【海贼王编程冒险 - C语言海上篇】库函数怎样模拟实现？

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
int MyStrlen(char* str)
{
  int len = 0;
 
  while (str[len] != '\0')
    len++;
 
  return len;
}
 
int main()
{
  char str[50] = { "Hello,world!" };
 
  int ans = MyStrlen(str);
 
  printf("%d\n", ans);
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
char* MyStrcpy(char* str2, char* str1)
{
  char* p = str2;
 
  while (*p++ = *str1++)
    ;
 
  return str2;
}
 
int main()
{
  char str1[50] = { "Hello,world!" };
  char str2[50];
 
  MyStrcpy(str2, str1);
 
  printf("%s\n", str2);
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
int MyStrcmp(const char* str1, const char* str2)
{
  int i = 0;
  while (str1[i] != '\0' && str2[i] != '\0' && str1[i] == str2[i])
    i++;
 
  return str1[i] - str2[i];
}
 
int main()
{
  const char* str1 = "apple";
  const char* str2 = "banana";
  const char* str3 = "apple";
 
  int ans1 = MyStrcmp(str1, str2);
  int ans2 = MyStrcmp(str1, str3);
 
  printf("%d\n%d", ans1, ans2);
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
char* MyStrcat(char* str1, const char* str2)
{
  char* re = str1;
  while (*str1)
    str1++;
 
  while (*str2)
  {
    *str1 = *str2;
    str1++;
    str2++;
  }
 
  *str1 = '\0';
 
  return re;
}
 
int main()
{
  char str1[50] = "Hello,";
  const char* str2 = "world!";
 
  printf("%s\n", MyStrcat(str1, str2));
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
char* MyStrstr(const char* str1, const char* str2)
{
  if (*str2 == '\0')
    return (char*)str1;
 
  while (*str1)
  {
    const char* s1 = str1;
    const char* s2 = str2;
 
    while (*s1 && *s2 && (*s1 == *s2))
    {
      s1++;
      s2++;
    }
 
    if (*s2 == '\0')
      return (char*)str1;
 
    str1++;
  }
 
  return NULL;
}
 
int main()
{
  const char* str1 = "Hello world";
  const char* str2 = "world";
 
  char* ans = MyStrstr(str1, str2);
 
  if (ans)
    printf("%ld\n", ans - str1);
  else
    printf("没找到\n");
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
 
void* MyMemcpy(void* brr, const void* arr, size_t size)
{
  char* b = (char*)brr;
  const char* a = (const char*)arr;
 
  for (size_t i = 0; i < size; i++)
    b[i] = a[i];
 
  return brr;
}
 
int main()
{
  int arr[] = { 1, 2, 3, 4, 5 };
  int brr[5] = { 0 };
 
  MyMemcpy(brr, arr, sizeof(brr));
 
  int size = sizeof(brr) / sizeof(brr[0]);
 
  for (int i = 0; i < size; i++)
  {
    printf("%d ", brr[i]);
  }
 
  return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
 
#include <stdio.h>
#include <string.h>
#include <cassert>
 
void* MyMemmove(void* dest, const void* src, size_t size)
{
  assert(dest && src);
  char* ret = (char*)dest;
  if (dest < src)
  {
    while (size--)
    {
      *(char*)dest = *(char*)src;
      dest = (char*)dest + 1;
      src = (char*)src + 1;
    }
  }
  else if (dest > src)
  {
    while (size--)
    {
      *((char*)dest + size) = *((char*)src + size);
    }
  }
  return ret;
}
 
int main()
{
  int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9,10 };
 
  MyMemmove(arr + 3, arr, 20);
 
  for (int i = 0; i < 10; i++)
  {
    printf("%d ", arr[i]);
  }
 
  return 0;
}