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

Data Structures
struct	string_writer_t
	String Writer structure. More...

Macros
#define	__swprintf   swprintf
	internal helper macro

Functions
static void	string_writer_init (string_writer_t *sw, void *buffer, size_t len)
	Initialize a string writer structure.
static size_t	string_writer_len (const string_writer_t *sw)
	Get the size of the string contained by the string writer.
static const char *	string_writer_str (const string_writer_t *sw)
	Get the string contained by the string writer.
int	__swprintf (string_writer_t *sw, FLASH_ATTR const char *restrict format,...)
	Write a formatted string to a buffer The string will be truncated if there is not enough space left in the destination buffer.
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.

Macro Definition Documentation

__swprintf

#define __swprintf   swprintf

internal helper macro

Definition at line 96 of file string_utils.h.

Function Documentation

__swprintf()

int __swprintf	(	string_writer_t *	sw,
		FLASH_ATTR const char *restrict	format,
			...
	)

Write a formatted string to a buffer The string will be truncated if there is not enough space left in the destination buffer.

A terminating \0 character is always included.

Parameters

[in]	sw	String Writer to write to
[in]	format	format string to write

Returns

number of bytes written on success -E2BIG if the string was truncated

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 141 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

string_writer_init()

static void string_writer_init ( string_writer_t *  sw, void *  buffer, size_t  len  )

inlinestatic

Initialize a string writer structure.

Parameters

[out]	sw	String Writer object to initialize
[in]	buffer	destination buffer
[in]	len	size of the destination buffer

Definition at line 60 of file string_utils.h.

string_writer_len()

static size_t string_writer_len ( const string_writer_t *  sw )

inlinestatic

Get the size of the string contained by the string writer.

Parameters

[in]

sw

String Writer to query

Returns

size of the string

Definition at line 75 of file string_utils.h.

string_writer_str()

static const char * string_writer_str ( const string_writer_t *  sw )

inlinestatic

Get the string contained by the string writer.

Parameters

[in]

sw

String Writer to query

Returns

the string assembled by string writer

Definition at line 85 of file string_utils.h.

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