ex23.c

#include <stdio.h>
#include <string.h>
#include <time.h>
#include "dbg.h"

#define LAYDUFF(x,y) \
  case (8 * x + y + 1) : *to++ = *from++

#define SEVEN_AT_ONCE(x) \
  LAYDUFF(x,6); \
  LAYDUFF(x,5); \
  LAYDUFF(x,4); \
  LAYDUFF(x,3); \
  LAYDUFF(x,2); \
  LAYDUFF(x,1); \
  LAYDUFF(x,0)

#define EIGHT_AT_ONCE(x)  \
  LAYDUFF(x,7); \
  SEVEN_AT_ONCE(x)

// Time a function call (or any block of code)
//  logs an info message telling how long the call took
#define TIME(M, func_name) do { \
  time_t before, after;  \
  before = time(0);     \
  do {M} while(0);                    \
  after = time(0);      \
  log_info("%s took %.25f seconds", func_name, difftime(before, after));  \
  } while(0)




int normal_copy(char *from, char *to, int count)
{
  int i = 0;

  for(i=0; i< count; i++) {
    to[i] = from[i];
  }

  return i;
}

int duffs_device_32(char *from, char *to, int count)
{
  {
    int n = (count + 31) / 32;

    switch(count % 32) {
      case 0: do{ *to++ = *from++;
                SEVEN_AT_ONCE(3);
                EIGHT_AT_ONCE(2);
                EIGHT_AT_ONCE(1);
                EIGHT_AT_ONCE(0);
             } while(--n > 0);
    }
  }

  return count;
}

int duffs_device_8(char *from, char *to, int count)
{
  {
    int n = (count + 7) / 8;

    switch(count % 8) {
      case 0: do{ *to++ = *from++;
                SEVEN_AT_ONCE(0);
             } while(--n > 0);
    }
  }

  return count;
}


int zeds_device(char *from, char *to, int count)
{
  {
    int n = (count + 7) / 8;

    switch(count % 8) {
      case 0: 
again: *to++ = *from++;

      case 7: *to++ = *from++;
      case 6: *to++ = *from++;
      case 5: *to++ = *from++;
      case 4: *to++ = *from++;
      case 3: *to++ = *from++;
      case 2: *to++ = *from++;
      case 1: *to++ = *from++;
              if(--n > 0) goto again;

    }
  }

  return count;
}

int valid_copy(char *data, int count, char expects)
{
  int i = 0;
  for(i=0; i< count; i++) {
    if(data[i] != expects) {
      log_err("[%d] %c != %c", i, data[i], expects);
    }
  }

  return 1;
}

int main(int argc, char *argv[])
{
  char from[1000] = {'a'};
  char to[1000] = {'c'};
  int rc = 0;

  // setup the from to have some stuff
  memset(from, 'x', 1000);
  // set it to a failure mode
  memset(to, 'y', 1000);

  check(valid_copy(to, 1000, 'y'), "Not initialized right.");

  //use normal copy to

  TIME(rc = normal_copy(from, to, 1000);, "Normal Copy");
  check(rc = 1000, "Normal copy failed: %d", rc);
  check(valid_copy(to,1000, 'x'), "Normal copy failed");

  //reset
  memset(to, 'y', 1000);

  // duffs version 8
  TIME(rc = duffs_device_8(from, to, 1000);, "Duffs Device 8");
  check(rc = 1000, "Duff's device 8 failed: %d", rc);
  check(valid_copy(to, 1000, 'x'), "Duff's device 8 failed copy.");

  //reset
  memset(to, 'y', 1000);

  // duffs version 32
  TIME(rc = duffs_device_32(from, to, 1000);, "Duffs Device 32");
  check(rc = 1000, "Duff's device 32 failed: %d", rc);
  check(valid_copy(to, 1000, 'x'), "Duff's device 32 failed copy.");

  //reset
  memset(to, 'y', 1000);


  // zeds version
  TIME(rc = zeds_device(from, to, 1000);, "Zeds Device 8");
  check(rc = 1000, "Zed's device failed: %d", rc);
  check(valid_copy(to, 1000, 'x'), "Zed's device failed copy.");


  // this is a stupid example, but cool implications
  TIME({ printf("Hello World"); while(0) { printf("asdfasdfa"); } }, "Code block");


  return 0;
error:
  return 1;
}