snippets/C/mmap-mem.c

   1 /*
   2  * Memory allocation with mmap()
   3  *
   4  * Luiz Fernando N. Capitulino
   5  * <lcapitulino@gmail.com>
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <stdarg.h>
  12 #include <sys/mman.h>
  13
  14 #define DEFAULT_SIZE 10 /* will be 10k */
  15
  16 static void print(const char *msg, ...)
  17 {
  18         va_list params;
  19
  20         fputs("-> ", stderr);
  21
  22         va_start(params, msg);
  23         vfprintf(stderr, msg, params);
  24         va_end(params);
  25
  26         getchar();
  27 }
  28
  29 int main(int argc, char *argv[])
  30 {
  31         char *p;
  32         size_t bytes;
  33
  34         bytes = DEFAULT_SIZE;
  35         if (argc == 2)
  36                 bytes = (size_t) strtol(argv[1], NULL, 10);
  37
  38         bytes *= 1024;
  39
  40         print("Will allocate %d kBytes", bytes / 1024);
  41
  42         p = mmap(NULL, bytes, PROT_READ | PROT_WRITE,
  43                  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  44         if (p == MAP_FAILED) {
  45                 perror("mmap()");
  46                 exit(1);
  47         }
  48
  49         memset(p, 0, bytes);
  50
  51         print("Allocated %d kBytes", bytes / 1024);
  52
  53         munmap(p, bytes);
  54
  55         print("Memory is now freed");
  56
  57         return 0;
  58 }