Daniel Axtens <d...@axtens.net> writes:
> Hi
>
>> -static char __init *prom_strcpy(char *dest, const char *src)
>> +static ssize_t __init prom_strscpy_pad(char *dest, const char *src, size_t
>> n)
>> {
>> - char *tmp = dest;
>> + ssize_t rc;
>> + size_t i;
>>
>> - while ((*dest++ = *src++) != '\0')
>> - /* nothing */;
>> - return tmp;
>> + if (n == 0 || n > INT_MAX)
>> + return -E2BIG;
>> +
>> + // Copy up to n bytes
>> + for (i = 0; i < n && src[i] != '\0'; i++)
>> + dest[i] = src[i];
>> +
>> + rc = i;
>> +
>> + // If we copied all n then we have run out of space for the nul
>> + if (rc == n) {
>> + // Rewind by one character to ensure nul termination
>> + i--;
>> + rc = -E2BIG;
>> + }
>> +
>> + for (; i < n; i++)
>> + dest[i] = '\0';
>> +
>> + return rc;
>> }
>>
>
> This implementation seems good to me.
>
> I copied it into a new C file and added the following:
>
> int main() {
> char longstr[255]="abcdefghijklmnopqrstuvwxyz";
> char shortstr[5];
> assert(prom_strscpy_pad(longstr, "", 0) == -E2BIG);
> assert(prom_strscpy_pad(longstr, "hello", 255) == 5);
> assert(prom_strscpy_pad(shortstr, "hello", 5) == -E2BIG);
> assert(memcmp(shortstr, "hell", 5) == 0);
> assert(memcmp(longstr, "hello\0\0\0\0\0\0\0\0\0", 6) == 0);
> return 0;
> }
>
> All the assertions pass. I believe this covers all the conditions from
> the strscpy_pad docstring.
>
> Reviewed-by: Daniel Axtens <d...@axtens.net>
Thanks.
I'll also drop the explicit nul termination in patch 2, which is a
leftover from when I was using strncpy().
cheers
