Utility functions that are missing in <tt>string.h</tt>

This header provides utility functions that the standard C libs string.h lacks, such as explicit_bzero. More...

Detailed Description

This header provides utility functions that the standard C libs string.h lacks, such as explicit_bzero.

Files
file	string_utils.h
	Utility functions that are missing in string.h

Functions
static void	explicit_bzero (void *dest, size_t n_bytes)
	Like memset(dest, 0, n_bytes), but secure.
ssize_t	strscpy (char *dest, const char *src, size_t count)
	Copy the string, or as much of it as fits, into the dest buffer.
const void *	memchk (const void *data, uint8_t c, size_t len)
	Check if the entire buffer is filled with the same byte.

Function Documentation

explicit_bzero()

static void explicit_bzero ( void *  dest, size_t  n_bytes  )

inlinestatic

Like memset(dest, 0, n_bytes), but secure.

Unlike memset(dest, 0, n_bytes), this will zero out the memory even in cases the compiler would optimize out the call to memset().

Note

This is only sensible to use for sensitive data. For non-sensitive data, keep using memset() for performance reasons.

Parameters

[in,out]	dest	Memory to clear
[in]	n_bytes	Size of memory to clear in bytes

Definition at line 65 of file string_utils.h.

memchk()

const void * memchk	(	const void *	data,
		uint8_t	c,
		size_t	len
	)

Check if the entire buffer is filled with the same byte.

Parameters

[in]	data	The buffer to probe
[in]	c	The byte to check of
[in]	len	Size of the buffer

Returns

NULL if the entire buffer is filled with c

pointer to the first non-matching byte

strscpy()

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

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

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.

Parameters

[out]	dest	Where to copy the string to
[in]	src	Where to copy the string from
[in]	count	Size of destination buffer

Precondition

The destination buffer is at least one byte large, as otherwise the terminating zero byte won't fit

Returns

the number of characters copied (not including the trailing zero)

Return values

-E2BIG

the destination buffer wasn't big enough