C-language STR partial function implementation

int m_strstr (const char*dst,const char*sub)

{

if (DST = = NULL | | sub = = NULL)

return NULL;

int d_length = strlen (DST) + 1;

int s_length = strlen (sub) + 1;

int dst_index;

int sub_index;

Int J;

for (dst_index = 0; Dst_index < d_length; ++dst_index)

{

Sub_index = 0;

if (dst[dst_index] = = Sub[sub_index])

{

j = Dst_index;

while (dst[j] = = Sub[sub_index])

{

++sub_index;

++j;

if (Sub_index = = (s_length-1))

return dst_index;

}

}

}

return-1;

}

char* m_strcpy (char* DST, const char* SRC)

{

if (DST = = NULL | | src = = NULL)

return NULL;

char* dst_t = DST;

while (*dst_t++ = *src++);

return DST;

}

void* m_memmove (void* dst,const void* src,int count)

{

if (DST = = NULL | | src = = NULL)

return NULL;

char* dst_t = (char*) DST;

char* src_t = (char*) src;

int s_length = strlen (src_t) + 1;

if ((int) DST < (int) src | | (int) DST > (int) src + s_length)

{

while (count--)

{

*dst_t++ = *src_t++;

}

}

Else

{

while (count)

{

* (dst_t + count) = * (src_t + count);

count--;

}

}

return DST;

}

int m_strcmp (const char* DST, const char* SRC)

{

assert (DST = = NULL);

ASSERT (src = = NULL);

while (*dst++ = = *src++) && (*dst! = ') && (*src! = '));

return *DST-*src;

}

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C-language STR partial function implementation