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  1. // Join items on output stream. (2.00)
  2.  
  3. #include <stdlib.h>
  4. #include <string.h>
  5. #include <assert.h>
  6. #include <stdio.h>
  7.  
  8. // Utility.
  9.  
  10. void *xmalloc(size_t n)
  11. {
  12.     void *p = malloc(n);
  13.     assert(p != 0 || n == 0);
  14.     return p;
  15. }
  16.  
  17. void iter_swap(void *a, void *b, size_t n)
  18. {
  19.     char *x = a;
  20.     char *y = b;
  21.     for (size_t i = 0; i < n; i++) {
  22.         char t = x[i]; x[i] = y[i]; y[i] = t;
  23.     }
  24. }
  25.  
  26. void *reverse(void *base, size_t nitems, size_t itemsize)
  27. {
  28.     char *first = base, *last = first + nitems*itemsize;
  29.     if (first != last) {
  30.         for (;;) {
  31.             last -= itemsize;
  32.             if (first >= last) break;
  33.             iter_swap(first, last, itemsize);
  34.             first += itemsize;
  35.         }
  36.     }
  37.     return base;
  38. }
  39.  
  40. void *reverse_copy(const void *source, size_t nitems, size_t itemsize, void *dest)
  41. {
  42.     return reverse(memmove(dest, source, nitems*itemsize), nitems, itemsize);
  43. }
  44.  
  45. void ostream_join(const void *base, size_t nitems, size_t itemsize,
  46.                   void (*putitem)(const void *item, FILE *stream),
  47.                   const char* separator, FILE *stream)
  48. {
  49.     const char *first = base, *last = first + nitems*itemsize;
  50.     if (first != last) {
  51.         for (;;) {
  52.             putitem(first, stream);
  53.             first += itemsize;
  54.             if (first == last) break;
  55.             fputs(separator, stream);
  56.         }
  57.     }
  58. }
  59.  
  60. // Use.
  61.  
  62. void putint(const void *item, FILE *stream)
  63. {
  64.     fprintf(stream, "%d", *(const int *) item);
  65. }
  66.  
  67. void print_ints(const int *a, size_t n, int end)
  68. {
  69.     putchar('[');
  70.     ostream_join(a, n, sizeof *a, putint, ", ", stdout);
  71.     putchar(']');
  72.     putchar(end);
  73. }
  74.  
  75. void print_ints_backward(const int *a, size_t n, int end)
  76. {
  77.     int *temp = reverse_copy(a, n, sizeof *a, xmalloc(n * sizeof *a));
  78.     print_ints(temp, n, end);
  79.     free(temp);
  80. }
  81.  
  82. int main(void)
  83. {
  84.     int a[] = {1, 2, 3, 4};
  85.     print_ints(a, sizeof a / sizeof *a, '\n');
  86.     print_ints_backward(a, sizeof a / sizeof *a, '\n');
  87.     return 0;
  88. }
Success #stdin #stdout 0.01s 5280KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
[1, 2, 3, 4]
[4, 3, 2, 1]
https://ideone.com/ifkEhZ
language:
C (gcc 8.3)
created:
11 days ago
visibility:
public

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