lib/string: Add strscpy_pad() function

#ifndef __HAVE_ARCH_STRSCPY

ssize_t strscpy(char *, const char *, size_t);

#endif

/* Wraps calls to strscpy()/memset(), no arch specific code required */

ssize_t strscpy_pad(char *dest, const char *src, size_t count);

#ifndef __HAVE_ARCH_STRCAT

extern char * strcat(char *, const char *);

#endif

 * @src: Where to copy the string from

 * @count: Size of destination buffer

 *

 * Copy the string, or as much of it as fits, into the dest buffer.

 * The routine returns the number of characters copied (not including

 * the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.

 * The behavior is undefined if the string buffers overlap.

 * The destination buffer is always NUL terminated, unless it's zero-sized.

 * Copy the string, or as much of it as fits, into the dest buffer.  The

 * behavior is undefined if the string buffers overlap.  The destination

 * buffer is always NUL terminated, unless it's zero-sized.

 *

 * Preferred to strlcpy() since the API doesn't require reading memory

 * from the src string beyond the specified "count" bytes, and since

 *

 * Preferred to strncpy() since it always returns a valid string, and

 * doesn't unnecessarily force the tail of the destination buffer to be

 * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy()

 * with an overflow test, then just memset() the tail of the dest buffer.

 * zeroed.  If zeroing is desired please use strscpy_pad().

 *

 * Return: The number of characters copied (not including the trailing

 *         %NUL) or -E2BIG if the destination buffer wasn't big enough.

 */

ssize_t strscpy(char *dest, const char *src, size_t count)

{

EXPORT_SYMBOL(strscpy);

#endif

/**

 * strscpy_pad() - Copy a C-string into a sized buffer

 * @dest: Where to copy the string to

 * @src: Where to copy the string from

 * @count: Size of destination buffer

 *

 * Copy the string, or as much of it as fits, into the dest buffer.  The

 * behavior is undefined if the string buffers overlap.  The destination

 * buffer is always %NUL terminated, unless it's zero-sized.

 *

 * If the source string is shorter than the destination buffer, zeros

 * the tail of the destination buffer.

 *

 * For full explanation of why you may want to consider using the

 * 'strscpy' functions please see the function docstring for strscpy().

 *

 * Return: The number of characters copied (not including the trailing

 *         %NUL) or -E2BIG if the destination buffer wasn't big enough.

 */

ssize_t strscpy_pad(char *dest, const char *src, size_t count)

{

	ssize_t written;

	written = strscpy(dest, src, count);

	if (written < 0 || written == count - 1)

		return written;

	memset(dest + written + 1, 0, count - written - 1);

	return written;

}

EXPORT_SYMBOL(strscpy_pad);

#ifndef __HAVE_ARCH_STRCAT

/**

 * strcat - Append one %NUL-terminated string to another