2022-08-03 15:13:01 +08:00

110 lines
2.6 KiB
C

#include "string.h"
#include "glib.h"
/**
* @brief 拷贝整个字符串
*
* @param dst 目标地址
* @param src 源地址
* @return char* 目标字符串
*/
char *strcpy(char *dst, const char *src)
{
while (*src)
{
*(dst++) = *(src++);
}
*dst = 0;
return dst;
}
long strnlen(const char *src, unsigned long maxlen)
{
if (src == NULL)
return 0;
register int __res = 0;
while (src[__res] != '\0' && __res < maxlen)
{
++__res;
}
return __res;
}
/*
比较字符串 FirstPart and SecondPart
FirstPart = SecondPart => 0
FirstPart > SecondPart => 1
FirstPart < SecondPart => -1
*/
int strcmp(char *FirstPart, char *SecondPart)
{
register int __res;
__asm__ __volatile__("cld \n\t"
"1: \n\t"
"lodsb \n\t"
"scasb \n\t"
"jne 2f \n\t"
"testb %%al, %%al \n\t"
"jne 1b \n\t"
"xorl %%eax, %%eax \n\t"
"jmp 3f \n\t"
"2: \n\t"
"movl $1, %%eax \n\t"
"jl 3f \n\t"
"negl %%eax \n\t"
"3: \n\t"
: "=a"(__res)
: "D"(FirstPart), "S"(SecondPart)
:);
return __res;
}
char *strncpy(char *dst, const char *src, long count)
{
__asm__ __volatile__("cld \n\t"
"1: \n\t"
"decq %2 \n\t"
"js 2f \n\t"
"lodsb \n\t"
"stosb \n\t"
"testb %%al, %%al \n\t"
"jne 1b \n\t"
"rep \n\t"
"stosb \n\t"
"2: \n\t"
:
: "S"(src), "D"(dst), "c"(count)
: "ax", "memory");
return dst;
}
long strncpy_from_user(char *dst, const char *src, unsigned long size)
{
if (!verify_area((uint64_t)src, size))
return 0;
strncpy(dst, src, size);
return size;
}
/**
* @brief 测量来自用户空间的字符串的长度,会检验地址空间是否属于用户空间
* @param src
* @param maxlen
* @return long
*/
long strnlen_user(const char *src, unsigned long maxlen)
{
unsigned long size = strlen(src);
// 地址不合法
if (!verify_area((uint64_t)src, size))
return 0;
return size <= maxlen ? size : maxlen;
}