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  1.  
  2. #include <alloca.h>
  3. #include <assert.h>
  4. #include <stdarg.h>
  5. #include <stdbool.h>
  6. #include <stdio.h>
  7. #include <ffi.h>
  9. void rt_3addiii(int *res, int a, int b)
  10. {
  11. *res = a + b;
  12. }
  14. void rt_3subiii(int *res, int a, int b)
  15. {
  16. *res = a - b;
  17. }
  19. void rt_2eqbii(bool *res, int a, int b)
  20. {
  21. *res = a == b;
  22. }
  24. void rt_2if(bool test, ...)
  25. {
  26. va_list args;
  27. va_start(args, test);
  29. if (!test)
  30. {
  31. int num_skip = va_arg(args, int);
  33. for (int i = 0; i < num_skip; i++)
  34. {
  35. (void) va_arg(args, ffi_type*);
  36. (void) va_arg(args, void*);
  37. }
  38. va_arg(args, void(*)());
  39. }
  41. int num_args = va_arg(args, int);
  43. ffi_cif cif;
  44. ffi_arg ret;
  45. ffi_type **types = alloca(sizeof(ffi_type*) * num_args);
  46. void **values = alloca(sizeof(void(*)()) * num_args);
  48. for (int i = 0; i < num_args; i++)
  49. {
  50. types[i] = va_arg(args, ffi_type*);
  51. values[i] = va_arg(args, void*);
  52. }
  53. void (*fun)() = va_arg(args, void*);
  55. ffi_status result = ffi_prep_cif(&cif, FFI_DEFAULT_ABI, num_args, &ffi_type_void, types);
  56. assert(result == FFI_OK);
  57. ffi_call(&cif, fun, &ret, values);
  58. }
  60. int zero = 0;
  61. int one = 1;
  63. void ack(int *res, int m, int n);
  65. void ack_ret2(int *res, int m)
  66. {
  67. int temp;
  68. rt_3subiii(&temp, m, one);
  69. ack(res, temp, one);
  70. }
  72. void ack_rest2(int *res, int m, int n)
  73. {
  74. int temp1, temp2, temp3;
  75. rt_3subiii(&temp1, n, one);
  76. ack(&temp2, m, temp1);
  77. rt_3subiii(&temp3, m, one);
  78. ack(res, temp3, temp2);
  79. }
  81. void ack_ret1(int *res, int n)
  82. {
  83. rt_3addiii(res, n, one);
  84. }
  86. void ack_rest1(int *res, int m, int n)
  87. {
  88. bool temp;
  89. rt_2eqbii(&temp, n, zero);
  90. rt_2if(temp,
  91. 2, &ffi_type_pointer, &res, &ffi_type_sint32, &m, &ack_ret2,
  92. 3, &ffi_type_pointer, &res, &ffi_type_sint32, &m, &ffi_type_sint32, &n, &ack_rest2
  93. );
  94. }
  96. void ack(int *res, int m, int n)
  97. {
  98. bool temp;
  99. rt_2eqbii(&temp, m, zero);
  100. rt_2if(temp,
  101. 2, &ffi_type_pointer, &res, &ffi_type_sint32, &n, &ack_ret1,
  102. 3, &ffi_type_pointer, &res, &ffi_type_sint32, &m, &ffi_type_sint32, &n, &ack_rest1
  103. );
  104. }
  106. int wrap_ack(int m, int n)
  107. {
  108. int res;
  109. ack(&res, m, n);
  110. return res;
  111. }
  113. int main(int argc, const char *argv[])
  114. {
  115. for (int i = 0; i < 10; ++i)
  116. {
  117. printf("ack(3, 7) = %i\n", wrap_ack(3, 7));
  118. }
  119. }
  120.  
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