(program);
+  free(arrays);
+
+  return EXIT_SUCCESS;
+}