/* Code for exercise 5.8. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/// Note: Some compilers do not like the repeated "for (int k ..."// statement. A common trick to work around that anachronism, is to// define the following macro:// #define for if (0) ; else for#include <iostream>#include <time.h> // For clock()#include <stddef.h> // For size_t#include <string.h> // For memcpy()void copy_with_pointers(char const *src, char *dst,                        size_t n) {   for (size_t k = 0; k!=n; ++k)      *dst++ = *src++;}void copy_with_indices(char const *src, char *dst,                       size_t n) {   for (size_t k = 0; k!=n; ++k)      dst[k] = src[k];}int main() {   int const n_bytes = 100000;   int const n_calls = 100;   char *src = new char[n_bytes];   char *dst = new char[n_bytes];   // Reduce paging effects by accessing all bytes:   memcpy(dst, src, n_bytes);   clock_t start, end, reftime;   // Test 1 (reference time)   start = clock();   for (int k = 0; k!=n_calls; ++k)      memcpy(dst, src, n_bytes);   end = clock();   reftime = end-start;   // Test 2 (pointers)   start = clock();   for (int k = 0; k!=n_calls; ++k)      copy_with_pointers(src, dst, n_bytes);   end = clock();   cout << "With pointers: "        << static_cast<double>(end-start)/reftime        << " times slower than memcpy.\n";   // Test 3 (indices)   start = clock();   for (int k = 0; k!=n_calls; ++k)      copy_with_indices(src, dst, n_bytes);   end = clock();   cout << "With indices: "        << static_cast<double>(end-start)/reftime        << " times slower than memcpy.\n";   delete[] src;   delete[] dst;   return 0;}