common.c

#if CHAPTER >= 3
// common.c -- Defines some global functions.
//             From JamesM's kernel development tutorials.

#include "common.h"

// Write a byte out to the specified port.
void outb(uint16_t port, uint8_t value)
{
  asm volatile ("outb %1, %0" : : "dN" (port), "a" (value));
}

uint8_t inb(uint16_t port)
{
  uint8_t ret;
  asm volatile("inb %1, %0" : "=a" (ret) : "dN" (port));
  return ret;
}

uint16_t inw(uint16_t port)
{
  uint16_t ret;
  asm volatile ("inw %1, %0" : "=a" (ret) : "dN" (port));
  return ret;
}

// Copy len bytes from src to dest.
void memcpy(uint8_t *dest, const uint8_t *src, uint32_t len)
{
  for(; len != 0; len--) *dest++ = *src++;
}

// Write len copies of val into dest.
void memset(uint8_t *dest, uint8_t val, uint32_t len)
{
  for ( ; len != 0; len--) *dest++ = val;
}

// Compare two strings. Should return -1 if
// str1 < str2, 0 if they are equal or 1 otherwise.
int strcmp(char *str1, char *str2)
{
  while (*str1 && *str2 && (*str1++ == *str2++))
    ;

  if (*str1 == '\0' && *str2 == '\0')
    return 0;

  if (*str1 == '\0')
    return -1;
  else return 1;
}

// Copy the NULL-terminated string src into dest, and
// return dest.
char *strcpy(char *dest, const char *src)
{
  while (*src)
    *dest++ = *src++;
  *dest = '\0';
}

// Concatenate the NULL-terminated string src onto
// the end of dest, and return dest.
char *strcat(char *dest, const char *src)
{
  while (*dest)
    *dest = *dest++;

  while (*src)
    *dest++ = *src++;
  *dest = '\0';
  return dest;
}

int strlen(char *src)
{
  int i = 0;
  while (*src++)
    i++;
  return i;
}
#endif