C string functions, simple implementation

string.h

int memcmp(const void *lhs, const void *rhs, size_t count)
{
    const unsigned char *lhs_ptr = lhs;
    const unsigned char *rhs_ptr = rhs;
    while (count--) {
        int diff = (int) *lhs_ptr++ - (int) *rhs_ptr++;
        if (diff != 0) {
            return diff;
        }
    }
    return 0;
}

void *memcpy(void *dest, const void *src, size_t count)
{
    char *dest_ptr = dest;
    const char *src_ptr = src;
    while (count--) *dest_ptr++ = *src_ptr++;
    return dest;
}

void *memset(void *dest, int ch, size_t count)
{
    unsigned char value = (unsigned char) ch;
    unsigned char *dest_ptr = dest;
    while (count--) *dest_ptr++ = value;
    return dest;
}

static inline size_t strlen(const char *str)
{
    const char *end = str;
    while (*end) end++;
    return (size_t) (end - str);
}